Ric Messier wrote:
Good question. I did mean IP PBX SIP connect trunking. I'd normally think of carrier to carrier as transport or something similar rather than trunking.
SIP trunking simply refers to a static arrangement of IP endpoints for the purpose of setting up multiple sessions between them in order to pass traffic. It can either be access (for a customer) or traffic of an intra-industrial nature, such as private SIP peering between carriers or ITSPs. Also, the endpoints of a trunk need to be network elements related to service delivery rather than end-user handsets, ATAs and similar devices designed for end-user access. Client-side equipment designed for further switching - most notably, a PBX - qualifies under that definition, insofar as a PBX is a micro-switch of sorts, but anything that would be typically attached to that PBX as an extension does not. Like many terms imported into VoIP from the TDM world by marketing departments, the term "trunking" is neither precise nor astute. The essence of its original meaning, which draws on key pieces of electromechanical, digital and analog telephony history and heritage, is lost when marshaled in a VoIP context. "Trunks" make most sense when applied to physically distinctive bundles of circuitry intended to move traffic in between distribution nodes in an intensely hierarchical topology; most classically, the distribution nodes are central offices/telephone exchanges containing some sort of switch, but more recently, premise-based "miniature" switches like PBXs, which have the distinction of "internal" lines (to handsets) versus "outside lines" used for PSTN access, too. "SIP trunking" is really no better than "virtual PRI" in this respect. It's a transplanted figment of marketing imagination that otherwise lacks conceptual integrity from an engineering perspective - in my opinion, at least. Although, I suppose the notion of a VoIP "line" really takes the cake. Even a SIP "channel" is really pushing it; SIP does not establish "channels," it establishes sessions. Aside from certain logical configuration parameters (network and transport-layer reachability information) on equipment, there is no kind of intrinsic "container" in which those sessions participate, so there's nothing to "channelise" as with a T1 electrical or ISDN link-layer synchronous framing structure. -- Alex -- Alex Balashov Evariste Systems Web : http://www.evaristesys.com/ Tel : (+1) (678) 954-0670 Direct : (+1) (678) 954-0671 Mobile : (+1) (678) 237-1775