SIP/2.0 481 Call Leg Does Not Exist -- in lync

ISSUE 1: When make a call in lync client after certain message transaction lync caller get 481 Call Leg Does Not Exist .

SIP/2.0 481 Call Leg Does Not Exist
Authentication-Info: NTLM qop="auth", opaque="9436E22E", srand="8E281C5D", snum="12", rspauth="010000002be81caccb7d825264000000", targetname="FE.domain.local", realm="SIP Communications Service", version=4
From: <sip:demouser@edge.com>;tag=1375799463;epid=13757994
To: <sip:test3@fe.local>;tag=D5120ECF36260EB267FB812D17DAE391
Call-ID: 2jXhMAF7GVJhUA2Y8r4181MM6OlpCbvsjhzTH2Oc
CSeq: 1 CANCEL
Via: SIP/2.0/TLS x.x.x.x:59631;branch=2OyLJ5KO1GNvDbbGyOpb1pn8l2F1tFUmjiVRcvv1;received=192.168.0.101;ms-received-port=59631;ms-received-cid=1B2E00
ms-diagnostics: 2;reason="See response code and reason phrase";HRESULT="0xC3E93C09(PE_E_TRANSACTION_DOES_NOT_EXIST)";source="FE.domain.local"
Server: RTC/4.0
Content-Length: 0

WHY?

In that case it is not your problem. It means, the call that you are referring is already destroyed or cleaned from the knowledge of lync server.   

ISSUE 2: If this issue arise from remote to local or local to remote lync client call or external to internal moc call then this issue identified as another issue.

SIP/2.0 481 Call Leg/Transaction Does Not Exist

 WHY?

This means your local interface of lync server is failing certificate authentication with public interface of edge server. It means that certificate assignment is not correct for local and public interface of edge server.


SOLUTION: 

1.  Assign public cert to edge server's external interface.
    i).  Make sure that cert has the FQDN of edge server (ex: edge.domain.com)
    ii).  Make sure that cert has the FQDN of sip server (ex:sip.domain.com)
    iii).  Make sure that cert has the FQDN of avauth server (ex:av.domain.com)
    iv).  Make sure that cert has the FQDN of access server (ex:access.domain.com)
    v).  Make sure that cert has the FQDN of webconf server (ex:webconf.domain.com)

2. Assign local certificate to edge server local interface.
3. Assign local certificate to a/v server local interface.

The proper assignment of certificate what to follow has provided by microsoft as follows- 

Subject Name	Subject Alternative Name Entries/Order	CA	EKU	Assign To:
Consolidated Edge
access.contoso.com	sip.fabrikam.com sip.contoso.com access.fabrikam.com access.contoso.com	Public	Server/Client	Access Edge Server (assign from Edge Interfaces tab)
webcon.contoso.com	N/A	Public	Server	Web Conferencing Edge Server (assign from Edge Interfaces tab)
ocsedge.contoso.net	N/A	Internal	Server	Internal interface (assign from Edge Interfaces tab)
avauth.contoso.net	N/A	Internal	Server	A/V Authentication Port (assign from Edge Interfaces tab)