Integrated networking
Columbia University ELE6905, Spring 2004 Thursdays 10:00-12:30, Mudd Building rm. 545
Instructor Stephen Weinstein (Dept. of Elect. Eng.), [email protected]
Office hours: Thursdays 1:30-3, or by appointment.Lecture notes and references posting: http://www.cvn.columbia.edu/courses/Spring2004/ELENE6905.html
Class #8March 11, 2004
Today, class #6
Wired Access Networks
xDSL, cable data, PON
But first, a bit more discussion of token/leaky buckettraffic smoothing
- Token bucket imposes an average rate constraint, leaky bucket a peak rate constraint. Both offer some control of the duration of a high-speed burst from the source.
- Can be used to police a DiffServ Service Level Specification (part of an SLA) between two network domains, specifying how traffic crossing the boundary of the two domains is to be treated. In particular, how each other’s traffic is conditioned (limited and smoothed) at the boundary, and how packets can be labeled or relabeled for different treatments.
Token bucket (limits average rate)Periodic token deposit, Rav tokens/sec (independent of packet arrivals)
Bucket capacity C tokens
Serverqueue
One token withdrawn to serve a packet whenever a packet is present
Arriving trafficrate r packets/sec
Shaped output traffic
Leaky bucket (limits peak rate)One token deposited each time a packet arrives
Bucket capacity C tokens
Serverqueue
Tokens "leak" out at periodic rate Rp
Arriving trafficrate r packets/sec
Shaped output traffic
Burst length analysis of token bucket
Bucket size C.Tokens deposited in bucket at constant rate Rav.Token removed from bucket each time a packet is served.Packets arrive at a rate r packets/sec.
Assume token bucket initially full (C) after a period of little activity. High-speed burst of packets arrives at rate r > Rav and is immediately serviced, passing through at rate r, until the bucket empties (after which service is at Rav rate).
Tb = maximum burst length time until the bucket empties. C + RavTb = no. of tokens already in bucket or added over Tb.rTb = ni, of tokens withdrawn over Tb.
0 = C + RavTb - rTb, or Tb = C/(r-Rav)
Digital access networksThe communications facilities used between local/personal networksand metropolitan/core networks.
UWB(Ultra Wideband) LEOS, direct satellite
IEEE 802.16
xDSL(and ISDN)
Cellular mobile
Cable data
T-carrierservices
AccessnetworksPON
Wireless MAN
Powerline communications
Where is access networking heading?
The generic goal: An IP-oriented optical/electrical and optical/optical convergence architecture
Optical node
Optical metropolitanand core networks
optical fiber
Access network(optical, wireless, coax, twisted pair- it doesn't matter much)
Subscriber
IP servicesoverlay
Ethernet frames?
End-to-end Ethernet: A new communicationsparadigm, or just a fad?
Optical metropolitanand core networks
Access network
Ethernet frames
Ethernet card
Ethernet switch
LAN
Ethernetbridge(IEEE802.1D)
IP stack
IP on Ethernet
Optical framer
OXC
Ethernet switch
Access network
Ethernetbridge
Ethernet switch Ethernet switch
Ethernet bridge
Why are there many more cable data than ADSLsubscribers in the U.S.?
-Cable systems 15 years ago began major upgrades to HFC (hybrid fiber-coax) to reduce maintenance costs and improve transmission performance, before digital services came along. They were better prepared for digital services.
Headend
Runs of up to 20 amplifiers contributedto noise, distortion, frequent failures
-Cable systems have monopolies, but local telephone companies must lease facilities to competitors, discouraging major capital investment in access by telcos.
-Cable operators began with a broadband services perspective, while telcos were associated with (and thought like) telephone companies.
-ISDN was too little, too late.
Is any access system free from congestionproblems?
Basically no. All access systems have capacitybottlenecks because no carrier wishes to overinvestin excess capacity. Most capacity bottlenecks canbe relieved with additional investment in facilities.
xDSL (Digital Subscriber Line)
- Uses the telephone subscriber twisted pair, bypassing the voice switches with their 4KHz channel filters.
