Wide Area Networking Chapter 7 Halloween Version 1.0.

Wide Area Networking

Chapter 7

Halloween Version 1.0

Knowledge Checkpoints

• Common carriers and the nature of competition• How to improve WAN performance• Factors in selecting WAN services• The role of common carriers in organizational WANs• Four basic categories of WAN circuits• Dialed circuit services • Dedicated circuit services• Switched circuit services• Packet network services

Important WAN Terms

• Virtual Circuit (VC)– The connection between two frame relay ports

• Permanent Virtual Circuit (PVC)– A pre-defined VC

• Switched Virtual Circuit (SVC)– A VC that is established dynamically

• Data Link Connection Identifier (DLCI)– Virtual Circuit Identification Number

More Terms to Learn

• WAN

• ATM

• X.25

• DTE/DCE

• DSU/CSU

• Multiplexer

• Mux

• Store and forward

• Frame relay

• PAD• VoFR• FRAD• SNA• CIR• Cell

Checking on a Network Connection

Why didn’t the host respond?

Tracing the Hops

Which line is the router?

Introduction

• Wide area networks (WANs) connect backbone networks and MANs across longer distances, often hundreds of miles or more

• Most organizations cannot afford to build their own MANs and WANs, so they rent or lease circuits from common carriers such as AT&T, MCI, BellSouth, PACTEL or NYNEX

The Telephone Network

• A common carrier is a private company that sells or leases communications services and facilities to the public

• A common carrier that also provides local telephone services is called a local exchange carrier (LEC), while one that provides long distance services is called an interexchange carrier (IXC)

• In the United States, 90 percent of the telephone system used to be run by one common carrier, AT&T

Comparison of Telco Areas

Indianapolis

Evansville

South Bend

Attica

Terre Haute

Rising Sun

GaryMichigan City

New Albany

Fort Wayne

Richmond

West Lafayette

Area Code Map LATA Map

Columbus

(219)

(317)

(812)

Indianapolis

Evansville

South Bend

Attica

Terre Haute

Rising Sun

GaryMichigan City

New Albany

Fort Wayne

Richmond

West Lafayette

Columbus

(765)

GOLDMAN & RAWLES: ADC3e FIG. 01-04

Russiaville Russiaville

Carrier Service Areas

US West Northwestern Bell Mountain Bell Pacific Northwest Bell

Pacific Telesis Group Pacific Telephone Nevada Bell

Southwestern Bell Southwestern Bell Telephone

Ameritech Illinois Bell Indiana Bell Michigan Bell Ohio Bell Wisconsin Bell

Bell South Southern Bell Southeastern Bell

Bell Atlantic Bell of PA Diamond State Telephone New Jersey Bell Chesapeake & Potomac Bell Co's

NYNEX New England Telephone New York Telephone


DIALED CIRCUIT SERVICES

• PVCs– Statically Defined at

Configuration, Unless PVC Parameters Need to be Modified

– Connection is Always Configured Whether There is Information to Send or Not

• SVCs– Dynamically

Established When There is Information to Send (Call-by-Call Basis)

– Connection is Released When There is No More Information to Send

Differences Between Pvcs And Svcs

Dialed Circuit Services

• Dialed circuit services are the simplest and one of the most common types of MAN and WAN connection.

• This type of connection uses the normal telephone network. To use dialed circuit services, the user simply leases connection points into the common carrier’s network, then dials the host computer using a modem, and connects to the host system.

• Dialed circuit services may use different circuit paths between the two computers each time a number is dialed

Dialed Circuit Services

Direct Dialing

• Direct dialing (also called dial-up) is the most commonly used direct circuit service. Every time you call your Internet service provider from your home phone, you are using direct dialing.

• Charges for direct dialing are based on the distance between the two telephones (in miles) and the number of minutes the connection is used.

Wide Area Telephone Service (WATS)

• Wide Area Telephone Service (WATS) are a special rate service that allows direct circuit calls for both voice and data transmission to be purchased in large quantities.

• WATS is limited to one direction only; it is either outward dialing or inward dialing. In general, inward WATS uses the toll free 800, 877 and 888 area code series in North America, and similar numbers in other countries.

DEDICATED CIRCUIT SERVICES

Dedicated Circuit Services

• There are two main problems with dialed circuits. – Each connection goes through the regular telephone network

on a different circuit, which may vary in quality.

– The data transmission rates on these circuits are usually low 28.8 to 56 Kbps.

