Input port functions link lookup, layer forwarding line switch protocol termination fabric (receive) queueing physical layer: bit-level reception decentralized switching: link layer: e.g.,Ethernet using header field values,lookup output port using (chapter 6) forwarding table in input port memory(match plus action") destination-based forwarding:forward based only on destination IP address(traditional) generalized forwarding:forward based on any set of header field values Network Layer:4-16
Input port functions line termination lookup, forwarding queueing decentralized switching: ▪ using header field values, lookup output port using forwarding table in input port memory (“match plus action”) ▪ destination-based forwarding: forward based only on destination IP address (traditional) ▪ generalized forwarding: forward based on any set of header field values physical layer: bit-level reception switch fabric link layer protocol (receive) link layer: e.g., Ethernet (chapter 6) Network Layer: 4-16
Destination-based forwarding forwarding table Destination Address Range Link Interface 11001000000101110001000000000000 throuah 11001000000101110001000000000100 through 3 11001000000101110001000000000111 11001000000101110001100011111111 11001000000101110001100100000000 through 2 11001000000101110001111111111111 otherwise 3 Q:but what happens if ranges don't divide up so nicely? Network Layer:4-17
Q: but what happens if ranges don’t divide up so nicely? Destination-based forwarding 3 Network Layer: 4-17
Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address,use longest address prefix that matches destination address. Destination Address Range Link interface 110010000001011100010*** ★★★★★★★★ 0 11001000 0001011100011000 ★★★★★★★大 1 11001000 0001011100011*** ★大★★★★★★ 2 otherwise 3 11001000000101110001011010100001 which interface? examples: 11001000000101110001100010101010 which interface? Network Layer:4-18
Longest prefix matching when looking for forwarding table entry for given destination address, use longest address prefix that matches destination address. longest prefix match Destination Address Range 11001000 00010111 00010 11001000 00010111 00011000 11001000 00010111 00011 otherwise Link interface 0 1 2 3 *** ******** *** ******** ******** 11001000 00010111 00011000 10101010 examples: which interface? which interface? 11001000 00010111 00010110 10100001 Network Layer: 4-18
Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address,use longest address prefix that matches destination address. Destination Address Range Link interface 11001000 00010111 00010 女★★女大女女 0 11001000 00 00011000 女★★★★★★★ 1 11001000 match! 00011*** ★★大★★大为 2 otherwise 3 11001000 00010111 00010 10100001 which interface? examples: 11001000 00010111 0001100010101010 which interface? Network Layer:4-19
Longest prefix matching when looking for forwarding table entry for given destination address, use longest address prefix that matches destination address. longest prefix match Destination Address Range 11001000 00010111 00010 11001000 00010111 00011000 11001000 00010111 00011 otherwise Link interface 0 1 2 3 11001000 00010111 00011000 10101010 examples: which interface? which interface? *** ******** *** ******** ******** 11001000 00010111 00010110 10100001 match! Network Layer: 4-19
Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address,use longest address prefix that matches destination address. Destination Address Range Link interface 1100100000010111 00010女t 0 11001000 00010111 00011000 1 11001000 00010111 00011 ★士+★ 2 otherwise 金 3 match! 11001000 ↓ 0001011010100001 which interface? examples: 1001000 00010111 00011 00 10101010 which interface? Network Layer:4-20
Longest prefix matching when looking for forwarding table entry for given destination address, use longest address prefix that matches destination address. longest prefix match Destination Address Range 11001000 00010111 00010 11001000 00010111 00011000 11001000 00010111 00011 otherwise Link interface 0 1 2 3 11001000 00010111 00011000 10101010 examples: which interface? which interface? *** ******** *** ******** ******** 11001000 00010111 00010110 10100001 match! Network Layer: 4-20