- Supports (in some versions) normal analog telephone in addition to data services.
- Comes in various symmetric and asymmetric versions (next page).
- Performance, especially maximum dependable data rate, is dependent on distance from Central Office (or fiber node) and on crosstalk between twisted pairs in the same bundle.
Digital Subscriber Line Types (24-26AWG twisted pair)(POTS: Plain Old (analog) Telephone Service)
Name Rates down/up POTS Distance ISDN (Basic Rate) 144kbps/144kbps no 18KftADSL (Asymmetric 1.5-8 Mbps/128-640Kbps yes 6.5-24Kft Digital Subscriber Line)G.lite (ITU-T G.992.2) 0.78-4Mbps/<512Kbps yes <24Kf "splitterless"SHDSL (or just HDSL) 0.768Mbps each way no <18Kft (Symmetric High Speed DSL)G.shdsl (ITU-T G.91.2) 0.144-2.32Mbps each way no 12-20Kft "Multi-rate and extended reach" [http://www.cisco.com/warp/public/cc/so/neso/dsso/global/shdsl_wp.htm]
VDSL 26-55Mbps/2Mbps no ~1Kft (Very High Speed Digital Subscriber Line)
ADSL standard: T1.413-1998, "Network to Customer Installation Interfaces - Asymmetric Digital Subscriber Line (ADSL) Metallic Interface: November, 1998"available for $350 at www.atis.org/atis/docstore/doc_display.asp?ID=159
ADSL can operate much faster than a telephonemodem because the data signal bypasses thevoiceband filters of telephone switches
PSTNvoice carriersystem
PSTNswitch
ISP
3KHz voiceband filter
a) Dialup Modem
Line concentrator(the bottleneck)
Data network(s)
ISP
DSLAM
voice carriersystem
b) ADSL
ADSL modem with data passband filter
Line concentrator(voice bottleneck)
Voiceband filters
PSTN
Data bottleneck
trunk(s)Router
ADSL subscribertermination
Digital Subscriber Line Access Multiplexer
...
Typically an ATM switch
Commercial ref. for a DSLAM: http://www.adtran.com/static/docs/DOC000965.pdf
"G.lite" (G.992.2)Subscriber ADSL modem plugs into computer, just like a voiceband modem. So-called "Splitterless" system. Lower rate,smaller BW (512KHz upper edge).
Convenient installation, but unreliable inside wiringusually degrades performance
ADSL subscribertermination
To DSLAM
Commercial example: www.hellosoft.com/products/hdsl/hdsl.htm
ADSL modulation formats
- Primary standard: DMT (discrete multitone) Generate with Discrete Fourier Transform, as described previously.
138KHz 1.1MHz
Different data rates and amounts of transmitted power can be allocatedto different subbands, in accordance with transmission rate requirementand quality of channel at different frequencies.
May use QAM signal constellations of different sizesin different subbands.
sinc(f) spectrum (magnitude shown here) has nulls at carrierfrequencies of adjacent subbands, eliminating interbandinterference (in a system with no channel distortion).
~20KHz
Upstream
4KHz(POTS)
DMT/OFDM performance costs to maintainorthogonality of subbands
- Overhead from cyclic extension (extending blocks beyond multipath dispersion)
- Virtual (unused) subbands on the edges of the total band to avoid interference with other bands.
138KHz 1.1MHz
Filtered MultiTone (FMT)
A variation on DMT applied in VDSL. Mitigates DMT/OFDMperformance costs."With FMT, orthogonality between subchannels is ensured by usingnon-overlapping spectral characteristics instead of overlappingsinc(f) type spectra. Since the linear transmission medium doesnot destroy orthogonality achieved in this manner, cyclic prefixing isnot needed".
