15 213 The course that gives CMU its Zip Internetworking May 1 2001 Topics class30 ppt Protocol layering and encapsulation Internetworking with hubs bridges and routers The Internet Protocol IP The global Internet Typical computer system Keyboard Keyboard Processor Processor Interrupt Interrupt controller controller Mouse Mouse Keyboard Keyboard controller controller Modem Modem Serial Serialport port controller controller Printer Printer Parallel Parallelport port controller controller Local IO Local IOBus Bus Memory Memory IDE IDEdisk disk controller controller disk SCSI SCSI controller controller SCSI SCSIbus bus disk class30 ppt 2 Video Video adapter adapter Network Network adapter adapter Display Display Network Network cdrom CS 213 S 01 Generic network host protocol stack network adapter interface card software software hardware hardware software software hardware hardware link host OS code software software hardware hardware link link Interconnect Interconnect wires wires repeaters repeaters bridges bridges and androuters routers class30 ppt 3 CS 213 S 01 Protocols A protocol defines the format of packets and the rules for communicating them across the network Different protocols provide different levels of service simple error correction ethernet uniform name space unreliable best effort datagrams host host IP reliable byte streams TCP unreliable best effort datagrams process process UDP multimedia data retrieval HTTP Crucial idea protocols leverage off of the capabilities of other protocols class30 ppt 4 CS 213 S 01 interface between user code and OS code Sockets interface Protocol layering Protocols provide specialized services by relying on services provided by lowerlevel protocols i e they leverage lowerlevel services User Userapplication applicationprogram program FTP FTP Telnet Telnet WWW WWW email email Unreliable best effort datagram delivery processprocess User Userdatagram datagramprotocol protocol UDP UDP Unreliable best effort datagram delivery host host class30 ppt Transmission Transmissioncontrol control protocol TCP protocol TCP Internet InternetProtocol Protocol IP IP Reliable byte stream delivery processprocess Network Networkinterface interface ethernet ethernet hardware hardware 5 Physical connection CS 213 S 01 Encapsulation Application program User code OS code data data TCP TCPsegment segment header header data data IP IPdatagram datagram TCP TCPsegment segment header header header header data data Ethernet Ethernetframe frame IP IPdatagram datagram TCP TCPsegment segment header header header header header header data data IP TCP User Interface API OS adapter interface exception mechanism Adapter Adapter Network interface Network class30 ppt 6 CS 213 S 01 Basic network types System area network SAN Metropolitan area network MAN Local area network LAN Wide area network WAN same city 10 s of kilometers 800 Mb s Gigabit Nectar same room meters 300 MB s Cray T3E nationwide or worldwide 1000 s of kilometers telephone system 1 544 Mb s T1 carrier 44 736 Mb s T3 carrier Global Internet same bldg or campus kilometers 10 Mb sEthernet 100 Mb s Fast Ethernet 100 Mb s FDDI 150 Mb s OC 3 ATM 622 Mb s OC 12 ATM class30 ppt 7 CS 213 S 01 The internetworking idea Kahn 1972 Build a single network an interconnected set of networks or internetwork or internet out of a large collection of separate networks Each network must stand on its own with no internal changes allowed to connect to the internet Communications should be on a best effort basis black boxes later called routers should be used to connect the networks No global control at the operations level class30 ppt 8 CS 213 S 01 Internetworking challenges Challenges heterogeneity lots of different kinds of networks Ethernet FDDI ATM wireless point to point how to unify this hodgepodge scale how to provide uniques names for potentially billions of nodes naming how to find all these nodes forwarding and routing Note internet refers to a general idea Internet refers to a particular implementation of that idea The global IP Internet class30 ppt 9 CS 213 S 01 Internetworking with repeaters r Repeaters also called hubs r in the figure directly transfer bits from their inputs to their outputs r r r class30 ppt 10 CS 213 S 01 Internetworking with repeaters Telnet FTP HTTP email 10Base T application application transport transport network network data link data link physical physical Host on network A class30 ppt Repeater forwards bits 11 Host on network B CS 213 S 01 Internetworking with repeaters Pros and cons Pros Transparency LANS can be connected without any awareness from the hosts Useful for serving multiple machines in an office from one ethernet outlet Cons Not scalable ethernet standard allows only 4 repeaters more than 4 would introduce delays that would break contention detection No heterogeneity Networks connected with repeaters must have identical electrical properties class30 ppt 12 CS 213 S 01 Internetworking with bridges b Bridges b In the figure maintain a cache of hosts on their input segments b Selectively transfer ethernet frames from their inputs to their outputs b b class30 ppt 13 CS 213 S 01 Internetworking with bridges Telnet FTP HTTP email application application transport transport network network CSMA CD data link data link 10Base T physical physical Host on network A class30 ppt Bridge forwards ethernet frames 14 Host on network B CS 213 S 01 Pros Internetworking with bridges Pros and cons Transparency LANS can be connected without any awareness from the hosts popular solution for campus size networks Cons Transparency can be misleading looks like a single Ethernet segment but really isn t packets can be dropped latencies vary Homogeneity can only support networks with identical frame headers e g Ethernet FDDI however can connect different speed Ethernets Scalability tens of networks only bridges forward all broadcast frames increased latency class30 ppt 15 CS 213 S 01 Internetworking with routers Def An internetwork internet for short is an arbitrary collection of physical networks interconnected by routers to provide some sort of host to host packet delivery service host host host host internet internet host host host host class30 ppt 16 CS 213 S 01 Building an internet We start with two separate unconnected computer networks subnets which are at different locations and possibly built by different vendors AA BB CC XX YY ZZ adapter adapter adapter adapter adapter adapter adapter adapter
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