WAN

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WAN

• Wide Area Networks

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Review

• Capacity Allocation phone system
• Bandwidth Allocation data systems

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WAN Access
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WAN

• Intercommunication over public networks
• Typically slower and more expensive than backbone
  or LAN

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Connections

• Connection Oriented Circuits
• Have a mechanism to confirm delivery and assure
  that packets are processed in order
• Circuits
• Packet Assembly Devices
• Non-Connection Oriented Circuits
• Deliver packets individually without regard to
  message sequence

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Wan Resources

• Bandwidth
• Access
• Technology

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Bandwidth

• Total transport capacity

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North American Digital Hierarchy

• T0 56 8 Kbps 64 Kbps
• T1 1.544 Mbps 24xT0
• T2 6.312 Mbps 96xT0
• T3 44.736 Mbps 672xT0
• T4 274.176 Mbps 4032xT0

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Multiplexing and Wide Area Communication
MUX
VOICE STREAM
WAN LINK
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Multiplexing and Wide Area Communication
MUX
DATA STREAM A
DATA STREAM B
WAN LINK
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Node Functions

• Message forwarding
• Error detection and correction
• Traffic management

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CSU/DSUDigital Service Unit/Channel Service Unit
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Access

• Methods of controlling the WAN traffic

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Traffic Management

• Access Control
• Buffering
• Packet Discard

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Circuits vs Packets

• Circuits
• Switched
• path
• setup and teardown
• Permanent
• Packets
• datagram

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Switches

• Cut-through switch
• Store-and-forward switch

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Switches (Store Forward)
From A
H
Input Buffer
Proces- sor
H
Output Buffer
Input Buffer
Output Buffer
H
Input Buffer
Table of Addresses
To D
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Routers
From A
From B
Input Buffer
Output Buffer
Proces- sor
Input Buffer
Output Buffer
Input Buffer
Table of Addresses
To C
To D
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Router Functions

• Layer 1, 2, and 3 functions
• Packet passing
• Error correction
• Message routing
• Including circuit definition
• Protocol translation
• Firewall functions

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Circuit Logic
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Datagram Logic
Packet n
Packet 1
Packet 2
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Technologies

• Common WAN technologies.

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X.25

• Older protocol for using packet switched data
• Operates up to 56.6 Kbps
• Switched virtual circuit
• PAD

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TCP/IP

• Best Effort
• Addressing
• IPv4 vs IPv6
• Frame and Header

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TCP/IP
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OSI and TCP/IP
OSI
TCP/IP
7. Application
6. Presentation
Process Application
5. Session
4. Transport
Host to host (TCP)
3. Network
Internet (IP)
2. Data link
Network access
1. Physical
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Datagram Routing

• Best effort
• Error Control
• Traffic Management

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IP Header (Layer 3)
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TCP Header
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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)

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ISDN
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Frame Relay

• Frames relayed without reconstruction
• End to end error control using CRC error
  detection at layer 3 level
• Variable packet size
• Virtual circuit (usually permanent)
• Multiple data rates
• Committed Data Rate
• Peak data rate (discard eligible)

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ATM
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ATM Traffic Classes

• Type 1 Constant Bit Rate
• Type 2 Variable Bit Rate
• Type 3
• Type 4
• Type 5 IP Traffic

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ATM
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SNA

• Connection Oriented
• Centrally Managed

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WAN Costs

• Circuit Charges
• Committed Bandwidth
• Peak Bandwidth
• Discard Priority
• Latency

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WAN