1. In-network Support for VoIP and Multimedia Applications
Henning Schulzrinne
Dept. of Computer Science
Columbia University
May 2007
PRESTO (Princeton, NJ)

2. Overview signaling support for support for in-band media functionality
DOS prevention
permission-based networking
support for in-band media functionality
such as media translation
STUN/TURN support
code delivery
on-path caching for media streams
May 2007
PRESTO (Princeton, NJ)

3. Separation of signaling and media
Router functionality no excuse for merging application signaling and media
mobility (avoid “tromboning”)
logical separation of ISP/IAP and VSP
“network neutrality” issues
Thus, need media-path specific functions
Avoid application-specific traffic admission functions (IMS)
May 2007
PRESTO (Princeton, NJ)

4. SIP trapezoid SIP trapezoid destination proxy outbound proxy
(identified by SIP URI domain)
outbound proxy
1st request
SIP trapezoid
2nd, 3rd, … request
registrar
voice traffic
RTP
May 2007
PRESTO (Princeton, NJ)

5. Permission-based networking
may I send
100 kb/s?
NSIS (QoS)
yes, you may,
for 10 minutes
sets up pinhole
NSIS requests are rate-limited
possibly with proof-of-work
May 2007
PRESTO (Princeton, NJ)

6. NSIS (Next steps in signaling)
May 2007
PRESTO (Princeton, NJ)
Georgios Karagiannis

7. NSIS in brief “RSVP 2.0” Layer separation
unicast-focused, mobility, security
keeps soft state
sender or receiver-based
see RFC 4080 for requirements
Layer separation
GIST (NTLP) + NSLP1, NSLP2
Separate next-node discovery from signaling
UDP and router alerts for discovery
TCP/SCTP for signaling
May 2007
PRESTO (Princeton, NJ)

8. STUN/TURN support STUN: detect external IP addresses
can embed in NATs (= edge routers)
should be on public Internet and reasonably close (call setup delay)
TURN: relay node for “bad” NATs (“symmetric”)
Relays need to be close to media path
typically, operated by access provider
May 2007
PRESTO (Princeton, NJ)

9. Rentable in-network application logic
Not really routing or media path-related, but useful
better close to backbone than at edges
need to instantiate hundreds or thousands of clones
Example: SIP P2P networks
SIP proxy & registrar
media storage
(voic , media assets)
p2p node
generic
mapping
function
May 2007
PRESTO (Princeton, NJ)

10. Code delivery to on-path nodes
In progress: Using NSIS to deliver code to on-path nodes
NSIS well-suited since not constrained by MTU size
congestion-controlled
soft state and reroute discovery
Supports authentication and authorization
(Largely) avoids security issues
influence own traffic only
or offer services invoked by others
Open issue: near-path and off-path installation
May 2007
PRESTO (Princeton, NJ)

11. On-path caching for media streams
cache
media server
need cacheable protocols, not layer violations
May 2007
PRESTO (Princeton, NJ)

12. Conclusions Opportunities for (semi-)static and dynamic functionality
Functionality created by end users, VSPs, ISPs
On-path, near-path and off-path
on-path: DOS prevention
near-path: media relaying
off-path: P2P
Help with media flow enforcement
None of these require programmability, but helpful
May 2007
PRESTO (Princeton, NJ)