Switching Hardware 10/11/06 CS/ECE 438 - UIUC, Fall 2006 1 Switch - PowerPoint PPT Presentation

Switching Hardware 10/11/06 CS/ECE 438 - UIUC, Fall 2006 1

Switch Design Chicago Bloomington Champaign Indianapolis Springfield Effingham St. Louis 10/11/06 CS/ECE 438 - UIUC, Fall 2006 2

Switch Design Chicago Bloomington Champaign Indianapolis Springfield Effingham St. Louis 10/11/06 CS/ECE 438 - UIUC, Fall 2006 2

Switch Design Chicago Bloomington Champaign Indianapolis How should we Springfield design Champaign to accommodate Effingham St. Louis traffic flows? 10/11/06 CS/ECE 438 - UIUC, Fall 2006 2

Switch Design Chicago Bloomington Champaign Indianapolis How should we Springfield design Champaign to accommodate Effingham St. Louis traffic flows? 10/11/06 CS/ECE 438 - UIUC, Fall 2006 2

Contention 10/11/06 CS/ECE 438 - UIUC, Fall 2006 3

Contention  Bridges: same collision domain If an output port is busy when forwarding packet  from input port, cause collision 10/11/06 CS/ECE 438 - UIUC, Fall 2006 3

Contention  Bridges: same collision domain If an output port is busy when forwarding packet  from input port, cause collision  Switches: different collision domain Use CSMA/CD before sending packet onward  10/11/06 CS/ECE 438 - UIUC, Fall 2006 3

Contention  Bridges: same collision domain If an output port is busy when forwarding packet  from input port, cause collision  Switches: different collision domain Use CSMA/CD before sending packet onward   Buffer packets When output port is busy  When multiple packets are destined for same  output port 10/11/06 CS/ECE 438 - UIUC, Fall 2006 3

Switch Design Input Port Output Port Input Port Output Port Input Port Output Port Switch Fabric Input Port Output Port Input Port Output Port Input Port Output Port 10/11/06 CS/ECE 438 - UIUC, Fall 2006 4

Contention – Output Port Buffering standard checkout lines customer service B A trying to buy food you irate Bob Alice writing complaint waiting to return letter in triplicate penny given in error 1x6 switch 10/11/06 CS/ECE 438 - UIUC, Fall 2006 5

Contention – Input Port Buffering standard checkout lines customer service B Alice A waiting to return irate Bob penny given in error writing complaint letter in triplicate trying to buy food head-of-line you 1x6 switch blocking 10/11/06 CS/ECE 438 - UIUC, Fall 2006 6

Contention – Input Port Buffering standard checkout lines customer service cashiers are standing by! B Alice A waiting to return irate Bob penny given in error writing complaint letter in triplicate trying to buy food head-of-line you 1x6 switch blocking 10/11/06 CS/ECE 438 - UIUC, Fall 2006 6

Contention – Output Port Contention standard checkout lines customer service B irate Bob A writing complaint letter in triplicate Alice waiting to you return penny given in error waiting to complain 1x6 switch about head-of-line blocking 10/11/06 CS/ECE 438 - UIUC, Fall 2006 7

Contention – Buffering Capacity standard checkout lines customer service B A buffering capacity per output is finite you 1x6 switch (others turned away at door) 10/11/06 CS/ECE 438 - UIUC, Fall 2006 8

Contention – Back Pressure  Let the receiver tell the sender to slow down Propagation delay requires that the receiver  react before the buffer is full Typically used in networks with small  propagation delay switch 1 switch 2 “no more, please” 10/11/06 CS/ECE 438 - UIUC, Fall 2006 9

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 1 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 2 1 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 3 2 1 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 1 4 3 2 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 2 1 5 4 3 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). stop Switch Switch 3 2 1 6 5 4 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). stop Switch Switch 4 3 2 1 7 6 5 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). stop Switch Switch 5 4 3 2 1 8 7 6 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 6 5 4 3 2 1 9 8 7 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 6 5 4 3 2 1 9 8 Discard: 7 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 6 5 4 3 2 1 9 Discard: 8 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Contention – Back Pressure  NOTE Propagation delay requires that switch 2 exert  backpressure at high-water mark rather when buffer completely full. Backpressure is thus typically only used in networks with small propagation delays (e.g., switch fabrics). Switch Switch 6 5 4 3 2 1 Discard: 9 10/11/06 CS/ECE 438 - UIUC, Fall 2006 10

Switch Design Goals  Throughput  Number of packets a switch can forward per second  Scalability  How many input/output ports can it connect  Cost  Per port monetary costs 10/11/06 CS/ECE 438 - UIUC, Fall 2006 11

Special Purpose Switches  Problem Connect N inputs to M outputs  NxM (“N by M”) switch  Often N = M   Goals High throughput  Best is MIN(sum of inputs, sum of outputs)  Avoid contention  Good scalability  Linear size/cost growth  10/11/06 CS/ECE 438 - UIUC, Fall 2006 12

Switch Design  Ports handle complexity  Forwarding decisions  Buffering  Simple fabric  Move packets from inputs to outputs  May have a small amount of internal buffering 10/11/06 CS/ECE 438 - UIUC, Fall 2006 13

Switch Design Goals  Throughput Main problem is contention  Need a good traffic model  Arrival time  Destination port  Packet length  Telephony modeling is well understood  Until faxes and modems  Modeling of data traffic is new  Not well understood  Will good models help?  10/11/06 CS/ECE 438 - UIUC, Fall 2006 14