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Stream Control Transmission Protocol (SCTP) is a transport layer protocol similar to TCP, but is characterized as message-oriented protocol transporting a sequence of messages (each being a group of bytes) rather than an unbroken stream of bytes (TCP behavior). In SCTP, a sender sends a message in one operation, and that exact message is passed to the receiving application process in one operation.

The SCTP as a Transport preference and SCTP retransmission timer are configured from the SIP Trunk Group. The SCTP as a transport protocol and SCTP profile are configured in the SIP signaling port. The SCTP Profile CLI syntax is described below.

Command Syntax

% set profiles signaling sctpProfile <profile name> 
	heartbeatInterval <# seconds> 
	idleTimeout <# seconds> 
	inboundStreams <#> 
	initRetry <#> 
	orderedDelivery <disabled|enabled> 
	outboundStreams <#> 
	pathMtu <#bytes> 
	peerTransportAddresses <# addresses> 
	retransmissionsPerAssociation <#> 
	retransmissionsPerPath <#> 
	rtoInitial <# milliseconds> 
	rtoMax <# milliseconds> 
	rtoMin <# milliseconds> 
	sackDelay <disabled|enabled>

Command Parameters

The SCTP Profile Parameters are as shown below:

Table : SCTP Profile Parameters

Parameter

Length/Range

Description

sctpProfile

N/A

Name of SCTP profile.

heartbeatInterval

1-6

The SCTP Heartbeat Interval in seconds. (default = 4)

idleTimeout

0-86400

SCTP Idle Timeout Interval in seconds. (default = 3600)

inboundStreams

1-32

The number of Inbound Streams for this SCTP profile. (default = 1)

initRetry

1-10

The SCTP Max INIT retry. (default = 8)

orderedDelivery

N/A

Enable flag to use ordered delivery in SCTP.

  • disabled (default)
  • enabled

outboundStreams

1-32

The number of Outbound Streams for this SCTP profile.

pathMtu

1000-1500

The SCTP Path MTU in bytes. (default = 1500)

peerTransportAddresses

1-2

The number of Peer Transport Addresses for this SCTP profile. (default = 1)

retransmissionsPerAssociation

0-20

The Maximum retransmissions per SCTP association. (default = 0)

retransmissionsPerPath

1-10

The number of Retransmissions per path for this SCTP profile. (default = 8)

rtoInitial

50-500

The SCTP RTO Initial in milliseconds. (default = 50)

rtoMax

200-5000

The SCTP RTO Max in milliseconds. (default = 200)

rtoMin

10-5000

The SCTP RTO Min in milliseconds. (default = 40)

sackDelay

N/A

Set flag to enable SACK Delay in SCTP.

  • disabled (default)
  • enabled

Command Example

In this example, the following steps are accomplished:

  • Create SCTP profile named "SCTP02" with following configuration: outboundStreams - 2, inboundStreams - 2, peerTransportAddress - 2, retransmissionsPerPath - 8, hearbeatInterval - 6, orderedDelivery - enabled, retransmissionPerAssociatioon - 1, rtoInitial - 100, rtoMax - 200, rtoMin - 50.
  • Configure SCTP as a transport protocol in SIP signaling port, and SCTP profile "SCTP02" is associated with the particular zone.
  • Configure SCTP as a Transport preference and SCTP retransmission timer to 50 seconds in the SIP Trunk Group.
  • Configure SCTP as a transport protocol in IP Signaling Profile.

Step 1:

% set profiles signaling sctpProfile SCTP02 outboundStreams 2 inboundStreams 2 peerTransportAddresses 2 retransmissionsPerPath 8 heartbeatInterval 6 orderedDelivery enabled retransmissionsPerAssociation 1 rtoInitial 100 rtoMax 200 rtoMin 50

% show profiles signaling sctpProfile SCTP02 
outboundStreams 2; 
inboundStreams 2; 
peerTransportAddresses 2; 
retransmissionsPerPath 8; 
heartbeatInterval 6; 
orderedDelivery enabled; 
retransmissionsPerAssociation 1; 
rtoInitial 100; 
rtoMin 50; 
rtoMax 200;

 Step 2:

% set addressContext ADDR_CONTEXT_1 zone ZONE_AS sipSigPort 2 transportProtocolsAllowed sip_sctp 
% set addressContext ADDR_CONTEXT_1 zone ZONE_AS sipSigPort 2 sctpProfileName SCTP02

 Step 3:

% set addressContext ADDR_CONTEXT_1 zone ZONE_AS sipTrunkGroup TG_SIPART_AS signaling transportPreference preference1 1 
% set addressContext ADDR_CONTEXT_1 zone ZONE_AS sipTrunkGroup TG_SIPART_AS signaling timers sctpRetransmitTimer 10

 Step 4:

 % set profiles signaling ipSignalingProfile DEFAULT_SIP egressIpAttributes transport type1 sctp

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