Ref: I. Berenguer & I. Wassell, "FMT Modulation: Receiver filter bank definition forthe derivation of an efficient implementation"www-lce.eng.cam.ac.uk/~ib226/papers/fmt_modulation.pdf
IDFTParalleldata
Bandpass versionsof a standard low-pass filter
Parallel/serial
Line signal
- Secondary standard: CAP (Carrierless Amplitude-Phase Modulation) Essentially the same as QAM (quadrature amplitude modulation), generated by direct inband digital techniques.
Store of inbanddigitally modulatedsignal sequences
Information streamPassband signalsamples
D/A Linesignal
By proper design, can generatesignals for an infinite variety ofinformation streams from a finiteset of stored inband digital segments
ADSL modem
Receivingfilter
ADSL modu-lator/filter
Telephonefilter
Data fromcomputer
Subscriber line
RJ-11 jack
Ethernet
Demodulation/equalization/detection
Pulseshaper
Coder/decoder
.138 1.1
0.3 3.3
Hybridcoupler
KHz
MHz
26 138KHz
Splitter
ADSL protocol stack
TCP/UDP
Computer(or appliance)
ADSL terminal
DSLAMData networkterminal
IP
PPPEthernet
Ethernet
ADSL
ATM(optional)
ADSL
ATM(optional)
SONET
ATM(optional)
IP IP
ISP (InternetService Provider)
SONET
ATM(optional)
IPPPP
TCP/UDP Protocol servicessuch as DHCP
Exchange office Subscriber
The future of xDSL?
-Existing full-length subscriber line ADSL doesn’t work (at any attractive rate) on a significant percentage (30%?) of subscriber lines. VHDSL will develop as fiber nodes come closer to subscribers.
-Requires capital investment in metropolitan data networking to alleviate congestion as subscriber population grows.
Telcos want exclusive right to offer xDSL on their subscriber lines; enthusiastic deployment and performance advances depends on that. [They object to unbundling rules.]
-Unbundling rules (carriers required to "unbundle" their facilities and lease the pieces to service competitors at reasonable rates)
Telcos may be holding back on broadband access (especially VHDSL) until their monopoly is comparable with cable's.
Central Office Telco ADSL
Co-located competitor ADSL?
Telco-built subscriber lines
Cable Data System
DOCSIS: Data-Over-Cable Service Interface Specifications: Radio Frequency Interface Specification SP-RFIv1.1-I06-001215, Cable Laboratories, December 15, 2000
Main DOCSIS Technical SpecificationsModulation Bandwidth (MHz) Data Rate(Mbps)
Down 64 or 256 QAM 6 27 or 36 Up QPSK or 16-QAM 0.2-3.2 0.32-10
In both directions: MPEG-2 framing, Reed-Solomon forward errorcorrection coding, DES encryption.
Upstream Medium Access Control: Packet-based, contention and reservation slots, QoS capabilities.
Management: SNMP, with MIB definitions.
Residential network interface: 10BT Ethernet (USB and IEEE 1394 planned).
Business network interfaces: 10/100BaseT, ATM, FDDI
Spectrum utilization (within the cable)
5 42 50 8606MHz channelizationMHz
Upstream (0.2-3.2MHz channels in usable parts of this noisy spectrum)
Downstream
Each downstream channel can be used for:-One analog TV signal, or-Six-seven 4Mbps MPEG-2 digital TV signals, or-One 19Mbps HDTV signal plus two digital TV signals, or-Data (e.g. Internet downloads) at 30Mbps.
64-QAM or 256-QAM used downstream for high spectral efficiency.
................................
Coaxial cabledistribution network
Cable Headend
...
E/OO/E
Backbone network
Cable ModemTermination System (CMTS)
...
Combiner (mux)
Analog headend term
Analog signal modulators(6MHz channels)
Digital satelliteprogramming
Analogsatelliteprogramming
Single-modeoptical fibersOC3-OC12
125-500subscri-bers
Ethernet
Digital or Analog TV
QAM receiver
Cable modem:QAM receiver,QPSK transmitter
MPEG, control functions
T T
Splitter
R ... ...
