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Direct Attach cabling & SFP Transceiver compatibility at Comware-Based Switches

lorn10
Advisor

Direct Attach cabling & SFP Transceiver compatibility at Comware-Based Switches

Hi to all!

Because I have lost somewhat the perspective here follows now some very technical questions.

At first, how it looks about Direct Attach on Comware-Based Switches? If the SFP+ module, which will add two additional regular SFP+ slots, is installed, Direct Attach works. So far so clear, - Direct Attach usually only works on SFP+ slots.

However, it seems that some (other) vendors have implemented similar concepts also for their normal SFP (non plus) based network devices. Of course, these proprietary “Direct Attach solutions” never reach higher speeds then the SFP standard (4 or 8 Gbit/s) can offer. Exist there any such Direct Attach alternative for former 3Com network devices?

What’s about all these SFP Fiber Channel Transceivers? They only work on special Fiber Channel compatible hardware and NOT on Comware-Based HP switches, right? I have found some nice Fiber Channel “Direct Attach” Cables from HP. However, these are most likely incompatible with 3Com 4800G and HP A5500-EI switch series. Can someone confirm this?

For example, the part numbers of these are:
HP 509506-001 --> HP 2M SFP 4GB FIBRE CHANNEL CABLE
HP 509506-002 --> HP 0.5M SFP 4GB FIBRE CHANNEL CABLE
HP 509506-003 --> HP 0.5M SFP 4GB FIBRE CHANNEL CABLE

And finally, to make the whole topic even more complex; Intel is producing some really interesting SFP Transceivers. For example, SFP Transceiver model TXN31115D100000 supports Fiber Channel at 4.25Gbps, (4X rate), 2.125Gbps (2X rate) and at 1.0625Gbps (1X rate). Additionally that Transceiver also supports Gigabit Ethernet rate (1.25Gbps) according to 1000Base-SX.

So far this Intel SFP Transceiver is compatible to Comware-Based switches; - it will run only in 1000Base-SX mode. It will definitely NOT work in any of these other faster Fiber Channel modes, right?

Thanks for any hint!

2 REPLIES
bakerbas
Advisor

Re: Direct Attach cabling & SFP Transceiver compatibility at Comware-Based Switches

So your questions are around Fibre Channel Transceiver support on Comware switches. Just to be clear the only Comware switches which support native FC (currently 4/8Gb) are the 5900CP-48XG switch and the Modular 5930s with the Universal Port module installed. The quick specs will list the supported FC optics, but other optics may work, they may just not be officially supported or tested. It seems to me that the FC cables should work, but i haven’t tested them.

HP does have a very cool universal optic for these switches which supports both Ethernet (10GbE), as well as native FC (4/8/16Gb). It is a great choice which provides flexibility and it is inexpensive.

I am not aware of the Intel options you mentioned.

lorn10
Advisor

Re: Direct Attach cabling & SFP Transceiver compatibility at Comware-Based Switches

Thanks bakerbas for your answer.

Well it seems that I haven’t understood the correct functionality of Fiber Channel.

After the study of the corresponding Wikipedia article I have now realize that Fiber Channel or better Fibre Channel has nothing to do with TCP & IP communication. Instead of TCP, Fibre Channel has its own Fibre Channel Protocol which is a distant derivate of the old SCSI technology.

According to this, Fibre Channel is clearly NOT designed to connect two normal (IP based) network Ethernet switches together. Fibre Channel seems to be made predominantly for ultra-fast storage connection / attachment.

Regarding stacking two Ethernet switches together there exist better (and simpler) ways like the mentioned SFP+ Direct Attach cabling or other vendor specific proprietary solutions. With normal SFP, only 1000Base gigabit Ethernet is possible. To some point that’s really disappointing.

The original SFP standard has a performance capability of around 5 Gbps per second. All these 1000Base SFP Modules only deliver 1.25 Gbps, which is just a quarter of the theoretical SFP performance. The largest part of the whole SFP performance is therefore not used.

A really nice thing would be a 10GBASE SFP (non-plus) Transceiver which would negotiate at 10 Gbps but which would internally limit to 5 Gbps. :)

Or, even crazier, - someone should urgently specify a 5GBASE Ethernet standard. Two of them could be bundled for a 10GBASE connection. My 3Com 4800G and most other SFP switches will then have automatically the capability of 2x 10 Gbps connections (4x 5 Gbps). ;):)