Reliable User Datagram Protocol - Avaya Nortel Communication Server 1000 Manual

42 Description
Signaling and messaging
The IP Line application sends Scan and Signaling Distribution (SSD)
messages to the Call Server through the system ELAN subnet. When tone
service is provided, the service is signaled to the LTPS by using new SSD
messages sent through the ELAN subnet.
Signaling protocols
The signaling protocol between the IP Phone and the IP Telephony node is
the Unified Networks IP Stimulus Protocol (UNIStim). The Reliable User
Datagram Protocol (RUDP) is the transport protocol.

Reliable User Datagram Protocol

Reliable User Datagram Protocol (RUDP) is used for:
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For more information, see
Description
Signaling messages between the LTPS and IP Phones use RUDP. Each
RUDP connection is distinguished by its IP address and port number.
RUDP is another layer on top of User Datagram Protocol (UDP). RUDP is
proprietary to Nortel.
The features of RUDP are as follows:
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When a data sequence is packetized and sent from source A to receiver
B, RUDP adds a number to each packet header to indicate its order in the
sequence.
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Copyright © 2003–2008, Nortel Networks
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signaling between the Call Server and the LTPS
signaling between the IP Telephony node and the IP Phones
provides reliable communication system over a network
packets are resent if an acknowledgement message (ACK) is not
received following a time-out
messages arrive in the correct sequence
duplicate messages are ignored
loss of contact detection
If the packet is successfully transmitted to B, B sends back an ACK to A,
acknowledging that the packet has been received.
If A receives no message within a configured time, it retransmits the
packet.
If B receives a packet without having first received its predecessor,
it discards the packet and all subsequent packets, and a NAK (no
Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
"ELAN TCP transport" (page 43).