Switch or network adaptor
Network termination
To PSTN
Set-top box
Telco return accessconcentrator (TRAC)
Local server facility
Operations Support
Security &AccessController
R T T
Fiber node(O/E, E/O)
Contention in shared coaxial cable tree
Remote server facility
T T T T
Contention for (upstream) bandwidth in theDOCSIS MAC (medium access control)
Resources are allocated as "minislots" of upstream transmission time.
Client sources
Medium
Mediator
Requests
Alloc.
Mapping MAC frame into minislots
Example MAC frame
Minislots 6.25μsGrant: 4 x 6.25μs 6.25μs 6.25μs
fragmentation
Later grant for remainder of request
In the upstream direction, transmission time is slotted into minislots for TDMA (time division multiple access). The time duration of a packet transmission is a power of two multiple of 6.25s minislot increments. If grant isn’t sufficient, MAC frame is fragmented andpart is sent later.
Used by others
Medium Access Protocol management message
Requests
CMTS
Slots not yet mapped
Maintenance
Cable modem transmit opportunity
Requestcontentionarea
Slots previouslymapped
Information elements assign slots to different modems
Minislot allocation for upstream traffic
(Cable Modem Termination System)
Request contention resolved through backoff algorithm.
The future of cable data and the comparisonwith xDSL?
-Cable operators (at least in U.S.) are advanced in broadband digital services (entertainment as well as Internet access) and with further innovations may continue in lead.
-Congestion on shared coaxial cable tree can be resolved by splitting the fiber node (making two nodes, each of which takes half the lower distribution tree). (This requires capital investment!)
Fiber node(O/E, E/O)
400 subscribers
Fiber node(O/E, E/O)
200 subs
Fiber node(O/E, E/O)
200 subs
(more)
-Modern cable plants can offer high-speed data service to almost all of their customers, unlike ADSL that can only be offered to about 70%.
-Telcos still ahead in quality of plant engineering and maintenance.
-Telcos may catch up and pass cable operators when and if the investment cable operators made in fiber nodes is matched by telco investment in fiber nodes (to implement VHDSL).
-Both systems have capacity bottlenecks, but cable's may be more expensive to resolve.
-xDSL and cable data likely converge to a common "fiber to the neighborhood" architecture with a variety of "last mile" transmission media.
PON (Passive Optical Network)
A passive splitter in the field reduces cost and makesfiber to the home/business more practical. May replaceT-carrier access systems and services.
Passive splitter
Metropolitan/core networks
Telco servingoffice
COterminal
Up to 64 broadcast drops
ATM or (newer)Ethernet basedtransmissions
ONU
PON interfaces
Tutorial ref: www.iec.org/online/tutorials/epon/topic04.html?Next.x=37&Next.y=14
COterminal
DS-1DS-3OC-3OC-12
IP router
ATM switch
DS-1DS-3
POTS
PBX
ONUEnet
Dedicated wavelength
Layers 2/3 switching & routingData provisioning in 64kbps increments up to 1 Gbps
EPON (Ethernet PON)
Objectives:
- Point-to-multipoint, low-cost architecture using single-mode fiber.
- Access network distances (at least 10km)
- Standard Ethernet frames, no contention
- Standard 1 Gigabit Ethernet rate
- Minimum 1:16 split
- Replacement for earlier ATM PON
Ref (brief tutorial): www.ieee802.org/3/efm/public/jul01/tutorial/pesavento_1_0701.pdf
EPON (Ethernet PON)
Downstream:
OLT
Optical lineterminal
21 13
ONU1
splitter
Users
ONU2
ONU3
1
2
3
21 13
211
3
21 13
11
2
3
All packets broadcast to all ONUs, where Ethernet frames for particularusers are separated on the basis of the MAC (medium access control)addresses.
