Open Source Mobile Communications: Issueshttps://osmocom.org/https://osmocom.org/favicon.ico?16647414092019-08-15T15:04:11ZOpen Source Mobile Communications
Redmine OsmoMGW - Bug #4153 (New): 3G voice broken with ALu 9361 femtohttps://osmocom.org/issues/41532019-08-15T15:04:11Zdev_zzo
<p>Hello,</p>
<p>I am trying to create a setup with various Osmocom components to get the Alcatel-Lucent 9361 femtocells I have to function as a small 3G network. Currently, I am experiencing issues with 3G voice calls, quite similar to the ones described in <a class="issue tracker-1 status-3 priority-2 priority-default closed" title="Bug: 3G voice broken, CS RAB Assignment is not working (Resolved)" href="https://osmocom.org/issues/3411">#3411</a> / <a class="issue tracker-2 status-3 priority-2 priority-default closed behind-schedule" title="Feature: remove nano3G IuUP "Initialization ACK" hack when IuUP proxy is in place (Resolved)" href="https://osmocom.org/issues/2459">#2459</a> / <a class="issue tracker-2 status-3 priority-2 priority-default closed behind-schedule" title="Feature: Implement way how to handle IuUP on RTP endpoints (Resolved)" href="https://osmocom.org/issues/1937">#1937</a>: the voice call is dropped.</p>
<p>I have traced the issue to the following code: <a class="external" href="https://github.com/osmocom/osmo-mgw/blob/9aaaab6b3b5a541a6c17077f5f1f8bc00ba77152/src/libosmo-mgcp/mgcp_network.c#L873">https://github.com/osmocom/osmo-mgw/blob/9aaaab6b3b5a541a6c17077f5f1f8bc00ba77152/src/libosmo-mgcp/mgcp_network.c#L873</a></p>
<p>The femtocell rejects the IuUP message due to a CRC mismatch and indeed, when the bytes are patched, the header CRC is not updated and therefore cannot match.</p>