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048866: Packet Switch Architectures

048866: Packet Switch Architectures. Introduction. Dr. Isaac Keslassy Electrical Engineering, Technion isaac@ee.technion.ac.il http://comnet.technion.ac.il/~isaac/. Course Content. Most of the results in the course are less than 10 years old! Material is new and still changing…

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048866: Packet Switch Architectures

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  1. 048866: Packet Switch Architectures Introduction Dr. Isaac Keslassy Electrical Engineering, Technion isaac@ee.technion.ac.il http://comnet.technion.ac.il/~isaac/

  2. Course Content • Most of the results in the course are less than 10 years old! • Material is new and still changing… • No reference book available yet… • Uses slides by Profs. Nick McKeown and Balaji Prabahakar (Stanford) 048866 – Packet Switch Architectures

  3. Outline • Background • What is a router? • Why do we need faster routers? • Why are they hard to build? • Architectures and techniques • The evolution of router architecture. • IP address lookup. • Packet buffering. • Switching. 048866 – Packet Switch Architectures

  4. What is Routing? D R3 R1 R4 D A B E R2 C R5 Destination Next Hop F D R3 E R3 F R5 048866 – Packet Switch Architectures

  5. What is Routing? R3 R1 R4 D A 1 4 16 32 D Ver HLen T.Service Total Packet Length Fragment ID Flags Fragment Offset B E TTL Protocol Header Checksum 20 bytes Source Address R2 C R5 Destination Address Destination Next Hop F D R3 Options (if any) E R3 Data F R5 048866 – Packet Switch Architectures

  6. What is Routing? R3 R1 R4 D A B E R2 C R5 F 048866 – Packet Switch Architectures

  7. Points of Presence (POPs) POP3 POP2 POP1 D POP4 A B E POP5 POP6 C POP7 POP8 F 048866 – Packet Switch Architectures

  8. Where High Performance Routers are Used (10 Gb/s) R2 (10 Gb/s) R1 R6 R5 R4 R7 R3 R9 R10 R8 R11 R12 R14 R13 R16 R15 (10 Gb/s) (10 Gb/s) 048866 – Packet Switch Architectures

  9. What a Router Looks Like Cisco GSR 12416 Juniper M160 19” 19” Capacity: 160Gb/sPower: 4.2kWFull rack Capacity: 80Gb/sPower: 2.6kWHalf-a-rack 6ft 3ft 2ft 2.5ft 048866 – Packet Switch Architectures

  10. Core Router Market • Estimates cover different parameters • Dell’Oro (Feb. 17, 2005): • $1.2 billion in 2004 (up 66%) • Includes high-end (10Gbps) router market • Dell’Oro (Feb. 21, 2006): • $4.4 billion in 2005 • Includes “worldwide service provider router market” • Infonetics (Feb. 21, 2006): • $5.2 billion in 2005 (up 31%) • Includes core/edge routers • Core router market • Relatively small (in comparison to enterprise market), but brings expertise to company • Vendors: Cisco, Juniper, Avici, Nortel, Lucent, Alcatel, Huawei, etc. 048866 – Packet Switch Architectures

  11. Router Market Source: Infonetics (Nov. 2004) 048866 – Packet Switch Architectures

  12. Basic Architectural Componentsof an IP Router Routing Protocols Routing Table Control Plane Datapath per-packet processing Forwarding Table Switching 048866 – Packet Switch Architectures

  13. Per-packet processing in an IP Router • Accept packet arriving on an incoming link. • Lookup: lookup packet destination address in the forwarding table, to identify outgoing port(s). • Header Processing: Manipulate packet header: e.g., decrement TTL, update header checksum. • Switching: Send packet to the outgoing port(s). • Buffering: Buffer packet in the queue. • Transmit packet onto outgoing link. 048866 – Packet Switch Architectures

  14. Generic Router Architecture Data Hdr Data Hdr IP Address Next Hop Address Table Buffer Memory Header Processing Lookup IP Address Update Header Queue Packet ~1M prefixes Off-chip DRAM ~1M packets Off-chip DRAM 048866 – Packet Switch Architectures

  15. Generic Router Architecture Data Data Data Hdr Hdr Hdr Header Processing Header Processing Header Processing Lookup IP Address Lookup IP Address Lookup IP Address Update Header Update Header Update Header Address Table Address Table Address Table Data Data Hdr Hdr Data Hdr Buffer Manager Buffer Memory Buffer Manager Buffer Memory Buffer Manager Buffer Memory 048866 – Packet Switch Architectures