• An alternative is to establish a private dedicated circuit, which the user leases from the common carrier for their exclusive use, 24 hrs/day, 7 days/week.


• Dedicated circuits are billed at a flat fee per month and the user has unlimited use of the circuit. Dedicated circuits require more care in network design than dialed circuits.

• There are five types of dedicated circuits:– Voice grade circuits– Wideband analog services– T Carrier circuits– SONET circuits– Digital subscriber line circuits

Dedicated Circuits for a WAN

Voice Grade Circuits

• Voice grade circuits are analog circuits that work in exactly the same manner as traditional telephone lines, except that you do not dial them.

• Dedicated voice grade channels often have conditioning (or equalization) done on them to improve data transmission quality by reducing noise and distortion.

Wideband Analog Services

• Wideband analog services are similar to voice grade circuits but they provide much greater bandwidth.

• Typically wideband analog services provide one 48,000 hertz bandwidth channel for use with frequency division multiplexing or as 12 individual voice grade channels (4000 Hz each).

T Carrier Circuits

• T Carrier circuits are dedicated digital circuits and are the most commonly used form of dedicated circuit services in North America today.

• Instead of a modem, a channel service unit (CSU) or data service unit (DSU) are used to connect the circuit into the network.

T Carrier Circuits

• A T-1 circuit (DS-1 circuit) provides a data rate of 1.544 Mbps. T-1’s allow 24 simultaneous 64 Kbps channels (with TDM) which transport data, or voice messages using pulse code modulation.

• A T-2 circuit (6.312 Mbps) is basically a multiplexed bundle of four T-1 circuits.

• A T-3 circuit (44.376 Mbps) is equal to the capacity of 28 T-1 circuits.

• A T-4 circuit (274.176 Mbps) is equal to the capacity of 178 T-1s.• Fractional T-1, (FT-1) offers portions of a 1.544 Mbps T-1 for a

fraction of its full costs.

T Carrier System

T-Carrier Designation DS Designation Speed

T-1

T-2

T-3

T-4

DS-0

DS-1

DS-2

DS-3

DS-4

64 Kbps

1.544 Mbps

6.312 Mbps

44.375 Mbps

274.176 Mbps

T-1 Frame Layout

1 0 0 0 0 0 0 1 1 1 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 0 1 1 0 1 0

Channel 1 (8 bits)

Channel 2 (8 bits)

Channel 3 (8 bits)

Channel 24 (8 bits)

Frame (193 bits)

T-1 Transmission Service (1.544 Mbps)

bits Framing bit marks the end of this 24-channel frame

24 channels/frame · 8 bits/channel

192 data bits + 1 framing bit

= 192 data bits/frame

= 193 total bits/frame

193 bits/frame · 8,000 frames/second sampling rate= 1,544,000 bits/second

= 1.544 Mbps

= DS-1

= T-1


Synchronous Optical Network (SONET)

• The synchronous optical network (SONET) has recently been accepted by the U.S. standards agency (ANSI) as a standard for optical (fiber) transmission at gigabits per second speed.

• The international telecommunications standards agency (ITU-T) also recently standardized a version of SONET under the name of synchronous digital hierarchy (SDH). The two are very similar and can be easily interconnected.

Synchronous Optical Network (SONET)

• SONET transmission speeds begin at the OC-1 level (optical carrier level 1) of 51.84 Mbps. Each succeeding rate in the SONET fiber hierarchy is defined as a multiple of OC-1.

• Several common carriers (MCI) now use OC-12 circuits at 622.08 Mbps to carry digitized voice traffic.

SONET

SONET Designation SDH Designation Speed

OC-1

OC-3

OC-9

OC-12

OC-18

OC-24

OC-36

OC-48

OC-192

STM-1

STM-3

STM-4

STM-6

STM-8

STM-12

STM-16

51.84 Mbps

155.52 Mbps

466.56 Mbps

622.08 Mbps

933.12 Mbps

1.244 Gbps

1.866 Gbps

2.488 Gbps

9.952 Gbps

SONET Framing

90 octets

9 r

ow

s

STS-1 frame

3 octets

Transport overhead

87 octets

Synchronous payload envelope

90 octets/row · 8 bits/octet = 720 bits/row

720 bits/row · 9 rows/frame = 6,480 bits/frame

6,480 bits/frame · 8,000 frames/second (sampling rate) = 51,840,000 bits/second

Transfer Rate of 51.84 Mbits/second


NY Information Technology Center

Digital Subscriber Line (DSL)

• DSL services are new and not all common carriers offer them.

