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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

Switches

Jean Walrand

U.C. Berkeley

www.eecs.berkeley.edu/~wlr

outline
Outline
  • Switch Characteristics
  • Examples
  • Functions
  • Output Buffer
  • Input Buffer
  • Virtual Output Buffer
  • Shared Memory
  • Modular
switch characteristics
Switch Characteristics
  • Ports
    • Fast Ethernet, OC-3, ATM, …
  • Protocols
    • ST, Link Agg., VLAN, OSPF, RIP, BGP, …
  • Performance
    • Throughput, 8-classes CoS, …
examples
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.

examples cont d
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.

examples cont d1
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, …
examples cont d2
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)
functions
Functions
  • Data Path and Control Path:

Note: Figure from Prof. Varaiya’s notes for EE228b

functions cont d
Functions (cont’d)
  • Data Path:
    • Extract header
    • Lookup forwarding rule
    • Queuing decision (drop, mark, queue)
    • Modify header
    • Store packet
    • Schedule transmission
    • Send packet
functions cont d1
Functions (cont’d)
  • Control Path
    • Routing table (IP, MPLS, ST, …)
    • Forwarding policies (RED, Policing, …)
    • Scheduling rules (WFQ, Priority, …)
functions cont d2
Functions (cont’d)
  • Timing:

Note: Figure from Prof. Varaiya’s notes for EE228b

functions cont d3
Functions (cont’d)
  • Table Lookup Example (routing)

Note: Figure from Prof. Varaiya’s notes for EE228b

functions cont d4
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

functions cont d5
Functions (cont’d)
  • Policing: Leaky Bucket

P bytes

Add P units

Capacity B

If overflow,

drop packet

or

mark packet

Leak Rate R

functions cont d6
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

functions cont d7
Functions (cont’d)
  • RED In and Out (RIO)

Prob.(drop IN)

Prob.(drop OUT)

qAV

IN = unmarked

OUT = marked

functions cont d8
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)

functions cont d9
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

functions cont d10
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

functions cont d11
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.

functions cont d12
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

output buffer
Output Buffer
  • Buffers at output ports
    • Limitation: Throughput < rate of shared bus

Note: Figure from Prof. Varaiya’s notes for EE228b

input buffer
Input Buffer
  • Buffers at input ports
    • Limitation: Head-of-Line blocking

Note: Figure from Prof. Varaiya’s notes for EE228b

virtual output buffer
Virtual Output Buffer
  • OUT buffers at each input port
    • Complexity: Matching Problem

Note: Figure from Prof. Varaiya’s notes for EE228b

virtual output buffer cont d
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

virtual output buffer cont d1
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

virtual output buffer cont d2
Virtual Output Buffer (cont’d)
  • i-SLIP (cont’d)

Request

Grant

Accept

Iter

2

3

1

1

3

2

Last Accept

Last Grant

shared buffer
Shared Buffer
  • One memory pool shared by flows
    • Limitation: Memory Speed

Note: Figure from Prof. Varaiya’s notes for EE228b

modular switches
Modular Switches
  • Space-Division Switching
    • Blocking