  16. Outline • Background • What is a router? • Why do we need faster routers? • Why are they hard to build? • Architectures and techniques • The evolution of router architecture. • IP address lookup. • Packet buffering. • Switching. 048866 – Packet Switch Architectures

  17. Why Do We Need Faster Routers? • To prevent routers from becoming the bottleneck in the Internet. • To increase POP capacity, and to reduce cost, size and power. 048866 – Packet Switch Architectures

  18. Why We Need Faster Routers 1: To prevent routers from being the bottleneck Single Fiber Capacity (commercial) Packet Processing Power ≥ 2x / year 2x / 18 months Source: SPEC95Int & Coffman and Odlyzko. 048866 – Packet Switch Architectures

  19. Why we Need Faster Routers 2: To reduce cost, power & complexity of POPs POP with smaller routers • Ports: Price >$50k, Power > 400W. • It is common for 50-60% of ports to be for interconnection. POP with large routers 048866 – Packet Switch Architectures

  20. Why are Fast Routers Difficult to Make? It’s hard to keep up with Moore’s Law: The bottleneck is memory speed. Memory speed is not keeping up with Moore’s Law. 048866 – Packet Switch Architectures

  21. Why are Fast Routers Difficult to Make?Speed of Commercial DRAM It’s hard to keep up with Moore’s Law: The bottleneck is memory speed. Memory speed is not keeping up with Moore’s Law. 1.1x / 18 months Moore’s Law 2x / 18 months 048866 – Packet Switch Architectures

  22. Why are Fast Routers Difficult to Make? It’s hard to keep up with Moore’s Law: The bottleneck is memory speed. Memory speed is not keeping up with Moore’s Law. Moore’s Law is too slow: Routers need to improve faster than Moore’s Law. 048866 – Packet Switch Architectures

  23. Router Performance Exceeds Moore’s Law Growth in capacity of commercial routers: Capacity 1992 ~ 2Gb/s Capacity 1995 ~ 10Gb/s Capacity 1998 ~ 40Gb/s Capacity 2001 ~ 160Gb/s Capacity 2003 ~ 640Gb/s Average growth rate: 2.2x / 18 months. 048866 – Packet Switch Architectures

  24. Outline Background What is a router? Why do we need faster routers? Why are they hard to build? Architectures and techniques The evolution of router architecture. IP address lookup. Packet buffering. Switching. 048866 – Packet Switch Architectures

  25. First-Generation Routers CPU Buffer Memory Route Table CPU Line Interface Line Interface Line Interface Memory MAC MAC MAC Typically <0.5Gb/s aggregate capacity Shared Backplane Line Interface 048866 – Packet Switch Architectures

  26. Second-Generation Routers Fwding Cache CPU Buffer Memory Route Table Line Card Line Card Line Card Buffer Memory Buffer Memory Buffer Memory Fwding Cache Fwding Cache MAC MAC MAC Typically <5Gb/s aggregate capacity 048866 – Packet Switch Architectures

  27. Third-Generation Routers Fwding Table Switched Backplane Line Card CPU Card Line Card Local Buffer Memory Local Buffer Memory Line Interface CPU Routing Table Memory Fwding Table MAC MAC Typically <50Gb/s aggregate capacity 048866 – Packet Switch Architectures

  28. Fourth-Generation RoutersMulti-Racks, Optical Links Optical links 100s of metres Switch Core Linecards 0.3 - 10Tb/s routers 048866 – Packet Switch Architectures

  29. (Future) Fifth-Generation RoutersOptical Switch Core Optical links 100s of metres Optical Switch Core Linecards 10-100Tb/s routers, in project 048866 – Packet Switch Architectures

  30. (Future) Sixth-Generation RoutersAll-Optical Routers Optical links 100s of metres Optical Switch Core Optical Linecards 100-1000Tb/s routers, in the far future 048866 – Packet Switch Architectures

  31. Outline Background What is a router? Why do we need faster routers? Why are they hard to build? Architectures and techniques The evolution of router architecture. IP address lookup. Packet buffering. Switching. 048866 – Packet Switch Architectures

