Nortel 1000 Fundamentals page 48

48 Planning and engineering
To illustrate this, consider the following high-level example:
Client A sends a TR/87 SIP INVITE to Node 1 to monitor DN 1000. The
TR/87 association is established. Client B then sends a TR/87 SIP INVITE
to Node 1 (the same node) to monitor DN 1000. Both sessions are
established successfully. As a result of this sequence, two TR/87 sessions
exist for DN 1000 through Node 1.
However, if Client B attempts to send a TR/87 SIP INVITE to Node 2 (which
has an AML link to the same call server as Node 1), the attempt to establish
the TR/87 session fails because the DN is already in use by Client A's
session through Node 1.
To solve this issue when you plan for capacity, SIP routing must ensure that
all TR/87 sessions for a DN always terminate on the same node when there
are multiple nodes for a single CS 1000 call server, as depicted in
"SIP CTI (TR/87) example" (page
This issue can arise in cases where a single user has multiple clients logged
on simultaneously (for example, a client at home, a client in the office, and a
mobile client; each with TR/87 capability).
Nortel Converged Office Fundamentals — Microsoft Office Communications Server 2007
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49).
Nortel Communication Server 1000
NN43001-121 01.03 Standard
Release 5.0 30 April 2008
Figure 16