SIP Challenges and Opportunities
28
SIP Challenges and Opportunities Name: Amir Zmora Title: Product Marketing Date: 17 Jan 2003
description
SIP Challenges and Opportunities. Name: Amir Zmora Title: Product Marketing Date: 17 Jan 2003. Dilbert wants to call the boss. Dogbert answers the call. Dilbert asks him to transfer to the Boss. The transfer fails. Why Did the Transfer Fail?. - PowerPoint PPT Presentation
Transcript of SIP Challenges and Opportunities
SIP Challenges and Opportunities
Name: Amir Zmora
Title: Product Marketing
Date: 17 Jan 2003
Dilbert wants to call the bossDogbert answers the callDilbert asks him to transfer to the BossThe transfer fails
Why Did the Transfer Fail?Why Did the Transfer Fail?
REFER has gone through many changes in various versions.
Ver 02 - Refer-To = ("Refer-To" | "r") ":" URL
Refer-To: SIP:[email protected]?Replaces…
Ver 04 - Refer-To = ("Refer-To" / "r") HCOLON ( name-addr / addr-spec )
Refer-To: SIP:[email protected]?Replaces…
Ver 06 - Refer-To = ("Refer-To" / "r") HCOLON ( name-addr / addr-spec ) * (SEMI generic-param)
Refer-To: <SIP:[email protected]?Replaces…>a=b
The <> are optional in ver 04. Sending the ver 04 example to UA supporting ver 06 will cause the Replaces to be related to the Header and not to the address.
Some changes are not backwards compatible
AGENDAAGENDA
The Challenges of VoIP Development
Do it yourself vs. Commercial Toolkits
Commercial Toolkit Requirements
RADVISION SIP Development Solution
The Challenges of VoIP Development
The Evolving SIP Protocol
SIP Development ChallengesSIP Development Challenges
TCP/IP, OS
SIP Transport SIP Message
Transaction
Dialog, Registration,User Agent Behavior
Proxy/Reg
Application (Features, services, UI …)
SIPExtensions
SIP is No Longer a Simple Protocol…SIP is No Longer a Simple Protocol…
Location DBRegistrationSpiralsLoops
REFERSIP-T…PRACKINFOSUBSCRIBE NOTIFY3GPPothers…REFERSIP-T…PRACKINFO
State MachineAuthenticationREFERRecord Routing
re-INVITELoose RoutingState MachineMapping
fragmentationSCTPIPv6Conn Mgmt
SCTPDNSUDPTCP
WhitespacesMultipart MIMEcompact form
SDPEncodingParsingMIME
ID MappingbranchCANCEL
TimersState MachineUDP
ReliabilityAuthentication100Rel
The “S” in SIP Doesn’t Stand for SimpleThe “S” in SIP Doesn’t Stand for Simple
Complex Dialog state machines PRACK, UPDATE…
Client side Authentication Re-INVITE after receiving 401/407
DNS SRV & NAPTR queries Sequence of 3 queries
Different function for IPv6
Different implementation on different OS
Loop/Spiral detection Spiral – Legal
Loop - Illegal
Many more…
Example of Complexity- RoutingExample of Complexity- Routing Routing decision – Loose vs. strict routing
Complex routing algorithm – Destination address should be taken from: Request URI, Rout, Via, Received?
Backwards compatibility with Strict-Routing
Proxy Adds P2 and P3 to route
P1 P2 P3Visited Network Home Network
Without Loose Routing
INVITEb@UA1
Example of Complexity - REFERExample of Complexity - REFER REFER Method REFER Method
for Transfer services
Specified in:
draft-ietf-sip-refer-05.txt
draft-ietf-sip-cc-transfer-05.txt
Full support
Automatic operation + callbacks
Uses NOTIFYNOTIFY extension to report result of Transfer
Transferor Transferee Transfer | | Target | INVITE | | |<-------------------| | | 200 OK | | |------------------->| | | ACK | | |<-------------------| | | | | |<< ”Please transfer | | |<< me to bob” | | | | | | INVITE (hold) | | |------------------->| | | 200 OK | | |<-------------------| | | ACK | | |------------------->| | | REFER | | |------------------->| | | 202 Accepted | | |<-------------------| | | | INVITE | | |------------------->| | | 200 OK | | |<-------------------| | | ACK | | |------------------->| | NOTIFY (200 OK) | | |<-------------------| | | 200 OK | | |------------------->| | | BYE | | |------------------->| | | 200 OK | | |<-------------------| | | | BYE | | |<-------------------| | | 200 OK | | |------------------->|
SIP Standard Inconsistencies and Interoperability Issues
SIP Standard Inconsistencies and Interoperability Issues
• Inconsistencies in REFER
• Changes in retransmission timers
• Changes in CANCEL
• Response code for INVITE inside INVITE has changed
• MaxForward has become mandatory
• Transaction key identifier rules was changed
• CallLeg identifier was changed
• Prefix added to Via Branch
• LR was added to Route for Loose Routing support
• CANCEL became invalid for general transactions
New Changes Are Not Always Backwards Compatible
Developers Need to Ensure Their Products Comply With New Version of Standard
The Evolving Baseline SIP
RFC 2543 Established – Aug 99bis 00 – July 00bis 00 – Aug 00bis 01 – Aug 00bis 02 – Sept 00bis 02 – Nov 00bis 03 – May 01bis 04 – July 01bis 05 – Oct 01bis 06 – Jan 02bis 07 – Feb 02bis 09 – Feb 02
RFC3261 – June 02
Plus hundreds of Drafts that constantly change
SIP Development ChallengesSIP Development Challenges
Interoperability
Many independent implementations of SIP with varying degrees of maturity
Good interoperability requires investment:
participation in SIPit events
tested with various equipment vendors
SIP Development ChallengesSIP Development Challenges
Extensibility
SIP is a highly extensible protocol
Stack design must accommodate current and future needs
Modular design and multi-level API are a must
Maintainability
SIP is still a moving target
Constant flow of changes in baseline protocol and extensions
Cost of keeping a SIP stack up-to-date is high
(cont.)
