Reminder • Midterm next Tuesday • One routing question for chapter 5 • Understand distinction between link state, distance vector, SPF

cs233/333 Lecture 8

Midterm Review Cont. • Protocol hiearchies and reference models • Know the ISO and Arpanet reference models and have a good understanding of protocol layering from the viewpoint of design and implementation.

• Physical Layer • Transmission Media • Know basic properties of magnetic media, twisted pair, and fiber. cs233/333 Lecture 8

Midterm Review Cont. • Wireless transmission, cell radio and satellite basics • Understand the basic properties of different parts of the electromagnetic spectrum used for the transmission of data: short and long wave radio, microwave, infrared and visible light.

• Be familiar with ISDN and basic cellular radio concepts. The basic communications satellite technology for LEO and geosynchronous should be familiar as well as the trade-off between satellite and fiber. cs233/333 Lecture 8

Midterm Review Cont. • Data Link Layer • Be very familiar with Framing, error detection and correction

• Data Link Protocol Analysis • Be familiar with stop and wait, simplex vs. duplex, one bit sliding window, go back n, and selective repeat.

• Be familiar with the process of using a finite state automata to analyze a protocol (there will be no Petri model questions.) cs233/333 Lecture 8

• Protocol examples: be familiar with SDLC, SLIP and PPP

• Protocols 1-6

Midterm Review Cont. • Network Layer • Connection{less} vs packet/virt. cir. • SPF,flooding, distance vector and link state routing

• Counting to infinity • Split Horizon. • Hierarchial routing • (to page 364 in Tanenbaum) cs233/333 Lecture 8

Routing

cs233/333 Lecture 8

• Sink trees • No Loops, finite and bounded • Packet will be delivered • Shortest Path First • Possible meanings for shortest • Hops • Distance • Cost • Dijkstra’s algorithm • Demonstrate book example • Compute in advance

Routing • Flooding • All packets everywhere • Routing in adverse conditions • Default Routing • Hierarchy of “smarter” routers • Flow Based Routing • Use Load • Packet delay • Precalculate optimal flow cs233/333 Lecture 8

Distance Vector Routing • Very common • DecNet, Appletalk, RIP, CISCO, SUN, etc. • This is the routing that comes enabled on most kinds of computers

• Will work ok for most LANSs • Dynamic calculation of routes • Table updated for every router • Distance and first step • Distance may be hops, miles, cost, delay, cs233/333 Lecture 8

etc.

• Broadcast that information

Problems with Distance Vector Routing • Good news travels fast • Costs one table upgrade period per hop • Bad news travels slow • Counting to infinity example • Split Horizon hack • Don’t report distances to routers on same line

• Solves simple cases • Still breaks on more complex examples cs233/333 Lecture 8

Link State Routing • Distance vector no longer used on large WANs • Link State Procedure • Find neighbors • Test delay to neighbors-- send echo • Broadcast to all routers • Each router computes shortest path to all other routers

• Can use Dijkstra cs233/333 Lecture 8

• Problems • Distribution of updates • source, seq number, age • Network can partition if update breaks

Hierarchical routing • Hierarchy of routing protocols used at different levels

• This is what happens in practice • Lowest level, workstations, use default router • LAN routers use SPF • First level WANs use private Link State • Corporate WANs, small ISPs • Core Internet networks use link state • Exterior protocols (RGP) exchange data cs233/333 Lecture 8

with first level WANs.

• Keeps router table size manageable on core Internet and on first level networks.

Broadcast Routing • Routing addresses on LANs and WANS • Multicast Routing • Group management • Ethernet multicast • Ethernet group addresses • Long unused, now becoming important for multimedia, i.e. streaming video and sound.

• Mulipath routing • Packets to and from may differ. cs233/333 Lecture 8

Mobile Hosts • Home and foreign agents • 802.11b • IBSS - “ad hoc” • Independent Basic Service Set • BSS - base stations • Basic Service Set • ESS - roaming • Extended Service Set cs233/333 Lecture 8

IP addresses • IP v 4 • Four “octets” (Bytes) of address • Class addresses • Class A, B, C,D • Classless addresses • CIDR • packet vs byte

cs233/333 Lecture 8

Flow Control • Leaky bucket • Token bucket • packet vs byte

cs233/333 Lecture 8