Wide Area Networks

CS 363

DePaul University

Questions on Final?

Group Evaluations

• 25 points per group member, including yourself

• Distribute total number of points across group members as you see fit

• Hand in now

Wide Area Networks

• Defined=>

• Transmission strategies:– PSTN– Leased circuits– Fiber– Microwave/Satellite– Wireless– Internet

Metropolitan Area Networks

WANS

• Enterprise Networks– DePaul’s network

• Global Networks– The Internet

PSTN Connectivity

• Circuits come in from CO

• Connect at Demarc in building

• Provide following services:

PSTN Services

• Switched 56• X.25• T1• T3• Frame Relay• SMDS• ISDN• ATM

PPP

• multiprotocol

• negotiates and registers IP assignments on dial-up

• negotiates header compression

• relatively good security

SLIP

• only TCP/IP

• requires manual IP registration

• no security

• not really faster than PPP

Problem:

• You are responsible for setting up some remote workstations and a server that will be connected to the Internet. The workstations will be connecting to the server using standard telephone ines. You know that SLIP and PPP are useful protcols for your situation. Your boss comes in and says, “I think SLIP is the protocol we should start using here. What do you think?” What protocol would you recommend? List three advantages to the recommended protocol.

Circuit Switching

• like voice call on PSTN

• dedicated channel-always up

• no channel access delay

• inefficient use of transmission media

• requires more bandwidth

• connection delays

Message Switching

• no dedicated path

• messages contain source and destination info

• also referred to as store-and-forward networking

• ex: e-mail

Message Switching, cont.

• Pros: – efficient traffic management through prioritization– reduction of network traffic congestion– efficient use of data channels– asychronous communication across time zones

• Cons:– delays caused by store-n-forward– unsuitable for real-time applications

Packet Switching

• Advantages of circuit and message switching without any of the disadvantages

• Independent routing of packets– bandwidth/load balancing– dynamic rerouting

• Packet size restricted for efficiency and speed

Datagram Packet Switching

• post-office analogy

Virtual Circuit Packet Switching

• Virtual circuit (logical connection)

• All packets between the same start and end point use same logical connection (route)

• Used primarily for real-time, connection-oriented services like video and audio

Planning for Packet Switching

• Pros– PS improves use of network bandwidth– PS has shorter transmission delays than circuit

switching because of small packet size

• RAM vs. Hard drive=>PS requires more RAM; MS requires more hard drive space

• Processor=>PS requires more processing power than MS

• Lost Packets=>sequencing

Connections

• Dial-up

• Dedicated Analog

Connections, Cont.

• Digital– T-carrier– Switched 56

X.25 and Frame Relay

ATM

ISDN

FDDI

SONET