• Two general categories of DSL services have emerged in the marketplace. – Symmetric DSL (SDSL) provides the same transmission

rates (up to 128 Kbps) in both directions on the circuits.

– Asymmetric DSL (ADSL) provides different data rates to (up to 640 Kbps) and from (up to 6.144 Mbps) the carrier’s end office. It includes an analog channel for voice transmissions.

Digital Subscriber Line (DSL)

• A new version of ADSL called Very high rate Digital Subscriber Line (VDSL) has been designed for use over local loops of 1000 feet or less. It uses FDM to provide three channels:– Normal analog channel– Upstream digital 1.6 Mbps channel– Downstream digital 51.84 Mbps channel.

ADSL Technology Implementation

Central Office voice switch

Central Office data switch

Rack mounted ADSL modems

PSTN

analog phone

ADSL modem

10baseT ethernet NIC

up to 6 Mbps

up to 640 Kbps

POTS

HOME

Local Carrier Central Office

Internet


CIRCUIT SWITCHED SERVICES

Circuit Switched Services

• The major problem with dedicated circuit services it that the user must carefully plan all circuits needed.

• In contrast, switched circuits work much like dialed circuits. The user buys a connection into the common carrier’s network from the end points of the WAN, without specifying all the interconnecting circuits needed.

• The primary differences from dialed circuits is that the circuits are entirely digital and that they offer higher data transmission rates.

Circuit Switched Services

Narrowband Integrated Services Digital

Network

• The first generation of Integrated services digital network (ISDN), commonly called narrowband ISDN, combines voice, video, and data over the same digital circuit.

• ISDN has long been more of a concept than a reliable service in North America.

• Acceptance has been slowed because equipment vendors and common carriers conflicting interpretations of ISDN standards.

Narrowband Integrated Services Digital

Network

• Narrowband ISDN offers two types of service:– Basic rate interface (BRI, basic access service or

2B+D) provides two 64 Kbps bearer (B) channels and one 16 Kbps control signaling (D) channel.

– One advantage of BRI is it can be installed over existing telephones lines. (if less than 3.5 miles).

– Primary rate interface (PRI, primary access service or 23B+D) provides 23 64 Kbps ‘B’ channels and one 64 Kbps ‘D’ channel. (basically T-1 service)

Broadband Integrated Services Digital

Network• The second generation of ISDN is called

Broadband ISDN (B-ISDN). B-ISDN is a circuit switched service and is backwardly compatible with ISDN.

• B-ISDN is currently offered in three services:– Full duplex channel at 155.2 Mbps.– Full duplex channel at 622.08 Mbps.– Asymmetrical service with two simplex channels

(Upstream at 155.2 Mbps, downstream at 622.08 Mbps).

•Narrowband ISDN Architecture Information

Services

Transport category

Transport capacity

Transport architecture

Inter-switch protocol and

switching architecture

Video freeze-frame Voice Data

LAN Interconnect Full motion video

Voice Data

BRI (Basic Rate Interface)

PRI (Primary Rate Interface)

2-wire Dial-up

T-1

Signalling System 7 (SS7)

2 B + D 2 · 64 Kbps 128 Kbps + 16 Kbps 16 Kbps 144 Kbps

23 B + D 23 · 64 Kbps B channels + 64 Kbps D channels 1.536 Mbps


ISDN

ISDN Technology

router

LAN hub

server

ISDN IMUX

ISDN terminal adapter

remote access server

server

analog phone

ISDN PC adapter card

LAN hub

router512 Kbps

4 x 128 KbpsISDN IMUX

4 x 128 Kbps512 Kbps

ISDN BRI service

ISDN PC adapter card

ISDN BRI service

analog phone

ISDN Service

routerLAN hubISDN

terminal adapter

routerLAN hub

ISDN terminal adapter


ISDN Architecture

ISDN network

Codec

Video

Codec

Video

Voice

Data Data

Voice

ISDNISDN


ISDN Network

Multiple PVCs per Access Line

Before: Circuit switched

After: Frame relay, single access line, multiple PVCs

Single access leased line

Frame Relay Network

Modem pool

Multiple leased lines

Multiple PVCs

FRAD

FRAD

FRAD

FRAD


PACKET SWITCHED SERVICES

Packet Switched Services

• Packet switched services enable multiple connections to exist simultaneously between computers.

• With packet switching users buy a connection into the common carrier network, and connects via a packet assembly/ disassembly device (PAD).