Headend (e.g. CO terminal)
Optical network unit
Ethernet packet
Header
Data field (up to 1500 bytes for 10Mbps)
Preamble(7 bytes)
Start of frame delimiter (1 byte)
Type, or length of data field (2 bytes)
Pad (0-46 bytes)
Checksum (2 bytes)
Destination address (2 or 6 bytes)Source address (2 or 6 bytes)
Example of MAC address: 00-50-DA-CE-E2-76
6 bytes (each hexadecimal pair is one byte)
EPON
Upstream:
OLT
Optical lineterminal
211 3
ONU1
splitter
Users
ONU2
ONU3
1
2
3
2
1
3
1
2
3
Synchronized system does upstream time slicing, so there are no collisionsand no need for packet fragmentation.
"MAC uses existing PAUSE control frame or other control messages."
11
33
3 3
3 3
EPON optical aspects
OLT
ONU11:N opticalsplitter
ONU2
ONU3
λ1Mediumaccesslogic
λ2
R
TWDM
MediumaccesslogicR
TWDM
Full duplex operation using separate wavelengths. (example: 1550nm/1310nm)
Headend permits only one subscriber at a time to transmit.
End users see only traffic from headend, not from each other.
Data
Review for the midterm exam
Sampling theorem:For x(t) bandlimited to (-W, W) Hz,
Analog to digital conversion
x(t) = x(n/2W)sin[2W(t-n/2W)]/[2W(t-n/2W)]n
Interpolation function (what is itsfrequency spectrum?)
T= 1/2W
T 2T3T 4T
5Ttime (sec)
Reconstruction formula above realized in a low-pass filter limited to what frequencies?What are advantages of digitized media?Does a digitized media stream necessarily use less bandwidth than the original analog media signal?
LEOS, direct satelliteIEEE 802.16
IR
Wireless LAN(IEEE 802.11) Subscriber
line
Local areanetworks(LANs)
Cellular mobile
Infrastructure network types
Cable data
Switched Ethernet T-carrier
services
Accessnetworks
SONET ring,RPR
Metropolitanarea networks(MANs)
Core (or long haul)networks
1-10GbpsEthernet
Optical Core Network(DWDM)
Satellitetransport,broadcasting
Personal Area NetworksBluetooth
PON
Resilient Packet Ring
Wireless local loop("wireless MAN")
UWB
request transport
Application
Transport
Network
Link, Phys
request link access & physical commun.
Application
Transport
Network
Link, Phys
Packet transfer
Transport data package transfer
Information unit transfer
request packet forwarding
Physical network
Protocol layers offering services to higher layersand peer-to-peer interaction across networks
Virtual Circuits, e.g. in ATM
Pools of capacity for different services
CBRVBRABR
guaranteed peak capacityguaranteed average capacity
whatever is left over
CBRVBRABR
CBR: Continuous bit rateVBR: Variable bit rateABR: Available bit rateUBR: unrestricted bit rate, best effort service
Public Internet(or any data network)
Destin.host
Enterprise networksegment
Enterprise networksegment(or individualremote host)
Encrypted end-end packet
Firewallrouter
Encapsulating "tunnel" packetaddressed to firewall
Virtual Private Network
VoIP (general concepts of Internet-PSTN interworking)
codecMikeSpkr
UDP/IP/Phys
RTP
Echo canceler
Internet
IP telephone (H.323 compliant)
Peer-to-peerIP communication
Internet/PSTNGatewayPSTN
Addr. Dir.
PSTNtelephone
Mediagatewaycontroller
H.248
Signaling (e.g. SIP)
IP address xxx.xx.xxx.xx
bufbuf
Tel number (212) 854-xxxx
IP tel.
Telephony ApplicationPort zz
Spectrum policy (e.g. renting spectrum in bandwidthand time) and applications of software-defined radio
- Multiple air interfaces.
- Agility to move between available time/bandwidth slots rather than stick to fixed assignments.
Frequency
Time
Infrastructure and ad-hoc modes
AccessPoint Ad-hoc mode
(peer to peer relay)
Infrastructure mode
AccessPoint
Backbone network,wired or wireless
Network interoperability at PHY/MAC levels vs.network interoperability at network level (IP) Challenges for PHY/MAC interoperability:- Matching different protocol implementations of different operators- Matching rate offerings in the digital hierarchy- Coordinating operations and management functions (protection/restoration, traffic engineering, comparable service features and performance, ...)
