The Session Initiation Protocol (SIP) - a data communications protocol used for setting up n-way multimedia sessions in either a unicast or multicast way. IETF RFC 2543 specifies this protocol.

As mentioned above the Session Initiation Protocol (SIP) is a (multimedia) communications protocol. In particular this signalling protocol allows for the establishment of sessions over packet based networks. This protocol has been particularly important in the implementation of IP telephony functionality, which provides for relatively cheap telephone (and other media) connections using the Internet.

Current implementations of SIP generally run atop the TCP and UDP protocols layers (i.e. the Internet), but it can be implemented over ATM, X25, frame relay and carrier pigeon networks without change.

Some of the main characteristics/advantages of this protocol include:

  • It includes all the general standard call-forwarding techniques.
  • Personal mobility, i.e. it allows a user to be identified by a location independant address
  • Setting up of multiparty calls.
  • Dynamic feature negotiation.

Competing/related technologies include H.323 and MGCP/Megaco.


Sip (sip), v. t. [imp. & p. p. Sipped (sipt); p. pr. & vb. n. Sipping.] [OE. sippen; akin to OD. sippen, and AS. sUpan to sip, suck up, drink. See Sup, v. t.]


To drink or imbibe in small quantities; especially, to take in with the lips in small quantities, as a liquid; as, to sip tea. "Every herb that sips the dew." Milton.


To draw into the mouth; to suck up; as, a bee sips nectar from the flowers.


To taste the liquor of; to drink out of. [Poetic]

They skim the floods, and sip the purple flowers.


© Webster 1913

Sip, v. i.

To drink a small quantity; to take a fluid with the lips; to take a sip or sips of something.

[She] raised it to her mouth with sober grace;
Then, sipping, offered to the next in place.


© Webster 1913

Sip, n.


The act of sipping; the taking of a liquid with the lips.


A small draught taken with the lips; a slight taste.

One sip of this
Will bathe the drooping spirits in delight
Beyond the bliss of dreams.

A sip is all that the public ever care to take from reservoirs of abstract philosophy.
De Quincey.


© Webster 1913

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