CS536-2009-04-15 - CS536: Link Layer Charles Killian...

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CS536: Link Layer Charles Killian Transport Layer 1
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Announcements Final Project (due 4/30) No class Apr 21 or 23 HW4 Assigned Tomorrow Taking the qualifier? Are you available immediately following the exam period? Network Layer 4-2
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IP Switching: ATM Under IP When ? 1997 Where ? Transactions on Networking Who ? Peter Newman Greg Minshall Tom Lyon Ipsilon Networks 5: DataLink Layer 5-3
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Who Is Ipsilon ? Created in 1996 Free enterprise networks from Cisco Created quite a commotion Antistandardization rhetoric Choruses of the complexity of dogmatic routing vs. fast switching Backed by Cabletron, DEC, and Nokia owned minority stake 5: DataLink Layer 5-4
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What is IP Switching NOT talking about a basic IP switch (as in hub, switch, router) Talking about an ATM switch network functioning for IP 5: DataLink Layer 5-5
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Motivation ATM Switches are cheaper and faster than IP routers Simpler routing algorithm means this will likely stay the same IP networking is ubiquitous Existing IP/ATM approaches hide the network from IP 5: DataLink Layer 5-6
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What is ATM Under IP? Take an ATM switch Remove ATM software Install IP software for switching over ATM hardware Identify flows worth switching Transparently send them using ATM from edge-to-edge of the AS Route other packets using standard IP routing 5: DataLink Layer 5-7
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How does it work? Forward ATM packets normally On IP packet arrival Classify packet Determine if worth converting to circuit Send request for prior-hop to send using ATM circuit id X If forwarding to be done via ATM, remove certain headers and encapsulate packet remainder When exiting network, reconstruct IP packet to forward 5: DataLink Layer 5-8
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Details Ingress router removes TTL in checksum Egress router stores source IP, dest IP, ports, IP TTL value Adds TTL back to checksum Checksum is part of flow classifier! Receiver driven change to circuits 5: DataLink Layer 5-9
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More Details Circuit routing is soft state Refreshed periodically Failures do not invalidate “circuits” as a whole, but rather are patched up IP Multicast supported (combo ATM and IP multicast) 5: DataLink Layer 5-10
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Experimental Setup Simulation-based 3 packet traces 5 minute trace from San Francisco FDDI ring • 1995, Sept. • Timestamp, IP, port, packet length • Does not include TTL! • Too short to stabilize # flows 10 minutes from same place • 1996, Feb. (8:30a, 1:45p) • Timestamp, full IP, TCP, & UDP headers Used traffic classification to decide to switch flows 5: DataLink Layer 5-11
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Results Trace 1: 84% flows and 91% bytes switched 92 new flows per second 15,500 average flows Trace 2: (20% fewer TCP packets, 60-84% more UDP) 2.5% difference in packets switched Lower switching gain • What is switching gain? Why does it matter?
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This note was uploaded on 10/24/2009 for the course CS 536 taught by Professor Sonia,f during the Spring '08 term at Purdue University-West Lafayette.

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CS536-2009-04-15 - CS536: Link Layer Charles Killian...

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