Preserving P-Asserted Identity formats on a Cisco SBC

Not sure if this is really applies to anyone’s deployment out there but this is an issue I recently encountered with a Cisco Session Border Controller and P-Asserted Identity (PAI). When the SBC received a SIP packet from our application it changed the PAI format from tel: to sip:xxxxxx@xx.xx.xx.xx. Not that there is any rule that says this cannot be done, it was slightly annoying and breaking our application. Below is the code that fixed this issue.

voice service voip
asserted-id pai
voice class sip-profiles 1
request INVITE sip-header P-Asserted-Identity modify "<sip:(.*)@.*>" "tel:\1"
dial-peer voice 811 voip
  voice-class sip profiles 1
dial-peer voice 8112 voip
  voice-class sip profiles 1

The SIP profile should be applied to your outbound dial peers. Although this shows some flexibility of the CUBE to make this adjustment, it would not have been required if it had not changed the PAI in the first place!

Update: Our application developer informed me that some service providers my require the tel: format. Qwest only supports tel URI but XO supports SIP URI as examples. So having the ability to do either is a good thing.

For more information on PAI check out the IETF website and RFC 3325

1 comment:

  1. great info - having to tweak PAI for peering with Verizon.


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