Hi, I would like have some advice regarding connecting 2 routers back to back using V.35 interface. How much bandwidth I can attain in this manner ? Is it possible to get beyond 2Mbps !! and is it ok if I use this configuration in a production environment ?
Can someone please give a few pointers regarding the issue ?
According to this page recommended maximum is only 48Kbps, which is really low. I suspect this is an old document (for Cisco 7000 platform). I've been using V.35 interfaces for 2Mbps connections routinely for past 10 years without problems. Also the newer documents do mention speeds that are much higher than those humble few Kbps:
So back to original question - one can get up to 8Mbps over V.35 connection, but it depends on the hardware configuration.
I suspect that the recommendation they speak of is not Cisco's, but the CCITT's. The V.35 spec actually calls out only one speed of use:
48K. But as you say, well beyond that is no problem (and very common) for V.35. In general, for differential signals like V.35 and RS-422, the shorter the distance and lower capacitance of the cable, the faster you can go.
So the OP won't run into an electrical limitation. That leaves the question of what the serial port can handle, which is also not likely to be a issue.
------------------------------------------------------------------------ Steve Schefter phone: +1 705 725 9999 x26 The Software Group Limited fax: +1 705 725 9666
Thank you all for you comments. So, in summary we can use back to back configuration and depanding upon the distance and lower capacitance of the cable, and the hardware capability of the routers. I guess its not of a issue if one of the router is of NOT cisco make.
This brings up memories of 2 unrelated (but similar) situations that I ran into with V.35 in 1996. We had been using V.35 at 2Mb for many years, and in one situation we ran into an issue with a new V.35 connection between an IBM 3746 and Cisc 4700 Router (the 4700 was providing clocking) . If I remember correctly, the Cisco 4700 Docs of the time suggested that ~35ft was the maximum distance recommended, whereas the IBM Docs suggested that 50ft was fine (using IBM cable of course). We tried several local "tricks" to get this working over 45ft of cable but had regular errors (at a fairly low rate) at the 4700 end. Eventually we were able to shorten the cable to about 36ft and it all ran clean.
However this got us interested because we had never seen any issues with 2Mb at 50ft, and theoretically, you probably could run 100Mb over V.35, provided the cable length was short enough. Our research turned up a little known fact that the particular model of serial port card (I cannot remember what exact 4700 Serial card it was, except it had 6 ports on it) we were using in the 4700 had a "known cable length limitation", and that testing with a different Serial card the 4700 worked fine at 2Mb over 50ft.
So there are the published specs and each manufacturers implementation of those specs.........;-)