Trunks and M:N Routing
As organizations began to expand Lync Server
2010 Enterprise Voice services, a common pain point was the fact that
PSTN gateways could only be associated with a single Mediation server
or pool. This was an improvement over the Office Communications Server
2007 R2 limitation in which each PSTN gateway required a separate
Mediation server, but it still created some unnecessary headaches in
trying to design a resilient solution.
For example, a common use case for a remote
site was to place a Survivable Branch Appliance or Server in the site,
and configure a gateway to interact with that server. For redundancy,
though, it was desirable to create a separate connection between a
Mediation server pool in the datacenter to make and receive calls using
that gateway in case the Survivable Branch Appliance or Server was
offline. This was possible only using tricks like creating a second
“virtual” PSTN gateway object with a DNS name and associating the
virtual PSTN gateway to the Mediation server pool in the datacenter.
The disadvantage to this approach was that it usually required
organizations to skip TLS security on the gateway due to certificate
subject name mismatches, depending on which pool was interacting with
the gateway.
Lync Server 2013 has again improved the SIP
trunk experience and now defines trunks between PSTN gateways and
Mediation server roles instead of directly assigning a PSTN gateway to
a Mediation role. This allows the same gateway within the topology to
be referenced by multiple trunks that are accessed in a prioritized
order. Trunks are now based on the Mediation Server FQDN, a listening
port on the Mediation Server, the PSTN gateway FQDN, and a listening
port on the PSTN gateway. This change allows more flexibility on the
Lync side and allows each Mediation Server to listen on multiple ports
for incoming calls.
Inter-Trunk Routing
In previous versions of Lync Server 2010, all
calls had to either start with or terminate on a Lync endpoint. There
was no way to route calls through Lync Server between two IP PBXs or
gateways. Inter-trunk routing in Lync Server 2013 allows for this
scenario to take place, which might help organizations gradually move
users to Enterprise Voice. Lync Server 2013 can be deployed as shown in
Figure 1, such that it is “in front of” an existing
PBX, and owns the core routing logic that allows calls to still reach
users on a legacy PBX, or even allows calling between two existing PBX
systems.
Figure 1. Inter-trunk routing.
Call control is achieved by assigning PSTN
Usage objects directly to a trunk, which dictates how calls will be
routed when they reach the Lync Mediation servers. This opens up new
migration strategies, and requires fewer modifications to systems
outside of Lync such as the IP PBX or media gateway.
Calling Party Manipulation
A really big pain point in Lync has been the
lack of control over the calling party, or source, telephone number
display in outbound calls. Trunk translation rules in Lync Server 2010
allowed modification of the called, or dialed, party, but had no
support for the calling number. The best Lync could do was remove the
leading + sign before sending the call to a PSTN gateway. The end
result was that administrators had to manage translation rules both
within Lync and at the media gateway, which undoubtedly led to
inconsistencies and troubleshooting issues down the road.
Lync Server 2013 has introduced the
capability to manipulate the calling party on trunk translation rules
in addition to the called party. Administrators now have a single point
of configuration for basic number manipulations, which should help
simplify deployments. Media gateways can still be useful for advanced
manipulations specific to a T1 or E1 circuit, but are no longer
required for the outbound calling party.
Voice Mail Escape
Many organizations have jumped to capitalize
on the simultaneous-ring feature of Lync, which enables users to answer
calls to their work phone number at a Lync endpoint, or on a mobile
phone over their cellular connection. This flexibility enables workers
to never miss an important call, even if they step away from their desk.
The downside to this feature was that if the
user’s mobile phone was turned off, or possibly was out of range for a
cellular signal, the call would end up being answered by the user’s
cellular voice mail system. This created an inconsistency in the
greetings heard by callers and in how users managed their voice mail
messages because some work messages were now in their personal cellular
store.
Lync Server 2013 now allows a parameter called PSTNVoiceMailEscape
timer to be set on a voice policy that specifies the number of
milliseconds for which Lync Server should ignore a call being answered
by a simultaneous-ring target. The overall concept here is that
administrators can dictate a time value that is probably too soon for a
human to answer a call, which means the user’s cellular voice mail
probably answered. After this is detected, Lync Server 2013 ends the
call to the simultaneous ring target, but continues to ring the user’s
Lync endpoints. If the call still goes unanswered, the call is routed
to Exchange Unified Messaging for voice mail.
Response Group Managers
The Response Group Managers feature of Lync
Server 2013 enables administrators to delegate control over Response
Groups to specific users, which gives them access to the Lync Server
Control Panel. Within the panel the Response Group Managers can see
only Response Group workflows assigned to them, and can then manage the
queues and groups belonging to that workflow.
This is a nice addition for small departments
that would like control over their own workflows because it lets them
manage agents, business hours, music on hold, and the entire workflow
without opening a ticket with the Lync Server administrators.
Call Forwarding Restrictions
A common policy issue in previous versions of
Lync Server was that numbers a user was allowed to call also dictated
the numbers a user could configure as call forwarding or simultaneous
ring destinations. This made it impossible for administrators to allow
users to make calls to international locations, but only allow the
users to simultaneously ring a national or local number. In practice
many organizations just lived with this issue and would retroactively
review call-detail reports to determine whether any user was incurring
unusual charges.
Lync Server 2013 now
enables administrators to configure separate call forwarding policies
for each voice policy, and prevent call forwarding from leaving the
organization or incurring toll charges.
IPv6 Support
Lync Server 2013 has added support for IPv6
addressing of all server roles, which can operate in a mixed IPv4 and
IPv6 mode as organizations begin migrating internal networks to IPv6.
There is no support for down-level clients
like Office Communicator 2007 R2 or Lync 2010 in a dual-stack site, so
companies need to first migrate users to Lync Server 2013 in order to
implement IPv6 support.
Note
Some of the advanced voice features
such as Call Admission Control, E911, and Media Bypass do not fully
support IPv6. The Lync Phone Edition software also does not support
IPv6. Organizations requiring these features should plan on supporting
a dual-stack approach for this release.
