[cisco-voip] Modem Passthrough Dramas

[Amit Kumar]

Hello Drew,

Can you please try removing stcapp register capability command, then give
it a try.
On 04-Mar-2014 4:14 am, "Drewbles" <drewbles80 at gmail.com> wrote:

> Hi,
>
> I have a client that is currently planning a big bang cut over from an
> Ericsson MD110 to CUCM 9.1. I have recently found out that they have
> hundreds of modems that are connected to analog lines hanging off the
> MD110. These are dialled from other internal modems and also external
> parties calling into the modems directly via DID. During and after the
> migration to CUCM they will be leaving the modems on the analog lines
> connected to the MD110 and will be slowly moved over later on.
>
> I have configured the gateways for modem passthrough and it seems to be
> working. I can see some calls switchover (using 'debug voip rtp session
> named-event' and seeing event 192 & 193) but some other will not negotiate.
> At the moment calls to and from the MD110 are via two 3925 gateways using
> multiple E1s to the MD110 and SIP to CUCM. These gateways also provide
> connectivity to the PSTN. The problems calls are dialling the modems from a
> modem connected to a VG2XX. The VG224/VG204s are running SCCP.
>
> I can all calls negotiate modem passthrough by looking at the output of
> 'show call active voice brief' while the modems are negotiating. This is
> from the terminating gateway (3925) of a failed call:
>
> 0    : 179 -1510115396ms.1 (16:31:39.074 AEST Mon Mar 3 2014) +0 pid:0
> Originate  connecting
>
> dur 00:00:28 tx:1409/224504 rx:1408/224344 dscp:0 media:0 audio tos:0xB8
> video tos:0x0
>
> IP 172.28.100.1:24898 SRTP: off rtt:2ms pl:25190/0ms lost:0/0/0
> delay:65/65/65ms g711ulaw TextRelay: off Transcoded: No
>
> media inactive detected:n media contrl rcvd:n/a timestamp:n/a
>
> long duration call detected:n long duration call duration:n/a timestamp:n/a
>
> LostPacketRate:0.00 OutOfOrderRate:0.00
>
>   MODEMPASS nse buf:0/0 loss 0% 0/0  last 2519s dur:0/0s
>
> For example a call that works is:
> [PSTN modem] --E1--> [3925] --E1--> [MD110] --> [modem] - 100% success rate
>
> If I then dial from a modem connected to a VG204 to the same modem
> connected to the MD110 it fails. Call flow is:
> [VG204 modem] --SCCP--> [CUCM] --SIP--> [3925] --E1--> [MD110] --> [modem]
> - 100% failure
>
> However if I dial the PSTN modem in the first example from the VG204 modem
> the call is successfully:
> [VG204 modem] --SCCP--> [CUCM] --SIP--> [3925] --E1--> [PSTN modem]
>
> I don't have specific dial peers configured on the VG204 or the 3925
> gateway configured for fax/modem but I do have the following global
> commands:
>
> *VG204*
> voice service voip
>  modem passthrough nee codec g711ulaw
> !
> stcapp register capability 0/0 modem-passthrough
>
> *3925*
> voice service voip
>  fax protocol t38 nse version 0 ls-redundancy 0 hs-redundancy 0 fallback
> pass-through g711ulaw
>  modem passthrough nee codec g711ulaw
>
> I do have fax relay configured on the 3925 but I have also tried changing
> it to fax passthrough with no change in the behaviour of the modems calls.
>
> I know it's a big long winded but if anyone can provide feedback or
> suggestions that would be much appreciated. Happy to provide debugs.
>
>
> Cheers,
>
> Drew.
>
>
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>
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