Links []jpgs/courses/hsnets/lecture-link-hsn... · 2010-09-29 · LL.1.3 Physical media types and...

KU EECS 881 – High-Performance Networking – Links

– 1 –

© James P.G. SterbenzITTCHigh-Performance Networking

The University of Kansas EECS 881Links

© 2004–2010 James P.G. Sterbenz16 September 2010

James P.G. Sterbenz

Department of Electrical Engineering & Computer ScienceInformation Technology & Telecommunications Research Center

The University of Kansas

[email protected]

http://www.ittc.ku.edu/~jpgs/courses/hsnets

rev. 10.1

16 September 2010 KU EECS 881 – High-Speed Networking – Links HSN-LL-2

© James P.G. SterbenzITTC

LinksOutline

LL.1 Transmission and physical mediaLL.2 Link layer technologiesLL.3 Link layer componentsLL.4 Support for higher layers


– 2 –



LinksOutline

LL.1 Physical transmissionLL.2 Link technologies

LL.3 Link layer componentsLL.4 Support for higher layers

network

application

session

transport

network

link

end system

network

link

intermediatesystem

network

link

intermediatesystemnetwork

link

intermediatesystem

application

session

transport

network

link

end system



Network Link Principle L-II

Network links must provide high-bandwidth connections between network nodes. Link-layer protocol processing should not introduce significant latency.

Ideal NetworkNetwork Link Principle

networkCPU

M app

end system

CPU

M app

end system

intermediatesystemR = ∞

D = 0


– 3 –



LinksLL.1 Physical Media and Transmission

LL.1 Transmission and physical mediaLL.1.1 Analog and digital signalsLL.1.2 Communication challengesLL.1.3 Physical media types and performanceLL.1.4 Line coding and symbol rate

LL.2 Link layer technologiesLL.3 Link layer componentsLL.4 Support for higher layers



Transmission and Physical MediaLL.1.1 Analog and Digital Signals




– 4 –



CommunicationSignal Types

• Transmission of a signal through a medium





• Analog signal: time-varying levels– electrical: voltage levels– photonic: light intensity


– 5 –





• Analog signal: time-varying levels– electrical: voltage levels– photonic: light intensity

• Digital signal: sequence of bits represented as levels– electrical: voltage pulses– photonic: light pulses– two levels for binary digital signal

– more levels in some coding schemes more later



CommunicationDigital vs. Analog

• Digital bits are reconstructed at the receiver

0

1

time


– 6 –




• Digital bits are reconstructed at the receiver– all transmission is actually analog!– frequency response determines

• pulse rate that can be transmitted• shape of pulse → ability for receiver to recognise pulse

0

1

time




0

1

0

1

harmonic

harmonic

time

time

• Digital bits are reconstructed at the receiver– all transmission is actually analog!– frequency response determines

• pulse rate that can be transmitted• shape of pulse → ability for receiver to recognise pulse

– high-frequency attenuation reduces quality of pulse

attenuated frequencies

adapted from [Tanenbaum 2003]


– 7 –



CommunicationMedium Types

• Guided through waveguide– wire (generally copper)– fiber optic cable



CommunicationMedium Types

• Guided through waveguide– wire (generally copper)– fiber optic cable

• Unguided (wireless) free space propagation– wireless

(generally implying RF – radio frequency)• free-space optical


– 8 –



Transmission and Physical MediaLL.1.2 Communication Challenges





CommunicationChallenges1

• Goal: receiver reconstruct signal transmitter sent


– 9 –




• Goal: receiver reconstruct signal transmitter sent• Noise makes this difficult

– background noise No interferes with the signal bit energy Eb• SNR: signal to noise ratio = 10 log10 (Eb /No ) dB

– interference from other signals in shared medium• collisions among multiple transmitters• jamming from adversaries

– imperfections in the physical medium that alters the signal• especially in fiber optic cables








• Attenuation over distance that reduces the amplitude– 10 log10 (Et /Er ) dB


– 10 –








• Attenuation over distance that reduces the amplitude– 10 log10 (Et /Er ) dB

• Frequency response of the medium




• Result: difficulty in reconstructing signal


– 11 –




• Result: difficulty in reconstructing signal• Analog: distortion of received waveforms




• Result: difficulty in reconstructing signal• Analog: distortion of received waveforms• Digital: bit errors – an artifact of distortion

– distance attenuation reduces level of pulse– frequency attenuation distorts shape of pulse– distortion changes shape of pulse– dispersion smears pulses


– 12 –




• Result: difficulty in reconstructing signal• Analog: distortion of received waveforms• Digital: bit errors – an artifact of distortion

– distance attenuation reduces level of pulse– frequency attenuation distorts shape of pulse– distortion changes shape of pulse– dispersion smears pulses

• Physical and link layer devices help– amplifiers ameliorate attenuation– regenerators and repeaters reconstruct digital signals

• spaced closely enough to keep bit error rate low



Transmission and Physical MediaLL.1.3 Physical Media Types and Performance




– 13 –



Link Types and TopologiesPoint-to-Point vs. Shared Medium

• Point-to-point links– one transmitter per medium

• dedicated• multiplexed (layer 2) more later






• Shared medium (multiple access)– multiple transmitters per medium

implication?


– 14 –






• Shared medium (multiple access)– multiple transmitters per medium– results in contention for medium

problem?







• medium access control (MAC) neededlecture MW


– 15 –







• medium access control (MAC) neededlecture MW

– examples• wireless networks• original Ethernet



Physical Media TypesWire

• Unshielded twisted pair– cheap, moderate bandwidth (~100Mb/s)

• Shielded twisted pair– expensive, higher bandwidth

• Coaxial cable– expensive, high bandwidth (~ 500 MHz)


– 16 –



Physical MediaWire: Twisted Pair

• UTP: unshielded twisted pair– twisting reduces radiation and noise susceptibility– used for most wired LANs

• CAT-{5|6|7} for data applications such as Ethernet• 100 Mb/s supported over 100 m for 100BaseT Ethernet

– legacy telephone wiring• supports much lower data rates (1–10 Mb/s)• used by DSL (digital subscriber line)

• STP: shielded twisted pair



Physical MediaWire: Shielded Twisted Pair

• UTP: unshielded twisted pair• STP: shielded twisted pair

– adds conducting shield outside of twisted pair– more resistant to noise than UTP– more expensive than UTP– used in IBM Token Ring LANs– no longer commonly used


– 17 –



Physical MediaWire: Coaxial Cable

• High quality shielded cable– used in some LANs (and early Ethernet)– used in CATV (RG6 better than RG59)

• HFC: hybrid fiber coax for data• 10 Mb/s downstream shared | 300 kb/s upstream typical

Cuconductor dielectric

insulatorshield insulating

jacket



Physical MediaFiber Optics

• Fiber optics– bandwidth ≈ 20 THz within 800–1700 nm– attenuation [dB/km]– dispersion: waveform smearing limits bandwidth-×-distance

Much more about optical communication in EECS 881


– 18 –



Physical MediaFiber Optic Cable

• Lightwave travels along glass or plastic core– multimode: reflected along core/cladding boundary– single mode: guided with no reflections

• Transmitter– LED or solid-state laser

glass or plastic core glass or

plasticcladding

insulatingjacket



Physical MediaFiber Optic Modes

• Multimode: 50 – 85 μm core– signal reflected in multiple modes– intermodal dispersion limits length to a few km

why?

reflections


– 19 –



Physical MediaFiber Optic Modes

• Multimode: 50 – 85 μm core– signal reflected in multiple modes– intermodal dispersion limits length to a few km

why?

• Single mode: 8–10 μm core– core acts as waveguide with no reflections– suitable for 10s of km between digital regenerators

reflections



Physical MediaFiber Optic Cable Constraints

• Attenuation– distance– frequency

• Dispersion: smearing limits bandwidth-×-delay– intermodal: different modes travel different distances– chromatic: different wavelengths travel different velocities– polarisation mode: diff. polarisation states travel at diff. v

• Nonlinearities limit WDM– stimulated Raman scattering (due to molecular vibrations)– stimulated Brillouin scattering (acoustic wave interaction)– carrier-induced cross-phase modulation (c ↑ w/other signals)– four-wave mixing (3 wavelengths induce fourth sum/diff)


– 20 –



Physical MediaWireless Free Space

• Signals transmitted through free space– no waveguide

• Spectrum (λf = c ; c = 3×105 km/s)– only some spectrum usable for communication– RF: radio frequency– optical

• infrared 800–900 nm = 333–375 THz 41 THz spectrum

Much more about wireless communication in EECS 882[http://www.ntia.doc.gov/osmhome/allochrt.pdf]



Physical Media TypesWireless Free Space Licensing

• Licensed and regulated spectrum– ITU (international) and each country (FCC in US) regulate– most frequency bands require license to transmit

• e.g. broadcast TV, radio, amateur radio, GMRS

– some bands do not require explicit license application• e.g. US CB, FRS


– 21 –



Physical Media TypesMicrowave Terrestrial Links

• Microwave links – typically point-to-point directional links– once ubiquitous for long-distance telephony

• 4 GHz TD radio and 6 GHz TH radios• mostly replaced by fiber optic cables

– subject to fading during rain storms– new interest for local loops and MANs



Physical Media TypesSatellite Characteristics

• Satellite orbit characteristics

• Tradeoffs– cost per satellite (GEO), high link power, high delay– total cost of constellation, constellation management

270 ms3 (plus polar)36786 kmGEOgeosynchronous EO

~35–85 ms~105 000 km –15 000 km

MEOmedium earth orbit

~1–10 ms~50–1000100 km –1 000 km

LEOlow earth orbit

Link DelayConstellation SizeAltitudeType


– 22 –



Physical Media TypesMicrowave Satellite Links

• Satellite links

IssuesBandwidthTypical Frequency [GHz]

Band

rain fade3.5 GHz3020Ka

rain fade500 MHz1411Ku

terrestrial interference500 MHz6.04.0C

low aggregate BW70 MHz2.21.9S

low aggregate BW15 MHz1.61.5L

UplinkDownlink



Physical Media TypesWireless RF Spectrum

• Unlicensed spectrum– regulations for use (FCC 15.243–249)

• e.g. max xmit power• e.g. spread spectrum parameters

– ISM: industrial, scientific, and medical• 900 MHz, 2.4 GHz, 5.8 GHz, …

– UNII: unlicensed national information infrastructure• 5.8 GHz

– may be use by anyone for any purpose (subject to regulations)

– interference a significant problem• e.g. 2.4 GHz FHSS cordless phones against 802.11b• e.g. interference among 802.11 hubs in dense environments


– 23 –



Physical Media TypesWireless RF Antennæ and Attenuation

• Antennæ– omnidirectional: RF radiated in all directions– directional: focused beam of radiation

• reduces contention and improves spatial reuse• significantly complicates network design: beam steering• laser/maser: focused coherent light/microwave transmission

• Attenuation– signal strength decreases as 1/r 2 in perfect medium– signal may decrease as 1/r x with multipath interference

• rural environments: x > 2• urban environments: x → 4



Physical Media PerformanceVelocity

• Velocity v = c /n [m/s]– speed of light c = 3×105 km/s– index of refraction n

Consequences?


– 24 –



Physical Media PerformanceVelocity and Delay

• Velocity v = c /n [m/s]– speed of light c = 3×105 km/s– index of refraction n

• Delay d = 1/v [s/m]– generally we will express delay in [s] given a path length



Physical Media PerformanceLink Length

• Link Length– distance over which signals propagate

• point-to-point: wire or fiber length• shared medium: longest path through medium

– constrained by physical properties of medium

Consequences?


