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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
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