Download Network

WAN
Wide Area Networks
Review:
Capacity Allocation: phone system
Bandwidth Allocation: data systems
WAN Access
Network
WAN
Intercommunication over public networks
Typically slower and more expensive than
backbone or LAN
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
Wan Resources
Bandwidth
Access
Technology
Bandwidth
Total transport capacity
North American Digital
Hierarchy
T0
T1
T2
T3
T4
56 + 8 Kbps
1.544 Mbps
6.312 Mbps
44.736 Mbps
274.176 Mbps
64 Kbps
24xT0
96xT0
672xT0
4032xT0
Multiplexing and Wide
Area Communication
MUX
VOICE STREAM
WAN
LINK
Multiplexing and Wide
Area Communication
MUX
DATA STREAM A
WAN
LINK
DATA STREAM B
Node Functions
Message forwarding
Error detection and correction
Traffic management
CSU/DSU:
Digital Service Unit/Channel Service Unit
Access
Methods of controlling the
WAN traffic
Traffic Management
Access Control
Buffering
Packet Discard
Circuits vs Packets
Circuits
Switched
path
setup and teardown
Permanent
Packets
datagram
Switches
Cut-through switch
Store-and-forward switch
Switches (Store & Forward)
From A
H
Input Buffer
Input Buffer
Input Buffer
Processor
Output Buffer H
Output Buffer H
Table of
Addresses
To D
Routers
From A
From B
Input Buffer
Input Buffer
Input Buffer
Processor
Output Buffer
Output Buffer
Table of
Addresses
To C
To D
Router Functions
Layer 1, 2, and 3 functions
Packet passing
Error correction
Message routing
Including circuit definition
Protocol translation
Firewall functions
Circuit Logic
Source
Destination
Setup
Message & ACK’s
Teardown
Datagram Logic
Packet n
Packet 2
Packet 1
Technologies
Common WAN
technologies.
X.25
Older protocol for using packet switched
data
Operates up to 56.6 Kbps
Switched virtual circuit
PAD
TCP/IP
Best Effort
Addressing
IPv4 vs IPv6
Frame and Header
TCP/IP
OSI Layer
User
File
Layers
Transfer
(FTP)
Internet Protocols
Simple TELNET Routing
Information
Mail
(RIP)
Transfer
(SMTP)
Simple
Network
Management (SNMP)
User Datagram (UDP)l
Transport Transmission Control
(TCP)
Internet Internet Control Message
Address
Network
Protocol (ICMP)
Resolution
(IP)
(ARP)
Ethernet, Token Ring, etc.
Data Link
Twisted Pair, Fiber, Coax, Wireless
Physical
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
1. Physical
Network access
Datagram Routing
Best effort
Error Control
Traffic 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)
Offset
Location of current fragment in
message
Number of frame to be acknowledged
next
Number of 32 bit words in header
Reserved
Not used
Acknowledgement Number (32 bits)
Flags
Window
Checksum (16 bits)
Urgent Pointer
Number of frames sender can accept
without buffer overflow
IP Addressing
32 bits (4 bytes)
Network address +
Host address
Classes
A:
B:
C:
126 nets, 3 bytes of client addresses
2 bytes of client addresses (e.g. OU)
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 size
Virtual circuit (usually permanent)
Multiple data rates
Committed Data Rate
Peak data rate (discard eligible)
ATM
Generic Flow
Control
Virtual Path
Identifier
Virtual Channel
Identifier
Payload Type
Identifier
Cell Loss
Priority
Header Error
Correction
Data
Virtual Circuit
(not used)
4 bit
1 byte
2 bytes
3 bit
1 = discard
eligible
1 bit
48 bytes
ATM Traffic Classes
Type
Type
Type
Type
Type
1 Constant Bit Rate
2 Variable Bit Rate
3
4
5 IP Traffic
ATM
SNA
Connection Oriented
Centrally Managed
WAN Costs
Circuit Charges
Committed Bandwidth
Peak Bandwidth
Discard Priority
Latency
WAN