Which “SIP” Does Your Network Speak?


As a good ol’ boy growing up in the Midwestern United States, I felt I needed a translator when I first visited the UK over 20 years ago (yikes!). Even though English was the primary language, the UK had different words for everyday items I thought were common. I knew soccer meant “football” in the UK, but I didn’t know that a cookie was called a “biscuit,” a truck was called a “lorry”, fries were called “chips,” and chips were called “crisps.” Boy, was I confused, especially with respect to my favorite food, “chips” – guess which one!

Session Initiation Protocol (SIP) communications have much in common with my early UK travel experience. Because the standards for SIP have been somewhat left open to interpretation, manufacturers have created products and solutions based on SIP with various “idioms” and “dialects.” So who, or what, is responsible for making sure that all SIP devices understand each other? How does one interwork or normalize SIP so that all endpoints in the network understand each other and are able to properly communicate? Meet the Session Border Controller (SBC).

At a high level, we can think of SIP interworking, a feature in most SBCs, as a kind of grammar correction between SIP idioms and dialects. At a more detailed level, SIP interworking involves modifying the contents of the signaling packet, which may include both the SIP header and the Session Description Protocol (SDP) body that define the media packet contents to match the way that different devices and different networks speak SIP. For example, service provider X’s core network might display a SIP Uniform Resource Identifier (SIP URI) using one format (e.g., sip:jane@company.com), while service provider Y’s core network displays a SIP URI using another (e.g., sip:jdoe@home.company.com). In this situation, SIP interworking is required to go into the packet headers and alter the SIP URI naming convention both for the ingress (incoming) and egress (outgoing) SIP packets, so that they match the way service provider X and service provider Y are used to seeing them.

While SIP interoperability will remain an issue for the foreseeable future, SBCs will certainly mitigate those issues and deliver on the promise of any-media, any-device communications. Enterprises and service providers simply need to look for a robust, secure and scalable SBC product portfolio, such as the Sonus SBC portfolio. The Sonus portfolio reflects the reality of SIP interoperability and provides flexible, reliable methods for SIP translation between networks and network devices.


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