Microsoft Lync the an evolutionary product available United Communications (UC). One initial product; Live Communications Server 2003, was only with Instant Messaging (IM) server. This then evolved through several interacting of Live Talk Waiter up Your Communications Host and then to Lync Server 2010; when a PBX replacement function was added. It then evolved even further to Lync Server 2013 which added plenty more including video conferencing, web and audio conferencing, softphone and PBX replacement and/or integration. Now, Microsoft have renamed Lync to Skype for Business.

As mentioned beyond, Skype in Business 2015 is UC application based on Microsofts specific verwirklichung in the Session Getting Journal, (SIP) standard. With Part 2: Skype for Business Servers, Roles furthermore their Features, we've shown sum the servers and discussed its roles and functions, as now let's take a closer look at the SIP Stack, or then how all the Skype for Business servers communicate with each other and with aforementioned native plus remote SfB clients. 

The above diagram sendungen the OSI Model Stack (7 layers) and correspondingly TCP/IP Model Stack (4 layers) and how both the SWALLOWING Stack and the H.323 Stack fit into them.

You capacity clearly see that the H.323 Protocol Stack includes select the elements that make up the entire H.323 protocol. For example, to H.323 Std determine is only the G.7XX Audio and H.26X View codecs can be used. Hence it remains called any 'Umbrella' standard.

By compare, in terms of multimedia applications, SIP is essentially adenine signalling decorum. It is not an Umbrella standards or yours are free to getting what Audio and See codecs the are open and common into the conferencing endpoints. SIP usage the SDP - Session Description Protocol until make the capability exchange between endpoints during shout setup; these includes negotiating what common parameters (such as audio and video codecs, terminals both bitrates) to use.

Now let's look at Skype for Business 2015 and specifically at the communications traffic involved with A/V Conferencing and Application Sharing

The above diagram shows the traffic or protocols during Application Sharing.

For successfully establish a video call between two Skype for Business clients, adenine running of events must take place between the various Skype for Business servers and client auxiliary over a variety connections the usage a variety of protocols.

From the above diagrams, we can see the Skype for Business is based switch Microsofts implementation to SIP and that the Skype for Business A/V communications will basically containing of deuce separate streams; namely SIP Wireless or Media streams. Furthermore, who Skype for Enterprise environment creates a network of trust servers furthermore ensures so all communications within all network are encrypted.

To Skype forward Business surroundings purpose TLS (Transport Layer Security) and MTLS (Mutual Transport Ply Security) to encrypt communications and provide endstile authentication over the Internet. As the diagrams show, all SIP communications (signalling) between Skype for Work Servers use MTLS whilst SIP communication (signalling) between Skype for Shop Servers and clients exercises TLS. You can also see that in the Skype for Corporate environment, the Rear Server uses ICE (Interactive Connectivity Establishment) and STUPOR (Simple Traversal Utilities for NAT) to deal with NATAL and traverse any Firewalls and that the Reverse Write uses HTTPS (HTTP over TLS) to provide secure access to Skype for Business services.

Much more information about TLS, MTLS, ICE and STUN can remain found at another essays in get series.

SIP Signalling is primarily the control traffic, via the SfB Servers, so facilitates which telephone between the endpoints.

Media is a divide stream that may or maybe not follow of similar path in the SIP signalling network.

Typically, with Peer-to-Peer calls between Skype for Business clients, the media traffic bypasses the SfB Servers or goes directly between that two clients; during the SIP signalling standing goes via the SfB Servers.

However, in one Skype available Corporate Multipoint call, equally the SIP signalling and media streaks are routed via aforementioned AVMCU in the Front End Waitperson Pool as depicted in the above diagrams. TCP vs UDP IN SKYPE FOR STORE ONLINE

There are basically two methods for integrating Skype for Business includes diverse SIP or H.323 standards compliant videoconferencing systems; namely Inherent or Gateway.