At network level: How does IP avoid these complexity problems? What kinds of agreements are still needed?
Network vulnerabilities- Physical damage and congestion.- Congestion.- Cyber attacks.- Cascading failures.Everyday restoration mechanisms, such as SONET ring, and breaksthat cannot be managed by everyday restoration mechanisms.
Add/drop multiplexer
Normalpath
X
Restorationpath
Damaged conduit
e.g. efficient use of capacity from statistical multiplexing of different sources (What is the difference from a circuit-switched network?) and resilience (why?)
packetizer
packetizer
packetizer
Aggregated traffic
silent
silent
talking
Packet networking advantages
Router functions
Transfer
Lookuptable
Classifier
Destinationaddress
IP packet
Schedulingalgorithm(what kinds ofservice disciplines?)
Scheduler
Input port 1Queue 1
State
Output port 1
to output port 1, toppriority
to outputport m,top priority
RoutingAlgorithm(what is OSPF?)
Link states fromneighboring nodes
Transfer
Classifier
Server
Queue n
Scheduler
Queue 1State
Output port m
Server
Queue nto outputport m,lowest priority
Input port m
MPLSMulti-Protocol Label Switching
ApplicationRTP, RTP
TransportTCP, UDP
NetworkIP, DiffServ, SLA, traffic smoothing & policing
Link or MACLink-level framing, circuit switching,medium contention resolution
Packet transfer(IP addresses)
Transport data package transfer (port numbers)
Information unit transfer(stream IDs)
Physical networkPhysicalPlug interfaces, modulation
SessionHTTP
Client-server requests/responses
HTMLSIP
JAVA, CORBA,SOAP
IP protocol stacks
Successive encapsulation
UDP protocol unit IP packet IP header
UDP header
Application-level information unit (e.g. mediaencapsulation)
AIUheader
Ethernet frame
IPv4 address classes A,B,C – How the 32 bitsare used
0 1 8 16 24 31 Network ID
CLASS A Bit number
0 Host ID
Fraction of alladdresses
1/8
For the relatively small number of networks supporting a verylarge number of hosts computers.
Can address up to 27 = 128 networks, each with up to224 = 16,777,216 host computers.
What is the address depletion problem addressed by IPv6, and whatare the major differences between IPv4 and IPv6? How can addresstranslation mitigate the address depletion problem?
TCP and UDP
Provide an end to end (application to application) transport service.
TCP (transport control protocol): Reliable, connection- oriented service.
UDP (user datagram protocol): Unreliable datagram service (but no delays for retransmissions!)
What are the major similarities and differences between TCP andUDP? What is sliding window flow control in TCP?
Internet
ApplicationRTP1
UDPIP
Physical
Stream DataControl messages
RTP2
Session 1 (audio) port x
Session 2 (video) port y
RTP Audio and Video Sessions
ApplicationRTP1
UDPIP
Physical
RTP2
Internet QoS with DiffServ, SLA, MPLS
DSCP (Differentiated Services CodePoint) marking(for class of traffic).Possible traffic smoothing.
Clientnetwork
ISP network with DiffServ-capable routers
Traffic conditioning part of SLA regulatesvolume of submitted traffic for each DSCP
DiffServ PHBs invokedby DSCP markings
Traffic-engineered links using MPLS
ISP ingress router
Policing of submitted traffic
Direction of traffic
Clientnetwork
DiffServ Classes
EF (expedited forwarding): Specified PIR (peak information rate) and bounded delay (e.g. for voice). The EF PHB implements a pass-through service with no queueing delays or delay jitter .
AF1-AF4 (assured forwarding): Preferred forwarding at routers to minimize packet losses. Each level has a specified CIR (committed information rate) and PIR.
BE (best effort): Packets utilize whatever capacity is left after preferred classes are accommodated.
