QMCS 370 - Class Today

1
QMCS 370 - Class Today

• Homework
• Packet notes/recap
• TCP/IP
• Packet Formats
• Options

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Packet notes

• Elements
• Error detection
• ACKs (what about NAKs?)
• Flow control
• Packet Duplication
• Practical Objectives
• Error detection not always error recovery
• Flow control
• Efficiency
• Addressability

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TCP/IP in Practice

• Stacking for Routers
• Role of IP vs TCP vs UDP
• IP talks between hosts
• TCP/UDP connects IP to processes

4
Router Stacking

• Which layers are in endpoint hosts?
• Which stack layers are in routers?

5
Probably Roger Needham

• Any problem in computer science can be solved by
  adding another layer of indirection
• The rationale behind the IP layer

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IP Internet Protocol

• Applications dont use IP directly
• IP talks between hosts, not processes
• IP only has host-related addressing
• Key point what do addresses mean at a given
  level of the protocol stack?
• Missing information must be filled in by other
  layers

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UDP User Datagram Protocol

• Easy protocol just carries the port number
• NO guarantee of delivery
• NO guarantee of delivery in order
• Packet duplication is possible

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TCP

• The reliable protocol
• Flow control Error detection and correction
• Assembles data into a stream of bits and bytes
• Packets are placed in order of transmission
• Setting up a connection
• SYN
• SYN-ACK
• ACK
• Reliability and flow control
• Sequence Numbers
• Sliding Window
• Ending a connection
• FIN in each direction

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Packet Contents/Formats

• Link layer (generic)
• IP V4
• IP V6
• UDP
• TCP

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Interesting TCP/IP Options

• IP
• experiments
• traceroute
• security
• address extensions
• source routing
• multicast

• TCP
• experiments
• echo (now obsolete)
• time stamping
• alternate checksums
• record boundaries
• compression

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