– 25 –



Physical Media PerformanceLink Length and Attenuation

• Link Length– distance over which signals propagate

• point-to-point: wire or fiber length• shared medium: longest path through medium

– constrained by physical properties of medium

• Attenuation: decrease in signal intensity• over distance expressed as [dB/m]• at a particular signal frequency

dB

m

mdB



Physical Media PerformanceFrequency Response and Attenuation

• Frequency range and attenuation– ability to propagate signals of a given frequency

• Characteristics of guided media– wire: generally falls off above a certain fmax

– fiber optic cable & free space transparent to certain rangesanalogy:UV blocking sunglasses (high attenuation )

vs.standard glass (moderate attenuation )

vs.UV transparent black light glass (low attenuation )


– 26 –



Physical Media PerformanceFrequency Response and Attenuation: Optical

• Fiber-optic cable transparency bands– 1300 and 1550 nm– 850 nm for lower cost

850nm

1300nm

1550nm

1.20.8 0.9 1.4 1.6

1

2

0

Atte

nuat

ion

[dB

/km

]

Wavelength [μm] [adapted from Tannenbaum 2003]



Physical Media PerformanceFrequency Response and Attenuation: RF

• Atmospheric transparency bands– RF: 10MHz – 10GHz

• VHF meter band, UHF millimeter band– Infrared: N-band

RF

0.5

1.0

0.0

Atm

osph

eric

Opa

city

Wavelength [m] | Frequency [Hz]

10µm0.1nm 10nm 10m 100m 1km1m10cm1cm1mm100µm1µm1nm 100nm

adapted from[coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html]

10THz1EHz 10Pz 10MHz 1MHz 100KHz100MHz1GHz10GHz100GHz1THz100THz100PHz 1PHz

N

UHF VHF

microwave shortwave


– 27 –



Physical Media TypesPerformance Characteristics Summary

428–750 THzvisible

0.3–428 THzinfrared 1/r 23.3 s/km1.0c

1–300 GHzmicrowave

Wireless

0.2–0.5 dB/km5 s/km0.68c120–250 THz1700–800 nmglassOptical fiber

7.0 dB/km4 s/km0.66–0.95c0–500 MHzcoax

0.7 dB/km5 s/km0.67c0–1 MHztwisted pairWire

Typical AttenuationDelayVelocity

Frequency RangeMediumType



Transmission and Physical MediaLL.1.4 Line Coding and Symbol Rate




– 28 –



Line Coding and Symbol RateLine Coding

• Line coding– way in which bits are encoded for transmission

• digital (binary, trinary, …) or analog modulation



Line Coding and Symbol RateSymbol Rate

• Line coding– way in which bits are encoded for transmission

• digital (binary, trinary, …) or analog modulation

• Symbol rate– baud rate [symbols/s]

• baud = b/s only if one symbol/bit

– clever encodings (e.g. QAM) allow high baud rates


– 29 –



Line Coding and Symbol Rate Example Codes

• Analog line coding: – modulate a carrier

• Amplitude modulation– each symbol a different level

• Frequency modulation– each symbol a different frequency

• Phase modulation– each symbol a different phase

• Combinations possible– e.g. amplitude and phase

0 0 1 0 0 1 0 1 1 1

00 10 01 01 11 00 10 01 01 11



Line Coding and Symbol RateExample: QPSK and QAM

• Combination of amplitude- and phase-modulation– allows more bits per symbol

• QAM: quadrature amplitude modulation– quadrature = 4 phases carried on two sine waves– PAM is case for only one phase– QPSK is case for only one amplitude

844QAM-256

643QAM-64

442QAM-16

241QPSK

Bits/SymbolPhasesAmplitudesName


– 30 –



Line Coding and Symbol RateExample: QPSK and QAM

• QAM: amplitude- and phase modulation• Represented by constellation diagram

– amplitude is distance from origin– phase is angle

0°180°

90°

270°

0°180°

90°

270°

0°180°

90°

270°

QAM-64QAM-16QPSK



Transmission and Physical MediaHigh-Performance Network Summary

• Improved performance of links dependent on:– physical media type– dedicated vs. shared links– minimisation of impairments

• attenuation• noise (e.g. twisted pairs, shielding)

– more sophisticated coding techniquesto maximise symbol rate

• e.g. QPSK → QAM-n


– 31 –



LinksLL.2 Link Layer Technologies

LL.1 Transmission and physical mediaLL.2 Link layer technologies

LL.2.1 Services and interfacesLL.2.2 Point-to-point dedicated links

examples: Ethernet, 802.16, DSLLL.2.3 Point-to-point multiplexed links

examples: SONET/SDH, OTNLL.2.4 Shared medium links

examples: Ethernet, token ring, 802.11, 802.15, HFC




Link LayerHybrid Layer/Plane Cube

physicalMAC

link

networktransport

sessionapplication

data plane control plane

plane

management

social

virtual link

L1

L7L5L4L3

L2L1.5

L8

L2.5

Layer 2:hop-by-hopdata transferin data and control planes


– 32 –



Links and LANsLL.2.1 Link Layer Services and Interfaces









Link LayerService and Interfaces

• Link layer is HBH analog of E2E transport layer– transport layer (L4) transfers packets E2E


– 33 –





• Link layer (L2) service to network layer (L3)– transfer frame HBH (hop-by-hop)

• sender: encapsulate packet into frame and transmit• receiver: receive frame and decapsulate into packet







– error checking / optional correction or retransmission• recall end-to-end arguments:

E2E reliability with HBH error control only for performance


– 34 –








E2E reliability with HBH error control only for performance – flow control possible but not generally needed at link layer

• parameter negotiation typical (e.g. data rate)








E2E reliability with HBH error control only for performance – flow control possible but not generally needed at link layer

• parameter negotiation typical (e.g. data rate)

• Link layer multiplexing and switching


– 35 –




• Link layer frame encapsulates network layer packet– packet (NPDU – network layer protocol data unit)– frame (LPDU link layer protocol data unit)

• frame = header + packet + (trailer)

network layer

MAC/phy layer

link layer

network layer

MAC/phy layer

link layer

NPDU

NPDU TH

NPDU

NPDU TH

…10111001010…



Link LayerFunctional Placement

• Link layer functionality per line interface– end system: network interface (NIC)– switch/router: line card

switch

forwarding

line card

framespackets

line card

line card

line card

end system

network interface

mem CPU

routing

frames


– 36 –



Link TechnologiesBandwidth Scalability

• Link protocol bandwidth scalability– variable: generally not practical for component manufacture– discrete: power-of-two or order-of-magnitude– permit evolution

• minimal standards rewriting at link layer• may need new physical layer standards

Link Protocol Scalability Principle L-8C

Link protocols should be scalable in bandwidth, either variably or in discrete intervals (power-of-two or order of magnitude). Header/trailer lengths and fields that relate to bandwidth should be long enough or contain a scale factor.



Link TechnologiesIEEE 802

• IEEE 802 LAN/MAN standards [IEEE 802.1]– www.ieee802.org

• Definition of LAN/MAN protocols for L1–L2– 802.2 : logical link control– 802.n : MAC and physical media dependent

LLC sublayerlogical link control

MAC sublayermedium access control

MI sublayermedia independent

PMD sublayerphysical media dependent

physicallayer

linklayerMAClayer

802.2

802.n

PMD1 PMD2 PMDk


– 37 –



Link TechnologiesImportant IEEE 802 Protocols

media independentLAN/MANIEEE 802.1architecture

media independentLAN/MANIEEE 802.2LLC

WMAN (WiMAX)

WPAN

WLAN (Wi-Fi)

Token ring

Ethernet

Common name TechnologyScopeStandard

MAN

PAN

LAN

LAN

LAN/MAN/(WAN)

RFIEEE 802.16

RFIEEE 802.15

RF, (IR)IEEE 802.11

wireIEEE 802.5

wire, fiberIEEE 802.3

• Many other 802.n protocols– some important, but obsolete, e.g. 802.5– some never important, e.g. 802.6 DQDB– some likely to become important, e.g. 802.15, 802.16– the jury is still out on others, e.g. 802.17, 802.20, 802.22



Links and LANsLL.2.2 Point-to-Point Dedicated Links








– 38 –



Link TechnologiesPoint-to-Point Dedicated Links

• Sequence of framed packets along a link– space division mesh network– multiplexing occurs at a higher layer

• network layer (e.g. IP forwarding)• transport layer (e.g. TCP sockets)

H Tpayload H Tpayload H Tpayload



Point-to-Point LinksExample5.M 802.16

• IEEE 802.16 more detail in EECS 882 lecture WN– part of 2nd set of 802 wireless protocols (802.15 & 802.16)– design motivated by MMDS– no similarity to 802.11/Ethernet framing or operation

802.16 WMAN

802.11 WLAN

802.15WPAN

10 km


– 39 –



Point-to-Point LinksExample5.M 802.16

• WirelessMAN: Wireless Metropolitan Area Networks– IEEE 802.16 grouper.ieee.org/groups/802/16

• Metropolitan wireless networks– originally intended for fixed wireless access– standardisation and replacement for MMDS in 10 – 66 GHz– 802.16a additional operation in licensed bands 2 – 11 GHz– 802.16b additional operation in unlicensed 5.8 GHz band

• Later support for mobility– 802.16e– overlaps with IEEE 802.20 MBWA charter



Point-to-Point LinksExample5.M 802.16 WiMAX

• WiMAX– worldwide interoperability for microwave access– www.wimaxforum.org– 802.16 service deployment and architecture

• needed by carriers• similar in concept to WiFi for 802.11

• 802.16 ≠ WiMAX


– 40 –



Point-to-Point LinksExample5.M 802.16 Topology: Links

• Mesh of point-to-point full duplex links• FDD (frequency division duplex)

– uses two frequencies

• TDD (time division duplex)– up and downstream share single frequency



Point-to-Point LinksExample5.M 802.16 Link Characteristics

• 802.16 (original)– 10-66 GHz licensed spectrum; LOS (line of sight)– 2 – 5 km transmission radius– 32 – 134 Mb/s

• 802.16a and 802.16b– 2 – 11 GHz; non-LOS– 7 – 10 km typical; 50 km max transmission radius– 75 Mb/s

• 802.16e (mobile)– 2 – 6 GHz; non-LOS– 2 – 5 km transmission radius– 15 Mb/s


– 41 –



Point-to-Point LinksExample5.M 802.16 Topology: Nodes

• Base station– directly connected to Internet infrastructure– arranged as mesh with other base stations

• Fixed subscriber station– 802.16 communication with base station– connected to LAN infrastructure, e.g.

• Ethernet• 802.11

• Mobile node– 802.16e



Point-to-Point LinksExample5.M 802.16 Topology: PMP Mode

• PMP: point-to-multipoint topology– BS: base station

• communicates with multiple SSs• typically sectorised cell using multiple directional antennæ

– SS subscriber stations• communicate through BSs

STASTA

AP

BSS 1Internet

BSSS

802.11 and Ethernet LAN

STA

SS


– 42 –



Point-to-Point LinksExample5.M 802.16 Topology: Mesh Mode

• Mesh mode (PMP and mesh)– BS – SS (as in PMP)– BS – BS multihop relay to SS– BS – BS mesh network (e.g for backhaul)– SS – SS ad hoc mode

Internet

BS

BSSTASTA

AP

BSS 1

SS


STA

SS

SS



Point-to-Point LinksExample5.M 802.16e Topology: Mobile Terminals

• Mobile terminals (PMP and mesh)– BS – MT SS– SS – MT SS ad hoc mode– MT SS – MT SS ad hoc mode

Internet

BS

BS

SSMT

STASTA

AP

BSS 1

SS

SSMT


STA


– 43 –



Point-to-Point LinksExample5.M 802.16 Evolution

• 802.16 licensed spectrum uses highest frequencies– highest rate– adaptive coding: tradeoff between distance and rate

• 802.16m– advanced air interface targetted to 4G cellular– data rates of 100Mb/s mobile, 1Gb/s fixed

• Higher rate links– may need to use millimeter-waveband (60–90 GHz)

• 10 Gb/s links possible• proprietary transceivers now available



Point-to-Point LinksExample5.M 802.16 Link Characteristics

75 Mb/snon-LOS5.8 GHz UNII802.16b

point-to-multipoint

point-to-point

pt-to-ptpt-to-mp

topology

3–5 km8–36 Mb/s24–40 GHz2– 3 GHz

LMDSMMDS

2010

2006

2002

2001

year

TDD & FDDMIMO

OFDMA

non-LOSOFDMA

non-LOSOFDMOFDMA

LOSSC

TDD & FDD

coding duplex

2–5 km

7–10 km

2–5 km

typicalrange

5–40 MHz

1.25–20 MHz

channel BW

34–134 MB/s10–66 GHz

licensed802.16

75 Mb/s2–11 GHz

licensed802.16a

typical goodput

Link type

≤100 Mb/s*≤1 Gb/s

450 MHz– 3.6 GHz

licensed802.16m

15 Mb/s*2–6 GHz802.16e

payloadMAC rateband

*mobile


– 44 –



Point-to-Point LinksExample5.D DSL Residential Broadband

• DSL (digital subscriber line) also xDSL– based on PSTN local loop infrastructure