• Packet switching splits messages into small segments called packets (usually 128 bytes).


• Packets from separate messages are interleaved with other packets for transmission.

• Although the packets from one data stream may mix (interleave) with several other data streams during their journey, it is unlikely that packets from two different data streams will travel together during the entire length of their transmission.


There are two methods used to route packets:• A Datagram is a connectionless service which adds a

destination and sequence number to each packet, in addition to information about the data stream to which the packet belongs. Packets may follow a different route, and are reassembled at the destination.

• In a Virtual circuit the packet switched network establishes an end-to-end circuit between the sender and receiver. All packets for that transmission take the same route over the virtual circuit that has been set up for that transmission.

http://www.kidsdomain.com/holiday/halloween/clipart/k-witch3.gif


• Packet switched services are often provided by different common carriers than the one from which organizations get their usual telephone and data services.

• Therefore, organizations often lease dedicated circuits from their offices to the packet switched network point-of-presence (POP).

Datagram Delivery on a Packet-Switched Network

PAD

Packet assembler/

disassembler

fun datacommisDA SA N DA SA NDA SA NDA SA N

PAD fundatacomm isDA SA NDA SA NDA SA N DA SA N

isfun datacomm

4 3 2 1

4 32 1

4 3 2 1

1. Datagrams enter the packet switched network in proper sequence order

2. Datagrams arrive at destination PAD in random sequence, which give new meaning to intended message

3. Destination PAD resequences datagrams in proper order

DA SA N

- destination address - source address - datagram sequence number

Packet assembler/

disassembler

Packet-switched network

data


data comm is fun

data comm is fun

Circuit Switching vs.

Packet Switching

PADPAD

Packet-switched network (Public data network)

Central Office

Packet assembler/

disassembler

Packet assembler/

disassembler

Data enter the packet-switched network one packet at a time; Packets may take different physical paths within packet-switched networks.

Packet Switching

Voice or data

Voice or data

All data or voice travel from source to destination over the same physical path

Circuit Switching

Switch Dedicated Circuits


X.25

• The oldest packet switched service is X.25, a standard developed by ITU-T. X.25 offers datagram, switched virtual circuit, and permanent virtual circuit services.

• Although widely used in Europe, X.25 is not widespread in North America. The primary reason is transmission speed, now 2.048 Mbps (up from 64 Kbps).

Point-to-Point vs. End-to-End Error Correction

X.25

X.25

X.25

X.25

X.25

X.25

X.25

X.25

PAD

PAD

1 32 4

56 7

X.25 Packet-switched network

Steps in X.25 Error Correction 1. Regenerate CRC-16 2. Compare with transmitted CRC-16 3. Send ACK or NAK to sending node 4. Wait for retransmitted packet and repeat point-to-point error

detection and correction

FR

FR

FR

FR

FR

FR

FR

FR

FRAD

FRAD

1

Frame relay network

Steps in Frame Relay Error Correction 1. Regenerate CRC-16 2. Compare with transmitted CRC-16 3. Discard bad frames 4. Repeat process on next frame

point-to-point error detection

end-to-end error correction


Frame Relay Frame Layout

E A

D E

B E C N

F E C N

C or R

FLAG DLCI FLAGINFORMATION Packet Variable

Number of Octets

FRAME CHECK Sequence CRC-16

E A

1 bit

DLCI

1 bit

1 bit

1 bit

1 bit

1 bit

8 bits 6 bits 4 bits Variable length 16 bits 8 bits

1 octet2 octets1 octet 1 octet 1 octet

HEADER TRAILER

Variable length

FLAG EA C or R DLCI EA DE BECN FECN DLCI INFORMATION FRAME CHECK FLAG

unique bit sequence that indicates beginning of frame extended address -- standard address is two octets, this bit setting can extend address to 3 or 4 octets command or response -- application specific -- not used by standard frame relay protocol data-link connection identifier (address) -- identifies particular logical connection over a single physical path extended address -- standard address is two octets, this bit setting can extend address to 3 or 4 octets discard eligibility -- used by frame relay switches for flow control backward explicit congestion notification -- used by frame relay switches for flow control forward explicit congestion notification -- used by frame relay switches for flow control data-link connection identifier (address) -- identifies particular logical connection over a single physical path minimum number of octets - enough to make total frame at least 7 octets long. Maximum number of octets is 8000. Carries upper layer data frame check sequence for error detection - also called cyclic redundancy check unique bit sequence that indicates end of frame


