Discussion slides for the SIP forum IPv6 task group conference call 12/12/12 covering issues with SIP DNS, SIP and locating next hop in a dual stack world and issues with Server Based ALG decisions for media paths.

1. SIP & IPv6
Dual stack issues
SIP Forum Conference call 12.12.12
oej@edvina.net
onsdag 12 december 12

2. Agenda
• Locating SIP servers in a dual stack world
• Happy Eyeballs and SIP
• UA media address familiy capability
onsdag 12 december 12

3. Living in a dual stack
world
• RFC 3261 supports either IP4 OR IPv6
• We need to adopt to a dual stack world in order to
enable IPv6 migration
• RFC 6157 attempts to handle this, but focuses on
media
• ICE supports dual stack media negotiation (with the
IPv6 priority addition)
Let’s separate SIP and media
sessions (RTP/MSRP/T.38)
onsdag 12 december 12

4. Locating SIP servers
RFC 3263
• Clearly says that a SIP device needs to look
up IPv4 or IPv6
• We need to replace ”or” with ”and” and
apply happy eyeballs to find the next hop.
64 times T1 for failover will NOT be
accepted by users
onsdag 12 december 12

5. I see two issues
• Indicating preference of address family in
DNS SRV records
• Setting up a connection to a dual stack
server from a dual stack client
• HAPPY EYEBALLS FOR SIP!
• Affects STCP,TCP and UDP transports
onsdag 12 december 12

6. Locating a SIP server
• NAPTR doesn’t bother with address family
• SRV records point to host names
• Hosts can be single stack IPv4, single stack
IPv6 or dual stack.
• NAPTR can be used to indicate preference
of transport. SRV can be used to indicate
preference of address family.
SIP
onsdag 12 december 12

7. The IPv6 preferred chain
;; Priority Weight Port Target
IN SRV 10 3 5060 server1.sipguru.no.
IN SRV 10 1 5060 server2.sipguru.no.
IN SRV 20 1 5060 server3.sipguru.no.
IN SRV 20 2 5060 server4.sipguru.no.
_sip._udp.sipguru.no
Priority 10 Priority 20
Server1 75% Server2 25% Server3 33% Server4 67%
A A
AAAA AAAA AAAA AAAA
No IPv4 records!
onsdag 12 december 12

8. SIP & Happy eyeballs
onsdag 12 december 12

9. Happy SIP UAs
IPv4 IPv4
IPv6 IPv6
• Two network paths to the same service
from the same device
onsdag 12 december 12

10. Oh no.
IPv4 IPv4
IPv6 IPv6
• If the first selected path doesn’t work,
what’s the failover time?
• This will affect SIP Trunking (SIPconnect)
onsdag 12 december 12

11. Http Solution
• Happy Eyeballs
• RFC 6555 by Dan Wing
• http://ipv6friday.org/blog/2012/04/happyeyeballs/
Needs to be applied to SIP.
onsdag 12 december 12

12. UA capability
Discovering support for IPv6 and/or IPv4
onsdag 12 december 12

13. UA IPv6 capability
• In some cases, a SIP Server needs to know if a
UA is single stack IPv4, single stack IPv6 or
dual stack
• Signalling address family is not proof enough. A
dual stack SIP client may decide to send over
IPv4 - which doesn’t reveal the IPv6 capability
• This applies to server-based NAT traversal
support
onsdag 12 december 12

14. Hosted RTP proxys
• The proxy receives signalling with IPv6
• Checks all the contacts associated with an AOR
• How does it detect dual stack clients?
• What does it base a decision for adding an IPv4-
IPv6-rtpproxy on?
• Either dual registrations or a contact capability
indication.
onsdag 12 december 12

15. SIP Outbound
• Can be used
• Two registers with REG-ID over IPv4 and two with
the same REG-ID over IPv6 or two registrations
with dual contacts
• Four flows to maintain
• Not very practical
• Lack of Outbound implementations
• Not a short-term fix with a simple upgrade path for firmware
onsdag 12 december 12

16. The short term fix
• A way to indicate UA media capability for
various address families in the contact
• This way, server can make policy decisions
on media NAT support
onsdag 12 december 12

17. Suggested priority
• Happy eyeballs-fixes for SIP - SIP in a dual
stack network
• Add dual stack indication in Contact
• Make it possible for SIP Forum members to
add IPv6 in dual stack mode without adding
support requests...
onsdag 12 december 12

18. SIPit 30
• Raleigh-Durham, NC, USA
• February 18-22
• Sponsor: Cisco
• Will include IPv6 testing!
• Online tests will also be available latest in Jan
2013
http://www.sipit.net
onsdag 12 december 12

19. STAY CONNECTED.
Add IPv6 to your unified communications platform today.
Join us here:
twitter.com/sipv6
6 edvina.net/sipv6
facebook.com/sipv ts:
Vendor tests at SIPit even
Development discussion: www.sipit.net
list
sip-implementors mailing
onsdag 12 december 12

20. Final message:
No,WebRTC will not solve all these issues.
;-)
onsdag 12 december 12