WAN

Wide Area Networks

Review:

Capacity Allocation: phone systemBandwidth Allocation: data systems

WAN Access

Network

WAN

Intercommunication over public networks

Typically slower and more expensive than backbone or LAN

Connections

Connection Oriented CircuitsHave a mechanism to confirm delivery and

assure that packets are processed in orderCircuitsPacket Assembly Devices

Non-Connection Oriented Circuits Deliver packets individually without

regard to message sequence

Wan Resources

BandwidthAccessTechnology

Bandwidth

Total transport capacity

North American Digital Hierarchy

T0 56 + 8 Kbps 64 KbpsT1 1.544 Mbps 24xT0T2 6.312 Mbps 96xT0T3 44.736 Mbps 672xT0T4 274.176 Mbps

4032xT0

Multiplexing and Wide Area Communication

VOICE STREAM

WANLINK

MUX

Multiplexing and Wide Area Communication

DATA STREAM A

WANLINK

DATA STREAM B

MUX

Node Functions

Message forwardingError detection and correctionTraffic management

CSU/DSU:Digital Service Unit/Channel Service Unit

Access

Methods of controlling the WAN traffic

Traffic Management

Access ControlBufferingPacket Discard

Circuits vs Packets

CircuitsSwitched

pathsetup and teardown

Permanent

Packetsdatagram

Switches

Cut-through switchStore-and-forward switch

Switches (Store & Forward)

Input BufferProces-

sor

Output Buffer

H

To D

Table ofAddresses

Input Buffer

Input BufferOutput Buffer

From A

H

H

Routers

Input Buffer

Proces- sor

Output Buffer

From A From B

To C To D

Table ofAddresses

Input Buffer

Input BufferOutput Buffer

Router Functions

Layer 1, 2, and 3 functions Packet passing

Error correction

Message routingIncluding circuit definition

Protocol translation Firewall functions

Circuit Logic

Source Destination

Setup

Message & ACK’s

Teardown

Datagram Logic

Packet n Packet 1Packet 2

Technologies

Common WAN technologies.

X.25

Older protocol for using packet switched data

Operates up to 56.6 KbpsSwitched virtual circuitPAD

TCP/IP

Best EffortAddressingIPv4 vs IPv6Frame and Header

TCP/IP

OSI Layer Internet ProtocolsUserLayers

FileTrans-fer(FTP)

SimpleMailTransfer(SMTP)

TELNET RoutingInformation(RIP)

SimpleNetworkManage-ment (SNMP)

Transport Transmission Control(TCP)

User Datagram (UDP)l

Network AddressResolution(ARP)

InternetProtocol(IP)

Internet Control Message(ICMP)

Data Link Ethernet, Token Ring, etc.

Physical Twisted Pair, Fiber, Coax, Wireless

OSI and TCP/IP

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data link

1. Physical

OSI TCP/IP

Process & Application

Host to host (TCP)

Internet (IP)

Network access

Datagram Routing

Best effortError ControlTraffic Management

IP Header (Layer 3)Version =4

Header length In bytes

Type of service Characteristic of route

Total length Length of the packet

Source port identifier Port identifier for host process

Fragment offset Position (8 byte units) from message start

Time to live Allowed seconds

Protocol ID of Transport layer protocol (TCP = 6)

Header checksum

Source address 32 bits

Destination address 32 bits

Options + Padding

Data

TCP Header

Source port (16 bits) Ports of communicating processes

Destination port (16 bits) “

Sequence Number (32 bits) Location of current fragment inmessage

Acknowledgement Number (32 bits) Number of frame to be acknowledgednext

Offset Number of 32 bit words in header

Reserved Not used

Flags

Window Number of frames sender can acceptwithout buffer overflow

Checksum (16 bits)

Urgent Pointer

IP Addressing

32 bits (4 bytes) Network address + Host address

Classes A: 126 nets, 3 bytes of client addresses B: 2 bytes of client addresses (e.g. OU) C: 1 byte of client addresses (256)

ISDN

Frame Relay

Frames relayed without reconstruction

End to end error control using CRC error detection at layer 3 level

Variable packet sizeVirtual circuit (usually permanent)Multiple data rates

Committed Data Rate Peak data rate (discard eligible)

ATM

Generic FlowControl

Virtual Circuit(not used)

4 bit

Virtual PathIdentifier

1 byte

Virtual ChannelIdentifier

2 bytes

Payload TypeIdentifier

3 bit

Cell LossPriority

1 = discardeligible

1 bit

Header ErrorCorrectionData 48 bytes

ATM Traffic Classes

Type 1 Constant Bit RateType 2 Variable Bit RateType 3Type 4Type 5 IP Traffic

ATM

SNA

Connection OrientedCentrally Managed

WAN Costs

Circuit ChargesCommitted BandwidthPeak BandwidthDiscard PriorityLatency

WAN