LS:SIP – 01 – Peers -> SIP – 017 – Sends Outstanding

The SIP peers counter on the Edge server collects failed connections attempts to federated partners, and is  reset after reboot.

If the counter is reporting a high value for a particular sip peer and not others, it is likely that federation is not allowed to that domain. If you do not have an open federation policy and have a requirement to communicate with the domain, it should be added to the allowed list in Lync. The other common scenario is that the Edge peer is not allowing communication from your own SIP domain, or it is down.

If the counter is reporting a high value for multiple domains then there could be more cause for concern. Check your federation settings and make sure that the Edge server can communicate on the federation port 5061.

To view the counter open Performance Monitor and add LS:SIP – 01 – Peers -> SIP – 017 – Sends Outstanding:

To allow open federation make sure "Enable partner domain discovery" is ticked:

If you don't have "Enable partner domain discovery" enabled, then you will need to add the domain you wish to communicate with to the allowed list:

Additionally if you are using SCOM you may see the following alert generated:

Alert: The number of messages that are currently present in the outgoing (send) queues.
Source: LS Access Edge Component [server.domain.co.nz]
Path: server.domain.co.nz
Last modified by: System
Last modified time: 10/06/2012 1:28:11 PM Alert description: Perf Object Name: LS:SIP – 01 – Peers Perf Counter Name: SIP – 017 – Sends Outstanding Perf Counter Value: 1001

The Lync Management pack for SCOM 2007 R2 was mentioned in the Lync 2010 release notes as having an issue reporting this data correctly. If you use this version of SCOM the resolution noted is to disable the alert. Here's an excerpt from that document:

Alerts from Monitor "SIP Proxy: Sends Queued" May Be Inaccurate

Issue:

When Microsoft System Center Operations Manager 2007 R2 management pack is deployed to monitor Lync Server 2010, the alert "The average time (in seconds) the messages delayed in outgoing (send) queues" may be incorrect.  The underlying performance counter CS Registrar SIP -01 Peers -SIP  017 -Send Outstanding reports multi-instance values. The instances _Total and Clientsare not filtered out, causing incorrect alerts.

This situation applies only to deployments that deployed System Center Operations Manager management pack to montior Lync Server 2010.

Resolution:

Disable this monitor in the System Center Operations Manager 2007 R2 Operations console, as follows: 

1. Navigate to the Alert details view.

2. Click Alert Monitor.

3. Click the Overrides tab, and then click Disable.