• Local loop reuse– entire local loop: central office to home

reuse

new

reuse

reuse

Infrastructure

widespreadtwisted pairDSL

copper

fiber

shared coax

Medium

futureBPL

emergingFTTX PON

widespreadHFC

DeploymentTechnology



Point-to-Point LinksExample5.D DSL Residential Broadband Overview

• DSL (digital subscriber line) also xDSL– based on PSTN local loop infrastructure

• Local loop reuse– entire local loop: central office to home– may be hybrid

• fiber to neighbourhood node (e.g. FTTN, VDSL)• twisted pair to and in home

• POTS sharing alternatives– transparent multiplexing with POTS for residential use– dedicated pair originally for business use

• DSL forum dslforum.org


– 45 –



Point-to-Point LinksExample5.D ADSL Original Motivation

• ADSL (asymmetric DSL) [ANSI T1.413] / [ITU G.992.1 ]– developed by Bellcore in late 1980s to deliver video to home

• video market didn’t develop and not enough streams supported• but demand for always-on higher-rate Internet access did

– assumed asymmetric data access• Web access and video download• not peer-to-peer file sharing• exploits asymmetry to reduce interference in DSLAM

– frequency multiplexed with POTS• uses DMT coding to provide • requires splitter in home to segregate data from POTS



Point-to-Point LinksExample5.D ADSL Standards Development

• Original development: Bellcore• Early deployments in the 1990s

– CAP (carrierless amplitude phase modulation) line coding• First standard: [ANSI T1.413] 1995 updated 1998

– DMT (discrete multitone) line coding• Subsequent standards: ITU Q.99X

– handshake procedures [Q.994.1] 2003 between transceivers– progressive increases in line rate with DMT enhancements

• Industry forum: DSL Forum technical reports– www.dslforum.org/techwork/treports.shtml– DSL forum rounds up; rates more optimistic than standards


– 46 –



Point-to-Point LinksExample5.D HDSL Motivation

• HDSL [G991.1] 1999– replacement for T1 (1.544 Mb/s) and E1 (2.048 Mb/s) loops– repeaters not needed– 2 dedicated pairs cannot be shared with POTS– generally only used by businesses– realatively expensive due to market and tariffs

• SHDSL [G991.2]– higher rate evolution of HDSL– 2.312 Mb/s over 2 pairs in 2001

5.696 Mb/s over 4 pairs in 2003



Point-to-Point LinksExample5.D ADSL Modulation and Spectrum

• POTS telephony – UTP (unshielded twisted pair) local loop– analog baseband signal to 12 kHz– significantly more bandwidth available with clever coding

• ADSL uses frequencies above 12 kHz– upstream: 25.875 – 138 kHz– downstream: 138 – 1104 kHz

12kHz 26kHz 138kHz

voice downstream data upstream data


– 47 –



Point-to-Point LinksExample5.D ADSL CO and Residence Architecture

• DSL multiplexed with POTS between home and CO– splitters on each side

PC

DSL

NID5

central office

Internet

PSTN

DSLAM

DSLAM: DSL access multiplexerNID: network interface deviceDSL×: hub or switch with DSL modem

split

split

split



Point-to-Point LinksExample5.D DSL Lite Motivation

• ADSL Lite [ITU G.992.2 ] 1998– eliminates need for splitters– DSL modems can be plugged into any jack


– 48 –



Point-to-Point LinksExample5.D DSL Lite Architecture

• DSL multiplexed with POTS between home and CO– subscriber side does not need splitter– DSL modems can be plugged into any RJ-11 phone jack

PC

NID5

central office

Internet

PSTN

DSLAM

DSLAM: DSL access muxNID: network interface deviceDSL×: hub or switch with DSL modem

split

split

DSL



Point-to-Point LinksExample5.D ADSL2 Motivation

• ADSL2– splitter [ITU G.992.3 ] 2002 updated 2005

– splitterless [ITU G.992.3 ] 2002

– evolution of ADSL and ADSL lite to higher rates– choice of longer reach or higher rates than ADSL

• ADSL2+ (extended bandwidth ADSL2) [ITU G.992.5 ]– doubles ADSL2 carrier frequency and rates


– 49 –



Point-to-Point LinksExample5.D VDSL Motivation

• VDSL (very-high-speed DSL) [ITU G.993.1 ] 2004– field trials began in the mid 1990s

• Higher rates than available with ADSL– by using FTTN (fiber to the node)– but reusing twisted pair into home– symmetric VDSL: 26 Mb/s full duplex up to ~300 m– asymmetric VDSL: 52 Mb/s downstream, 12 Mb/s upstream

• VDSL2 [ITU G.993.2 ] 2006– higher rate version of VDSL– symmetric VDSL2: 100 Mb/s full duplex– degraded to ADSL-like performance for long reach



Point-to-Point LinksExample5.D DSL Link Characteristics

2006

2004

2005

2002

2002

1999

19951999

20012003

1998

Year

splitterDMT1–3.5 Mb/s8–12 Mb/sPOTS sharedG.992.3ADSL2

DMT

QAMDMT

DMT

DMT

DMT

DMT

TCPAM

2B1QCAP

Coding

hybrid

hybrid

POTS shared

POTS shared

POTS shared

POTS shared

ded. 2-pairded. 4-pair

dedicatedtwo pairs

Type

splitterless1–3.5 Mb/s8–12 Mb/sG.992.4ADSL2 Lite

split1–3.5 Mb/s24 Mb/sG.992.5ADSL2+

100 MB/s

26 Mb/s52 MB/s

1.535 Mb/s

6.144 Mb/s

2.312 Mb/s5.696 Mb/s

1.544 Mb/s2.048 Mb/s

Down R

FTTN

FTTN

splitterless

requires splitter

HDSL successor

T 1 c i r c u i tE1 extension

NotesLink Type

300 m100 Mb/sG.993.2VDSL2

300 m26 Mb/s12 MB/s

G.993.1VDSL

3 km512 kb/sG.992.2ADSL Lite

3 km640 kb/sT1.413G.992.1ADSL

2.312 Mb/s5.696 Mb/sG991.2SHDSL

1.544 Mb/s2.048 Mb/sG991.1HDSL

RangeUp RateStandard


– 50 –



Point-to-Point LinksExample5.D ADSL Summary

• Advantages of ADSL– reuse of existing local loops in their entirety

• shared with POTS without need for additional pair

– dedicated point-to-point links• bandwidth not shared with other users• better latency characteristics



Point-to-Point LinksExample5.D ADSL Summary

• Advantages of ADSL– reuse of existing local loops in their entirety

• shared with POTS without need for additional pair

– dedicated point-to-point links• bandwidth not shared with other users• better latency characteristics

• Disadvantages of ADSL– lower rates than FTTN architectures (VDSL and HFC)– rate dependent length, gauge, wire and termination quality– blocked by load coils (POTS line extenders)– ADSL lite limited by number and spacing of bridge taps


– 51 –



Point-to-Point LinksExample5.D VDSL Summary

• Advantages of VDSL– reuse of existing twisted pair from street to premise

• Disadvantages of VDSL– significant incremental cost of deployment over ADSL– rate drops rapidly with distance– rate highly dependent on wire gauge and quality



Point-to-Point LinksExample5.D DSL Summary

• Advantages of VDSL– reuse of existing twisted pair from street to premise

• Disadvantages of VDSL– significant incremental cost of deployment over ADSL– rate drops rapidly with distance– rate highly dependent on wire gauge and quality

• Advantage of HDSL/SDSL– T1/E1 repeaterless circuit extension over existing local loop

• Disadvantage of HDSL/SDSL– traditionally limited to businesses due to rate structure


– 52 –



Point-to-Point LinksExample5.D DSL Summary and Evolution

• Advantages of DSL– reuse of existing local loop (ADSL)– reuse of existing loop from street to house (VDSL)

• Disadvantages of DSL– shared medium infrastructure– usable data rate and latency per user highly variable

• Evolution for high speed– hack of local loop infrastructure for Internet access– physical layer coding improvements limited to several Mb/s– VDSL replaces of legacy infrastructure with fiber

• significant cost but not all the way to the residence



Links and LANsLL.2.3 Point-to-Point Multiplexed Links








– 53 –



Multiplexing and SwitchingSynchronous TDM Links

• Synchronous time-division multiplexing (STDM)– n × R/n rate signals combined– fixed-size slots round-robin : 0, 1,… n–1, 0, 1,… n-1, 0, …

Advantages?Disadvantages?

H1 2H2 H3 T2





+ Simple multiplexing scheme– Difficult to efficiently use link

– time slot allocation problem– wasted/oversubscribed slots

H1 2H2 H3 T2


– 54 –





+ Simple multiplexing scheme– Difficult to efficiently use link

– time slot allocation problem– wasted/oversubscribed slots

• Common in PSTN-derived systems (e.g. SONET)

H1 2H2 H3 T2



Multiplexing and SwitchingAsynchronous TDM Links

• Asynchronous time division multiplexing (ATDM)– aka statistical multiplexing– variable size time slots

Advantages?Disadvantages?


– 55 –



Multiplexing and SwitchingAsynchronous TDM Links

• Asynchronous time division multiplexing (ATDM)– aka statistical multiplexing– variable size time slots

– May be more complex– unless FIFO service discipline which is unfair

+ Better link efficiency+ each sender uses proportion of link needed



Point-to-Point LinksExample5.0 ITU Transport Networks

OTN: optical transport network

SDH: synchronous digital hierarchy

EthernetATM/B-ISDN

ASON

GMPLSPNNI

GFP CBRkSDH/SONET ATM ETH

GFPCBRk AAL

proprietary DWDM

OTN

CBR

IP

ASON

PNNI

GMPLS

control planes


– 56 –



Point-to-Point LinksExample5.0 ITU Transport Networks

• Data and management planes– OTN: optical transport network– SDH: synchronous digital hierarchy– Ethernet– ATM/B-ISDN: asynchronous transfer mode / broadband ISDN

• Control plane (layer 2 switching)ASON: automatically switched optical network– GMPLS: generalised multiprotocol label switching (L 2.5)

• RSVP-TE, CR-LDP (IETF deprecated)

– PNNI: (ATM) private NNI signalling (layer 3 switching)



Link TechnologiesExample5.0 Generic Framing Procedure (GFP)

• Data encapsulation transport networks ITU-T G.7041

– OTN, SDH/SONET– 4B common header (length, HEC)– client specific headers

• Transfer of: – variable size frames (GFP-F)

• IP, PPP• Ethernet MAC

– block code (transparent – GFP-T)• FCS• ESCON/FICON


– 57 –



Link TechnologiesExample5.0 GFP Formats

Core header4B

PLI2B PDU length indicatorcHEC2B core header CRC-16 HEC

Payload4–65536B

payload headers4–64B

type2B PTI3b payload type id (data/mgt)PFI1b payload FCS identifierEXI4b extension header indicator

tHEC2B CRC-16extension header field0-60BeHEC2B CRC-16

client payload (x43+1 scrambled)FCS CRC-32 (optional)4B

client payload information field

FCS

type

tHEC

eHEC

ext header

PLI

cHEC



idleidle

idle

idle

idle idle idle idle idle idleidleidle idle idle idle

idle idle

idle

Link TechnologiesExample5.0 GFP in OTN

• GFP frames in OPUk– OH PSI = 05

• GFP frames arbitrarily packed in OPU– frames (8B–64KB) may span multiple OPUs– idle frames fill gaps

OP

Uk

OH

05


– 58 –



Point-to-Point LinksExample5.1 SONET/SDH

• WAN/MAN synchronous optical links– SDH: synchronous digital hierarchy (ITU-T)– SONET: synchronous optical network (Bellcore, ANSI)

