What is the "backplane"?

[RicN]

Perhaps a stupid question, but what does the word "backplane" mean when talking about switches, and what is its importence?

[cenk sasmaztin]

backplane switch mainboard
all module or ports connect on backplane

backplane capacity between ports or modules comminication on switch

please look my attachment

[Mohieddin Kharnoub]

Hi

Adding to CENK info.

You have Passive Backplane and Active Backplane.

Passive: Where you don't have Controller (Management) on the board . Example: 8200 series.

Active: Where you have Controller and management of the switch on board. Example: 5400 series.

Good Luck !!!

[RicN]

cenk sasmaztin:

>backplane capacity between ports or modules comminication on switch

So does the backplane capacity tell how much traffic the switch could handle at a given moment? Or can I assume that if I have a 24 port 100mbit switch that I could send 100 mbit/s full duplex on all ports at the same time? Or is it the backplane that could set the limit for this?


Mohieddin Kharnoub:

>Passive: Where you don't have Controller (Management)
>on the board . Example: 8200 series.

>Active: Where you have Controller and management
>of the switch on board. Example: 5400 series.

What is the difference between active and passive in performance?

And what is the Controller and Management? :)

[Richard Brodie_1]

"Or can I assume that if I have a 24 port 100mbit switch that I could send 100 mbit/s full duplex on all ports at the same time? "

That's a fairly safe assumption, except on a really budget module because it's not too demanding. If you have a switch with half a dozen modules, each with 48 Gigabit ports, then backplane bandwidth is more of an issue.

[RicN]

Richard:

>That's a fairly safe assumption, except on
>a really budget module because it's not too
>demanding. If you have a switch with half a
>dozen modules, each with 48 Gigabit ports,
>then backplane bandwidth is more of an issue.

Thank you for your answer!

So it is possible for larger switches with, as in your example, 48 GB ports - that the backplane actually sets a limit for the traffic through the ports?

How is the backplane performance expressed in technial / sales terms? How well does Procurve switches scale?

[Matt Hobbs]

From a performance perspective, yes the backplane can be a limiting factor. Fortunately most gigabit ProCurve switches these days are considered wirespeed (i.e, can switch frames as fast as theoretically possible).

Have a look through the reviewers guide, it gives you some great information on the particular product - e.g. http://www.hp.com/rnd/pdfs/ProCurve_Switch_5400zl_Series_Reviewers_Guide.pdf

If you look at the specs of the 5406, you can see it has a backplane of 346 Gbps. This is calculated by:

1. Each module has a 28.8 Gbps link to the backplane. (More than enough for 24 Gigabit ports, but not quite enough for 4 wirespeed 10 Gig ports)

2. 6 slots, multiplied by 28.8 = 172.8 Gbps

3. For full duplex, we double it, 172.8 x 2 = 345.6 Gbps

[cenk sasmaztin]

hi RicN
connect to switch port or module backplane on switch each port 100 or 1000 mbps connect switch backplane
but provision asic switch different way connect backplane each module two line connect backplane

for example
5400 switch have active backplane
switch fabric chip on backplane board
each module two 14.4 Gpbs link connect backplane namely one module 28.8 Gbps connect back plane

8212 switch have passive backplane
switch fabric chip on switch fabric module
each module connect two 14,4 Gbps line to fabric module
back board not keep fabric chip



backplane calculator

we have 100 Mbps 24 port 1000Mbps 2 port swtich for example 2626

100 Mbps x2(full duplex)200Mbps one port x 24 port = 4800 Mbps**

1000Mbps x2(full duplex)2000Mbps one port x 2 port = 4000 Mbps

4000Mbps+4800 Mbps =8800 Mbps =8,8 Gbps real backplane requirement
please look back plane capacity 2626 switch www.procurve.com


but chasis type switch different back plane capacity because each module seperate like switch


cenk

[RicN]

Thank you very much both Matt and Cenk!

Firstly, I just read this in the specification of some switch:

"Throughput: 10.1 million pps"

What is the unit "pps"? Something per second probably, but what? :)


Matt:

>1. Each module has a 28.8 Gbps link to the
>backplane. (More than enough for 24 Gigabit ports,
>but not quite enough for 4 wirespeed 10 Gig ports)

But can that 28.8 Gbps cover 24 Gigabit ports sending and recieving at full speed in full duplex? (theoreticaly)


Cenk:

I am still unsure if I understand correctly. The switch fabric, is that the part of the switch hosting the actual ports? What is the advantage for keeping that separated from the backplane?

[cenk sasmaztin]

hi RicN
throughput: 101 million pps(packet per secont)

all interface one sec/packet receive and transmit capacity

1. Each module has a 28.8 Gbps link to the
>backplane. (More than enough for 24 Gigabit ports,
>but not quite enough for 4 wirespeed 10 Gig ports)

yess only two ten Gig port running same module
other two ten Gig module out of action full performance



Cenk:

I am still unsure if I understand correctly. The switch fabric, is that the part of the switch hosting the actual ports? What is the advantage for keeping that separated from the backplane?


each module running interior switching and connect backplane with two line (14.4Gbps x2) one fabric chip be happen crash all switch running %50 persormance not interruption
8212 switch easy change fabric chip because fabric chip residing switch front panel(switch fabric module)
but 5400 active backplane and fabric chip residing in switch

all other 24 -48 port switch one fabric chip and each module connect same chip

cenk

[Matt Hobbs]

The 28.8 Gbps is full duplex, so yes, more than enough for bi-directional traffic for 24 Gigabit Ports.

pps is packets per second. Usually calculated by 64 Byte packets. (smallest Ethernet frame).