• OSI layer 4
• Between network (below) and session (above)
• Lowest of the end-to-end layers
• Can provide either connection-oriented or connectionless service
• Will study TCP and UDP in more detail
  

• End-to-end delivery
• Depends on network layer to operate over internetwork
• May need to break message into packets (segmentation)
• Quality of Service negotiation
• also known as QOS
• transmission parameter values specified in request
• can be negotiated between sender and receiver
• Connection control
• establish connection
• maintain connection
• terminate connection
• three-way handshake (request, confirm, confirm ack)
• two-army problem
• Addressing
• network layer addresses machine
• must be able to address a running application (process)
• Reliable delivery
• segmentation if necessary
• no lost segments
• no duplicate segments delivered
• segments correctly reassembled (sequence #s)
• end-to-end error detection and correction
• network layer may cause error not caught at datalink layer
• correction means retransmission
• Flow control
• end-to-end flow control
• typically use sliding window
• window size can vary to accommodate differences in xmit rates and traffic
  (receiver can lengthen or shorten as appropriate)
• window sizes can be negotiated
• Congestion control
• related to but distinct from flow control
• refers to delays incurred in internet
• possibly reduce delays by using smaller segments
• segment sizes can be negotiated
• Multiplexing
• transmit segments from multiple streams via same virtual circuit
• use multiple virtual circuits to transmit one segment streams

Related Home Pages: notes | CSC 465 | Peter Sanderson | Computer Science | SMSU

Peter Sanderson ( pete@csc.smsu.edu )