VON Europe 2000 - 06-19-00 SIP Update Jonathan Rosenberg Chief Scientist co-chair, IETF SIP Working Group

www.dynamicsoft.comVON Europe 2000 - 06-19-00SIP Update

SIP Update

Jonathan Rosenberg

Chief Scientist

co-chair, IETF SIP Working Group


Summary of SIP WG Status Nearly 200 Attendees at IETF 47 in Adelaide, Australia, March 2000

31 Active Internet Drafts

Nearly 20 Documents As Agreed Upon Work Items

Half a Dozen Design Teams Focusing on Specific Documents

Most Deliverables Before 2001


Management and Auto-configuration SIP MIB

Management of proxy, redirect, registrar and user agents Based on existing MIBs in existing boxes Initial draft defines extensive monitoring capabilities Traps and configuration need to be done Expected completion end of 2000

DHCP Option for SIP Servers User agent can learn where to register and where to send requests Use existing DHCP servers Draft currently under IESG review for RFC


Management and Autoconfiguration cont.

Service Location Protocol (SLP) Templates SLP allows clients to discover servers based on capabilities SLP template for SIP allows discovery of SIP servers based on

capabilities IPSec and TLS transports CPL support Support for caller preferences

Has already been registered with IANA


Originally Developed by ISC Inter-softswitch communications ISUP transparency

Now a SIP Working Group Item INFO method extension

Mid-call ISUP messages Under IESG review

ISUP to SIP message conversions

MIME payload type for ISUP Nearing completion

Umbrella specification

SIP-T

MGCSCTP

MegacoT1

SS7

SIP-T

SCTP

Megaco

T1

SS7SG

MGC

SG

Proxy Server


“Infrastructure” Improvements Reliability of Provisional Responses

SIP Provisional responses are not currently reliable Convey ringing and call queue status PSTN interoperability mandates these be reliable Extension allows them to be retransmitted and acknowledged Specification currently in IETF working group last call


“Infrastructure” Improvements cont.

Session Timer SIP has no end-to-end keepalive for an active session This is needed for several applications

NAT/firewall traversal Billing

Session timer allows session to be periodically refreshed Can even recover from end system crash Completion near end of June 2000


SIP Caller Preferences SIP Extensions for Specifying

Caller Preferences and Callee State Presence!

Preferences Carried in INVITE Setup Message

Preferences for Reaching callee at home or work Fax, video, audio call Mobile or landline Secretary or voicemail Priority locations

Expected Completion July 2000

Preference Video

Proxy Server


SIP and QoS Problem

Resource reservation and call signaling are separate

Call setup needed to obtain IP addresses for reservation

Call setup can succeed, while Reservation Fails

Solution Couple resource reservation and

signaling at end system Define general pre-conditions to

session establishment COMET method indicates conditions

are met

INV

183 Progress

PRACK

Caller Callee

200 OK

ACK

Resource Reservation

Ringing

Pickup

Media

COMET


State Mechanism HTTP Supports Notion of Cookies

Data passed from server to client Client passes data back to server in

subsequent requests Cookie content opaque to client

Cookies Provide Many Benefits Session management Fault tolerance Scalability

Define the Same in SIP Passed from proxies to UA Passed back in subsequent requests

for same call

INVITE

200 OKState: Proxy1 foo,

Proxy2 bar

BYEState: Proxy1 foo,

Proxy2 bar

Proxy Server


Third Party Call Control Many Services Require Network

Entity to Create Calls Between Pairs of Users or Services IVR services Click to dial Prepaid calling

Third Party Call Control Mechanism Allows a User Agent to Do This Not a SIP extension at all Manipulates SDP in SIP messages so

that media flows between users

12

3

45

6

INVITEno SDP

200

ACK

INVITESDP (2)

200

ACK

Application Server

RTP


Firewall and NAT Traversal Need for Secure Traversal of SIP and Its Signaled Sessions

Through NAT and Firewall

SIP is a Session Control Protocol IP address and ports appear in body of protocol Fundamental to SIP operation Bad for NAT traversal

SIP NAT ALG Needed

But, Embedding ALG in NAT is Not Good Scaling Separation of function Expertise issue


Proposed Solution Separate Application Layer

NAT/Firewall from IP Layer NAT/Firewall

Have Application Specific Devices (Proxies) Perform Application Layer NAT Expertise problem solved Separation of function - enables growth Scaling much better

Use application layer load balancing techniques

IP NAT only box can be fast

SIP

Control

RTP

Proxy Server

Firewall/NAT


IETF Efforts on Firewall Traversal SIP Working Group

Informational RFC will be developed Summarizes SIP operations needed in firewall controlling proxy Discusses problems and issues Call flows and examples

FOGLAMPS BoF Session Pre-Working Group Looking at developing the protocol between firewall controlling proxy

and firewall Currently working on requirements for this protocol


The Missing Piece Control Protocol Between

SIP ALG and IP NAT/Firewall

Main Requirements Binding request: give a private

address, obtain a public address

Binding release Open Hole (firewall) Close hole (firewall) Group bindings

INVITEBIND REQ

BINDING

INVITE

200 OK

200 OKOPEN

ACK

ACK

Proxy Server Firewall


Information Resource Jonathan Rosenberg

[email protected] +1 973.952.5000