# T38 Passthrough - T38FaxMaxDatagram default value?

**URL:** <https://community.asterisk.org/t/t38-passthrough-t38faxmaxdatagram-default-value/29887>\
**Category:** Asterisk Support\
**Created:** [November 26, 2009, 7:48pm UTC](https://community.asterisk.org/t/t38-passthrough-t38faxmaxdatagram-default-value/29887 "2009-11-26T19:48:57Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![system](https://global.discourse-cdn.com/asterisk/original/2X/4/475d0c889911cfb84ac4881ad6df8b523e3f9105.png) [@system](https://community.asterisk.org/u/system)\
**Post date:** [November 26, 2009, 7:48pm UTC](https://community.asterisk.org/t/t38-passthrough-t38faxmaxdatagram-default-value/29887/1 "2009-11-26T19:48:57Z")

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I have a Asterisk (ver 1.6.1.10) with T38 passthrough in the following setup -

SIP Trunk Service Provider – Asterisk – Quintum GW - Fax Machine

When sending Fax, the 200 OK response from Quintum does not contains T38Faxdatagram Attribute; and from the following debug messages

[Nov 26 10:54:14] ERROR[8980] udptl.c: Buffer overflow detected (6 + 3 \> 0)

It seems that Asterisk treat T38FaxMaxDatagram (no attribute in response) as 0.

Since the T38FaxMaxDatagrami is an optional parameter in T38 spec; how to interpret the “none exist” parameter in 200 OK response ? can we assume it is 0 (as implemented in Asterisk) or we should consider it as the confirmation of using our T38FaxMaxDatagram value in Re-Invite.

Thanks for any comments.