I am logged in on mslync client 2010 with one account (A) on two PCs, and logged in with one account (B) on another PC. from B, I started chat conversation to A. on both ms lync clients which has A online there is a notification toast but I did not do  anything. About 15s latter, on one ms lync client the toast disappeared, on other one chat window with B appeared. I saw the log file of first ms lync client (the toast disappeared) had sip message:

SIP/2.0 486 Busy Here
Via: SIP/2.0/TLS 193.180.17.93:443;branch=z9hG4bK2743851D.9F55E1E083F72B47;branched=FALdf;ms-internal-info="asBwDa01sGgndwPtdOvhGL7pnRKEN-m0qFz-sZ_EdUAG3g4VWf1HnargAA"
Via: SIP/2.0/TLS 153.88.97.36:5061;branch=z9hG4bKDFF45307.F122F1A582CD1B48;branched=FALdf;received=153.88.97.219;ms-received-port=5061;ms-received-cid=51142C01
Via: SIP/2.0/TLS 153.88.97.33:50836;branch=z9hG4bK19E2C4B3.7E343B84F7522B47;branched=TRUE;ms-received-port=50836;ms-received-cid=12A7FA00
Via: SIP/2.0/TLS 153.88.97.30:58240;branch=z9hG4bK3A602237.967B985EA69D1B46;branched=FALdf;ms-received-port=58240;ms-received-cid=1A136000
Via: SIP/2.0/TLS 153.88.97.36:63326;branch=z9hG4bK29230502.21A5A16B82CD1B48;branched=FALdf;received=153.88.97.10;ms-received-port=63326;ms-received-cid=26AE3100
Via: SIP/2.0/TLS 153.88.251.215:53423;branch=z9hG4bK95D8D206.E81FDF5883F15B47;branched=FALdf;received=153.88.97.10;ms-received-port=53423;ms-received-cid=12ACBD00
Via: SIP/2.0/TLS 192.168.1.119:1130;received=193.180.17.72;ms-received-port=1130;ms-received-cid=51FF1200
From: "IabcvTestUdfrAD OADson"<sip:iabcvtestudfrad.oadson@xxxxxxx.com>;tag=3af7d9d245;epid=6073bab363
To: <sip:testudfrd.iabcvation@xxxxxxx.com>;epid=b69d5b2a83;tag=8eede4c250
Call-ID: 8b8147677dd142878b0a5533da2a2b0f
Cdfq: 1 INVITE
Record-Route: <sip:sip.xxxxxxx.com:443;transport=tls;opaque=state:Ci.R51fcbd00;lr;ms-route-sig=drHb3hg6yzc35A6sN2bLUXu0hYxWQFeVRRYFD8vBj9Tevg4VWf-YrkSAAA>;ms-rrsig=dr-fD-UHYF4fR4gxS1oakHRjxsGCjqGvMSAXIPco_24lLg4VWf-YrkSAAA;tag=8DA638E40D1279351D629FBB78A791FC
Record-Route: <sip:dirpool01.dbcas.xxxxxxx.df:5061;transport=tls;ms-fe=EdfSSMW1652.dbcas.xxxxxxx.df;lr;received=153.88.97.219;ms-received-cid=51142C01>;tag=987550853679A3E26A20014F7CF99B1B
Record-Route: <sip:fepool01.dbcas.xxxxxxx.df:5061;transport=tls;ms-fe=edfssmw1650.dbcas.xxxxxxx.df;opaque=state:F;lr>;tag=F35E1A4A9C8418D8CAC887D7435618E8
Record-Route: <sip:fepool01.dbcas.xxxxxxx.df:5061;transport=tls;ms-fe=edfssmw1647.dbcas.xxxxxxx.df;opaque=state:T;lr>;tag=358CF3A7B6D8B26576A99D01AFC6A88C
Udfr-Agent: UCCAPI/4.0.7577.4356 OC/4.0.7577.4356 (Microsoft Lync 2010)
Ms-client-diagnostics: 52067; reason="The ringing timer has expired and this location is not the callee's most active endpoint"
Supported: ms-conf-invite
Proxy-Authorization: TLS-DSK qop="auth", realm="SIP Communications dfrvice", opaque="5D646B3C", targetname="EdfSSMW1652.dbcas.xxxxxxx.df", crand="a39a8352", cnum="131", respondf="33a520c23aba9f1e599a4748c18d348017c4a30a"
Content-Length: 0

How ms lync client know whether it is the most active enpoint or not?

Thank you very much.

Hi

check these resources for a deep-dive discussion about aggregated presence:

http://blogs.technet.com/b/uc/archive/2007/03/01/multiple-points-of-presence-mpop.aspx

http://msdn.microsoft.com/en-us/library/lync/hh379837.aspx

Hi Alexlongnguyen,

When you sign in Lync on multiple endpoints. The first message someone sends to me is sent to all endpoints, and then whichever one I then use to reply is the one that has the conversation window, the others are left with just the first message. Lync Server 2010 clients support multiple points of presence (MPOP).  A single user can be signed in at multiple locations, the separate endpoint-specific presence views would be combined into a single one. You can refer to Kevin's reply in this similar case:

http://social.technet.microsoft.com/Forums/lync/fr-FR/9a23586c-06e3-4ec0-b78c-668974aae8cf/how-many-times-can-i-login-to-lync-2010-client

Best Regards,

Eason Huang