SIP Explained Gary Audin Delphi, Inc. Delphi-inc@att.net Sponsored by www.telecomreseller.com

Speaker Background Communications and security consultant for 36 years Speaker at Enterprise Connect, ITExpo and 100s of user conferences Article and blog sites: www.nojitter.com www.webtorials.com www.telecomreseller.com www.networkworld.com www.acuta.org www.searchunifiedcommunications.com © Delphi, Inc. 2014

SIP Trunking Presentation “Successful SIP Trunking” Wednesday 5:30 and Thursday 1:00 PM Telecom Reseller theater exhibit # Presenters: Gary Audin and Steve Johnson © Delphi, Inc. 2014

Session Initiation Protocol A protocol is an information exchange procedure, a set of rules. SIP is a protocol to establish , manage, and terminate a connection (session) that is media independent. SIP is not specifically designed for digital voice. SIP operates over an IP network. © Delphi, Inc. 2014

SIP Does This It locates the user and determines which end system will be used in the proposed session. It then learns the user's availability (is the user busy; can he/she be disturbed?). It determines the capabilities available at the user end system for the session such as what media is supported. It establishes the session. It manages the session, handling call termination, call transfer, changes to session parameters, and so forth. It is a peer-to-peer protocol running over UDP and TCP. © Delphi, Inc. 2014

SIP Features User location can determine the end system to be used for communication User availability determines the willingness of the called endpoint to engage in communications User capabilities can determine the media and media parameters to be used Session setup endpoint ringing, establishment of session parameters at both called and calling endpoints Session management including session transfer and termination, changing session parameters, and invoking services © Delphi, Inc. 2014

What’s in a SIP Session “Session” = exchange of data between an association of participants Users can move among endpoints Users may have multiple names and addresses Users may communicate in different media SIP enables internet endpoints: To discover each other To characterize the session The location infrastructure supports name mapping and redirection services Endpoints can add/remove participants from session Endpoints can add/remove media from session © Delphi, Inc. 2014

Not Part of SIP SIP is not a vertically integrated communications system. It is ONLY a component. SIP is independent of the services offered. SIP provides mechanisms that can be used to implement different services. SIP can locate a user and deliver content to the user’s current location. SIP does not offer conference control services nor prescribe how a conference is to be managed. © Delphi, Inc. 2014

SIP Does Not SIP does not define the media carried (voice, video, IM, data, games, graphics, photos…) SIPPING 19 defines a minimum set of telephony features not SIP SIP trunks are not able to provide interoperability between different vendors’ IP PBXs © Delphi, Inc. 2014

SIP Components SIP is built upon a client/server architecture User Agents (SIP Phones, SIP PCs, other endpoints) Servers (Used to locate SIP users or to forward messages) SIP Gateways: To PSTN for telephony interworking To H.323 for IP Telephony interworking Client - originates message Server - responds to or forwards message © Delphi, Inc. 2014

Multimedia Protocol Stack © Delphi, Inc. 2014

SIP Signaling Paths © Delphi, Inc. 2014

SIP Trunk Benefits Flexible provisioning Provider competition and enterprise leverage Eliminate VoIP gateways Reduced conferencing costs Low cost or free international calling On-Net free calling © Delphi, Inc. 2014

SIP Trunk Connections Legacy PBX VoIP Gateway SBC SIP Service Provider T1/E1/PRI Connections Most legacy PBXs can upgrade to support some IP network connections usually IP phones. The IP connections are essentially supported by an internal gateway function. Most legacy PBXs are not upgradable for SIP trunk connections.   An alternative is to deploy a separate external gateway to conned to a SIP service. The gateway connects to multiple T1, E1, and PRI ports on the legacy PBX. The gateway translates the signaling and possibly to the voice codec into a SIP trunk operation. There are many non-PBX vendors offering this type of gateway. The gateway should be connected to a session border controller to the SIP network for security reasons. Because the session border controller sits between the gateway and SIP provider, the SIP provider is not affected by this arrangement. It looks like any other session border controller. There may however be some feature limitations because the gateway may not be able to translate all of them in to the SIP interface. PSTN SBC IP PBX © Delphi, Inc. 2014

SIP Trunk Providers Can connect using vendor specific versions of SIP trunk software Standard SIP trunk connection is via SIPconnect (not a standard but an agreed upon recommendation from the SIP Forum http://www.sipforum.org/sipconnect) SIPconnect version 1.1 is the latest one May limit the media carried: Voice only Video maybe Secure connections maybe Fax maybe 911 and E911 information maybe © Delphi, Inc. 2014

Session Border Controllers A firewall rule set while also map layer 5 to layer 7 addresses Intrusion detection and prevention Denial-of-service (DoS) attack prevention VPN separation for shared resources SIP-Transport Layer Security (TLS) handshaking for authentication and encryption of SIP signaling Secure Real Time Protocol (RTP) support Support for IPsec tunnels Transcoding, or conversion between different VoIP codec technologies © Delphi, Inc. 2014

Where Are the Problems? Delphi, Inc.

SIP Trunk Issues Firewall Problems: Can block SIP packets Cannot translate IP packet addresses TCP may be used instead of UDP One way audio Dropped connections Call transfer failure Registration failure © Delphi, Inc. 2014

State of SIP Relatively easy to implement Has gained considerable vendor and provider acceptance Allows flexible service creation Extensible and scalable Wide range of supporting products and services Does not make PSTN interworking easy Will not solve all IP Telephony issues such as QoS © Delphi, Inc. 2014

Resources Online education and certification www.thesipschool.com “Ten SIP Trunk Equipment License Issues That Can Ruin Your Day (or Month)” http://www.webtorials.com/content/2013/03/ten-sip-trunk-equipment-license-issues-that-can-ruin-your-day-or-month.html “Avoiding SIP Trunking Equipment Problems” http://www.webtorials.com/content/2013/02/avoiding-sip-trunking-equipment-problems.html “How to avoid SIP Trunk Implementation Problems” http://www.webtorials.com/content/2013/01/how-to-avoid-sip-trunk-implementation-problems-1.html “Easy SIP Trunking; No Yet”, http://www.telecomreseller.com/2011/09/19/easy-sip-trunking-not-yet/ “Is IPv6 Good for VoIP? http://www.webtorials.com/content/2013/01/is-ipv6-good-for-voip.html © Delphi, Inc. 2014

FINI Gary Audin Delphi-inc@att.net VN 703 908 0965 www.telecomreseller.com © Delphi, Inc. 2014