Transcript Session 9 PowerPoint Slides

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:
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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
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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
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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
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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, connectionoriented 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