3750 Switch terms

[JustForVoice_2]

Hi,

while I was reading QoS for 3750 switch, I found the following paragraph from: "Catalyst 3750 Switch Software Configuration Guide"

Because the total inbound bandwidth of all ports can exceed the bandwidth of the stack ring, ingress queues are located after the packet is classified, policed, and marked and before packets are forwarded into the switch fabric. Because multiple ingress ports can simultaneously send packets to an egress port and cause congestion, outbound queues are located after the stack ring.

Any body can help me to understand the meaning of the follwoing terms:

• Stack ring.
• Switch fabric.

Regards,

[Collin Clark]

JustForVoice wrote:
Hi,
while I was reading QoS for 3750 switch, I found the following paragraph from: "Catalyst 3750 Switch Software Configuration Guide"
Because the total inbound bandwidth of all ports can exceed the bandwidth of the stack ring, ingress queues are located after the packet is classified, policed, and marked and before packets are forwarded into the switch fabric. Because multiple ingress ports can simultaneously send packets to an egress port and cause congestion, outbound queues are located after the stack ring.
Any body can help me to understand the meaning of the follwoing terms:
Stack ring.
Switch fabric.
Regards,

Stack Ring: Cisco StackWise Plus technology is built on the highly successful industry leading StackWise technology, which is a premium stacking architecture optimized for GbE. StackWise technology was designed to respond to additions, deletions, and redeployment while maintaining constant performance. The stack behaves as a single switching unit that is managed by a master switch elected from one of the member switches. The master switch automatically creates and updates all the switching and optional routing tables. A working stack can accept new members or delete old ones without service interruption. StackWise creates a highly resilient single unified system of up to nine switches, providing simplified management using a single IP address, single telnet session, single command-line interface (CLI), auto-version checking, autoconfiguration, and more. StackWise Plus supports all the features of StackWise and provides backward compatibility with the existing Cisco Catalyst 3750 Series Switches while enhancing the throughput of the system up to 64 Gbps. StackWise Plus also enables local switching in Cisco Catalyst 3750-X Series Switches. Local switching packets coming into a port in the Cisco Catalyst 3750-X Series or 3750-E Series Switch destined for another port in the same switch do not have to traverse through the stack ring, thus increasing the forwarding capacity of the switch.

Switch Fabric: http://en.wikipedia.org/wiki/Switched_fabric

The switch fabric is the place where traffic goes to get from port X to port Y on the switch.

Hope it helps.

[JustForVoice_2]

Thank you Collin,

it is clear now for switch fabric but not too much regarding stack ring.

I know the meaning of stack and how to configure the master switch and how to manage. but from my first post:

outbound queues are located after the stack ring

and from your post:

Local  switching packets coming into a port in the Cisco Catalyst 3750-X  Series or 3750-E Series Switch destined for another port in the same  switch do not have to traverse through the stack ring,

So, again what is the meaning of stack ring ? it seems like some thing inside the swithc.

[Reza Sharifi]

Hi,

Stack ring bandwidth depends on the stack cabling. If the stack is           connected at full bandwidth, you receive 32Gbps bandwidth. This bandwidth is           shared by all the switches in the stack.

So, for example if you have a 3750-E switch and issue command

C3750-E#sh switch stack-ring speed

Stack Ring Speed        : 16G
Stack Ring Configuration: Half
Stack Ring Protocol     : StackWisePlus
C3750-E#

As you can see the speed is 16G, but if you stack 2 3750-E switches together you will see this:

C3750-E#sh switch stack-ring speed

Stack Ring Speed        : 32G
Stack Ring Configuration: Full
Stack Ring Protocol     : StackWisePlus
C3750-E#

So, it is 16 vs 32 Gig

HTH

Reza

[JustForVoice_2]

Thank you Reza

from:

Because the total inbound bandwidth of all ports can exceed the bandwidth of the stack ring,

can I say the following if we have 2 * 3750 switches each one 48 ports then the total inbound bandwidth will be 48 * 1 G then the total bandwidth 48 G per 1 switch and for 2 switches it will 96 G > 32 G stack ring

[Reza Sharifi · Accepted solution]

According to this link, table 8 for E series switches:

64-Gbps, high-speed StackWise Plus stacking

160-Gbps wire rate, nonblocking switching fabric capacity

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps7077/product_data_sheet0900aecd805bbe67.html

So 64-Gbps, high-speed StackWise Plus stacking means for 2 switch and a single swich should be 32Gig, but I anly see 16 and 32

The data I provided are from E-series switches in stack and non-stack mode

in non-stach it show the speed of 16Gig and when stacked 32Gig total.

to me, this looks like oversubscribing

[JustForVoice_2]

Thank you too much