• Standards suite:– architecture G.803, T1.105– framing and multiplexing G.707, T1.105.02– equipment G.671, G.783– physical interfaces G.691, G.692, T1.105.06, T1.106– OAM&P G.784, G.831– protection G.841, T1.105.01



Point-to-Point LinksExample: SONET/SDH5.1 Multiplexing Hierarchy

• Path F3– linkL2 between switchL3-to-switchL3 (ATM or IP switch)– STS-n generation, HEC, and framing

• Line (SDH digital section) F2– de/multiplexing STS-n ↔↕ STS-N– concatenation 4×STS-n ↔ STS-4n

• Section (SDH regenerator section) F1– STS-n transport, framing, scrambling

• Photonic section– between EO STS-n→OC-n – OC-n→STS-n OE– between EOE regeneration


– 59 –



Point-to-Point LinksExample5.1 SONET/SDS Link Structure

• SONET/SDH path– SONET/SDH link (edge-to-edge of SONET subnet)– appears as L2 link to L3 routers/switches

• SONET/SDH tandem connection– bundle of STS-n /STM-n transported as group (no add/drop)

• SONET line / SDH multiplex section– transmission line across regenerators (may be multiple)

• SONET section / SDH regenerator section

(regen) section

PTE

STELTE

STE

TE: terminatingequipment

TCTE

PTE

LTE

TCTE

sectionsectionsection section section section

line / multiplex section line linelinelinetandem connection

path



Point-to-Point LinksExample5.1 US Multiplexing Structure

• Synchronous transport signals (STS)on optical carriers (OC)– used for higher-level aggregation of voice circuits– OC-n c data services (c= concatenated super-rate)

•••

OC-3

DS-3STS-1

DS-2

DS-0

T1T3

OC-12OC-48

OC-192

• • •

OC-3cOC-12cOC-48cOC-192c

OC-768

24:1

4:1

4:1

4:1

3:1

7:1

4:1

4:1

PDH (EECS780 LL)


– 60 –



Point-to-Point LinksExample5.1 STS-1 Frame Format

• STS-1 frame [810B] arranged 9 rows × 90B [ANSI T.105.1]– transport overhead: 9 × 3B

• section overhead 3×3B and line overhead 6×3B– envelope capacity: 9 × 87B– SPE (synchronous payload envelope): floats in envelope capacity

• path overhead: 9 × 1B at 1st byte in each SPE row• stuff bits: 9 × 2B at 30th and 59th byte in each SPE row• information payload: 9 × 84B

SPE

secovhd

lineovhd

envelopecapacity

path

ovhdtransport

overhead



Point-to-Point LinksExample5.1 STS-1 Floating Payload

• STS-1 SPE floats in STS-1 payload envelope– SPE may begin anywhere within envelope– H1H2 pointer in LOH indicates offset to beginning of SPE

lineovhd

secovhd

secovhd

lineovhd

path

ovhd

SPE j

STS-1 frame i

STS-1 frame i +1


– 61 –



Point-to-Point LinksExample5.1 STS Path Overhead

• Path overhead (POH)– SONET edge-to-edge– signalling between path terminating equipment (PTE)– 1 column of POH per multiplexed path– STS-n c has only a single POH column

• POH content– payload-independent functions– mapping-dependent overhead: dependent on payload type– application-specific functions– undefined overhead for future use



Point-to-Point LinksExample5.1 STS-1 Path Overhead

• J1 STS Path tracepath access pointID to verifyconnectivity

• B3 BIP-8 bit-interleaved parity for path error monitoring

• C2 STS path signal label identifies payload content / defect

• G1 path status returned from receiving PTE

• F2 path user channel for arbitrary PTE–PTE signalling

• H4 multiframe indicator for VTs and virtual concatenation

• Z3Z3 growth 2B reserved for future use

• N1 tandem connection maintenance and data link

J1B3C2G1F2H4Z3Z4N1


– 62 –



SONET Transport NetworksExample5.1 STS-1 Section Overhead

• A1A2 Framing= F6 28

• C1 ID(depricated)

• J0 section trace verify connectivity between STEs• Z0 section growth 1B reserved for future use• B1 BIP-8 bit-interleaved parity for section error monitoring• S media-dependent bytes• E1 orderwire voice channel between STEs• F1 section user channel for arbitrary STE–STE signalling• D1D2D3 section data comm. channel 192kb/s alarms, OAM

secovhd

lineovhd

envelopecapacity



SONET Transport NetworksExample5.1 STS-1 Line Overhead

• H1H2 pointeroffset to 1stbyte of SPE

• H3 pointer action adjust input buffer fill for freq justification• B2 BIP-8 bit-interleaved parity for line error monitoring• K1K2 APS channel APS signalling between LTEs• D4–D12 line data comm. channel 576kb/s for alarms, OAM• S1 synchronisation messaging for clock sync• M0M1 line REI remote error indication; returns # BIP-8 errors• Z1Z1 line growth 2B reserved for future use• E2 orderwire voice channel between LTEs• D13–D156 extended data comm. chan 9216kb/s (OC-768)

secovhd

lineovhd

envelopecapacity


– 63 –



SONET Transport NetworksExample5.1 Higher-Level Rates

• SONET and SDH designed to be scalable– in rate– in multiplexing structure

• STS-n– synchronous transport signal multiplexed from n × STS-1– useful for aggregated services

• STS-n c– synchronous transport signal at rate n × STS-1– provides single data stream

• no need to stripe across n streams and maintain skew



TDM Transport NetworksExample5.1 SONET/SDH Comparison

synchronousplesiochronousSynchronisation

.155 – 40 Gb/s1.5 – 45 Mb/sRates‡

transparentopaqueTransparency

54Levels*

TDMTDMMultiplex domain

electronicelectronicMux & switching

opticalelectronicTransmission

OTN OTMOTN DWSDH/SONETPDH

* as currently defined in standards, not including sub- and intermediate levels‡ approximate as currently defined in standards, not including STS-1 and sub-rates (DS0 and VTs)


– 64 –



TDM Transport NetworksExample5.1 SONET/SDH Hierarchy

139.42 Gb/s153.94 Gb/s2 405 367 B82 944 B159.25 Gb/sSTM-1024cOC-3072c

Payload rateLink Type

48/53 SONET1.0 SONETN ×87×9 – 9 BN ×3×9 BN × 51.84 Mb/sSTM-(N/3)cOC-N c

34.85 Gb/s38.48 Gb/s601 335 B20 736 B39.81 Gb/sSTM-256cOC-768c



544.09 Gb/s600.77 Mb/s9 387 B324 B622.08 Mb/sSTM-4cOC-12c

135.63 Mb/s149.75 Mb/s2 340 B81 B155.52 Mb/sSTM-1cOC-3c

44.87 Mb/s49.54 Mb/s774 B27 B51.84 Mb/sSTM-0STS-1

ATMmaxSONETPayloadTransport

OverheadRateSDHSONET



Link TechnologiesMultiplexed Links

• Optical WDM– synchronous TDM: time division multiplexing– asynchronous time division multiplexing (statistical)– number of wavelengths inversely proportional to distance

• stimulated Raman scattering due to molecular vibrations• stimulated Brillouin scattering interacting with acoustic waves• carrier-induced cross-phase modulation causes phase shifts• four-wave mixing induces sum and difference frequencies

H3 T3payload

H2 T2payload

H1 T1payload


– 65 –



WDM MultiplexingMultiplexing Degree

• Constrained by nonlinearities– stimulated Raman scattering (molecular vibrations)– stimulated Brillouin scattering (acoustic waves)– carrier-induced cross-phase modulation (increased velocity)– four-wave mixing (FWM): λi + λj – λk

• Cost tradeoff (OC-192 in early 2000s):– system cost of bleeding edge OEO vs. multiple sets

WDM Multiplexing Degree Tradeoff L-??

The optimal degree of wavelength division multiplexing is a tradeoff between the cost per wavelength of higher rates vs. the costs of multiple wavelengths.



Multiplexed LinksExample5.A OTN

• OTN: Optical transport network• ITU-T standards suite:

– architecture G.871/Y.1301, G.872– OTH framing/multiplexing G.709/Y.1331– equipment G.798– physical interfaces G.694, G.959.1, G.8251– OAM&P G.874, G.875– protection G.873– ASON G.8080/Y.1304

automatically switched optical network


– 66 –



Multiplexed LinksExample5.A OTN Overview

• Trails– undirectional and bidirectional– point-to-point and point-to-multipoint

• Interfaces– OUNI (OIF standards)– IrDI / E-NNI interdomain– IaDI / I-NNI intradomain

• Framing and multiplexing hierarchy– digital wrapper

•digital encapsulation with associated overhead– optical transport module (OTM)

•optical/photonic with non-associated overhead



Multiplexed LinksExample5.A OTN Interfaces

• ONNI: optical network node interface– Interdomain: IrDI (data) / E-NNI (signaling exterior NNI)

• May or may not terminate OCh– Intradomain: IaDI (data) / I-NNI (signaling interior NNI)

• IrVI/IaVI: inter-/intra vendor interface

• OUNI: optical user–network interface

OTNa OTNb

ONNIIrDI

E-NNI

OUNI


– 67 –



Multiplexed LinksExample5.A OTN Multiplexing and Framing

• Digital over optical multiplexing hierarchy– Client trail (SONET, ATM, GFP)– Digital wrapper (in band)

• OPUk – OCh payload unit• OPU1 ≈ 2.4Gb/s, OPU2 ≈ 10Gb/s, OPU3 ≈ 40Gb/s

– OTM n.m – optical transport module• OCh optical channel

– edge-to-edge lightpath between 3R• out of band signalling overhead• n = max number of wavelengths• m = rate identifier =

– {1,2,3,…} OPUk TDM– {…12,23,123} combinations



Multiplexed LinksExample5.A OTN Framing and Multiplexing

client

OPUk

ODUk

OTUk

OCh

OCGn.m

OMSn.m

OTSn.m

…

OCC PL

OMS OH

OTS OH

OCC OH

OSC

hues of IR

DW

OTM


– 68 –



Multiplexed LinksExample5.A OTN Digital Wrapper

• OPUk – OCh payload unit: carries client signals– OPU1 ≈> 2.4Gb/s– OPU2 ≈> 10 Gb/s– OPU3 ≈> 40 Gb/s– OPU4 ≈> 160 Gb/s

• ODUk – OCh data unit (digital path)

• OTUk – OCh transport unit (digital section)

ODUk OH OP

Uk

OH OPUk payload

(client signal)FEC (optional)RS(255,239)

OTUkOHfr align



Multiplexed LinksExample5.A OTN Digital WrapperOPU

• OPUk – OCh payload unit: carries client signals– OPU1 ≈ 2.4Gb/s, OPU2 ≈ 10Gb/s, OPU3 ≈ 40Gb/s– OPUk OH

• PSI1B: payload structure identifier – PT {CBR (SONET) , ATM, GFP, bit stream, Ethernet?}

• ODUk – OCh data unit (digital path)



– 69 –



Multiplexed LinksExample5.A OTN Digital WrapperODU

• OPUk – OCh payload unit: carries client signals• ODUk – OCh data unit (digital path)

– ODUk OH• PM3B: path monitoring• TCM1–618B: tandem connection monitoring• GCC1,24B: general comm channels for ASON signaling• APS/ACC4B: auto protection switching & prot comm channel• FTFL1B: fault type and location reporting comm channel• EXP2B: experimental (vendor/service provider)• RES9B: reserved (000000000)




Multiplexed LinksExample5.A OTN Digital WrapperOTU

• OPUk – OCh payload unit• ODUk – OCh data unit (digital path)

• OTUk – OCh transport unit (digital section)– 1 + x + x3 + x12 + x16 scrambled– Frame alignment7B

– OTUk OH• SM3B: section monitoring• GCC02B: general comm channel 0 for ASON signaling• RES2B: reserved (00)

– FEC1024B• optional RS(255,239) per row• zero if FEC not used


– 70 –



Multiplexed LinksExample5.A OTN Optical Transport Module

• Multiplexing hierarchy– OCh optical channel (between 3R, 3ROADM, 3ROXC)– OMS optical multiplex section (between PADM, PXC)– OTS optical transport section (between 2R, OMS, OAmg)