Leased Lines

Frame Relay

ATM

X.25

SMDS

$.167B

$1.6B

$2.6B

$6.8B

Market Forecast by WAN Technology

Public FrameRelay

ATMDS-3/E-3DS-3/E-3

DS-1/E-1DS-1/E-1

DS-0DS-0

X-25

InternationalFR

InternetAccess IP

ManagementReports

ISDNISDN

DS-3/E-3DS-3/E-3

Dial AccessDial Access

Dial Dial AccessAccess

FRAccess

Understanding Public Frame Relay Services

WAN Set-up

Frame Relay

• Frame relay is a newer packet switching technology that transmits data faster than X.25. It differs from X.25 and traditional networks in three important ways:

• 1. Frame relay only operates at the data link layer.• 2. Frame relay networks do not perform error control.• 3. Frame relay defines two connection data rates that

are negotiated per connection and for each virtual circuit as it is established. (Committed information rate and Maximum allowable rate).

Major Components of a Wide Area Network Architecture

User demands

Interface specifications

Access line

Network services

Network-to-Network interface

Network architecture

Switching architecture

Transmission architecture

Voice Data Imaging FaxVideo


Frame Relay

• Different common carriers offer frame relay networks with different transmission speeds: 56 Kbps to 45 Mbps.

• At present, frame relay suffers from the same problems as ISDN - a lack of standards.

SVC Technical Framework

FrameRelayNetwork

A BInformation

Information

Information

Information

SetupSetup

ConnectConnectConnectConnect

ReleaseRelease

Release CompleteRelease Complete

ReleaseRelease

Release CompleteRelease Complete

SetupSetup1

4

5

7

2

3

6

7- Denotes period of time- Denotes period of time

Call ProceedingCall Proceeding2

DisconnectDisconnect

6

Asynchronous Transfer Mode (ATM)

• Asynchronous transfer mode (ATM) is one of the fastest growing new technologies, and is similar to frame relay.

• All data are packet-switched, and there is no error control at the intermediate computers within the network; error control is the responsibility of the source and destination.


• Asynchronous Transfer Mode (ATM) (a.k.a. cell relay) is a technology originally designed for use in wide area networks that is now often used in backbone networks.

• ATM backbone switches typically provide point-to-point full duplex circuits at 155 Mbps (total of 310 Mbps).

Implementation of ATM Technology

ATM switch

ATM switch connections running at 155Mbps, upgradeable to 2.4 Gbps or higher.

ATM Backbone Network

Bridge or Router with ATM module - also known as an

ATM Access Switch

10 Mbps 16 Mbps

100 or 155 Mbps

155 Mbps

155 Mbps

Corporate Servers or High Speed Workstations with

155 Mbps NICs

25 Mbps ATM workgroup

concentrator

Local Clients and Servers with 25Mbps ATM NICs

25 Mbps

100 Mbps or 155 Mbps connection from workgroup concentrator to

ATM switch.

ATM WAN

Services

10Mbps Token Ring

MAU

Token Ring LAN (16Mbps)

10Base-T hub

Ethernet LAN (10Mbps)

ATM switch

ATM switch

155 Mbps

155 Mbps


ATM Network


• ATM has three important differences from frame relay:– ATM uses fixed packet lengths of 53 bytes (5 bytes of

overhead and 48 bytes of user data), which is more suitable for voice transmissions.

– ATM provides extensive quality of service (QoS) information that enables the setting of very precise priorities among different types of transmissions (i.e., voice, video & e-mail).

– ATM is scaleable. It is easy to multiplex basic ATM circuits into much faster ATM circuits.


ATM is a switched network but differs from switched ethernet and switched token ring in four ways:1. ATM uses fixed-length packets of 53 bytes.2. ATM provides no error correction on the user data.3. ATM uses a very different type of addressing from

traditional data link layer protocols such as ethernet or token ring.

4. ATM prioritizes transmissions based on Quality of Service (QoS).


Asynchronous Transfer Mode (ATM) is connection-oriented so all packets travel in order through the virtual circuit. A virtual circuit can either be a:

• Permanent Virtual Circuit (PVC) - defined when the network is established or modified.

• Switched Virtual Circuit (SVC) - defined temporarily for one transmission and deleted with the transmission is completed.

ATM and Traditional LANs

• ATM uses a very different type of protocol than traditional LANs. It has a small 53-byte fixed length packet and is connection-oriented.Ethernet and token ring use larger variable length packets and are typically connectionless.

