Stream Control
Transmission Protocol
(SCTP)
SIP can use stream control transmission protocol (SCTP) to provide
reliable end-to-end transport over an IP based network.
The benefits of using SCTP over transmission control protocol (TCP)
or user datagram protocol (UDP) for transport are:
• improvements on the weaknesses of TCP and UDP for telephony
applications,
• provides the reliability of multiple paths between endpoints (per
association), and
• suitability for applications beyond SIP.
The Session Initiation Protocol (SIP) - Interface Specification,
235-900-344 document explains the interface implementation in
greater detail.
Endpoints
An SCTP endpoint is assigned to a processor group and each endpoint
is identified by an address known as the SCTP transport address. An
SCTP transport address consists of an SCTP port number and a list of
one or more IP addresses. The SCTP transport address uniquely
identifies an SCTP endpoint. The SCTP port number is used to send
and receive messages. Each SIP PH processor group in an office can
support one SCTP endpoint. Refer to Figure 2-11, “SCTP Endpoints”
(2-19).
An endpoint with more than one IP address in its SCTP transport
address list is called a multi-homed SCTP endpoint. An endpoint can
be configured with multiple network interface cards (NIC) each with
its own IP address, or multiple IP addresses can be assigned to one
NIC. On the 5ESS
®
switch, the SIP PH processor group is the NIC
and it can be assigned two IP addresses. When two IP addresses are
assigned to a SIP PH processor group, at any one time one will be the
serving SIP PH and the other will be the non-serving SIP PH. Both IP
addresses will be assigned to the SIP PH performing the serving
function.
An upper layer protocol like SIP may need to communicate with peers
physically accessed through separate IP networks. In this case, an
Signaling View
Architecture
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2-18
Lucent Technologies 235-200-118
Issue 3.02B, March 2007
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