CS 152 Computer Architecture and Engineering Lecture 22 Routers 2005 11 15 John Lazzaro www cs berkeley edu lazzaro TAs David Marquardt and Udam Saini www inst eecs berkeley edu cs152 CS 152 L22 Routers UC Regents Fall 2005 UCB 1 Last Time Internet Architecture ISO Layer Names IP packet Layer 3 WiFi and Cable Modem packets Layer 2 Radio cable waveforms Layer 1 801 11b WiFi packet IP Packet For this hop IP packet sent inside of a wireless 801 11b packet CS 152 L22 Routers Cable modem packet IP Packet For this hop IP packet sent inside of a cable modem DOCSIS packet UC Regents Fall 2005 UCB 2 Today Router Design Router 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 CS 152 L22 Routers UC Regents Fall 2005 UCB 3 Last time Cables meet in Hawaii CS 152 L22 Routers UC Regents Fall 2005 UCB 4 Last time Routers are like hub airports In 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 CS 152 L22 Routers UC Regents Fall 2005 UCB 5 The Oahu router Assume each line is 160 Gbits sec each way Oregon Japan Router Fiji CA Hawaii IP packets are forwarded from each inbound Layer 2 line to one of the four outbound Layer 2 lines based on the destination IP number in the IP packet CS 152 L22 Routers UC Regents Fall 2005 UCB 6 Challenge 1 Switching bandwidth At line rate 5 160 Gb s 100 GB s switch Latency not an issue wide slow bus OK FIFOs FIFOs Japan Fiji Oregon CA Hawaii Japan Fiji Oregon CA Hawaii 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 CS 152 L22 Routers UC Regents Fall 2005 UCB 7 Challenge 2 Packet forwarding speed Japan Which Buffers line For each packet delivered by each inbound line the router must decide which outbound line to forward it to Also update IP header Line rate 160 Gb s Average packet size 400 bits Packets per second per line 400 Million Packets per second 5 lines 2 Billion Thankfully this is trivial to parallelize CS 152 L22 Routers UC Regents Fall 2005 UCB 8 Challenge 3 Obeying the routing ISA Network Working Group Request for Comments 1812 Obsoletes 1716 1009 Category Standards Track F Baker Editor Cisco Systems June 1995 Requirements for IP Version 4 Routers 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 CS 152 L22 Routers UC Regents Fall 2005 UCB 9 The MGR Router A case study IEEE ACM TRANSACTIONS ON NETWORKING VOL 6 NO 3 JUNE 1998 237 A 50 Gb s IP Router Craig 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 Winterble Abstract Aggressive research on gigabit per second networks has led to dramatic improvements in network transmission speeds One result of these improvements has been to put pressure on router technology to keep pace This paper describes a router nearly completed which is more than fast enough to keep up with the latest transmission technologies The router has a backplane speed of 50 Gb s and can forward tens of millions of packets per second fully capable of driving the new generation of links OC 48c at 2 4 Gb s A multigigabit router a router capable of moving data at several gigabits per second or faster needs to achieve three goals First it needs to have enough internal bandwidth to move packets between its interfaces at multigigabit rates Second it needs enough packet processing power to forward several million packets per second MPPS A good rule of thumb based on the Internet s average packet size of approximately 1000 b is that for every gigabit per second of bandwidth a router needs 1 MPPS of forwarding power 1 Third the router needs to conform to a set of protocol standards For Internet protocol version 4 IPv4 this set of standards is summarized in the Internet router requirements 3 Our router achieves all three goals but for one minor variance from the IPv4 router requirements discussed below This paper presents our multigigabit router called the MGR which is nearly completed This router achieves up to 32 MPPS forwarding rates with 50 Gb s of full duplex backplane capacity 2 About a quarter of the backplane capacity is lost to overhead traffic so the packet rate and effective bandwidth UC Regents Fall 2005 UCB are balanced Both rate and bandwidth are roughly two to ten times faster than the high performance routers available today 10 The MGR Router was a research project in late 1990 s Kept up with line rate of the fastest links of its day OC 48c 2 4 Gb s optical Index Terms Data communications internetworking packet switching routing I INTRODUCTION T Architectural approach is still valid today RANSMISSION link bandwidths keep improving at a seemingly inexorable rate as the result of research in transmission technology 26 Simultaneously expanding network usage is creating an ever increasing demand that can only be served by these higher bandwidth links In 1996 and 1997 Internet service providers generally reported that the number of customers was at least doubling annually and that per customer bandwidth usage was also growing in some cases by 15 per month CS 152 L22 Routers Unfortunately transmission links alone do not make a network To achieve an overall improvement in networking MGR top level architecture A 50 Gb s switch is the centerpiece of the design Cards plug into the switch Card Card Card Card Card Card Switch Card Card In best case on each switch epoch transaction each card can send and receive 1024 bits to from one other card CS 152 L22 Routers UC Regents Fall 2005 UCB 11 MGR cards come in two flavors Line card A card that connects to Layer 2 line Different version of card for each Layer 2 type Line Line Line Engine Engine Line Switch Line Engine Forwarding engine Receives IP headers over the switch from line cards and returns forwarding directions and modified headers to line card CS 152 L22 Routers UC Regents
View Full Document
Unlocking...