OTS…OTS

OMS

PADMτ

OCh

OTS... PADM

OMS

OTS

OMS

OCh

OTS



Multiplexed LinksExample5.A OTN Optical Multiplexing Hierarchy

• Optical channel OCh– edge-to-edge optical linkL2

– connection rearrangement for flexible routing (ASON)– information integrity– OAM&P

• Optical multiplex section OMS– wavelength de/multiplexing ↔↕– integrity, OAM&P

• Optical transmission section OTS– medium specific transmission– OAM&P, integrity, survivability


– 71 –



Multiplexed LinksExample5.A OTN Optical Transport Module

• Types– OTM-n.mn channels, m rates

• n = {1,2,3,12,23,123} k individually or in combination• Non-associated OSC (optical supervisory channel)

– OTS and OMS overhead out of band

– OTM-n r.m n channels, m rates• Reduced functionality: no specified OSC, OTS/OMS OH not

required

– OTM-0.m 1 channel, m={1,2,3}=k• No OTS/OMS overhead



Multiplexed LinksExample5.A OTN Comparison

synchronoussynchronoussynchronousplesiochronousSynchronisation

2.4 – 160 Gb/s2.4 – 160 Gb/s.155 – 40 Gb/s1.5 – 45 Mb/sRates‡

transparenttransparenttransparentopaqueTransparency

3354Levels*

WDMTDMTDMTDMMultiplex domain

photonicelectronicelectronicelectronicMux & switching

opticalopticalopticalelectronicTransmission

OTN OTMOTN DWSDH/SONETPDH

* as currently defined in standards, not including sub- and intermediate levels‡ approximate as currently defined in standards, not including STS-1 and sub-rates (DS0 and VTs)


– 72 –



Multiplexed LinksExample5.A OTN OTH Rates

100G159.15 Gb/sSTS-3072c159.25 Gb/s15 232 B1024 B64 B172.80 Gb/sOPU4

~640 Gb/sOPU5

6549565535

39.79 Gb/s

9.96 Gb/s

2.49 Gb/s

GFP+CRCmax

16×4 B

64 B

64 B

64 B

DW OH

= SONETline rate

39.81 Gb/s

9.95 Gb/s

2.49 Gb/s

622.08 Mb/s

155.52 Mb/s

51.84 Mb/s

OPU ratePayloadsLink type

3808×4 B256×4 B255/(239–k) × SONETOPUk

40GSTS-768c15 232 B1024 B43.02 Gb/sOPU3

10GSTS-192c15 232 B1024 B10.71 Gb/sOPU2

1GSTS-48c15 232 B1024 B2.67 Gb/sOPU1

STS-12c–

STS-3c–

STS-1–

EthernetSONETOPU

PayloadFECOTU/OchrateOTH



Links and LANsLL.2.4 Shared Medium Links








– 73 –



Link TechnologiesShared Medium Links

• Frames sharing a medium– MAC: medium access control needed to arbitrate

• e.g. TDMA, dynamic TDMA: time division multiple access• e.g. CDMA: code division multiple access

Medium Access Control Principle L-II.2

The MAC protocol should efficiently arbitrate the shared medium, in either a fair manner or with the desired proportion.

H 4H Tpayload 22 1

3 4



Shared Medium Links: LANExample5.2 Ethernet

• Early LAN technology (1973)– DIX: Digital, Intel, Xerox– IEEE 802.3 EECS 780

• Shared wire medium– CSMA/CD MAC– performs well in light load < 50%– performs poorly in heavy load > 80%

• Dominant 1980s LAN– token ring only significant competitor– evolved 10 to 100 Mb/s to … trailer

4B

MAC header

14B

length / type

destinationaddress

sourceaddress

FCS

frame body

38 – 1492 B

10101010 1010101010101010 10101010

10101010 1010101110101010 10101010

preamble+SFD

LLC

SNAP

pad

LLC/MAC subheader

8B


– 74 –


© James P.G. SterbenzITTCShared Medium Links: LAN

Example5.2 802.3 Evolution to Higher Rates

• Scaling to high data rates– 10 Mb/s → 100 Mb/s → 1 Gb/s → 10 Gb/s → 40/100 Gb/s– → 802.3u → 802.3ab → 802.3an → 802.3ba Cu– → 802.3z → 802.3ae → 802.3ba fib.

• fiber standards and deployment first for 1 and 10 Gb/s• consistent with aggregation for enterprise and metro use

• More sophisticated coding– DSSS → OFDM → STBC

• MAC and link framing enhancements– slot time increase, frame extension, and bursting for 1 Gb/s– elimination of CSMA/CD for 10 Gb/s: full duplex only



Shared Medium Links: LANExample5.2 Ethernet Evolution

• …Evolved to 1 Gb/sProblems?

trailer4B

MAC header

14B

length / type

destinationaddress

sourceaddress

FCS

frame body

38 – 1492 B

10101010 1010101010101010 10101010

10101010 1010101110101010 10101010

preamble+SFD

LLC

SNAP

pad

LLC/MAC subheader

8B


– 75 –




• …Evolved to 1 Gb/s• Problems: Ethernet design

– not inherently scalable• 100 Mb/s: several-year standards battle

– designed for shared medium• thickwire and thinwire with taps• later hubs with half-duplex pt-to-pt links• CSMA/CD time constants and overhead

trailer4B

MAC header

14B

length / type

destinationaddress

sourceaddress

FCS

frame body

38 – 1492 B

10101010 1010101010101010 10101010

10101010 1010101110101010 10101010

preamble+SFD

LLC

SNAP

pad

LLC/MAC subheader

8B




• …Evolved to 1 Gb/s• Problems: Ethernet design

– not inherently scalable• 100 Mb/s: several-year standards battle

– designed for shared medium• thickwire and thinwire with taps• later hubs with half-duplex pt-to-pt links• CSMA/CD time constants and overhead

• 802.3z decision– retain CSMA/CD– modify MAC for higher rates

trailer4B

MAC header

14B

length / type

destinationaddress

sourceaddress

FCS

frame body

38 – 1492 B

10101010 1010101010101010 10101010

10101010 1010101110101010 10101010

preamble+SFD

LLC

SNAP

pad

LLC/MAC subheader

8B


– 76 –




• …Evolved to 1 Gb/s• Modifications

– still supporting CSMA/CD• slot time increased × 8

– 512b → 512B

• extension trailer need for longer slotproblem?

trailer4B

MAC header

14B

length / type

destinationaddress

sourceaddress

FCS

frame body

38 – 1492 B

10101010 1010101010101010 10101010

10101010 1010101110101010 10101010

preamble+SFD

LLC

SNAP

pad

LLC/MAC subheader

8B






– 512b → 512B

• extension trailer need for longer slot– larger minimum frame size– but very inefficient for small frames

solution?

ext

frame1

ext

frame2

ext

frame3


– 77 –






– 512b → 512B

• extension trailer need for longer slot– larger minimum frame size– but very inefficient small frames

• frame bursting– burst of frames in a single slot– significantly increased efficiency

ext

frame1

ext

frame2

ext

frame3

frame1

frame2

frame3




• …Evolved to 10 Gb/sProblems?


– 78 –




• …Evolved to 10 Gb/s• Problems?

– CSMA overheads and time constants much bigger problem• further scaling of slot time and extension headers not practical

Solution?


© James P.G. SterbenzITTCShared → Dedicated Links: LAN

Example5.2 Ethernet Evolution• …Evolved to 10 Gb/s• Solution

– half-duplex shared medium probably never used at 1 Gb/s– 802.ae decided to completely eliminate CSMA/CD– only point-to-point full-duplex dual cables supported


– 79 –



Dedicated Links: LANExample5.2 Ethernet Evolution

• …Evolved to 10 Gb/s• Modification

– point-to-point only• initially fiber only (802.3ae) later copper (802.3ak / 802.3an)

– full duplex only (separate xmit and recv cables required )• no CSMA/CD or related slot and distance constraints• no extension trailer needed• frame bursting not needed nor supported

– compatible with SONET coding and physical transmission• pacing for 10Gb/s (LAN) → 9.95 Gb/s (WAN)• § in table



Deidcated Links: LANExample5.2 Ethernet Evolution

• …Evolving to 40 Gb/s and 100 Gb/s– 802.3 HSSG (high speed study group)– 802.3ba: May 2010 target for standard

• Objectives– 40 Gb/s for SONET OC-192 and OTN ODU3 compatibility

• will probably see deployment before 10 GB/s

– 100 Gb/s for Ethernet order-of-magnitude trajectory– single- and multimode fiber and short-reach copper

• 10-km multimode distance for MANs

– full duplex only– 802.3 backward compatible framing


– 80 –




• …Evolve to 1 Tb/s?




• Ethernet also evolving from LAN to MAN technology– IEEE 802.3 retains control of MAC and PHY standards

• ITU-T Ethernet transport networks– ITU-T G.8010 series specifications– specification of Ethernet in transport networks– relationship to SONET/OTN transport networks

• Metro Ethernet service deployments– MEF: Metro Ethernet Forum

• www.metroethernetforum.org

• implementation agreements and specifications


– 81 –



Shared and Dedicated Links: LANExample5.2 Ethernet Link Characteristics

F

FFFF

H | FH | FH | FH | F

H | FH | FHH | F

HHH | F

H

Full

38 B

38 B

38 B+

≤448 /burst

38 B

38 B

10 B

Ovhd

4K BsharedManchestercoax2.94 Mb/s1972-1976

PARC

38–1492 Bswitchpt-2-pt– 40 kmunder

development40/100Gb/s

802.3ba40GBase100GBase

10 Gb/s802.3ae

2002802.3an

1 Gb/s802.3z

1998

100 Mb/s802.3u

1995

10 Mb/sDIX 1980

802.3 1985

Rate | Year

8B10B FCS64B/66B

64B/66B §

4B/5B|PAM58B/10B FCS8B/10B FCS8B/10B FCS

4B/5BPAM5x58B/6T4B/5B

Manchester

Coding

65 m –40 km

100 m

100 m25 m

316 – 5000 m275 – 550 m

100 m100 m

†full duplex 100 m412 – 2000† m

500 –2500* m185 – 925* m

*w/repeaters 100 m

RangeLink Type

38–1492 Bswitchpt-2-pt

parallel fiberfiberfiber

4 pair UTP-7

10GBaseX10GBaseR10GBaseW10GBaseT

38–1492 Bswitchpt-2-pt

4 pair UTP-6twinax STP↑λ sm fiber↓λ mm fiber

1000BaseT 1000BaseCX1000BaseLX1000BaseSX

38–1492 Bstar:hub/

switch

2 pair UTP-52 pair UTP-34 pair UTP-3

mm fiber

100BaseTX100BaseT2100BaseT4100BaseFX

38–1492 Bsharedshared

hub

thick coaxthin coax

2 pair UTP-3

10Base510Base210BaseT

PayloadTopologyMedia



Shared Medium Links: LANExample5.T Token Ring (TR)

• Early LAN technology (1972)– DCS and Cambridge rings provided foundation– IBM LAN technology; standardised as IEEE 802.5

• Shared wire medium– token passing ring– performs well to heavy load > 80%

• 16 Mb/s TR significantly outperformed 10Base5

• Significant 1980s LAN– but Ethernet had greater market share– evolved to 16 Mb/s (1988)– evolution to hubs required double STP to end systems


– 82 –



Shared Medium Links: LANExample5.T FDDI: Evolution & Death of TR

• Logical successor: FDDI– fiber distributed digital interface– only 100 Mb/s LAN technology of time

• ANSI X3.139-1987 (MAC), X3.148.1988 (PHY)• 100BaseT vs. 100BaseVG wars hadn’t even begun• OC-3 ATM LANs were just appearing (and expensive)

• Dual fiber token-passing ring– contra-rotating rings with automatic protection from cuts

• single ring option with no protection

– later adapted for STP and UTP-5: CDDI (copper DDI)



Shared Medium Links: LANExample5.T FDDI: Evolution & Death of TR

• FDDI-II proposal for integrated services– slotted ring adds circuit service to basic FDDI packet service

