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1. multiplexed utilization of• ordered set of goalsInternet Protocols Design Philosophy
existing networks
• not all goals have been met8. account for resources7. low effort to attach a host6. cost effective5. permit distributed management of resources4. accommodate a variety of network types3. support multiple types of communications service 2. survivability in the face of failure
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Packets!
– contains destination and sourcepackets– handled independently of preceding or following– self contained• packet (a.k.a. datagram)more efficient switching method– Kleinrock’s work showed packet switching to be a• basic decision: use packets not circuits
internetwork address
- (^) reliability (where needed) done at higher levels – (^) net may drop, duplicate, or deliver out of order– (^) no delivery guarantees – may contain processing hints (e.g. QoS tag) Dest Addr (^) Src Addr (^) payload ocsity.co
Review: Technology Advances
10sUsers/Machine 464
16 Address Bits 15,000155Mb/s
9600b/sNetwork B/W 5,00050GB
10MBDisk Capacity 2,000256MB
128KBDRAM Capacity 20,000$
$100K$/MIPS
1,000^1000
1 MIPS
Factor^1999
communities• (Almost) free machines, really expensive humans, and• Cheap machines, expensive humans• Expensive machines, cheap humans 1981
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The Network
is the Computer
mainframe mini – “Smaller, cheaper, more numerous”•^ Relentless decentralization
- More computers (^) (^) more data communication (^) PC (^) (^) palms (^) (^) ubiquitous/embedded
- (^) Human (^) communication– Parallel computing– Sharing of data– Efficient sharing of machine resources•^ (Shifting) reasons computers talk to each other
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• Can’t build a network by requiring• (b) multiple-access: ethernet, FDDI• (a) point-to-point: ATMDirectly Connected
all nodes to be
nodes that can attach to a shared mediaterms of the number of wires or the number ofdirectly connected to each other: scalability in(b) (a)
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• Nice property: scalable aggregate throughputswitches• Hosts vs. “the network,” which is made of• Circuit switching vs. packet switchinghosts switches Switched Network
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get to it?•^ Routing: given a destination address, how do you•^ How do you name and address hosts?•^ How do hosts share links?gateway Some Hard Questions
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for example “128.36.229.231•^ For convenience, each host also has a human-friendly host name:everything•^ IP addresses are the universal IDs that are used to name – Consists of a network address and a host IDas 128.36.229.231– Written down in a “dot notation” for “ease” of readings such•^ An IP address is:– Ran out of numbers and there are schemes to extend– We will tell you what “IP” is later•^ Each machine is addressed by a 32-bit integer: IP addressIP addresses and Hosts Names
” is “concave.cs.yale.edu”
- (^) Question: how do you translate names into IP addresses?
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administrative controlunder a singleone or more name servers• Each zone corresponds toCyndra^ netra hierarchy into zonesMath^ CS^ Physics• Divide up the nameCisco... yahooYale^ MIT^ edu^ com^ gov^ mil DNS Zones and Name Servers
(^) org (^) net (^) uk ocsity.co fr
• Most name servers also perform lookup cachingto other name servers• Name servers reply with answers or forward request• Clients send queries to name serversCS name server EE name serverYale name serverRoot name serverHierarchy of Name Servers
ocsity.co Cisco name server
abstractions such as transformation of different data formats^ •^ Top three layers are not well-defined, all have to do with application leveland reliability, at the unit of messages^ •^ Transport: provides process-to-process semantics such as in-order-deliveryhandles hop-to-hop routing, at the unit of packets •^ Network:^ •^ Data link: provides “ frames ” abstraction•^ Physical: handles bits PhysicalData linkNetworkTransportSessionPresentationApplicationOSI Architecture
PhysicalData linkNetworkTransportSessionPresentationApplication
PhysicalPhysicalData linkData linkNetworkNetworkwithin the networkOne or more of the nodes ocsity.co
- (^) Not strictly layered, “hour-glass shape,” implementation-centric• (^) On top of those are the application protocols• (^) UDP (User Datagram Protocol): unreliable messages (maybe faster)• (^) TCP (transmission Control Protocol): reliable, in-order streamconnection, defines common methods of exchanging packets• (^) IP (Internet Protocol): focal point of the architecture, provides host-to-hostadaptors and OS device drivers• (^) Lowest level: hardware specific, implemented by a combination of network• (^) Protocols: abstract objects that makeup a layerTCPFTP (^) HTTPReality: the “Internet” Architecture
ocsity.co FDDI^ ATMethernet^ IP UDPNFS^ NV
