Lync Client Discovery Process

Another well document process.  This is note for myself so i don’t have to GOOGLE/BING it everytime ii need to look it back up:

The Old Client Sign-In Process

Let’s begin by looking at the client sign-in process in a Lync 2010 environment in which CU4 isn’t installed. To set up the infrastructure for the client sign-in process, you need to create the internal DNS SRV record, _sipinternaltls._tcp.domain (where domain is your domain’s name), which allows users to connect automatically. This SRV record accompanies the A record for the server or the virtual IP (VIP) of the load balancer. Together, they allow clients to find and sign into their registered Lync 2010 pool. For example, if the domain is contoso.com, the path for signing in follows this order:

  1. _sipinternaltls._tcp.contoso.com (SRV record for internal Transport Layer Security—TLS—connections)
  2. _sipinternal._tcp.contoso.com (SRV record for internal TCP connections)
  3. _sip._tls.contoso.com (SRV record for external TCP connections)
  4. sipinternal.contoso.com (A record for the Front End pool)
  5. sip.contoso.com (A record for the Front End pool when the client is on an internal network; A record for the Access Edge Server when the client is external with no VPN access)
  6. sipexternal.contoso.com (A record for the Access Edge Server when the client is external with no VPN access)

The New Client Sign-In Process

The client sign-in process has changed quite a bit since the introduction of the mobility discovery process. SRV records are used to assist the mobile clients with the sign-in process, no matter whether the mobile clients are inside or outside the organization. For example, if the domain is contoso.com, the path for signing in follows this order:

  1. lyncdiscoverinternal.contoso.com (A record for the Autodiscover service for internal connections directed to internal Web services)
  2. lyncdiscover.contoso.com (A record for the Autodiscover service for external Web services)
  3. _sipinternaltls._tcp.contoso.com (SRV record for internal TLS connections)
  4. _sipinternal._tcp.contoso.com (SRV record for internal TCP connections)
  5. _sip._tls.contoso.com (SRV record for external TCP connections)
  6. sipinternal.contoso.com (A record for the Front End pool)
  7. sip.contoso.com (A record for the Front End pool when the client is on the internal network; A record for the Access Edge Server when the client is external with no VPN access)
  8. sipexternal.contoso.com (A record for the Access Edge Server when the client is external with no VPN access)

Thanks Bryon Spurlock for the nicely written article http://windowsitpro.com/lync/lync-client-discovery-process

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