• Translation must be done to enable the LAN packets to flow over the ATM backbones. There are two approaches LAN encapsulation (LANE) and Multiprotocol over ATM (MPOA).


Translating from Ethernet or token ring into ATM is not simple.

First the Ethernet address must be translated into an ATM virtual circuit identifier for the circuit that leads from the edge switch to the edge switch nearest the destination.

Once the virtual circuit address for the destination data link layer address has been found, it can be used to transmit the packet through the ATM backbone.

LAN Encapsulation (LANE)


• Once the virtual circuit is ready, the LAN packet is broken into the series of ATM cells, and transmitted over the ATM backbone using the ATM virtual circuit identifier.

• Unfortunately this process can cause quite a delay (a reduction of 40 to 50 %).

• Multiprotocol over ATM (MPOA) is an extension to LANE.

Switched Multimegabit Data Service (SMDS)

• Switched multimegabit data service (SMDS) is an unreliable packet service like ATM and frame relay.

• Like ATM and frame relay, SMDS does not perform error checking; the user is responsible for error checking.

• SMDS is not yet a widely accepted standard.

Northrop Grumman Network

Can You Describe This Network?

Addressing & Forwarding with ATM

Virtual Circuits

IMPROVING MAN/WAN PERFORMANCE

Improving MAN/WAN Performance

• Improving MAN/WAN performance is handled in the same way as improving LAN performance.

• You begin by checking the devices in the network, by upgrading the circuits between computers, and by changing the demand placed on the network.

MAN/WAN Performance • Performance Checklist

• Increase Computer and Device Performance– Upgrade devices– Change to a more appropriate routing protocol (either static or dynamic)

• Increase Circuit Capacity– Analyze message traffic and upgrade to faster circuits where needed– Check error rates

• Reduce Network Demand– Change user behavior – Analyze network needs of all new systems– Move data closer to users

Improving Device Performance

• One way to improve network performance is to upgrade the devices and computers that connect backbones to the WAN.

• Another strategy is to examine the routing protocol, either static or dynamic. Dynamic routing will increase performance in networks which have many possible routes from one computer to another, or those in which message traffic is “bursty.”

Improving Circuit Capacity

• The first step is to analyze the message traffic in the network to find which dedicated point-to-point circuits are approaching capacity.

• The capacity may be adequate for most traffic, but not for meeting peak demand. One solution may be to add a circuit switched or packet switched service that is only used when demand exceeds circuit capacity.

• Sometimes a shortage of capacity may be caused by a faulty circuit. Before installing new circuits, monitor the existing ones to ensure that they are operating properly.

Reducing Network Demand

• One step to reduce network demand is to require a network impact statement for all new application software developed or purchased by the organization.

• Another approach is to shift network usage from peak or high cost times to lower demand or lower cost times.

• The network can be redesigned to move data closer to the applications and people who use them.

SELECTING MAN/WAN SERVICES

Selecting MAN/WAN Services

• A 1995 survey of network managers found that:– 45 percent of WAN costs were for network management

(primarily support staff salaries).– 35 percent was spent on services (leasing data circuits from

common carriers).– Only 20 percent was spent on equipment.

• The most expensive part of the WAN will be the people require to plan, install, and operate it, so pick one that is easy to manage.

• It costs more to lease services from common carriers than to buy hardware, so selection decisions should be driven more by the services.

Commonly Available Services

Type of Service Approximate Data Rates

Dialed Circuit ServicesVoice-grade 28.8 Kbps to 56 Kbps

WATS 28.8 Kbps to 56 Kbps

Dedicated Circuit ServicesVoice-grade 28.8 Kbps to 56 Kbps

Wideband analog 288 Kbps to 274 Mbps

T-carrier 64 Kbps to 274 Mbps

SONET 52 Mbps to 622 Mbps

Commonly Available Services

Type of Service Approximate Data RatesCircuit Switched Services

Narrowband ISDN 128 Kbps to 1.5 MbpsBroadband ISDN 155 Mbps to 622

Mbps

Packet-Switched servicesX.25 56 Kbps to 2 MbpsFrame relay 56 Kbps to 45 MbpsATM 1.5 Mbps to 622 MbpsSMDS 56 Kbps to 45 Mbps

Key Issues in Selecting a Carrier

• Vendor capabilities

• Capacity

• Flexibility

• Control

• Reliability

Value Added Networks and Virtual Private

Networks

• Several companies offer value added networks (VANs) that are alternatives to building networks by leasing circuits from common carriers. VANs provide additional services over and above those provided by common carriers.

