Actually implementing a voice solution FR PVC based between one central and manny distant sites. The QOS for voice is ensured using LLQ with FRF.12. CRTP is also used. Platforms used are 3660 and 26xx. We are encountering BIG voice quality issues on the 3660 platform using 12.2 mainline IOS as soon as the data rate on PVC goes near to CIR value (80% CIR). We are very concerned about that and actually searching for a more stable IOS release which can ensure the QOS needs or if there are other similar experiences in same environment.
I will be able to have that information only on monday!
I can add that from the voice perspective the 26xx and 3660 configurations are IDENTICAL! We have ALWAYS problems only in the direction 3660->26xx which indicates problems in handling the interleaving. At 3660 end we could always hear perfectly the voice originating from the 26xx end regardless of the load.
I have tested almost all IOS images available on 12.2 mainline! Also lab tests with identical configs were unable to reproduce the problem! FR provider was asked to increase the PVC CIR above the one configured on routers (on routers 128Kbps and SP has used 135Kbps) - same problems. Some times the problems are appearing at about 30-40Kbps traffic (near CIR voice becomes almost silence...).
I don't think that the problem can be because of hardware. Now the question is
1)was this a new installation or the exhisting one?
2)Was this setup ever worked? (Meaning was this problem there in the past or its newer one)
Now if the problem is there from bigining, then i don't doubt on hardware.
Now good to know that the issue is there in one direction only. so voice packets are getting dropped at either on 3660 or 26xx router. So those commands "sh frame pvc x/y" with "sh interface " should prove something.
2) Worked only once with 12.2.6a for some days (according to customer) but never after!
Found A LOT of problems in fast switching in 12.2 code which does NOT match packets to corresponding classes but to default one... Disabling fast switching - all starts matching correctly but voice quality problems still manifest. I suspect LFI working from time to time (like the VoIP on ISDN bug?)
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