• But 100BaseT killed FDDI (and ATM to the desktop)• High-speed token ring (HSTR) proposals DOA

– 100 Mb/s 803.5t 1998 draft (a few products)– 1Gb/s 803.5v working group


– 83 –



Shared Medium Links: LANExample5.T Ring LAN Characteristics

token

token

DTR

token*

slot

token

access

100 m

2 km

250 m†

link range

0 – 4522 B28 B2×ring200 km4B/5Bfiber100 Mb/sFDDI 1988

28 B

21 B

21 B

22 b

OH

ring2.5 Mb/sDCS 1972

100 Mb/s

100 Mb/s100 Mb/s

1 Gb/s

4 Mb/s16 Mb/s

10 Mb/s

rate

MLT-3

MLT-34B/5B

8B/10B FCS

Δ Manch.

coding

10 km

–

ring circum.Link type

0 – 4522 B2×ringSTPUTP-5CDDI

0 – 18279 Bstar

{US}TPfiberfiber

HSTR 802.5t1998 802.5t

802.5v

0 – 4529 B0 – 18279

BringSTP

Token Ring1981 IBM1985 802.5

16 bring2 x TPCambridge 1979

payloadtopologymedia

*DTR (dedicated token ring) for switched mode added in 1998 to 4 Mb/s and 16 Mb/s 802.5some switch/NICs supported full duplex at 32 Mb/s

†72 m for UTP



Shared Medium Links: WLANExample5.W 802.11

• IEEE 802.11– first of the 802 wireless protocols– design motivated by Ethernet

• sometimes called “wireless Ethernet”

802.16 WMAN

802.11 WLAN

802.15WPAN

50 m


– 84 –



Shared Medium Links: WLANExample5.W 802.11

• IEEE 802.11– wireless links based loosely on Ethernet framing

• 6B addresses, 4B FCS• 802.2 SNAP/LLC subheader

– enables simple cheap 802.3+802.11 hubs and switches

• Unlicensed ISM/U-NII bands: 900 MHz, 2.4, 5.8 GHz– significant interference from FHSS 2.4 GHz cordless phones



Shared Medium Links: WLANExample5.W 802.11 Wi-Fi

• Wi-Fi– Wi-iFi alliance: www.wi-fi.org– 802.11 standards compliance and interoperability testing– commonly (but incorrectly) used as synonym for 802.11


– 85 –



Shared Medium Links: WLANExample5.W 802.11 Coding and MAC

• IEEE 802.11 is CSMA and CDMA hybrid• Variety of coding schemes

– DSSS: direct sequence spread spectrum– FHSS: frequency hopping spread spectrum (rarely used)– OFDM: orthogonal frequency division multiplexing (newer)

• Over which CSMA/CA MAC is run– CSMA with optional RTS/CTS

performance implications?



Shared Medium Links: WLANExample5.W 802.11 Coding and MAC

• IEEE 802.11 is CSMA and CDMA hybrid• Variety of coding schemes

– DSSS: direct sequence spread spectrum– FHSS: frequency hopping spread spectrum (rarely used)– OFDM: orthogonal frequency division multiplexing (newer)– STBC: space-time block coding (newest)

• Over which CSMA/CA MAC is run– CSMA with optional RTS/CTS– RTS/CTS not needed for single user (dedicated link)

• and frequently turned off for multiple users


– 86 –



Shared Medium Links: WLANExample5.W 802.11 CSMA/CA MAC

• CSMA/CA: collision avoidance– RTS/CTS to reduce Pr[collision]

EECS 882• Sender

– sense, wait for DIFS, send RTS• Receiver

– wait for SIFS, return CTS• Sender

– wait for SIFS, transmit frame• Receiver

– wait for SIFS interval and return ACK

senseDIFS

7

RTS

SIFSCTS

SIFS

frame

SIFSACK



Shared Medium Links: WLAN Example5.W 802.11b

• IEEE 802.11b (HR – high rate)– 2.4 GHz ISM/U-NII band– formerly widest deployment– 11 Mb/s maximum MAC rate

• actual performance highly dependent on environment• 5Mb/s goodput typical over 60m range with few obstructions• adequate for most home, SOHO, and hotspot use• exceeds rate of most HFC and DSL access links

– DSSS coding; all stations use same chipping sequenceswhat does this mean?


– 87 –



Shared Medium Links: WLANExample5.W 802.11a

• IEEE 802.11a– 5.8 GHz ISM/U-NII band

• higher rate alternative to 802.11b but more expensive• simultaneously available with 802.11b

– a and b were IEEE 802.11 working group numbers

– 54 Mb/s maximum MAC rate• actual performance highly dependent on environment• 24Mb/s goodput over 35m range typical

– deployment limited to users that needed higher rate• high rate LAN applications• users and campuses with higher rate Internet access links

– e.g. T3, 100M/1G Ethernet, SONET



Shared Medium Links: WLANExample5.W 802.11g

• IEEE 802.11g (ER – extended rate)– 2.4 GHz ISM/U-NII band

• backward compatible with 802.11b• higher rate successor to 802.11b using OFDM

– 54 Mb/s maximum MAC rate• actual performance generally far less• higher usable rates at longer ranges than 802.11b• enhanced performance for

– enterprise and campus LANS– home and SOHO with premium broadband access

– has become most common deployment• virtually all laptops and hubs are now 802.11g• many are a/b/g compatible


– 88 –



address 1

Shared Medium Links: WLANExample5.W 802.11 Frame

• MAC Header [10–34B]– frame control [2B]– duration/ID [2B]– address 1 [6B]– address 2 [6B]– address 3 [6B]– sequence control [2B]– address 4 [6B]– QoS control [2B] (802.11e)– HT control [2B] (802.11n)

• Frame body [0–2312‐7955B]

• Trailer: FCS [4B] trailer4B

MAC header10–34B

frame controlduration / ID

sequence control

address 2

address 3

address 4

FCS

frame body

0 – 2312 B

– 7955 B(802.11n)

QoS controlHT control


© James P.G. SterbenzITTCShared Medium Links: WLANExample5.W 802.11 Evolution to Higher

Rates• Scaling to high data rates

– 802.11 → 802.11b → 802.11g → 802.11n → 802.11 VHT

• Increased frequency– 900 MHz → 2.4 GHz → (5.8 GHz) → 60 GHz (VHT)

• More sophisticated coding– DSSS → OFDM → STBC

• More sophisticated antennæ– single → MIMO

• MAC and link framing enhancements– single small frames → larger frames with burst ACKs


– 89 –



Shared Medium Links: WLANExample5.W 802.11n

• IEEE 802.11n (HT – high throughput)– next generation 802.11 currently under development– MAC rate of at least 100Mb/s

• Standard published 2009– based on EWC proposal; merge of TgnSync and WWiSE– process held up for several years by intellectual property

• CSIRO owns fundamental wireless networking patents

– products based on draft standards became widely available

• Many draft-compliant products now available– e.g. Mac laptops, consumer wireless base stations



Shared Medium Links: WLANExample5.W 802.11n Enhancements

• 802.11n physical layer– MIMO (multiple-in multiple-output) antennæ– spatial multiplexing and beamforming– new coding techniques

• 802.11n MAC– frame aggregation – block acknowledgements

• 802.11n link layer framing– new header fields– longer payload: up to 7955B


– 90 –



Shared Medium Links: WLANExample5.W 802.11n PHY Enhancements

• 802.11n physical layer: 600 Mb/s max rate– MIMO (multiple-in multiple-output)– antenna selection– spatial multiplexing (across MIMO antennæ)– beamforming (directional transmission)– channel bonding (2 × 20 MHz)– new coding

• STBC: space-time block code – redundant data across streams• LDPC: low density parity check – optimal error correction

• 802.11n MAC• 802.11n link layer framing



Shared Medium Links: WLANExample5.W 802.11n MAC Enhancements

• 802.11n physical layer• 802.11n MAC

– frame aggregation– shorter SIFS between give pair of STAs

• RIFS (reduced IFS) = 2μs instead of SIFS = 16μs

– block acknowledgements• introduced in 802.11e, modified for 802.11n

– power save multi-poll scheduling for medium access– reverse direction– protection mechanism for coexistence with 802.11abg

• 802.11n link layer framing


– 91 –



Shared Medium Links: WLANExample5.W 802.11n Link Enhancements

• 802.11n physical layer• 802.11n MAC• 802.11n link layer framing

– new header fields for HT (high throughput)• link adaptation and negotiation• antenna selection and steering• code selection

– QoS from 802.11e– longer max payload for greater efficiency: 7955 B



Shared Medium Links: WLANExample5.W 802.11n Frame Aggregation

• A-MPDU: aggregate MAC PDU– sequence of A-MPDU subframes– all destined to same receiver– all with same QoS ACK policy– up to 64KB long

• A-MPDU subframe– reserved [4b]– MPDU length [3B]– CRC‐8 [1B]– delimiter sig [1B] = 4E (ASCII N)– MPDU [0–7993?B]– pad [0‐3b]

length

MPDU frame

0 – 7993? B

CRCdelimiter signature

res

pad

length

MPDU frame

0 – 7993? B

CRCdelimiter signature

res

pad

subframe

MPDUdelimiter


– 92 –


© James P.G. SterbenzITTCShared Medium Links: WLAN

Example5.W 802.11n Block Acknowledgements

• Block acknowledgements– introduced in 802.11e

part of 802.11-2007modified in 802.11n

– negotiated between base station and terminal

• Types– immediate

• intended for high-speed; used in 802.11n

– delayed



Shared Medium Links: WLANExample5.W 802.11n Block Negotiation

• Block ACK initialisation– ADDBA add request– ADDBA add response

• Data transfer– after recommended RTS/CTS

• more important for larger transfer

• Block ACK termination– DELBA delete request– DELBA delete response

7

RTS

CTS

SIFS

frames

ACK

DELBARequest

BlockAck

ADDBAReq

ACK

ACK

ADDBAResp

RIFS


– 93 –



Shared Medium Links: WLANExample5.W 802.11n Block Transfer

• Block data transfer– after RTS/CTS– sequence of MPDUs– separated by RIFS

• Block acknowledgement– after end of MPDU block– BlockAckReq sent– BlockAck returned

• after SIFS in immediate mode

7

MPDU

BlockACK

BlockACKReq

MPDU

RIFS

MPDU

RIFS

SIFS



Shared Medium Links: WLANExample5.W 802.11 Future

• Work beginning on next version of 802.11– 802.11 VHT (very high throughput) SG (study group)– proposing PAR (project authorisation request)

• Diminishing returns possible in 2.4 and 5.8 GHz– next ISM bands at ~ 24 and 61 GHz– 802.15.3c standardising in 60 GHz band


– 94 –



Shared Medium Links: WLANExample5.W 802.11 VHT

• 802.11 VHT (very high throughput) SG (study group)– 61.25 GHz (61.0–61.5) commonly called 60 GHz

• Expected PHY modifications– new 802.11 clause for 60GHz ISM PHY

• possible relationship with 802.15.3c

– coexistance with other 60 GHz communication

• Expected MAC and link modifications– changes to support 60 GHz directional antennæ– multi-band capability– efficiency enhancements– fast session transfer to 802.11a/b/g/n (<6GHz)



Shared Medium Links: WLANExample5.W 802.11 Link Characteristics

24 Mb/s0–2304 B50 MHz3.7 GHzlicensed

2008802.11y

24 Mb/s0–2304 B6 – 54 Mb/s1 – 11 Mb/s

OFDM DSSS883.5 MHz2.4 GHz2003802.11g

2009

1999

1999

1997

1991

1970

year

*number non-overlapping

12|19|4

11|13|14|3

11|13|14|3

1

channels us/eu/jp/*

75 m

35 m

60 m

typicalrange

500 MHz

83.5 MHz300 MHz

300 MHz

83.5 MHz

83.5 MHz

26 MHz

2×100 kHz

channel bw (US)

