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Switches

Switches. Jean Walrand U.C. Berkeley www.eecs.berkeley.edu/~wlr. Outline. Switch Characteristics Examples Functions Output Buffer Input Buffer Virtual Output Buffer Shared Memory Modular. Switch Characteristics. Ports Fast Ethernet, OC-3, ATM, … Protocols

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Switches

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  1. Switches Jean Walrand U.C. Berkeley www.eecs.berkeley.edu/~wlr

  2. Outline • Switch Characteristics • Examples • Functions • Output Buffer • Input Buffer • Virtual Output Buffer • Shared Memory • Modular

  3. Switch Characteristics • Ports • Fast Ethernet, OC-3, ATM, … • Protocols • ST, Link Agg., VLAN, OSPF, RIP, BGP, … • Performance • Throughput, 8-classes CoS, …

  4. Examples • Cisco 12416: The Cisco 12416 Internet router is a 10 Gigabit, 16-slot chassis member of the Cisco 12000 series that provides a total switching capacity of 320 Gigabits per second (Gbps), with 20 Gbps (10 Gbps full duplex) capacity per slot. With its 16-slot chassis and extensive portfolio of line cards including the new Cisco 1-port OC-192c/STM-64c and Cisco 4-port OC-48c/STM-16c POS interfaces, the Cisco 12416 Internet router supports high-density ISP aggregation and point-of-presence (POP) consolidation.

  5. Examples (cont’d) • Cisco 3600 Voice over Frame relay (VoFR) and Voice over ATM (VoATM-AALS) on the digital voice interfaces (T1 and E1). Gateways for the PBX and PSTN for IP telephony, enabling applications like call transfers, holds, and conferencing.

  6. Examples (cont’d) • Extreme Networks - Summit • 48 10/100 ports • 2 GE (SX, LX, or LX-70) • 17.5Gbps non-blocking • 10.1 Mpps • Wire speed L2 • Wire speed L3 static or RIP • OSPF, DVRMP, PIM, …

  7. Examples (cont’d) • Foundry ServerIron • Server Load Balancing • Transparent Cache Switching • Firewall Load Balancing • Global Server Load Balancing • Extended Layer 4-7 functionality including URL-, Cookie-, and SSL Session ID-based switching • Secure Network Address Translation (NAT) and Port address translation (PAT)

  8. Functions • Data Path and Control Path: Note: Figure from Prof. Varaiya’s notes for EE228b

  9. Functions (cont’d) • Data Path: • Extract header • Lookup forwarding rule • Queuing decision (drop, mark, queue) • Modify header • Store packet • Schedule transmission • Send packet

  10. Functions (cont’d) • Control Path • Routing table (IP, MPLS, ST, …) • Forwarding policies (RED, Policing, …) • Scheduling rules (WFQ, Priority, …)

  11. Functions (cont’d) • Timing: Note: Figure from Prof. Varaiya’s notes for EE228b

  12. Functions (cont’d) • Table Lookup Example (routing) Note: Figure from Prof. Varaiya’s notes for EE228b

  13. Functions (cont’d) 001 1 • CIDR Lookup 00011 2 Ternary CAM 3 4 010011** 00011*** 001***** 11****** 3 2 1 4 010011 11 * = don’t care Returns first match Associated Data = Port

  14. Functions (cont’d) • Policing: Leaky Bucket P bytes Add P units Capacity B If overflow, drop packet or mark packet Leak Rate R

  15. Functions (cont’d) • RED: Random Early Discard Objectives: Reduce synchronization of sources Avoid penalizing bursts Drop more from more active sources Effectiveness: so so Operations: q H L Prob.(drop) 0.1 qAV H L

  16. Functions (cont’d) • RED In and Out (RIO) Prob.(drop IN) Prob.(drop OUT) qAV IN = unmarked OUT = marked

  17. Functions (cont’d) • Priority Scheduling: Priority 1 2 3 When finished transmitting a packet, serve next from first nonempty queue in order (1, 2, 3)

  18. Functions (cont’d) Weight • Deficit Round Robin (DRR) (5/10)R 5 (5/10)R 2 3 (5/10)R Get to new queue: Empty: Skip; Else: Add weight to credits Credits > 0 => serve one packet, subtract 1 credit per byte Credits < 0 => Go to next queue Repeat

  19. Functions (cont’d) 18 3 20 10 • DRR (cont’d) A 7 30 5 14 3 B Credits A: 0 7 -3 4 -16 - 9 -2 5 2 -16 … Credits B: 0 3 -11 - 8 -5 -2 1 -4 … Send 10 14 20 3 18 5

  20. Functions (cont’d) • Weighted Fair Queuing (WFQ) Weight (5/10)R 5 (5/10)R 2 3 (5/10)R Compute departure times from processor sharing queue with these weights. Serve next the queue with earliest deadline.

  21. Functions (cont’d) • WFQ (cont’d) Leaves at t 10 5 A 2 B 3 C 14 14 - 3/8 10 - 5/8 => Serve A t

  22. Output Buffer • Buffers at output ports • Limitation: Throughput < rate of shared bus Note: Figure from Prof. Varaiya’s notes for EE228b

  23. Input Buffer • Buffers at input ports • Limitation: Head-of-Line blocking Note: Figure from Prof. Varaiya’s notes for EE228b

  24. Virtual Output Buffer • OUT buffers at each input port • Complexity: Matching Problem Note: Figure from Prof. Varaiya’s notes for EE228b

  25. Virtual Output Buffer (cont’d) • Full-Throughput Scheduling:Maximum Weighted Matching A = 14 B + C > A + D => Serve (B, C) B = 11 C = 15 D = 10

  26. Virtual Output Buffer (cont’d) • i-SLIP 1. Request: Nonempty VOBs request to outputs 2. Grant: Outputs grant (in RR order) VOBs 3. Accept: Granted VOBs accepts (in RR order) 4. Iterate: Repeat after removing accepts

  27. Virtual Output Buffer (cont’d) • i-SLIP (cont’d) Request Grant Accept Iter 2 3 1 1 3 2 Last Accept Last Grant

  28. Shared Buffer • One memory pool shared by flows • Limitation: Memory Speed Note: Figure from Prof. Varaiya’s notes for EE228b

  29. Modular Switches • Space-Division Switching • Blocking

  30. Modular Switches (cont’d) • Non-Blocking

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