1 / 16

IP Switching and Label Switching

IP Switching and Label Switching. Raj Jain Professor of Computer and Information Sciences The Ohio State University Columbus, OH 43210 Jain@cse.ohio-state.edu These slides are available on-line at: http://www.cse.ohio-state.edu/~jain/cis788-99/. Switching vs routing IP Switching (Ipsilon)

mercia
Download Presentation

IP Switching and Label Switching

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IP Switchingand Label Switching Raj JainProfessor of Computer and Information SciencesThe Ohio State University Columbus, OH 43210Jain@cse.ohio-state.edu These slides are available on-line at:http://www.cse.ohio-state.edu/~jain/cis788-99/

  2. Switching vs routing • IP Switching (Ipsilon) • Tag Switching (CISCO) • Multi-protocol label switching Overview

  3. Routing vs Switching 164.107.61.201 3 • Routing: Based on address lookup. Max prefix match. Þ Search OperationÞ Complexity  O(log2n) • Switching: Based on circuit numbersÞ Indexing operationÞ Complexity O(1)Þ Fast and Scalable for large networks and large address spaces • These distinctions apply on all datalinks: ATM, Ethernet, SONET

  4. Router Switch Routing vs Switching (Cont) On ATM networks: • IP routers use IP addresses Þ Reassemble IP datagrams from cells • IP Switches use ATM Virtual circuit numbersÞ Switch cellsÞ Do not need to reassemble IP datagramsÞ Fast ATM Host ATM Host

  5. IP Switching • Developed by Ipsilon • Routing software in every ATM switch in the network • Initially, packets are reassembled by the routing software and forwarded to the next hop • Long term flows are transferred to separate VCs. Mapping of VCIs in the switch Þ No reassembly R R S S

  6. IP Switching (Cont) • Flow-oriented traffic: FTP, Telnet, HTTP, Multimedia • Short-lived Traffic: DNS query, SMTP, NTP, SNMP, request-response Ipsilon claimed that 80% of packets and 90% of bytes are flow-oriented. • Ipsilon claimed their Generic Switch Management Protocol (GSMP) to be 2000 lines, and Ipsilon Flow Management Protocol (IFMP) to be only 10,000 lines of code • Runs as added software on an ATM switch • Implemented by several vendors

  7. Ipsilon's IP Switching: Issues • VCI field is used as ID. VPI/VCI change at switch Þ Must run on every ATM switch Þ non-IP switches not allowed between IP switches Þ Subnets limited to one switch • Cannot support VLANs • Scalability: Number of VC > Number of flows.ÞVC Explosion. 1000 setups/sec. • Quality of service determined implicitly by the flow class or by RSVP • ATM Only

  8. Tag Switching • Proposed by CISCO • Similar to VLAN tags • Tags can be explicit or implicit L2 header L2 Header Tag • Ingress router/host puts a tag. Exit router strips it off. R R H UntaggedPacket H Tagged packet H H R

  9. Tag Switching (Cont) • Switches switch packets based on labels.Do not need to look inside  Fast. • One memory reference compared to 4-16 in router • Tags have local significance  Different tag at each hop (similar to VC #)

  10. R 164.107/16<2> 164.107/16<64> 164.107/16<5> Tag Switching (Cont) • One VC per routing table entry 3 64 164.107/16<3> R 2 R 164.107/16<3> 5 3

  11. Alphabet Soup • CSR Cell Switched Router • ISR Integrated Switch and Router • LSR Label Switching Router • TSR Tag Switching Router • Multi layer switches, Swoters • DirectIP • FastIP • PowerIP

  12. MPLS • Multiprotocol Label Switching • IETF working group to develop switched IP forwarding • Initially focused on IPv4 and IPv6. Technology extendible to other L3 protocols. • Not specific to ATM. ATM or LAN. • Not specific to a routing protocol (OSPF, RIP, ...)

  13. 20b 3b 1b 8b Label Exp SI TTL Label Stack Entry Format • Labels = Explicit or implicit L2 header • TTL = Time to live • Exp = Experimental • SI = Stack indicator ... L2 Header Label Stack Entry Label Stack Entry

  14. Label Label Stacks • Labels are pushed/popped as they enter/leave MPLS domain • Routers in the interior will use Interior Gateway Protocol (IGP) labels. Border gateway protocol (BGP) labels outside. • Bottom label may indicate protocol (0=IPv4, 2=IPv6) ... L2 Header LSE 1 LSE 2 LSE n 2 2 2 1 1 1 2 2 2

  15. Summary • IP Switching: Traffic-based, per-hop VCs, downstream originated • Tag switching: Topology based, one VC per route • MPLS combines various features of IP switching, Tag switching, and other proposals

  16. Key References • See http://www.cse.ohio-state.edu/~jain/refs/ipsw_ref.htm • IP switching, http://www.cse.ohio-state.edu/~jain/cis788-97/ip_switching/index.htm • Multiprotocol Label Switching (mpls) working group at IETF. Email: mpls-request@cisco.com

More Related