9.6 kb/s400 MHzALOHA

1 – 2 Mb/sDSSS915 MHzWavelan

OFDMMIMO

OFDM

DSSSFHSS

DSSSFHSS

coding

75 Mb/s

24 Mb/s

5 Mb/s

typical goodput

Link type

~ 1 Gb/s61 GHz802.11VHT

0–7955 B< 248 Mb/s2.4 GHZ5.8 GHz802.11n

0–2304 B6 – 54 Mb/s5.8 GHz802.11a

0–2304 B1 – 11 Mb/s2.4 GHz802.11b

0–2304 B1 – 2 Mb/s2.4 GHz802.11

payloadMAC rateband (US)


– 95 –



Shared Medium Links: WPANExample5.W Bluetooth and 802.15

• IEEE 802.15 and Bluetooth– part of 2nd set of 802 wireless protocols (802.15 & 802.16)– design motivated by Bluetooth consortium– no similarity to 802.11/Ethernet framing or operation

802.16 WMAN

802.11 WLAN

802.15WPAN

10 m




• PAN: local area network– links or subnetwork of shorter reach than LAN– replacement for interconnnect cables

• computer peripherals• mobile phone headsets

– private intimate group of personal devices [IEEE 802]• in personal operating space (POS)

– several meters: O (10 m)

• Examples– wired: USB, IEEE 1394 Firewire– wireless: IrDA, 802.15.1/Bluetooth, 802.15.3, Wireless USB


– 96 –




• Initial work done at Ericsson in Sweden– Bluetooth named after Harald I

• Bluetooth SIG (special interest group) formed 1998– mobile telephone vendors: Ericsson, Nokia– other electronics vendors: IBM, Intel, Toshiba

• Proprietary specification development– membership was required to see draft specifications– specifications now freely available (2.1 is current)

• www.bluetooth.com/Bluetooth/Learn/Technology/Specification

• Stovepipe protocol stack for very specialised domain– IEEE reworked PHY and MAC as 802.15.1



Shared Medium Links: WPANExample5.W Bluetooth Deployment Issues

• Problems and issues– closed development process driven by mobile telephony– incompatible with Internet and 802 architecture

• rectified by IEEE 802.15.1 (future?)

– interference not considered• interference with 802.11• poor scalability in dense deployments (e.g. 2001 CeBIT debacle)

– numerous security flaws– competition looming from wireless USB– architectural limitations …


– 97 –



Shared Medium Links: WPANExample5.W Bluetooth Architectural Limitations

• Significant architectural restrictions– 3-bit address space ⇒ only 8 active devices / piconet

• appalling lack of foresight– evidently driven mobile telephone marketing folk

• personal networks easily far exceed 8 devices• computer manufacturers (IBM, Intel) deny responsibility

– not appropriate for high-performance applications • modest transmission rate: 721 kb/s (later 3 Mb/s)• master/slave configuration

– problems largely rectified by IEEE 802.15.3• future uncertain



Shared Medium Links: WPANExample5.W 802.15 WPAN Overview

• WPAN: Wireless Personal Area Networks– IEEE 802.15 grouper.ieee.org/groups/802/15

• Personal and short-reach wireless network– shorter range than 802.11– initially motivated by Bluetooth & compatibility with 802.11


– 98 –



Shared Medium Links: WPANExample5.W 802.15 WPAN Standards

• IEEE 802.15– wireless personal area networks

• Personal and short-reach wireless network– 802.15.1: standardisation of Bluetooth physical/MAC layers– 802.15.2: co-existence of 802.11 and 802.15 in 2.4 GHz

• original goal of 802.15.1 was to interoperate with 802.11

– 802.15.3: high rate and larger addresses– 802.15.4: low energy for sensor networks– 802.15.5: mesh networking (work in progress)– 802.15 BAN SG (study group)



Shared Medium Links: WPANExample5.W 802.15.1 Physical Layer

• 2.4 GHz unlicensed ISM band• Three power classes: 1–100 mW with power control• Three line coding options: 1, 2, or 3 Mb/s• Low sensitivity receivers

– intended to permit low cost receivers


– 99 –



Shared Medium Links: WPANExample5.W 802.15.1 Medium Access Control

• TDD (time division duplexing)– simple to achieve over very short distances

• independent clocks are frequently synchronised

• FHSS (frequency hopping spread spectrum)– FHSS robust to narrow-band interference– pseudorandom hopping sequence determined by master– significant interference problems with 802.11 DSSS

master

slave

f(k) f(k+1) f(k+2) f(k+3) . . .f(k+6)f(k+4) f(k+5)



Shared Medium Links: WPANExample5.W 802.15.1 Frame Format: Access

• Access code [68 or 72b]– preamble [4b] alternating bit pattern

chosen so bit change to sync word– sync word [64b] derived from lower

address part of 48-bit MAC address– trailer [4b] alternating bit pattern

only if header follows

• Header• Payload


– 100 –



Shared Medium Links: WPANExample5.W 802.15.1 Frame Format: Header

• Access code• Header

– logical transport address [3b] LT_ADDR ASTONISHING!!

– type [4b] logical transport type andtraffic class

– flow [1b] control– ARQN [1b] ACK or NAK– SEQN [1b] 1-bit sequence no.– HEC [8b] header CRC

• Payload



Shared Medium Links: WPANExample5.W 802.15.1 Frame Format: Payload

• Access code• Header• Payload

– contents dependent on logical transport and packet type


– 101 –



Shared Medium Links: WPANExample5.W 802.15.1 Piconet

• Piconet : up to 256 devices– transmission range of master

M





• Master dictates timing– transmits in odd-numbered slots

M


– 102 –






• Slaves– max of only 7 active at a time– use even-numbered slots

S

S

S

M






• Slaves– max of only 7 active at a time– use even-numbered slots– all slave–slave communication through master

S

S

S

M


– 103 –






• Slaves– max of only 7 active at a time– use even-numbered slots– all slave–slave communication through master

• Parked (inactive) devices– max 247

S

P

S

S

P

P

P

M



Shared Medium Links: WPANExample5.W 802.15.1 Scatternet

• Scatternet– collection of piconets that share devices

• Barely mentioned in the Bluetooth specs– theoretical construct to deflect criticism on architectural

limits of Bluetooth?


– 104 –



Shared Medium Links: WPANExample5.W 802.15.3 Overview

• 802.15 Task Group 3: High Rate PANs– higher data rates– multimedia and QoS– ad-hoc and peer-to-peer networking– better co-existence with 802.11


© James P.G. SterbenzITTCShared Medium Links: WPANExample5.W 802.15.3 Physical Layer

Coding• 802.15.3 physical layer: 11 – 55 Mb/s

8-TCM64-QAM55 Mb/s

8-TCM32-QAM44 Mb/s

8-TCM16-QAM33 Mb/s

–DQPSK22 Mb/s

8-TCMQPSK11 Mb/s

CodingModulationRate

0°180°

90°

270°


– 105 –



Shared Medium Links: WPANExample5.W 802.15.3 Piconets

• Piconetshow to improve overBluetooth/802.15.1?




• Piconets: 64K devices– 16 b DEV address– peer-to-peer data

• doesn’t need to go via PNC

why do we need a controller?


– 106 –




• Piconets: 64K devices– 16 b DEV address– peer-to-peer data

• doesn’t need to go via PNC

– PNC piconet coördinator• beacons to all DEVs in piconet• distributes timing

PNC



Shared Medium Links: WPANExample5.W 802.15.3 Frame Format

• Header• Payload


– 107 –



Shared Medium Links: WPANExample5.W Additional 802.15.3 TGs

• 802.15.3 task groups• 802.15.3a: high rate alternative PHY

– group deadlocked and disbanded

• 802.15.3b: MAC amendment– corrections and updates to 802.15.3

• 802.15.3c: millimeter wave– alternate physical layer in millimeter wave bands



Shared Medium Links: WPANExample5.W 802.15.3a Alternative PHY

• 802.15.3a: alternative PHY for 802.3.15• Goal:

– higher data rate in excess of 100 Mb/s

• Multiple proposals– combined and down-selected to two competitors1. DS-UWB (direct sequence – ultra wide band)

• UWB pulses in two channels: 3.1–4.85 and 6.2–9.7GHz• 26 Mb/s – 1.32 Gb/s

2. MB-OFDM (multiband – orthogonal freq. div. multiplexing)• OFDM in 3.1 –10.6GHz band• 480 Mb/s per 528MHz of spectrum in 14 channels


– 108 –



Shared Medium Links: WPANExample5.W 802.15a Alternative PHY

• Problem:– deadlock between proposals

• Typical solutions to standards deadlock– compromise even if bad (e.g. ATM cell size)– do both as alternatives (not uncommon for IEEE 802)– choose one at higher level (difficult due to politics)– give up (perhaps let marketplace decide)

• 802.15.3 fate– one group was unwilling to compromise– study group disbanded– challenges: regulatory problems with UWB interference



Shared Medium Links: WPANExample5.W WiMedia MB-OFDM UWB

• WiMedia Alliance www.wimedia.org• Evolution of 802.15.3a MB-OFDM

– standardised as ISO/IEC 26907 and 26908


– 109 –


© James P.G. SterbenzITTCShared Medium Links: WPANExample5.W 802.15.3c Millimeter Wave

PHY• 802.15.3c: millimeter wave WPAN

– 57–64 GHz unlicensed spectrum– goal: data rate > 1 Gb/s up to 10 m

• Status– currently down to 9 proposals– goal to agree by end of 2007– goal to finish standard by end of 2008



Shared Medium Links: WPAN Example5.W 802.15 Link Characteristics

0–4096 B3–10 m53.3–480 Mb/s

MB-OFDM TFC

14 × 528 MHz UWB

30 channels7.4 GHz3.1–10.6

GHz UWB2005802.15.3aISO 29607Bluetooth 3.0

2009

2003

2004

20032005

2002

1998

year

5 × 15MHz

AFHSS79 × 1MHz

FHSS79 × 1MHz

FHSS79 × 1MHz

FHSS79 × 1MHz

channels

>10 m

1–100 m

1–100 m

1–100 m

1–100 m

1–100 m

typicalrange

~7 GHz

83.5 MHz

83.5 MHz

83.5 MHz

83.5 MHz

83.5 MHz

channel bw

721 kb/sTDMA/TDDGFSK2.4 GHzBluetooth 1.0

721 kb/sTDMA/TDD GFSK2.4 GHzBluetooth 1.1

802.15.1

QPSK/QAMTCM-8

π/4-DQPSK8-DPSK

TDMA/TDD GFSK

coding

<2.1 Mb/s

typical goodputLink type

~2 Gb/s57–64 GHz mm802.15.3c

11 – 55 Mb/s2.4 GHz802.15.3

2 Mb/s3 Mb/s2.4 GHzBluetooth 2.0

721 kb/s2.4 GHzBluetooth 1.2802.15.1

payloadMAC rateband


– 110 –



Shared Medium Links: WPANExample5.W Wireless USB Overview

• Wireless USB: Universal Serial Bus– wireless version from

www.usb.org/developers/wusb/

• USB– actually become the universal PC peripheral interconnect– largely replacing serial, parallel, and SCSI for consumers

• Wireless USB– high-rate wireless link with USB interface– 480 Mb/s at 3 m; 110 Mb/s at 10 m

• Wireless USB future uncertain



Shared Medium Links: RBBExample5.H HFC Residential Broadband

• HFC (hybrid fiber coax)– based on CATV distribution infrastructure– fiber to neighbourhood node– coax to and within home

reuse

new

reuse

reuse

Infrastructure

widespreadtwisted pairDSL

copper

fiber

shared coax

Medium

futureBPL

emergingFTTX PON

widespreadHFC

DeploymentRBB Technology


– 111 –



Shared Medium Links: RBBExample5.H HFC Network Architecture

• Head end is CATV equivalent to PTSN central office– fiber links from head end to fiber node in neighbourhoods

• optical ↔ electrical conversion

– coax distribution lines serve multiple houses (10 – 2000)• amplifiers may be used to extend coax runs• subscriber drops tap into distribution cable

OE

head endOE



Shared Medium Links: RBBExample5.H HFC Residential Architecture

• Data multiplexed with analog and digital TV channels– IP telephony delivered over data stream

head end

Internet

PSTN

CMTS: cable modem termination systemDOCSIS×: hub or switch with DOCSIS modemLIS: local insertion video server (weather, ads)TRAC: telco return access concentrator

OETRAC

CMTS

local

localstudio

LISVOD

PC

TV

TVIP

DOCIS


– 112 –



Shared Medium Links: RBBExample5.H HFC Modulation and Spectrum

• Data spectrum: FDM – frequency division multiplexed• Upstream: 5 – 42 MHz

– below broadcast channel 2– QPSK typical, QAM-16 optional

• Downstream: 91 – 857 MHz– spectrum divided with analog and digital television– QAM-64 or -256 downlink shared among users

• per user bandwidth depends on network engineering and load

5 42

up

54 88 108 857 MHz

FM

digital CATV channels

216 MHz

downstream DOCSIS data

VHF analog analog CATV channels



Shared Medium Links: RBBExample5.H HFC DOCSIS Overview

• Data over cable interface specification (DOCSIS)– Originally begun as IEEE 802.14– CableLabs standard specification

• DOCSIS 2.0 and 3.0 www.cablemodem.com/specifications/

– DOCSIS 2.0 standardised as ITU J.122

• DOCSIS versions– 1.0: downstream over HFC, upstream using POTS– 1.1: downstream and upstream using HFC– 2.0: higher upstream rate of 30.72 Mb/s – 3.0: higher upstream and downstream rates > 100 Mb/s


– 113 –



Shared Medium Links: RBBExample5.H HFC DOCSIS Protocol Stack

• DOCSIS standards– operations interfaces– security– MAC (+link)

• link framing• TDM downstream• TDMA upstream

– physical layer• RF on coax• QPSK/QAM

PHY

convergence

MAC

security

DIX/802.3 MAC

802.2 LLC

IP + ARP

UDP

DHCP TFTP SNMP securitymgt

EthernetLLC+MAC

MACfilter

PHY

cable modem mgt.