• A new type of VAN, called a virtual private network (VPN), or software defined networks, provide circuits that run over the Internet but appear to the user to be private networks.

Value Added Networks and Virtual Private Networks

• The primary advantage of the VPN is low cost.

• There are two important disadvantages of VPNs:– Traffic on the Internet is unpredictable.– There are several competing standards for Internet-

based VPN, so not all vendor’s equipment and services are compatible.

Why Connect Networks?

Enterprise Servers

Serves Entire CorporationDivisions/departmentsWeb/e-commerceExternal/remote access

RequirementsScalabilityReliability (24x7 operation)Security

Server Clustering

Several servers act as oneScalabilityRedundancy

Load Balancing

Servers are independent machinesRouter or other device assigns

requests to servers based on loads

Scalability andreliability

Geographic Decentralization

Client hosts use nearest server hostReduces transmission time and network load

Copying of all information (replication) or of only some information (caching)

NearestHost

Replicationor Caching

Main Host

Client

Network Management System

Network Management ConsoleIdeal: manage whole network from one

computer (NOC)Realistically: several NMCs manage different

parts of the network

LAN

LANNetwork ManagementConsole


Network Management SoftwareProbes monitor conditionsGraphical depiction of network

Management Information Base (MIB)Stores information about the networkRelational database MIB

NetworkManagementProgram


Managed Devices

Client PCs, servers, printers, switches, carrier transmission lines (T1s)

Must communicate with network management program

NMP

Managed Devices


Network Management AgentIn each managed deviceCommunicates with network management

program on behalf of the deviceHas local MIB about that managed deviceHas an impact on performance

NMA

NMP MIB


RMON Probes (TCP/IP)Remote monitoring probesRMON probes sit on LANsCollect local data on LAN trafficRMON agent gives the data to the NMP

NMP LAN

RMONProbe

Network Management Standards

Govern interactions between network management program and network management agentNMP sends requests (commands)NMA sends responsesNMA can issue alarms on own authority if

problems occur

NMA

NMP MIB

Request

ResponseAlarm


SNMP

Simple Network Management Protocol

From the IETF (TCP/IP)

Most widely used

Simplicity means low cost

Simplicity means limited in functionality

Primary focus is fault management but improving

SNMP

CarrierNetwork


Carrier Network Management Standards

Carriers have their own systems

Beginning to open their network management agents to customer queries

NMA

NMP MIB

Request

ResponseAlarm

Electronic Mail Messages

• Header– Searchable fields

• Body– Free-form text

– Moving beyond text

• Signature– Information about the sender, sent with every message

– Like letterhead in corporate letters

To: xxxxxRe: xxxxx---------xxxxx

Pat Lee, x4578

Computer ConferencingComputer Conferencing Program

Bulletin Board

Participant

MessageBeing

Submitted

MessageBeing

Posted

MessageBeing Read

Laterby Other

ParticipantParticipant

Computer Conferencing

• E-mail designed for one-to-one or one-to-few communication

• Computer conferencing is designed for group communication

• New messages are posted, can be read by others• Special tools for posting, reading• Administrative tools for conference manager

– Participant lists, voting, etc.

Electronic Mail System

Sender’s PC

ElectronicMailHost

ElectronicMailHost

ElectronicMailHost

Receiver’s PC

Message

Sending Outgoing Mail

• Simple Mail Transfer Protocol (SMTP)– TCP/IP host-host mail standard– Simple but effective– Becoming dominant– For PC to send to mail host– For one mail host to send to another

SMTPSMTP

Message Structure Standard

• Structure of Messages must be Standardized– To allow different systems to read the messages

– Format for header, body

• RFC 822– Dominant Internet standard

– Text-only headers and body

– Keyboard text only: Nothing for non-English languages


• Structure of Messages must be Standardized– To allow different systems to read the messages– Format for header, body

• MIME– Multipurpose Internet Mail Extensions– Allows multimedia headers, body– Not widely used for headers and bodies


• Structure of Messages must be Standardized– To allow different systems to read the messages– Format for header, body

• HTML– Rich text bodies– Graphics in bodies– Links to webpages– Implemented differently by different vendors– Looks terrible on incompatible systems

Electronic Document Management (EDM)

• Documents are widely used in organizations– Already created electronically– Problems in retrieval

• Organized storage and retrieval– Catalog entries with specific searchable fields– Full-text retrieval

