DHCP option for SIP servers Henning Schulzrinne Gautam

DHCP option for SIP servers Henning Schulzrinne Gautam Nair Columbia University 12/14/2021 SIP DHCP 1

Overview n n n SIP (RFC 2543) = Session Initiation Protocol Originally, mainly for setting up multimedia conferences and IP telephone calls Now also proposed for instant messaging and presence (SIMPLE WG) 12/14/2021 SIP DHCP 2

SIP servers n n SIP proxy server: routes requests Typically, found like email server (except via DNS SRV, not MX) Outbound proxy: used for all outbound requests, regardless of destination For firewall control, policy enforcement, name mapping 12/14/2021 SIP DHCP 3

How to find the SIP server n n n Needs to be configured into client Many clients are IP phones -> automate DHCP option 12/14/2021 length Sip. example. com SIP DHCP 4

Name resolution n 1. 2. 3. Note: this is probably a case that will appear more often Use SRV lookup for name If none, use CNAME/A/AAAA(? ) lookup Allow dotted-quad (128. 59. 16. 1) as exception since users will use it anyway (all applications do) 12/14/2021 SIP DHCP 5

Considerations n n Needs to work with existing DHCP servers -> DNS string (RFC 1035) 3 sip6 foobar2 de not likely to be workable, would need new entry type Characters are the same as in DNS entries, whatever that is exactly (ASCII, currently; see IDN) 12/14/2021 SIP DHCP 6

Summary n n Necessary for deployment of SIP Consensus of SIP working group May be applicable to other SRV-based lookups where numeric IP address is not appropriate DHCPv 6? 12/14/2021 SIP DHCP 7