UC Regents Fall 2005 © UCBCS 152 L22: Routers2005-11-15John Lazzaro (www.cs.berkeley.edu/~lazzaro)CS 152 Computer Architecture and EngineeringLecture 22 – Routerswww-inst.eecs.berkeley.edu/~cs152/TAs: David Marquardt and Udam Saini 1UC Regents Fall 2005 © UCBCS 152 L22: RoutersLast Time: Internet ArchitectureIP Packet801.11b WiFi packetFor this “hop”, IP packet sent “inside” of a wireless 801.11b packet.IP PacketCable modem packetFor this “hop”, IP packet sent “inside” of a cable modem DOCSIS packet.ISO Layer Names:IP packet: “Layer 3”WiFi and Cable Modem packets: “Layer 2”Radio/cable waveforms: “Layer 1”2UC Regents Fall 2005 © UCBCS 152 L22: RoutersToday: Router DesignRouter architecture: What’s inside the box?Forwarding engine: How a router knows the “next hop” for a packet.Switch fabric: When buses are too slow ... replace it with a switch!3UC Regents Fall 2005 © UCBCS 152 L22: RoutersLast time: Cables meet in Hawaii ...4UC Regents Fall 2005 © UCBCS 152 L22: RoutersLast time: Routers are like hub airportsIn Makaha, a router takes each Layer 2 packet off the San Luis Obispo (CA) cable, examines the IP packet destination field, and forwards to Japan cable, Fiji cable, or to Kahe Point (and onto big island cables).5UC Regents Fall 2005 © UCBCS 152 L22: RoutersThe Oahu router ...JapanFijiOregonCAHawaiiRouterAssume each “line” is 160 Gbits/sec each way.IP packets are forwarded from each inbound Layer 2 line to one of the four outbound Layer 2 lines, based on thedestination IP number in the IP packet.6UC Regents Fall 2005 © UCBCS 152 L22: Routers...Challenge 1: Switching bandwidth JapanFijiOregonCAHawaiiJapanFijiOregonCAHawaiiFIFOs FIFOsAt line rate: 5*160 Gb/s = 100 GB/s switch!Latency not an issue ... wide, slow bus OK.FIFOs (first-in first-out packet buffers) help if an output is sent more bits than it can transmit. If buffers “overflow”, packets are discarded. 7UC Regents Fall 2005 © UCBCS 152 L22: RoutersChallenge 2: Packet forwarding speedJapanFor each packet delivered by each inbound line, the router must decide which outbound line to forward it to. Also, update IP header. BuffersWhich line ???Line rate: 160 Gb/s Thankfully, this is trivial to parallelize ...Average packet size: 400 bitsPackets per second per line: 400 MillionPackets per second (5 lines): 2 Billion8UC Regents Fall 2005 © UCBCS 152 L22: RoutersChallenge 3: Obeying the routing “ISA”Internet Engineering Task Force (IETF) “Request for Comments” (RFC) memos act as the “Instruction Set Architecture” for routers. RFC 1812 (above) is 175 pages, and has 100 references which also define rules ...Network Working Group F. Baker, EditorRequest for Comments: 1812 Cisco SystemsObsoletes: 1716, 1009 June 1995Category: Standards Track Requirements for IP Version 4 Routers9UC Regents Fall 2005 © UCBCS 152 L22: RoutersThe MGR Router: A case study ...IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 6, NO. 3, JUNE 1998 237A 50-Gb/s IP RouterCraig Partridge, Senior Member, IEEE, Philip P. Carvey, Member, IEEE, Ed Burgess, Isidro Castineyra, Tom Clarke,Lise Graham, Michael Hathaway, Phil Herman, Allen King, Steve Kohalmi, Tracy Ma, John Mcallen,Trevor Mendez, Walter C. Milliken, Member, IEEE, Ronald Pettyjohn, Member, IEEE,John Rokosz,Member, IEEE, Joshua Seeger, Michael Sollins, Steve Storch,Benjamin Tober, Gregory D. Troxel, David Waitzman, and Scott WinterbleAbstract—Aggressive research on gigabit-per-second networkshas led to dramatic improvements in network transmissionspeeds. One result of these improvements has been to putpressure on router technology to keep pace. This paper describesa router, nearly completed, which is more than fast enough tokeep up with the latest transmission technologies. The routerhas a backplane speed of 50 Gb/s and can forward tens ofmillions of packets per second.Index Terms— Data communications, internetworking, packetswitching, routing.I. INTRODUCTIONTRANSMISSION link bandwidths keep improving, ata seemingly inexorable rate, as the result of researchin transmission technology [26]. Simultaneously, expandingnetwork usage is creating an ever-increasing demand that canonly be served by these higher bandwidth links. (In 1996and 1997, Internet service providers generally reported thatthe number of customers was at least doubling annually andthat per-customer bandwidth usage was also growing, in somecases by 15% per month.)Unfortunately, transmission links alone do not make anetwork. To achieve an overall improvement in networkingperformance, other components such as host adapters, operat-ing systems, switches, multiplexors, and routers also need toget faster. Routers have often been seen as one of the laggingtechnologies. The goal of the work described here is to showthat routers can keep pace with the other technologies and areManuscript received February 20, 1997; revised July 22, 1997; approvedby IEEE/ACM TRANSACTIONS ON NETWORKING Editor G. Parulkar. This workwas supported by the Defense Advanced Research Projects Agency (DARPA).C. Partridge is with BBN Technologies, Cambridge, MA 02138 USA, andwith Stanford University, Stanford, CA 94305 USA (e-mail: [email protected]).P. P. Carvey, T. Clarke, and A. King were with BBN Technologies,Cambridge, MA 02138 USA. They are now with Avici Systems, Inc.,Chelmsford, MA 01824 USA (e-mail: [email protected]; [email protected];[email protected]).E. Burgess, I. Castineyra, L. Graham, M. Hathaway, P. Herman, S.Kohalmi, T. Ma, J. Mcallen, W. C. Milliken, J. Rokosz, J. Seeger, M.Sollins, S. Storch, B. Tober, G. D. Troxel, and S. Winterble are with BBNTechnologies, Cambridge, MA 02138 USA (e-mail: [email protected];[email protected]; [email protected]; [email protected]; [email protected]).T. Mendez was with BBN Technologies, Cambridge, MA 02138 USA. Heis now with Cisco Systems, Cambridge, MA 02138 USA.R. Pettyjohn was with BBN Technologies, Cambridge, MA 02138 USA.He is now with Argon Networks, Littleton, MA 01460 USA (e-mail:[email protected]).D. Waitzman was with BBN Technologies, Cambridge, MA 02138 USA.He is now with D. E. Shaw and Company, L.P., Cambridge, MA 02139 USA.Publisher Item Identifier S 1063-6692(98)04174-0.fully capable of driving the new generation of links (OC-48cat 2.4 Gb/s).A multigigabit router (a router capable of moving dataat several gigabits per second or faster) needs to
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