• Management– Retention strategy

Lotus/IBM Notes

• Prototypical Groupware Tool– Set of highly integrated tools

• Word processing and other document-creation tools

• E-mail and Computer Conferencing• Retrieval tools• Coordination tools

– Plans timing of events– Tracks timing of events

Lotus/IBM Notes

• Application Development Tools– Very-high-level programming language– Create proposal tracking, other tools– Can also buy pre-made applications– Perhaps Notes’ greatest strength

Replication in Notes

• Files created on local Notes servers– Replicated to other Notes servers, often

overnight– Does not require replication speed of database

Notes Server BNotes Server A

Notes Server C

Replication ofNew and Modified Files

Room-to-Room Videoconferencing

Camera and Monitors

Codec

Roll-About System

Codec

Conference Room 1

Conference Room 2

CircuitTypically 56 kbps to T1/E1


• Monitors• Cameras• Controller for Meeting Leaders• Microphones

– Acoustics is the most difficult part to get right– Howl-around (screech) from feedback– Unnatural sounds– Requires careful room preparation


• CODECs: Translation

– Video signals from cameras are analog

– CODEC converts to digital for transmission on a digital line


• CODECs: Compression

– Videoconferencing codecs also compress the digital signal

– Lose quality at high compression: grainy pictures, jerky motion, buzzy sound

– Good at T1

– Usable at 64 kbps

Multipoint Conferencing Units

(MCUs)• Switch between any two rooms

• Multisite conferences

Site B(Not Involved)

Site B(Not Involved)

Site C(In Conference)

Site C(In Conference)

Site D(In Conference

Site D(In Conference

CommunicationLink

MCUMCU

Site A(In Conference)

Site A(In Conference)

Desktop Conferencing• Document Conferencing

– PC users can both see the document

– In whiteboard conferencing, can mark it up (write, draw on it): Only an image

User A User B

TransmissionLine

www.jroom.com

http://www.jroom.com/




– In program sharing, run a program and jointly edit a document

– One executes the program on their machine

– Both keyboards and mice are liveUser A User B

TransmissionLine


– In file transfer, one can send a file to another.

– Often, the finished document

User A User B

Desktop Conferencing• Desktop Videoconferencing

– Can see and hear each other

– ISDN is the slowest line for good desktop video

– Often used with document conferencing

User A User B

TransmissionLine

Videoconferencing Standards

• Proprietary Standards– Before, each vendor had their own proprietary

standards

• H.320

– Now, most follow the ITU-T’s H.320 standards

– Really a family of standards

– Members are still being added for new needs, such as desktop videoconferencing


• H.320 Family of Standards

– H.320: ISDN lines and leased lines and other circuit-switched lines

– H.323: LANs, IP networks, and other best-effort services

– H.324: Ordinary telephone lines


• T.120

– For document conferencing

– Supports markup

– Does not support program sharing

Electronic Meeting Room (EMR)

• The Need

– Managers spend 25% of the day in conference rooms

– When they get there, they have to leave their computer technology behind

– Meetings have problems that need to be addresses: lasting too long, some people being afraid to speak, etc.

An Electronic Meeting Room

(EMR)

Participant PCs Public Screenwith Projection

System

ModeratorPC

Serverwith Software

LAN


• Participant PCs– Each has their own PC

• Moderator PC– To control the meeting software

• Public Screen– To display shared information– Requires a projector

• LAN to link everyone together


• Server software– Toolbox of programs for various agenda items– Integrated: output of one passes to others

• Electronic Brainstorming– Generating ideas– Proven to be much faster than face-to-face

brainstorming– May generate more comments from low-level people

too intimidated to talk face-to-face


• Commenting on specific alternatives• Voting

– Can be anonymous

– Can analyze pattern of votes to indicate areas of disagreements

• Presentation of Reports– PowerPoint, etc.

• People have straight face-to-face discussions too

Adopting Groupware

• E-Mail Adoption is Easy– Individuals make the adoption decision

– Works if only some adopt

– Works even if use is mandated but some fail to adopt

• Groupware Adoption can be Difficult– Focus on the needs of groups rather than individuals

– Often, unless everybody in a group adopts, fails

Production Systems

• High-Volume Clerical Applications

• Imaging Systems– Convert many documents to images– Checks in banks, for instance

• Electronic Document Management (EDM)– Store large volumes of electronic documents– Powerful search and retrieval tools

Home Depot

Nortel Network

Hacienda-La Puente School District

Happy Halloween

Wide Area Networking Chapter 7 Halloween Version 1.0.

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