Twinax trivia check (was Re: Is there such a thing as a 10GBase-T SFP+ transciever)
On 2/1/2014 10:40 PM, Jima wrote:
+1. Cisco calls them Twinax, HP calls them DACs. I don't know what anyone else calls them as it hasn't come up in conversation for me.
I thought "Twinax" was an IBMish MILSPEC term. -- Requiescas in pace o email Two identifying characteristics of System Administrators: Ex turpi causa non oritur actio Infallibility, and the ability to learn from their mistakes. (Adapted from Stephen Pinker)
On 2/2/14, 7:30 AM, Larry Sheldon wrote:
On 2/1/2014 10:40 PM, Jima wrote:
+1. Cisco calls them Twinax, HP calls them DACs. I don't know what anyone else calls them as it hasn't come up in conversation for me.
I thought "Twinax" was an IBMish MILSPEC term.
twinax could refer to a specific technology or to the presence of dual inner conductors e.g. in contrast to coax or triax.
----- Original Message -----
From: "joel jaeggli" <joelja@bogus.com>
I thought "Twinax" was an IBMish MILSPEC term.
twinax could refer to a specific technology or to the presence of dual inner conductors e.g. in contrast to coax or triax.
Rather specifically, Twinax refers to cable with 2 center conductors in it's foam or plastic insulator *both within the same shield* -- generally, I think always, a balanced pair. Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://www.bcp38.info 2000 Land Rover DII St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 1274
These cables are most commonly known as "Direct Attach Copper SFP+" On Sunday, February 2, 2014, Jay Ashworth <jra@baylink.com> wrote:
----- Original Message -----
From: "joel jaeggli" <joelja@bogus.com <javascript:;>>
I thought "Twinax" was an IBMish MILSPEC term.
twinax could refer to a specific technology or to the presence of dual inner conductors e.g. in contrast to coax or triax.
Rather specifically, Twinax refers to cable with 2 center conductors in it's foam or plastic insulator *both within the same shield* -- generally, I think always, a balanced pair.
Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com <javascript:;> Designer The Things I Think RFC 2100 Ashworth & Associates http://www.bcp38.info 2000 Land Rover DII St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 1274
-- eSited LLC (701) 390-9638
On 2/2/2014 4:03 PM, Bryan Tong wrote:
These cables are most commonly known as "Direct Attach Copper SFP+"
The big issue appears to be that these are not always "consistently functional" crossing vendor lines (sometimes product lines within the same vendor). There does not appear to be any standardization in place. Not sure how much of this is picky vendor software looking for "branded" marks in their transceivers (e.g., Cisco "service unsupported-transceiver") versus true incompatibilities. We have had issues in test cases crossing vendor lines (Cisco / Brocade / Dell / HP) with a "twinax" link that just simply won't work. If anyone has a clear explanation or better understanding, I'm all ears. Personal experience comes from only a few testbed cases. Jeff
Most of the switch vendors have an "official" compatibility list, but I've found that generally the most common compatibility issue is active vs passive twinax. Brocade edge switches and nics are normally active only, which seems to come up a lot - because most short cables are passive unless they are brocade branded. >5m is normally the cutoff for passive twinax. Pretty much everything else I've encountered supports passive. For a while, the intel x520 nics, which are very common, didn't support active connections - but they have since released firmware that fixes this problem. Netapp's lower end gear doesn't support active twinax. ________________________________________ From: Jeff Kell [jeff-kell@utc.edu] Sent: Sunday, February 02, 2014 3:15 PM To: Bryan Tong; Jay Ashworth Cc: NANOG Subject: Re: Twinax trivia check (was Re: Is there such a thing as a 10GBase-T SFP+ transciever) On 2/2/2014 4:03 PM, Bryan Tong wrote:
These cables are most commonly known as "Direct Attach Copper SFP+"
The big issue appears to be that these are not always "consistently functional" crossing vendor lines (sometimes product lines within the same vendor). There does not appear to be any standardization in place. Not sure how much of this is picky vendor software looking for "branded" marks in their transceivers (e.g., Cisco "service unsupported-transceiver") versus true incompatibilities. We have had issues in test cases crossing vendor lines (Cisco / Brocade / Dell / HP) with a "twinax" link that just simply won't work. If anyone has a clear explanation or better understanding, I'm all ears. Personal experience comes from only a few testbed cases. Jeff
We've worked through the same issues with Brocade/Intel, although we found that even though Brocade specs active only, our ICX switches don't reject passive cables, although oddly the Intel branded passive cables show up as UNSUPPORTED (but FCI and Molex ones from Digikey show up as the correct length and correct type of cable). If you do decide to go generic make sure you check the sizing. Maybe Brocade SFP+ drive is weak but using some 28 AWG 5M cables we've seen it takes a lot of errors. Switching to 26 AWG or 24 AWG solved the issue. I suspect Brocade requires active just from their storage background. On Sun, Feb 2, 2014 at 5:49 PM, Murphy-Olson, Daniel E. <dolson@mcs.anl.gov>wrote:
Most of the switch vendors have an "official" compatibility list, but I've found that generally the most common compatibility issue is active vs passive twinax.
Brocade edge switches and nics are normally active only, which seems to come up a lot - because most short cables are passive unless they are brocade branded. >5m is normally the cutoff for passive twinax. Pretty much everything else I've encountered supports passive.
For a while, the intel x520 nics, which are very common, didn't support active connections - but they have since released firmware that fixes this problem. Netapp's lower end gear doesn't support active twinax.
________________________________________ From: Jeff Kell [jeff-kell@utc.edu] Sent: Sunday, February 02, 2014 3:15 PM To: Bryan Tong; Jay Ashworth Cc: NANOG Subject: Re: Twinax trivia check (was Re: Is there such a thing as a 10GBase-T SFP+ transciever)
On 2/2/2014 4:03 PM, Bryan Tong wrote:
These cables are most commonly known as "Direct Attach Copper SFP+"
The big issue appears to be that these are not always "consistently functional" crossing vendor lines (sometimes product lines within the same vendor). There does not appear to be any standardization in place. Not sure how much of this is picky vendor software looking for "branded" marks in their transceivers (e.g., Cisco "service unsupported-transceiver") versus true incompatibilities.
We have had issues in test cases crossing vendor lines (Cisco / Brocade / Dell / HP) with a "twinax" link that just simply won't work. If anyone has a clear explanation or better understanding, I'm all ears. Personal experience comes from only a few testbed cases.
Jeff
participants (7)
-
Brian Loveland -
Bryan Tong -
Jay Ashworth -
Jeff Kell -
joel jaeggli -
Larry Sheldon -
Murphy-Olson, Daniel E.