When placing a call to or from the Pexip service there is a search prioritisation that dictates the order that the destination address will be searched on both the Pexip network and external networks.
The searching include the interworking of protocols from the native SIP for registered standards based endpoints.
- We first look internally at our database to see if the domain has been registered in our service network, if it has we will attempt to connect the call internally first and stop the search.
- If the domain is not registered internally we will then perform a SRV lookup on SIP and try to connect the call. (Note: while SIP calls are attempted we wait for a response before proceeding.)
- If there is a _SIPS SRV record we will try that first, before we move to _SIP.
- If SIP fails to connect or has no records next we will search for S4B or Lync destinations with a _sipfederationtls. look up and attempt to connect if there is a result, TLS has a higher priority than TCP.
- Next we will attempt to look up _h323cs SRV records. If there's a result we will attempt to interwork to H.323 through Pexip as a gateway call.
- If all these fail then we will look up domain to see if there is an A-Record and if there is an A-Record we will attempt the connection on SIP to the result of that A record.
IP Address Searching
- First we attempt to connect the call using SIP TLS.
- Next we will attempt to connect using SIP TCP.
- Then we will we will attempt to interwork to H.323 through Pexip as a gateway call.