class30 ppt Protocol layering and encapsulation Internetworking with hubs bridges and routers The Internet Protocol IP The global Internet Topics May 1 2001 Internetworking The course that gives CMU its Zip 15 213 class30 ppt IDE disk controller Memory disk Interrupt controller Processor disk 2 Modem Printer Network Network adapter Parallel port controller CS 213 S 01 Display Video adapter Serial port controller Mouse cdrom SCSI bus SCSI controller Local IO Bus Keyboard controller Keyboard Typical computer system class30 ppt network adapter interface card protocol stack OS code link hardware software host 3 CS 213 S 01 Interconnect wires repeaters bridges and routers link hardware hardware link software software host Generic network 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 class30 ppt 4 CS 213 S 01 Crucial idea protocols leverage off of the capabilities of other protocols A protocol defines the format of packets and the rules for communicating them across the network Different protocols provide different levels of service Protocols 5 hardware Network interface ethernet Physical connection Reliable byte stream delivery processprocess CS 213 S 01 Transmission control protocol TCP Internet Protocol IP User datagram protocol UDP class30 ppt Unreliable best effort datagram delivery host host Unreliable best effort datagram delivery processprocess Protocols provide specialized services by relying on services provided by lowerlevel protocols i e they leverage lowerlevel services User application program FTP Telnet WWW email interface between user code and OS code Sockets interface Protocol layering data Ethernet frame IP datagram TCP segment header header header class30 ppt 6 Network data IP datagram TCP segment header header IP data TCP data TCP segment header OS code User code CS 213 S 01 Adapter Network interface Adapter OS adapter interface exception mechanism User Interface API Application program Encapsulation class30 ppt 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 Local area network LAN same room meters 300 MB s Cray T3E System area network SAN 7 CS 213 S 01 nationwide or worldwide 1000 s of kilometers telephone system 1 544 Mb s T1 carrier 44 736 Mb s T3 carrier Global Internet Wide area network WAN same city 10 s of kilometers 800 Mb s Gigabit Nectar Metropolitan area network MAN Basic network types class30 ppt 8 CS 213 S 01 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 Build a single network an interconnected set of networks or internetwork or internet out of a large collection of separate networks The internetworking idea Kahn 1972 class30 ppt 9 CS 213 S 01 Note internet refers to a general idea Internet refers to a particular implementation of that idea The global IP Internet 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 Challenges Internetworking challenges class30 ppt r r r r 10 CS 213 S 01 Repeaters also called hubs r in the figure directly transfer bits from their inputs to their outputs Internetworking with repeaters data link physical Host on network B data link physical Host on network A CS 213 S 01 network network 11 transport transport Repeater forwards bits application application class30 ppt 10Base T Telnet FTP HTTP email Internetworking with repeaters class30 ppt 12 CS 213 S 01 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 Cons Transparency LANS can be connected without any awareness from the hosts Useful for serving multiple machines in an office from one ethernet outlet Pros Internetworking with repeaters Pros and cons class30 ppt b 13 CS 213 S 01 Selectively transfer ethernet frames from their inputs to their outputs b b Bridges b In the figure maintain a cache of hosts on their input segments b Internetworking with bridges Bridge forwards ethernet frames 14 CS 213 S 01 Host on network B Host on network A class30 ppt physical physical 10Base T network network data link transport transport data link application application CSMA CD Telnet FTP HTTP email Internetworking with bridges class30 ppt 15 CS 213 S 01 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 Cons Transparency LANS can be connected without any awareness from the hosts popular solution for campus size networks Pros Internetworking with bridges Pros and cons class30 ppt host host 16 internet CS 213 S 01 host host 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 Internetworking with routers adapter adapter Ethernet adapter C adapter X network 2 ECE adapter Y class30 ppt 17 CS 213 S 01 ATM adapter Z Question How to present the illusion of one network network 1 SCS B A We start with two separate unconnected computer networks subnets which are at different locations and possibly built by different vendors Building an internet adapter adapter class30 ppt network 1 SCS B A adapter 18 adapter C router adapter X adapter Z CS 213 S 01 network 2 ECE adapter Y Next we physically connect one of the computers called a router in this case computer C to each of the networks Building an internet cont B adapter A adapter network 1 SCS 128 2 250 2 128 2 250 1 class30 ppt IP addresses 19 adapter adapter C router 128 2 250 0 128 2 80 0 adapter X adapter Y 128 2 80 2 adapter Z 128 2 80 3 CS 213 S 01 network 2 ECE 128 2 80 1 Finally we run a software implementation of the Internet Protocol IP
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