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Fibre Channel (SAN)

Posts: 0

Re: Ciena DWDM and Brocade ISL

Hi Tyrone,

currently it is difficult to measure latency on the Brocade side. If you use portcfglongdistance in LD mode the switch will measure the round trip time for a frame. This will be an indication of the latency of the link. Keep in mind that the latency is more important than the distance. Some WDM devices adds internal latency. This can result in "longer link".

It can happens that LD will allocate more buffer compared to the real physical link length. This can be an indication of the internal latency of your DWDM device.

Here is a formular to calculate the buffer value:

  • If QoS is enabled:

    (Reserved Buffer for Distance Y) = (X * LinkSpeed / 2) + 6 + 14

  • If QoS is not enabled:

    (Reserved Buffer for Distance Y) = (X * LinkSpeed / 2) + 6

Link speed (1,2,4,or 8)

Keep in mind that this calculation is based on full sized frames. If you have many small frames you need more buffer. If you check buffer credit zero value an it is an rapid increasing value  add some more buffers. After finding the good value change the LD mode to LS. If you have a redundant connection on the Ciena backend side make sure that you make your tests on the longer route.

The Ciena Management tool should provide some graphs with latency and bandwidth usage if the Brocade values didn't meet your requirements.



Regular Contributor
Posts: 165
Registered: ‎05-11-2011

Re: Ciena DWDM and Brocade ISL

Hi Tyron,

ask the following:

Which Fibre-Channel speed does the System and the installed SFP support?

(I saw in the technical Specs that the system is supporting 1 ,2 ,4 and 10G FC).

Ask them about the technical specs. for the installed SFP's. You will see if you can use SWL SFP(with Multimode Cable) or LWL SFP (with Single Mode Cable) between your Brocade and Ciena EQ.

Regards Ralf

Kind Regards
Posts: 0

Re: Ciena DWDM and Brocade ISL

Guys, sorry for the (extended) delay in replying. Thanks for all your contributions.

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