[cisco-nas] X.75 (LAPB-TA) sessions getting "stuck"? (AS5300, 12.3)

[Aaron Leonard]

> The weird thing is, the effect persists across calls.
> 
> So for the next call, it will behave identically - it will connect,
> exchange a few frames just fine, and then get stuck again.
> 
> What I did not test yet was to do multiple calls in parallel, to see
> whether the effect only hits a specific vty or "all of them".  Thanks
> for that idea.

I think the algorithm will always hit the first free vty.  So, if
let's say vty 0 is in use and vty 1 is (somehow) messed up, but free,
then the next LAPB-TA call would hit vty 1.  If, right after that,
another LAPB-TA call were to come in, it might hit vty 2 and maybe be
OK.

So if you could get the bad vty out of harms way (e.g. by removing
"transport input lapb-ta" from it), then this might get you going
again.

>>> (We could also downgrade to 12.2, if this is a new problem in 12.3...)
>> Yeah, if you just want to try different code versions, you could try
>> (among stuff that's still on CCO):
>>
>> 12.3(3i)
>> 12.2(15)T7
> 
> Under normal circumstances, I'd try 12.2 "main line" next - but since 
> you've recommended these two versions, what's special about them?  "Major
> surgery between 12.3(3) and 12.3(4)"?

Actually, the really nice code for the 5300 was the 12.2XB train.
Ah, 12.2(2)XB11 ... good times, good times.  (But you can't get it
any more.)  12.2(15)T7 is the closest that we have to 12.2(2)XB11, so
that's why I mentioned that.

12.2 mainline, on the other hand, was never used much on the 5300
- it didn't get the XB goodness.  It didn't support V.92, which we
made a big deal of back in the day, although looking back at it,
it didn't really add up to much.  So I suppose you could try 12.2
if you like.

When you come down to it, LAPB-TA never got exercised very much.
So I wouldn't expect to see much difference in different versions.

Best,

Aaron