Perhaps some of the most tangible, new, and exciting benefits of Lync Server are those related to the Enterprise Voice set of features. With the new release, Lync Server competes with the voice features provided by traditional PBXs. In fact, at VoiceCon 2010, Lync Server won the Voice RFP competition competing against the major PBX manufacturers.
Mediation Server Role Collocation
In prior versions of OCS, the Mediation Server was a dedicated role and required a one one relationship between the server and the gateway. OCS configuration enabled only a single, next-hop configuration from the Mediation Server to the media gateway (PBX, PSTN, and so on). Although certain gateway manufacturers were able to load-balance calls from the gateway to OCS, OCS was limited to only the single next hop. In Lync Server, the mediation role now runs on the Front End Server as a service. This concept of mediation server collocation provides tangible benefits from a topology, administrative, and user perspective.
With Lync Server, each Front End Server can have its own mediation service, enabling pools to route to gateways instead of the mediation servers. This enables multiple mediation servers to route to the same gateway or multiple gateways to route to a single mediation service.
This capability provides tremendous flexibility to design engineers and enterprises with a large number of PBX/PSTN trunks at a single site or many smaller sites. In previous versions of OCS, these scenarios required a mediation server at each location. In addition to a tangible reduction in servers, this topology change provides greater resiliency, more flexible routing choices, and more options for media flow.
One of original roles of the mediation server was to transcode between RealTime audio (RTAudio) and G.711 to integrate with standards-based media gateways and PBXs. With Lync Server, calls can be sent using G.711 directly to a supported gateway or PBX. Although low bandwidth signaling (SIP) still traverses the mediation service role, higher bandwidth media (RTP) flows directly from a Lync Server endpoint to the GW/PBX, bypassing the Mediation Server role.
This change provides several benefits, including
. Removes a potential single point of failure that a mediation server introduced
. Reduces the overall server footprint of OCS
. Reduces the number of hops a media stream takes
In addition, in scenarios where a branch appliance is deployed, calls from PBX users at a branch to Lync Server users at the same branch, media now remains at the branch. Prior to Lync Server, an extra mediation server at the branch was required to enable similar call flow.
Optional Dedicated A/V Conferencing Role
In scenarios that require heavy conferencing resources, or MCUs, the A/V Conferencing role can be split off from the Front End Server role. Multiple A/V servers can be placed in a pool and this A/V pool can be designated as the conferencing resource for many other pools. This topology offers a distinct advantage enabling conference-centric enterprises the capability to provide a highly available conferencing resource to the users, but also keeping this resource-intensive application isolated from the day-to-day IM presence and telephony services. Additionally, this enables an enterprise to virtualize basic telephony services while providing physical hardware for A/V services.
Call Admission Control and DiffServ
Although RTAudio is a flexible payload codec, many larger enterprises believe that Lync Server should support call admission control, or CAC, as well. Already a fixture in many
VoIP communications servers, call admission control is now configurable in Lync Server. With Lync Server, network managers can control the amount of bandwidth voice and video calls consume on a given link. By configuring the bandwidth policy service to control a specific site, calls can be rejected or rerouted to the PSTN when sufficient bandwidth is not available to complete the call. This ensures quality audio or video sessions. Enterprises can garner tremendous benefit from planning their CAC strategy prior to deployment.
Lync Server users benefit from its capability to leverage the concept of differential services code points (Diffserv—or DSCP) for audio and video traffic. By separating port ranges for audio and video, Lync Server enables network administrators to provide different per-hop behaviors (for example, EF or expedited forwarding) for these streams. This enables latency sensitive traffic to route ahead of web or other non-real-time traffic. Windows 7 and Vista desktops can leverage Windows-based QoS. This enables them to be provisioned to apply DSCP markings to packets based exclusively on application and port ranges.
By combining CAC, DSCP, and Windows-based QoS policies, network administrators can rely on Lync Server to adhere to the policies they create and deploy on their network to enable all packets to arrive as required and ensure a quality user experience.
Primarily developed for North America, enhanced 911 (E911) allows for additional information to be presented to the public service answering point (PSAP) that enables emergency personnel to obtain details about the specific location of an emergency call. These additional attributes are a building number, mailstop, cubicle number, or any other specific attribute that can save precious seconds in an emergency situation. Because VoIP is mobile, simply relying on a telephone number is not suitable for IP communications. The new location information service (LIS) role in Lync Server enables network identifiers such as switch ports, subnets, and wireless BSSID information to be matched up with location information and transmitted to the PSAP when setting up a 911 call. In addition to regulatory compliance benefits, e911 allows for a safer telephony environment. With Lync Server’s E911 service, end users trust that calls made to a 911 service will provide the vital details to emergency personnel.
Location can be set through the policy or manually. Visual indication of the current location is presented directly in the Lync Server client. E911 can also be configured to enable other onsite users to be automatically conferenced into an emergency call, enabling corporate first responders to be aware of 911 calls as they happen, which coordinates with police, fire, and other emergency services as they arrive.
Malicious Call Trace
When a Lync Server user receives a call that she deems is harassing or threatening, she can flag it in the call database. By alerting system administrators of this fact, they can quickly determine the source of the call and trace it back to its origin for evaluation by security personnel.
Caller ID Controls
Lync Server allows for a user’s caller ID to be modified dynamically based on the destination of the call—internal or external. This enables an enterprise to maintain full reverse name lookup to the corporate directory for internal calls, but provide a uniform departmental or location number to be presented when making external calls. This is used in certain situations such as outbound call centers, support desks, or any other situation where it is necessary to block caller ID digits to external parties. This can be set at a user level or by policy.
Lync Server response group agents can be placed in anonymous groups. This feature enables help desk personnel to participate in a response group without providing a name and number to internal users. Prior to Lync Server, users calling a response group saw the agent they were connected to in their Communicator client and frequently then bypassed the response group on subsequent calls, defeating the purpose of the group by failing to leverage the available pool of agents. Lync Server response groups in anonymous mode are suitable for use in scenarios where the agent’s number needs to be kept private.
On-Net and Off-Net Voice Routing
For an enterprise to benefit from a large geographically dispersed voice network with many PSTN egress points, the capability to route calls through these points is crucial. However, when the points are located in different cities or countries, each point can require different dialing formats, prefixes, or other access codes. This can add tremendous complexity to a corporate dialing plan. Fortunately, Lync Server provides central alternative routes and number-formatting changes to manipulate the dialed number prior to routing to a PBX or the PSTN.
Media Gateway Certification
Beginning with OCS 2007, Microsoft developed the open interoperability program (OIP) for PBX and gateway vendors to enable enterprises to determine whether a particular piece of hardware or software version is certified to work with OCS. Beginning with Lync Server, audio quality and performance testing is included in OIP certification. This enables systems engineers to design a solution that will perform properly for all communication modalities.
Source of Information : Pearson-Microsoft Lync Server 2010 Unleashed
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