CSE 588 - Spring 2002 - Transcription

University of Washington Department of Computer Science & Engineering

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*	Characteristics of a Network:
	Delivers data
	Heterogeneous in performance (speed, latency, loss rate)
	Wired/wireless
	Bus/switched
	Circuit/packet switched
	Packets may be:
		- corrupted
		- of limited size
		- reordered
		- dropped
		- lost
	May support:
		- real-time
		- multicast
		- guaranteed delivery
	Addressing mechanism


*	Level at which functionality should be placed
	Corrupt packet detection:
		Hosts
		And maybe routers/networks, especially if links are very
unreliable.

		Reasons for performing CRC on hosts:
		May not trust the network
		Need stronger error checking
		Routers can corrupt data

		Reasons for performing CRC in networks:
		Debuggability
		Speed/Performance
		Routing info can be corrupted (in which case packet is
discarded)
		Cost of ownership

	Retransmission:
		Hosts
		Network if needed (links are unreliable, for instance).

	Routine path of packets through the Internet:
		Local network--Host
		Remote--Usually the network/Internet, though source
routing may be an option.

	Packet Ordering:	
		Hosts

	Address assignment:
		Hosts

	Congestion Control, Resource Allocation:
		Network/Internet

	Flow Control:
		Hosts (in TCP)

	Resource reservation (network bandwidth, buffer, latency):
		Host asks, Network/Internet provide

	Mobile Hosts:
		Hosts, maybe Internet.


*	Different layers to consider:
	Network
	Router
	Host--transport
	Host--application
	Border router
	Name Server
	"Middle" boxes (such as load balancers)
	Human

Department of Computer Science & Engineering
University of Washington
Box 352350
Seattle, WA 98195-2350
(206) 543-1695 voice, (206) 543-2969 FAX
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