Transcript presentation source

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...
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RTP vs. UDP
Enet framing: postamble byte
Token Ring vs. Ethernet Reliability
Repeaters = Hubs = Layer 1 or 2?
Week 3: Architecture & Topology
Trends
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Focus on Campus/Enterprise networks
Use UW network as case study
Introduce DNS and DHCP
Continue to examine design issues/choices
Technology/Usage Trends
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TCP/IP
Switching & point-to-point links
Multimedia
Desktop web servers
Push publishing
Web caching
Non-locality of reference
Backbone Design Issues
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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
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Name Resolution
Host Configuration
Multimedia Support
Data Transport
Data Caching??
Management
Name Resolution
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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
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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
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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
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Multicast
QoS = Quality of Service
Performance = Speed + QoS
Is QoS important if you have enough
bandwidth?
Performance Elements
• Client Machine/Software
End-End
System
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Computer-to-Closet
Closet-to-BDF
BDF-to-Router
Router-to-Router
• Server Machine/Software
Network Core
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
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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
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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
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The Problem
History
Growth
Key Decisions
Topology Evolution
Future Choices
UW’s Network Problem
“Death of the net predicted; film at eleven”
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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
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Non-interactive: email
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...
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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
300
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Billions of Bytes each
November
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1990 1991 1992 1993 1994 1995 1996
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. 1992 ): Dual Routers
• Epoch 3 (c. 1995): Quad Ethernet Switches
• Epoch 4 (c. 1997): Quad Fast Ethernet Switches
UW Current Backbone Topology
S1
R1
S2
R2
To Building Subnets …
S3
R38
S4
R39
R40
UW Building Infrastructure
To Router Center
UW Future Topology Choices
• Ring?
• Mesh?
• Continue with Hierarchy?
Should we…
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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?
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Edges, nearest the end-systems
In each Building Distribution Frame
Centrally, at/near top of hierarchy
One arm router between VLANs
Decision Criteria
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Interoperability
Reliability
Performance
Fault Tolerance
Simplicity/Manageability
Cost
Conclusions?
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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