Service models security historyvideo

Introduction	COMPSCI 453 Computer Networks Professor Jim Kurose College of Information and Computer Sciences

		Class textbook:
 Network core
		Down Approach (8th ed.)
		J.F. Kurose, K.W. Ross
		J.F. Kurose, K.W. Ross
		Pearson, 2020

 Security

 History

applications
protocols
hardware, software

	end-to-end transfer of person plus baggage

ticket (purchase) baggage (check) gates (load)
runway takeoff
airplane routing

airplane routing

	ticketing service	ticket (complain)

Why layering?

Approach to designing/discussing complex systems:

 application:supporting network applications • HTTP, IMAP, SMTP, DNS  transport:process-process data transfer • TCP, UDP  network:routing of datagrams from source to destination • IP, routing protocols  link:data transfer between neighboring network elements • Ethernet, 802.11 (WiFi), PPP	application transport

application	Application exchanges messages to implement some	application
application		application
	Ht
	Transport-layer protocol transfers M (e.g., reliably) from
	one process to another, using services of network layer


link	transport layer-layer header Ht to create a	link
link	transport-layer segment	link


		destination

Services, Layering and Encapsulation M

	Ht
transport	Transport-layer protocol transfers M (e.g., reliably) from
transport	one process to another, using services of network layer
network	Hn	Ht
network

link	 network-layer protocol encapsulates	link

transport-layer segment [Ht | M] with

source
			destination
		• Hn used by network layer protocol to
		implement its service

link	Hl
link	Link-layer protocol transfers datagram [Hn\| [Ht \|M] from

	 link-layer protocol encapsulates network
	datagram [Hn\| [Ht \|M], with link-layer header	destination
		destination

switch

destination	Hn Ht	M

Introduction	COMPSCI 453 Computer Networks Professor Jim Kurose College of Information and Computer Sciences

		Class textbook:

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