  32. Generic Router Architecture Header Processing Header Processing Lookup IP Address Lookup IP Address Update Header Update Header Address Table Address Table Lookup IP Address Lookup IP Address Lookup IP Address Address Table Address Table Address Table Buffer Manager Buffer Memory Header Processing Buffer Manager Lookup IP Address Update Header Buffer Memory Address Table Buffer Manager Buffer Memory 048866 – Packet Switch Architectures

  33. IP Address Lookup Why it’s thought to be hard: It’s not an exact match: it’s a longest prefix match. The table is large: about 150,000 entries today, and growing. The lookup must be fast: about 30ns for a 10Gb/s line. 048866 – Packet Switch Architectures

  34. IP Lookups find Longest Prefixes 128.9.16.14 128.9.176.0/24 128.9.16.0/21 128.9.172.0/21 142.12.0.0/19 65.0.0.0/8 128.9.0.0/16 0 232-1 Routing lookup:Find the longest matching prefix (aka the most specific route) among all prefixes that match the destination address. 048866 – Packet Switch Architectures

  35. IP Address Lookup Why it’s thought to be hard: It’s not an exact match: it’s a longest prefix match. The table is large: about 150,000 entries today, and growing. The lookup must be fast: about 30ns for a 10Gb/s line. 048866 – Packet Switch Architectures

  36. Address Tables are Large Source: http://www.cidr-report.org/ 048866 – Packet Switch Architectures

  37. IP Address Lookup Why it’s thought to be hard: It’s not an exact match: it’s a longest prefix match. The table is large: about 150,000 entries today, and growing. The lookup must be fast: about 30ns for a 10Gb/s line. 048866 – Packet Switch Architectures

  38. Lookups Must be Fast Year Line 40B packets (Mpkt/s) 1997 622Mb/s 1.94 1999 2.5Gb/s 7.81 2001 10Gb/s 31.25 2003 40Gb/s 125 2005? 160Gb/s 500 048866 – Packet Switch Architectures

  39. Outline Background What is a router? Why do we need faster routers? Why are they hard to build? Architectures and techniques The evolution of router architecture. IP address lookup. Packet buffering. Switching. 048866 – Packet Switch Architectures

  40. Generic Router Architecture Header Processing Header Processing Header Processing Lookup IP Address Lookup IP Address Lookup IP Address Update Header Update Header Update Header Address Table Address Table Address Table Buffer Manager Buffer Manager Buffer Manager Buffer Memory Buffer Memory Buffer Memory Queue Packet Buffer Memory Queue Packet Buffer Memory Queue Packet Buffer Memory 048866 – Packet Switch Architectures

  41. Fast Packet Buffers Example: 40Gb/s packet buffer Size = RTT*BW = 10Gb; 40 byte packets Write Rate, R Read Rate, R Buffer Manager 1 packet every 8 ns 1 packet every 8 ns Buffer Memory Use SRAM? + fast enough random access time, but - too low density to store 10Gb of data. Use DRAM? + high density means we can store data, but - too slow (50ns random access time). 048866 – Packet Switch Architectures

  42. Outline Background What is a router? Why do we need faster routers? Why are they hard to build? Architectures and techniques The evolution of router architecture. IP address lookup. Packet buffering. Switching. 048866 – Packet Switch Architectures

  43. Generic Router Architecture Data Data Data Hdr Hdr Hdr Header Processing Header Processing Header Processing Lookup IP Address Lookup IP Address Lookup IP Address Update Header Update Header Update Header Address Table Address Table Address Table N times line rate 1 1 Queue Packet Buffer Memory 2 2 Queue Packet Buffer Memory N times line rate N N Queue Packet Buffer Memory 048866 – Packet Switch Architectures

  44. Generic Router Architecture Data Data Data Data Data Data Hdr Hdr Hdr Hdr Hdr Hdr Header Processing Header Processing Header Processing Lookup IP Address Lookup IP Address Lookup IP Address Update Header Update Header Update Header 1 1 Address Table Address Table Address Table 2 2 N N Queue Packet Buffer Memory Queue Packet Buffer Memory Scheduler Queue Packet Buffer Memory 048866 – Packet Switch Architectures

  45. Current Internet Router TechnologySummary There are three potential bottlenecks: Address lookup, Packet buffering, and Switching. Most difficult – and focus of this course! 048866 – Packet Switch Architectures

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