Do It Yourself vs. Commercial Toolkits
The Move from In-House Development To Commercial Toolkits/Solutions
Developers are Turning to Third Party Toolkits for VoIP Development
Developers are Turning to Third Party Toolkits for VoIP Development
Similar to the evolution of H.323, move from in-house to commercial toolkit as protocol takes hold
Save cost in man years
Provides already integrated SIP and SDP services
Encoding, sending, parsing, managing calls and transactions, and reliability/redundancy
Address continuing SIP interoperability issues
Vendor provides upgrades and application notes
Crucial in modifying existing products to comply with standard changes
You don’t re-invent the wheel
TCP/IP, OS
SIP Transport SIP Message
Transaction
Dialog, Registration,User Agent Behavior
Proxy/Reg
Application (Features, services, UI …)
SIPExtensions
Freeing Resources to Focus on Applications
Freeing Resources to Focus on Applications
Applicationcode
Applicationcode
STANDARD:
• RFC 3261 (SIP)
• SIP Extensions
• RFC 2327 (SDP)
Platform 3rdPartyPlatform 3rdParty
Commercial Toolkit Requirements
Building a SIP Endpoint Using a Vendor SIP Stack
Building a SIP Endpoint Using a Vendor SIP Stack
Network
SDPStack
SIPStack
Application
RTP/RTCPStack
Dialog Management
Registration
Authentication
Telephony (SIP-T, DTMF)
Call Control
More …
Media Description
Media Transport RTCP Reports
Killer
Building a SIP Endpoint Using a Vendor SIP Stack
Building a SIP Endpoint Using a Vendor SIP Stack
Interoperability and standards compliance
Toolkit must be tested in all SIPit events
Vendor should be involved in standard evolution
Extensibility
Modular design and multi-level APIs are required to provide flexibility
APIs should provide interface for proprietary message encoding and parsing
Maintainability
Version upgrades as part of maintenance agreement
Toolkit must be upgraded as standard evolves
RADVISION’s SIP Development Solutions
A Family of SIP Development SolutionsA Family of SIP Development Solutions
SIP Server Toolkit
IP Phone Toolkit
SIPToolkit
SIPDevelopment Solutions
ProLabTM TestManagement
Suite
SIP Development Solution Characteristics SIP Development Solution Characteristics Real-Time Performance
Internally multithreaded (SIP Stack and Server)
High call/transaction rate (calls per second)
Low memory-per-call/transaction and low footprint
Advanced Capabilities
High Availability support
Multi-Homed Host support
IPv6 Support
Interoperable
Tested with dozens of 3rd party SIP implementations
Customizable
Highly Configurable
Multiple compilation options
TransportI/F Layer
OS Abstraction Layer
SIP TKManager
Message SyntaxLayer
TransactionLayer
Dialog/RegistrationLayer
Application
SIP Toolkit ArchitectureSIP Toolkit Architecture
SIP Server ToolkitSIP Server Toolkit
Fully standard SIP Server functionality
Proxy server
Redirect server
Registrar server
B2BUA & Presence server (next version)
Stateless/Stateful
Forking
Loose routing
SRV and NAPTR DNS queries
Loop and spiral detection authentication
Message validation
Layered, modular architecture with multi-level API
Customizable automatic behavior
Extensible architecture
OS:
Solaris, Windows, Linux
Coming soon: VxWorks
SIP Server High-Level
Proxy Core
SIP Stack
SIP ServerManager
SIP ServerLow-Level
Application
SIP Server Toolkit ArchitectureSIP Server Toolkit Architecture
LocationDB
PresenceAgent Security
ProLab Test Management SuiteProLab Test Management Suite
Tests:
SIP (with extensions)
SDP
RTP/RTCP (both voice and video)
Distributed architecture:
Central Manager console (with GUI)
One or more test agents
Script Driven:
Intuitive scripting language
Can generate high load of calls/transactions per second
Statistics and message trace collection and display
Fully configurable test environment from central console
H.323 test agents can be integrated seamlessly
ProLab Test Management SuiteProLab Test Management Suite
RTP Analyzer ProLab Manager Test Scheduler
SIP Server SIP Test Agent H.323 Test Agent GK Agent
SIP H.323
ConclusionConclusion
SIP deployment brings exciting new features
SIP is still an evolving protocol
Interoperability is one of the major barriers for SIP deployment
Commercial vendors address interoperability issues
“Buy vs. Make” issue requires serious consideration