What is a DiffServ codepoint? What is an SLA? What is "colormarking"? What are token and leaky buckets?
Traffic conditioning in a network router
classifier
PacketsMeter/shaper
profile
conforming
drop-per
passed
dropped
Non-con-forming
DiffServ class marker(if not already marked)
To PHB scheduler
Best effortOther AF classes
EF
AF1
Conformance marker
conforming
drop-per
passed
dropped
Non-con-forming
To PHB scheduler
Meter/shaper
profile
Meter measures conformance with SLAShaper smooths traffic to conform with SLA
What are IntServ and DiffServ?
IntServ DiffServNo. of service classes 2 6 (incl AF1-4)Session state maintained Yes No (only preferred in network? service discipline)
Advance resource Yes (e.g. by No (SLA by customer
reservation? RSVP) and class)
Where would they tend to be used in networks? What are the IntServ and DiffServ classes?How can IntServ and DiffServ work together (at least be interfaced)
MPLS - what is it and what is it good for?
Paths for forwarding equivalence classes
San Francisco
New York
Chicago
St. Louis
Denver
NY to SFExpedited Forwarding traffic
NY to SFAll other traffic
What is "label swapping"?
Connectionless and Connection-Oriented
Datagrams
Connection-orientedstream
What is a virtual circuit?What is the difference between a switch and a router?
Cell switching (ATM)
-"Asynchronous" because cells need not arrive at a switch at fixed times.
-Resource reservation setup in advance through signaling.
-Offers quality of service (bandwidth/delay guarantees) in broadband networks.
Why a 53-byte cell?What is VCI swapping?What are the service types?What is a Virtual Path?What is an adaptation layer?
Synchronous, asynchronous, isochronous,plesiochronous
Synchronous: Data stream synchronized to a clock
time
Data stream 1 (e.g. a tributary as on last slide)
Data stream 2
What are TDM and TDMA?
High-speed Ethernet switch(Metropolitan Area 1Gbps/10Gbps)
PSTN access and metropolitan network
Terabitrouter
DWDM core network
PBX, LANOXC2
Lightpath shown with two redlinks and one green link
Framing (SONETand/or OTN) (Transp.)
(Opaque)
λ1 λ2
λ2
λ2
λ1
OXC3
OXC4
OXC1
λ1
SONETring
ADM
λ3
O/E E/O
(Opaque)
Optical networks: Metropolitan/core network integration
OTN: Optical Transport Network, ITU-T G.709
EthernetLAN
LightpathsWhat are WDM and DWDM?What are opaque and transparent optical switching?What is hierarchical optical switching?
cross-connect
opticalfibers
RepeaterOne fiber
Routing and wavelength assignment through an optical corenetwork continues to be a research topic
SONET framing (155.52Mbps SONET/SDH frame)
........................
........................
........................
........................
........................
........................
........................
........................
........................
9 rows
270 columns
First bytein frame
Last bytein frame
Transport overhead(section and line)
t=0
t=125μs(entire frame)
PayloadVirtual container (including path overhead)
Pointer to start ofvirtual container
What is GFP?
Fiber access systemsWhat are FTTC, FTTH, PON? What is VDSL?
SONETBroadband network(OC-3 to OC-48)
Telco servingoffice
VDSL on twisted pair, < 1000ft Up to 50Mbps (asymmetric)
TV
COterminal
ONU (fiber node)
Example product for either FTTH or FTTC:40-870MHz band downstreamon 1310nm and 1550nmcarriers, carrying "a full complement of analog and digital signals"[http://www.synchronous.net]
Fiber with subcarrier-multiplexedVDSL signal
What is modulation?Baseband/passband, PCM and PAM (M-level), Fourier transform (spectrum), spectral efficiency, PSK, QAM, CDMA, DMT/OFDM,signal constellations, noise immunity, UWB
Modulated transmissionsignal
signallevelsencoder
modulator
Carrier waveformBaseband information signal
Next week (March 18): Spring Break
Next class (March 25)
Midterm exam
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