A Microsoft Lync alternative


AG Projects is closely involved since 2005 with the menthor-ship, authoring of specifications and developing of software components in the public domain for the deliverables of SIP SIMPLE and STOX IETF working groups. These software components (SIP SIMPLE Client SDK, OpenXCAP, MSRPRelay and SylkServer) implement SIP applications beyond VoIP that complement existing SIP deployments. A SIP based platform using these components can compete with feature-rich commercial offerings, traditionally available only from closed vendors like Apple, Google and Microsoft. These offerings typically provide a rich multimedia communication experience with audio, presence, chat, file transfer, screen sharing, video and multimedia conferencing for all media.

A SIP end-product with such rich multimedia capabilities will compete in terms of features but a lower cost with Skype and Google Hangouts for residential customers and Microsoft Lync for corporate customers. AG Projects offers today these capabilities part of large scale deployments with its SIP Thor platform and as a hosted service at http://sip2sip.info service. This carrier-grade product is addressing the needs of large operators and is not properly positioned to address the particularities of corporate markets. This market required a different pricing model, smaller scale on-site deployments and integration with an existing PBX present on site (like Asterisk)


The goal of this project is to downscale SIP Thor platform features into a smaller deployable solution that can be installed in a zero-configuration style at customer premisses that address the needs of small to media enterprises from 10 to 500 seats. The solution would work with an existing PBX and the customer perception would be that it uses only the PBX. This setup will be able to compete in the market place with Microsoft Lync which provides such a collaborative solution either collocated or in the cloud.

Client Side (Blink)

Blink is a complete implementation of SIP SIMPLE specifications (RLS, XCAP, MSRP protocols).

Component Mac OSX Windows Linux Description
Presence Yes Yes Yes RLS
Contact List Yes Yes Yes XCAP
Audio Yes Yes Yes Opus codec
Chat Yes Yes Yes MSRP protocol
File Transfer Yes Yes Yes MSRP protocol
Multiparty Conferencing Yes Yes Yes RTP and MSRP
NAT Traversal Yes Yes Yes ICE & MSRP Relay
Screen sharing Yes Yes Yes VNC protocol
Video Yes UD UD H.264 codec
Multi-language Yes No No N/A
  • N/A = not applicable
  • UD = under development

Complete RFC and standards listed here http://icanblink.com/standards.phtml

Server Side (SylkServer)

SylkServer is an application server specialised in delivery of rich multimedia applications accessed by SIP User Agents and XMPP endpoints.

Component Linux Description
Multiparty Audio Conferencing Yes RTP mixer
Multiparty Chat Conferencing Yes MSRP Switch
Multiparty File Transfer Yes MSRP
Multiparty Video Conferencing No Colibri
Conference Participants Yes RFC4575
XMPP gateway Yes IETF STOX

Complete RFC and standards listed here http://sylkserver.com/get-started

Third-party Servers

  • AG Projects is part of the management team of OpenSIPS project where it maintains modules related to NAT traversal, presence and prepaid accounting. Presence Agent (RLS) is provided by OpenSIPS.
  • MSRP NAT traversal is provided by MSRPRelay and Contact List by OpenXCAP, both maintained by AG Projects

For the implementation of this project, VoIP applications and the functions performed by OpenSIPS related to SIP routing must be provided by the on-site PBX. The PBX must be able to route unmodified INVITE and SUBSCRIBE packages and subsequent messages art of their dialogs between Blink and SylkServer.

Ideally, the non-VoIP components should be integrated in SylkServer in case the solution should be deployable at customer premises.

Lync-Replacement.png (111.1 kB) Adrian Georgescu, 06/09/2014 01:37 pm