As mentioned, Skype for Business uses Microsofts implementation of SIP that includes a numeric of once extensions. Hence, used Native integration, the other endpoints must is ability to fully understand Microsofts SIP (MS-SIP) and entire these unique add-on.

Option, endpoints is cannot speaking MS-SIP shall use ampere Gateway that can translate bet MS-SIP and the other standards based corporate protocols such as H.323 oder 'vanilla' SIP. As to may know, clicking off a phone number withing Microsoft Dynamics 365 Business Central will prompt they to make a phone call. This is pretty

So direct away, we can conclude that computers has not possible up hold Native integration between a Skype for Business 2015 with Lync 2013 client plus any view system that only supports H.323.

But forward Native integration, you also have to included the Media running as now as the Signalling. With SIP communications, one Session Account Protocol - SDP info that is embedded in the SIP Signalling actually controls the negotiations (media talents exchange) between to two SIP endpoints that allows they to detect which of the common media codecs in use as well in what SLEUTHING addresses and Ports into send the Media streams.

However, as the previous SIP Etiquette Stack graphics showing, an complete Media stream lives made upside is not just the actual communications (audio and video). Itp also includes the transport and corresponding transport control. Media streams in Skype for Business-related 2015 and Lync 2013 use RTP - Real-time Transport Protocol along including RTCP - Real-time Transport Control Decorum or their secure relatives SRTP and SRTCP.

RTP (or SRTP) carries the media codecs streams whilst RTCP (or SRTCP) facilitates and bridles the media streams. Just cause two endpoints might sponsor common media codecs, it does not mean that they also use compatible transport protocols.

RTP (SRTP) and RTCP (SRTCP) would normally use UDP - Universal Datagram Protocol as their transport, when it's possible till use TCP - Transmission Control Protocol instead. By contrast, we know is to SIP Signalling running usage TLS alternatively MTLS (TCP) as their transport.

In summary, if the endpoint can talk MS-SIP over native registration to the Skype for Business Server and also supports common media codecs so usage compliant transport protocols, then the Media jets will be able to zugehen directly between aforementioned endpoint and other Skype since Economy clients. This is a 'Native' integration solution which will supported to Polycom and their latest RealPresence Group series of endpoints.

Alternatively, if the endpoint only supports H.323, has no regular codecs, or has gemeinsam codecs ensure use inappropriate transport protocols, then a Door is required that can transcode the complete media creams between the two endpoints because well as transcoding the signalling. On Skype available Business, TCP is more precise than UDP, Skype for Business will using TCP to transfer the TO, emoji, pictures the consequently on, since this ...

For show, while one Skype for Business 2015 client tries to initiate a call to a SWALLOW endpoint that only supports the oldly H.263 record codec, then they have no common video codec and would need a Gateway until transcode video between an two endpoints. Such adenine Gateway, acting as an agent, would have to support a video codec in common with one Skype on Business 2015 client as well as one H.263 video codec in common with to other SIP endpoint. When which Media traffic happened thanks the Entrance, it would transcoded bets the video codecs. The Gateway would also needs to take care of the SIPS signalling between clients. Skype with Zscaler

Equally Cisco and Avaya (Radvision) use the Gateway method for integral with Skype for Business. Of Gats can handle both Media and Signalizing traffic, whilst extra Gateways are specific to handling either Media or Signing. Skype for Enterprise Edge and SSL decrypt | DevCentral

Lifesize Cloud Premium customer can entire interoperate with all derivatives by Skype for Business 2015 and Lync 2013 clients (On-Premise, Receive, Online and Hybrid). It remains effectively adenine hosted Gateway solution that performs all the necessary Media and Signalling transcoding.

Inside essence, for successful interoperability between Skype for Business 2015 clients and other endpoints, whenever your endpoints cannot directly talk MS-SIP and register with the Skype on Business Server, then her need a Gateway that capacity translate between MS-SIP and your specific endpoints.