Agenda (Rev 1) Week 1: Internet History and Basic Concepts Week 2: Routing vs. Switching Week 3: Architecture and Topology Trends Week 4: Performance, Congestion Control Week 5: Multimedia Support, ATM vs. IP Week 6: Routing part 1 (Intro, RIP, OSPF) Week 7: Routing part 2 (BGP, state of the Internet) Week 8: Guest lectures: Greg Minshall, and ?? Week 9: Failure Modes and Fault Diagnosis Week 10: Product evaluation criteria

Loose Ends... RTP vs. UDP Enet framing: postamble byte Token Ring vs. Ethernet Reliability Repeaters = Hubs = Layer 1 or 2?

Week 3: Architecture & Topology Trends Focus on Campus/Enterprise networks Use UW network as case study Introduce DNS and DHCP Continue to examine design issues/choices

Technology/Usage Trends TCP/IP Switching & point-to-point links Multimedia Desktop web servers Push publishing Web caching Non-locality of reference

Backbone Design Issues Link Technology & Topology Routers vs. Switches vs. ATM Single vs. Multiprotocol Central vs. In-building Routers Low-Density vs. High-Density Routers Large vs. Small Subnets Address Management Redundancy

Core Network Elements everything except the end-systems Name Resolution Host Configuration Multimedia Support Data Transport Data Caching?? Management

Name Resolution DNS = Domain Name System Distributed, hierarchical directory service Maps host/service names to IP addresses Resiliency requires client failover Susceptible to bad data in root servers Growth of.com domain triggered crisis Need: security and dynamic update

Host Configuration RARP BOOTP (and variants) DHCP

Problems with DHCP Client bugs leading to duplicate addresses Scaling Redundancy Conflict with desktop server trend Conflict with network management needs How long should the leases be?

Data (Web) Caching Important for improving web performance Resiliency requires client failover Scalability requires server-server protocol ICP = Internet Caching Protocol Legal & Economic issues: copying & click-thrus

Data Transport Getting bits from A to B But how fast? How well? Not just unicast

Multimedia Support Multicast QoS = Quality of Service Performance = Speed + QoS Is QoS important if you have enough bandwidth?

Performance Elements Client Machine/Software –Computer-to-Closet –Closet-to-BDF –BDF-to-Router –Router-to-Router Server Machine/Software Network Core End-End System

High-Speed Technologies 100 Mbps –FDDI (MTU=4500) –100VG (MTU=1500) –100BaseT (MTU=1500) 155 Mbps –PPP over SONET OC3c –ATM over SONET OC3c 1000 Mbps –PPP over SONET OC24 or 48 –ATM over SONET OC24 or 48 –Gigabit Ethernet –HIPPI, Fiber Channel

Ethernet Performance Levels 10 Mbps –Shared –Dedicated (= Switched) –Dedicated Full-Duplex 100 Mbps –Shared –Dedicated (= Switched) –Dedicated Full-Duplex 1000 Mbps –Shared –Dedicated (= Switched) –Dedicated Full-Duplex

ATM Performance Levels 25 Mbps 155 Mbps (OC3) 622 Mbps (OC12) 1244 Mbps (OC24) 2488 Mbps (OC48)

Next-step Desktop Connectivity Switched 10 (Half Duplex) Shared 100 (Half Duplex) Switched 100 Would you rather have switched 10 or shared 100? What are the implications of each on the backbone?

Case Study: UW’s Campus Network The Problem History Growth Key Decisions Topology Evolution Future Choices

UW’s Network Problem “Death of the net predicted; film at eleven” More users More usage More demanding applications More bad guys Apparent slow-downs due to net congestion Delays still spotty, but expected to worsen

More Demanding Applications Non-interactive: Baseline interactive: telnet, web Multimedia: desktop conferencing, VOD High-end: Medical imaging, VR

Scaling Considerations Where do we feel the pressure from increasing use? –Performance (Speed + QoS) –Address Management –End-user Support

UW Network History 1988: five anti-interoperable campus nets... –3,000 machines on a bridged Ethernet –A large Micom terminal network –Separate library, hospital, and administrative nets 1997: one campus net with... –12,000 PCs –6,000 Macs –4,000 Unix workstations –3,000 X terminals –1,000 hubs, routers

UW Node Growth By 12/94 we had 17,000 nodes and 650 modems By 12/95 we had 22,000 nodes and 1,300 modems By 12/97 we had 27,000 nodes and 1,500 modems Run-rate had been 3k/year nodes, now flat… > Saturation at last??

UW Backbone Traffic

UW Key Decisions Use Internet standards (Interoperate!) Route only IP (Simplify!) Use lots of 10BaseT Ethernet (Cheap!) Use multiple links (Redundancy, loadsharing) Use lots of subnets (Isolate Faults) Use lots of switches (Isolate Traffic) Use DHCP (Automate!)

UW Topology Evolution Epoch 1 (c. 1989): Dual Shared Ethernet Cables Epoch 2 (c ): Dual Routers Epoch 3 (c. 1995): Quad Ethernet Switches Epoch 4 (c. 1997): Quad Fast Ethernet Switches

UW Current Backbone Topology S1S2S3S4 R1R2 R38R39R40 To Building Subnets …

UW Building Infrastructure To Router Center

UW Future Topology Choices Ring? Mesh? Continue with Hierarchy?

Should we… Use conventional routers? User “layer 3 switches”? Use edge routers, ATM core? Use Ipsilon IP switching? Use 3Com VLANs & Fast IP architecture? Use Cisco Tag switching?

Where to put Layer 3 Functionality? Edges, nearest the end-systems In each Building Distribution Frame Centrally, at/near top of hierarchy One arm router between VLANs

Decision Criteria Interoperability Reliability Performance Fault Tolerance Simplicity/Manageability Cost

Conclusions? Simplify! IP Rules! Ethernet simpler/cheaper than ATM Adequate Frame-based QoS still a question Avoid *having* to upgrade end-systems Caching becoming part of the network