SIPPING IEPREP Joint Meeting

1
SIPPING - IEPREP Joint Meeting

• Fred Baker - IEPREP co-chair
• Rohan Mahy - SIPPING co-chair

2
SIP Architecture review

• Proxies are call stateless -- in the Internet
  proxies dont have any linkage with QoS, or call
  counting
• Proxies are fast -- standardizing prioritization
  inside a proxy has questionable value
  (implementation specific)
• User Agents (Gateways, Phones, Media Servers) are
  responsible for requesting priority or preemption
  and doing the right thing (ex preempting
  focus, requesting QoS) when receiving it

3
Making a call in a hybrid network
PSTN
Internet
Issues Policy in call acceptance call
waiting, preemption (SIP) Policy in bandwidth
admission preferential reservation of
bandwidth (RSVP) Exchange with PSTN encoding and
values
PSTN
4
SIP-to-PSTN security requirements for prioritized
access to PSTN resources

• Henning Schulzrinne
• Columbia University

5
Security requirements

• End-to-end strong authentication and
  authorization of caller
• not just theft of service, but system
  stability/performance issue
• Intermediate (proxy?) authentication
• delegate responsibility
• not all VoIP gateways may be authentication-capabl
  e (many aren't)
• Need to authorize any assertion of priority and
  authenticate the originator

6
Security requirements

• Cross-domain
• IP endpoint may be in different admin. domain
  than gateway
• Require secrets not to be pre-installed
• useability from any device
• Authentication of PSTN gateway
• desirable required?

7
Privacy requirements

• Call content
• very likely ? separate docs
• Signaling (resource and/or call setup)
• reveals communication relationships
• cannot rely on hop-by-hop
• Fact of IEPREP call
• sensitivity likely same (or lower) as call
  signaling

8
Other open requirements questions

• Call routing based on support of resource
  priority
• support of specific IEPREP namespace?
• SIP URI of gateway enough?
• or "call using FOO priority service" ? no need
  to know gateway address
• avoid two-stage dialing
• Caller needs to discover support for namespaces
• may require different authentication

9
System assumptions

• What do we assume about the IP side?
• purpose-built require certain capabilities
  (signaling, resource reservation, security, ...)
• any network use SIP application on standard
  platform or plug in own SIP phone
• no network changes
• firewalls ? may not allow protocols beyond SIP
  and RTP
• any SIP (pay) phone
• no modifications to SIP phone
• not much beyond two-stage dialing possible?