RF on coax.

cat-n to CPE



Shared Medium Links: RBBExample5.H HFC DOCSIS Frame Format

• Convergence sublayer header– downstream: MPEG header type=data– upstream: PMD preamble

• MAC header– FC: frame control – type of header [1B]

– MAC_PARM: MAC parameters [1B]

– LEN: length of EDR+payload [2B]

– EHDR: extended header [0–240B]

– HCS: header check sequence [2B]

• Payload– Ethernet frame encapsulating user data Ethernet CRC

FC

LEN

HCS

EHDR

MPEG (downstream)PMD (upstream)

MAC_PARM

Ethernet header

IP packet


– 114 –



Shared Medium Links: RBBExample5.H HFC Link Characteristics

120 Mb/s

320 kb/s –30.72 Mb/s

320 kB/s –10.24 Mb/s

320 kB/s –5.12 Mb/s

Rate MACCodingCodingRate

QoSX.509 sec

TDMAS-CDMA

QPSK8-QAM

16-QAM32-QAM64-QAM

128-QAM

64-QAM256-QAM

30.342 Mb/s42.884 Mb/s2001J.122DOCSIS 2.0

2006

1999

1996

Year

160 Mb/s

30.342 Mb/s42.884 Mb/s

30.342 Mb/s42.884 Mb/s

Downstream

64-QAM256-QAM

64-QAM256-QAM

64-QAM256-QAM

QoSX.509 sec

QoSX.509 sec

PSTN upstream

NotesLink Type

TDMAS-CDMA

TCM

QPSK8-QAM

16-QAM32-QAM64-QAM

128-QAM

DOCSIS 3.0

Euro

TDMAQPSK16-QAMJ.112DOCSIS 1.1

TDMAQPSK16-QAMDOCSIS 1.0

UpstreamStandard



Shared Medium Links: RBBExample5.H HFC Summary

Advantages of HFC?


– 115 –




• Advantages of HFC– reuse of existing CATV plant

• but required upgrades for upstream channels

Disadvantages of HFC?





• but required upgrades for upstream channels

• Disadvantages of HFC– shared medium infrastructure– usable data rate and latency per user highly dependent on…

• number of homes in fiber node area• take rate (number of subscribers in fiber node area)• traffic demand


– 116 –



Shared Medium Links: RBBExample5.H HFC Summary and Evolution


• Disadvantages of HFC– shared medium infrastructure– usable data rate and latency per user highly variable

• Evolution for high speed– hack of video distribution network for Internet access– replacement of legacy wired CATV infrastructure with fiber

• but not all the way to the residence

– higher baud rate QAM coding with DOCSIS evolution



LinksLL.3 Link Layer Components

LL.1 Transmission and physical mediaLL.2 Link layer technologiesLL.3 Link layer components

LL.3.1 Amplifiers, regenerators, and repeatersLL.3.2 Multiplexors and cross-connectsLL.3.3 Bridges, hubs, and switches

LL.4 Support for higher layers


– 117 –



Link Layer ComponentsExample Types

• Amplifiers and regenerators– optical– microwave relays– bent-path satellite links

• Bridges and hubs• Multiplexors and cross-connects

– space division switches

• Time slot interchangers (TSI)– time division switches

• Optical wavelength converters



Link Layer ComponentsPerformance Requirements

• Performance requirements– must sustain link rate– must not introduce unacceptable delay

Link Layer Components L-IIc

Link layer components must sustain the data rate of the link, while not introducing significant delay.


– 118 –



Links and LANsLL.3.1 Amplifiers, Regenerators, and Repeaters






Link Layer ComponentsAmplifiers and Regenerators

• Amplifiers: analog– example: optical EDFA (erbium doped fiber amplifier)

every few hundred km


– 119 –



Link Layer ComponentsAmplifiers and Regenerators

• Amplifiers: analog– example: optical EDFA (erbium doped fiber amplifier)

every few hundred km

• Regenerators: A/D/A– 2R: regeneration and reshaping preserves timing– 3R: regeneration, reshaping, and retiming– examples:

• optical 2R and 3R• microwave relays• bent-path satellite links



Link Layer ComponentsLightpath Transparency

• Rate specific bit stream – OTN Och {2.5,10,40Gb/s}

• Bit stream– With 3R retiming– Protocol transparent

• Digital– With 2R regen– Timing transparent

• Analog (approximate)– With EDFAs– O-CDMA

• Photonic– Waveform O-CDMA– Quantum crypto

τ

τ


– 120 –



Link Layer ComponentsOptical Wavelength Converters

• O/E/O: convert through electronic domain– expensive– lose advantages of all-optical lightpaths



Link Layer ComponentsOptical Wavelength Converters

• O/E/O: convert through electronic domain– expensive– lose advantages of all-optical lightpaths

• Optical domain: future technology– cross-modulation: input modulates laser output at new λ– coherent effects: similar to four wave mixing

• Small cheap DWDM multiwavelength converters will– reduce some lightpath assignment constraints– will require modification of lightpath routing algorithms


– 121 –



Links and LANsLL.3.2 Multiplexors and Cross-Connects






Link Layer ComponentsMultiplexors and Cross-Connects

• Multiplexors / demultiplexors– aggregate multiple virtual links onto a physical link

• example: T-carrier, point-to-point SONET, WDM multiplexors• example: SONET ring add-drop multiplexors


– 122 –



Link Layer ComponentsMultiplexors and Cross-Connects

• Multiplexors / demultiplexors– aggregate multiple virtual links onto a physical link

• example: T-carrier, point-to-point SONET, WDM multiplexors• example: SONET ring add-drop multiplexors

• Cross-connects– layer 2 switch with relatively static configuration

• example: SONET cross-connect between rings



Multiplexors and Cross-ConnectsSONET Topology: Mesh

• SONET mesh– mesh of SONET links– switched at L3

• between ATM switches• between IP routers

IP

IP IP


– 123 –



Multiplexors and Cross-ConnectsSONET Topology: Rings

• SONET rings– multiplexed at L2

• 4:1 multiplexing for aggregation• ADMs for ring insertion/extraction

– switched at L2• cross-connects for

ring interconnection– fault tolerant

• dual ring APS– automatic protection

switching

XC

ADM



•••

•••

STS-n

STS-n

OC-n

OC-n

OC-m

Multiplexors and Cross-ConnectsSONET Add/Drop Multiplexors

• ADM: add/drop multiplexor– electronic device– optical transceivers

• Layer 2 insertion/extraction– of lower rate signals

• optical OC-m , m < n• electrical T-k , typically T3

– to/from OC-n SONET

• Typically on SONET ring– but may be point-to-point link


– 124 –



STS-n

STS-n

STS-n

STS-n

Multiplexors and Cross-ConnectsSONET Cross Connects

• XC: Cross-connect– electronic switch

• 2×2 switch shown• larger cross-connects possible

– optical transceivers

• Space division between:– point-to-point links– rings

• Time division– multiplexing hierarchy

OC-n

OC-n

OC-n

OC-n



Links and LANsLL.3.3 Bridges, Hubs, and Switches





– 125 –



Link Layer ComponentsBridges

• Bridges connect LAN segments– extend reach beyond limits– important for early LANS

• e.g. Ethernet extension






• Promiscuous– repeat (pass) all frames

network scalability?


– 126 –






• Promiscuous– repeat (pass) all frames– all interconnected segments share intra-segment frames

alternative?






• Learning bridge– learns local segment addresses

• snooped on source MAC address in frame header

– only repeat frames destined for other segments


– 127 –



Link Layer ComponentsHubs

• Early LANs dictated wiring topology – linear segments for Ethernet– rings for token ring

Problems?





• Office topology frequently didn’t match LAN topology– Ethernet bridges frequently needed to bridge hallways


– 128 –





• Office topology frequently didn’t match LAN topology– Ethernet bridges frequently needed to bridge hallways

• End user could take down network– by disconnecting network interface

• token ring• some Ethernet links (e.g. 10Base2)

– sys/netadmins would have to run from office to office

Response?




• Alternative– use a star wiring plan– host/station links all go to a hub in a wiring closet


– 129 –





• More flexible wiring plan• Central location for debugging





• More flexible wiring plan• Central location for debugging

Network scalability?


– 130 –





• More flexible wiring plan• Central location for debugging• Hub is still shared medium bottleneck

alternative?



Link Layer ComponentsLAN Switches

• Alternative– replace hub with a space division switch


– 131 –





• LAN switch– switches on layer 2 (MAC address) header– full bandwidth of each link available

• assuming non-blocking switch fabric







– not a substitute for L2 (IP) switch (router)why?


– 132 –







– not a substitute for L2 (IP) switch (router)– no IP routing and forwarding capability



LinksSupport for Higher Layers

LL.1 Transmission and physical mediaLL.2 Link layer technologiesLL.3 Link layer componentsLL.4 Support for higher layers


– 133 –



Link Support for Higher LayersLoss Characterisation

• Higher layer response depends on type of L2 loss– net configuration/rerouting based on path characteristics– transport layer response to corruption, fades vs. congestion

• Long term and aggregate path characteristics• Dynamic and per packet information

– reason for loss

Loss Characterisation Principle L-4F

Provide long-term and dynamic information on the reason for loss to high layers so that network and end-to-end mechanisms respond appropriately.



Link Support for Higher LayersFiltering

• Filtering PDUs not destined for higher layer protocols– PDU headers must be processed

• Discard early at low layers– minimises PDU processing by higher layers

Early Filtering Principle L-4f

Filter the incoming data not destined for a node as early as possible, and discard as much as possible at each layer.


– 134 –



Link Support for Higher LayersBroadcast Support

• Key infrastructure protocols need broadcast– e.g. ARP, DHCP

• Shared medium LANs/MANs support natively• Mesh networks need to provide broadcast emulation

Link Layer Multicast Principle L-2C

Shared medium links provide native support for broadcast, essential for higher-layer control protocols and in support of multicast applications. Nonbroadcast point-to-point mesh LANs should provide broadcast and multicast support.



LinksAcknowledgements

Some material in these foils comes from the textbook supplementary materials:

• Sterbenz & Touch,High-Speed Networking:A Systematic Approach toHigh-Bandwidth Low-Latency Communicationhttp://hsn-book.sterbenz.org

Links []jpgs/courses/hsnets/lecture-link-hsn... · 2010-09-29 · LL.1.3 Physical media types and...

Documents

Transcript of Links []jpgs/courses/hsnets/lecture-link-hsn... · 2010-09-29 · LL.1.3 Physical media types and...