18c - Router Design - Lookup Problem

18c - Router Design - Lookup Problem - Last Lecture:...

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Last Lecture: Network Layer 1. Design goals and issues 2. 3. Addressing, Fragmentation and reassembly 4. Internet Routing Protocols and Inter-networking 5. Router design 1. Short History + Router Architectures 2. Switching fabrics 3. Address lookup problem 6. Congestion Control, Quality of Service 7. More on the Internet’s Network Layer SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 1
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Last Lecture: Network Layer 1. Design goals and issues 2. 3. Addressing, Fragmentation and reassembly 4. Internet Routing Protocols and Inter-networking 5. Router design 1. Short History + Router Architectures 2. Switching fabrics 3. Address lookup problem 6. Congestion Control, Quality of Service 7. More on the Internet’s Network Layer SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 2
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Reminder on Router Architecture Lookup IP Address Update Header Header Processing Data Hdr Data Hdr ~1M prefixes Off-chip DRAM Address Table IP Address Next Hop Queue Packet Buffer Memory ~1M packets Off-chip DRAM SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 3
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Basic Requirements 1) Fast lookup and fast update 2) Scalable (speed & table size) 3) Inexpensive (fit in memory, e.g.) SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 4
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Lookups Must Be Fast 1. Lookup mechanism must be simple and easy to implement 2. Memory access time is the bottleneck 200Mpps × 2 lookups/pkt = 400 Mlookups/sec 2.5ns per lookup Year Aggregate Line- rate Arriving rate of 40B POS packets (Million pkts/ sec) 1997 622 Mb/s 1.56 1999 2.5 Gb/s 6.25 2001 10 Gb/s 25 2003 40 Gb/s 100 2006 80 Gb/s 200 SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 5
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Memory Technologies (2006) Note: rough estimates only. Manufacturer & technology & market dependent Technology Max single chip density $/chip ($/MByte) Access speed Watts/ chip Networking DRAM 64 MB $30-$50 ($0.50-$0.75) 40-80ns 0.5-2W SRAM 8 MB $50-$60 ($5-$8) 3-4ns 2-3W TCAM 2 MB $200-$250 ($100-$125) 4-8ns 15-30W SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 6
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(Ternary) Content Addressable Memory SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 7
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Lookup Problem: Protocol Dependent Networking Protocol Lookup Mechanism Techniques we will study MPLS, ATM (virtual circuits) Ethernet 1. Exact match search – Direct lookup – Associative lookup – Hashing – Binary/Multi-way Search Trie/ Tree IPv4, IPv6 (datagram) 2. Longest- prefix match search -Radix trie and variants -Compressed trie -Binary search on prefix intervals SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 8
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1. Exact Match – Virtual Circuit Reminder
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18c - Router Design - Lookup Problem - Last Lecture:...

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