CSCvf07153 is a pretty simple mistake exacerbated by inconsistent implementation from Cisco.

What is it? Cisco CUBE sends the local timezone of the router in SIP headers when the RFC specifies that GMT should always be used. This causes some SBCs to respond with 400 SIP Parser Error : Missing TIME ZONE and causes calls both inbound and outbound to fail.

The bug lists a workaround, yet the workaround is not complete for two reasons.

1. It only lists the Daylight Saving timezone and not the Standard timezone
2. It lists the timezones only in upper-case, but CUBE (3.16.7S) uses upper-case for Standard time and lower-case for Daylight Saving time.

TAC is updating the bug notes with this info, but it may not show up for a few days. Here’s a proper workaround. Replace CST/CDT/cst/cdt with your timezone:

voice class sip-profiles 27
  response ANY sip-header Date modify "CST" "GMT"
  response ANY sip-header Date modify "CDT" "GMT"
  request ANY sip-header Date modify "CST" "GMT"
  request ANY sip-header Date modify "CDT" "GMT"
  response ANY sip-header Date modify "cdt" "GMT"
  request ANY sip-header Date modify "cdt" "GMT"
  response ANY sip-header Date modify "cst" "GMT"
  request ANY sip-header Date modify "cst" "GMT"

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