Channel Partners

March 13, 2008

3 Min Read
SIP  101: Selling SIP Trunking

By Tom Cross

The panelists on the session Selling SIP Trunking at Channel Partners seem to have missed the mark in helping the SRO audience get to square one for selling SIP trunking. Without going into all the issues they could have and should have addressed here are three tips:

1.) What is SIP? Make sure you know what SIP means. It means Session Initiation Protocol. Basically, SIP provides signaling, like traffic lights, so SIP devices can call other SIP devices over a broadband internet connection. If you want to know more about the working of SIP protocol, get involved in technical discussions or getting your product interoperability compliant, go to the SIP Forum, a nonprofit industry interoperability organization at

2.) SIP devices can be hardphones, wireless phones, softphones (software) and other devices such as soda machines. SIP moves the intelligence into the device. That is, SIP devices communicate directly with one another. This is just like the way your PC communicates directly with a Web site. That means the features are in the device, not PBX. Practically speaking, this means I can use my laptop with softphone software as a telephone and can take it anywhere and plug in to an internet connection and begin making outgoing or receiving incoming calls from other SIP devices without a PBX. If I need to call outside my SIP network or receive a call, my SIP gateway provider (in this case gives me a PSTN number which you can call and no matter where I am you can call me. Features such as voice mail, transfer, conference, etc., can be added through software and from the gateway provider.

3.) Bandwidth planning is paramount. SIP devices use a CODEC, a fancy word for computer chip, to process calls into international standard formats. One is G.711 which is high-bandwidth, high-performance voice calls of 64 KBPS. Low-performance (much like cellular service) and low-bandwidth voice calls of 8 KBPS are G.729. The most important point is that in planning for SIP implementations allocate 80kbps-100kbps per call for G.711 and around 30kbps per call for G.729. That is, while G.711 provides for 64kbps of voice it needs more bandwidth because of the packetizing (overhead) for an IP network. Heres an easy rule of thumb, for G.711 take the total number of simultaneous (concurrent) calls times 100kbps and that is the bandwidth the customer needs for peak times. The customer benefits when users are not on the telephone, the bandwidth is automatically available for their data needs. Note: most SIP trunking providers have their own limitations on the number of calls and the available bandwidth. In other words, YMMV-your mileage may vary.

I hope these three tips have been of help. You can email editor Khali Henderson to let her know if you want more as we can provide you weekly Selling Tips for SIP, tech-tips and other useful tools to help you grow your SIP sales.

If you want to know more, this information is also part of OCS-101 and SIP Essentials 2.0c available in the onsite and online courses. The online version is $299 for SIP 2.0c and for $499 as part of OCS-101 Office Communications Server online version per person or less with discounts. For more information go to or please call Tom Cross at 303-594-1694 or [email protected]. Discounts are also available to members of the SIP Forum.

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