MN.IT has extensive experience with H.323 videoconferencing and has determined which deployment techniques provide the most reliability. As a result, MN.IT has established this "Best Practices" document for H.323 videoconferencing.
This document describes the basic network design and Quality of Service (QoS) issues for H.323 and explains the results from testing various video systems, MCUs and gateways.
This document also includes recommendations on the type of equipment and technology that best meets essential quality and H.323 standards required for its videoconferencing service. These recommendations are based on exhaustive test results and "lessons learned."
If you have questions regarding these technology recommendations, please contact MN.IT.
Testing has confirmed the importance of correctly configuring the system's Ethernet connection. Recent advances in switch and video conference system technology have necessitated that some systems be configured for auto-negotiate, while others must be hard coded for speed and duplex. Video systems are either hard-coded for full duplex or will properly negotiate full duplex. The final step in the video system installation process is site certification. MN.IT video technical staff will identify and correctly configure the system and switch (or if MN.IT does not have access to the switch, work with the customer to get it configured properly) for optimal performance.
Issues may occur when connecting non-Cisco devices or when using Cisco 3550 or a 2950 and using hard coding. Contact MN.IT if you have this sort of connection or you are not using Cisco hardware. This situation can be corrected with updated switch software.
System vendors now offer High Definition (HD) video systems. Some of these HD systems are not fully H.323 compliant. These non-compliant systems will not be certified for use on the MN.IT IP video network. Compliant systems are listed later in this document. These systems do provide a better picture (assuming the monitor can display them) than non-HD systems at 384Kbps. Bandwidth rates of 768Kbps or greater are required to take advantage of further improvements and rates of 1Mbps or more for HD transmission/reception. MN.IT video conferences are currently either 384Kbps or 768Kbps. As systems with greater capabilities are installed, MN.IT will scale the network as required.
See also the Real-Time QoS document.
MN.IT has determined that the best way to manage bandwidth contention is to connect the video equipment to a dedicated Ethernet segment on the router. A variation on this option is to have switches that support - and are properly configured for - the (Class of Service) 802.1P protocol connected to a separate Ethernet port on the router. This protocol marks video traffic as priority.
Based on testing various technologies and protocols, MN.IT has chosen to use the DSCP marking and Tandberg Gatekeepers to manage quality of service (QoS) over the network. The Tandberg Gatekeepers and DSCP configuration work together to insure that QoS is available for each video call.
Video calls unable to get the necessary QoS can be configured in the Gatekeepers to not complete. Some customers will have the ability to generate more QoS traffic then there is available QoS bandwidth. If video calls at your location are experiencing packet loss due to over-subscribing your QoS bandwidth, contact MN.IT. MN.IT will then configure your location to reject video calls that exceed the allotted QoS bandwidth. Video packets are marked for priority delivery (between MNET video locations using assigned video subnets) as they enter the local router, at the system or both. All calls, whether dialed IP or E.164 (a 10-digit phone number) between MNET video locations will get QoS. If a video system is not registered to a Gatekeeper, there is no way to block the call if there is no available QoS bandwidth. If this call is placed, it will complete and may over-run the QoS policing in the router. This may cause all currently connected calls to experience packet loss, appearing as distorted audio and/or broken and tiled video.
As of November 2008, all MNET locations had been converted to use the DSCP QoS model. This model provides better call accounting and the use of advanced video system features like H.264 (an advanced video coding algorithm providing better video at 384K), HD (High Definition), H.239 (separate video channel for transmission of PC images) and encryption.
At sites where multiple circuits are used, the circuits are bonded together using Multi-Link PPP in order to aggregate bandwidth. The use of multi-link PPP ensures that packets stay ordered correctly and provides for good load balancing across the circuits.
All MN.IT video service sites are in a video VPN within the MN.IT MPLS system. Having them in the same VPN helps enshure that the QoS configurations are correct and uniform.
The Cisco MCM and Proxy are no longer employed on MNET. Presently there are a few Cisco CUBEs (Cisco Unified Border Element) in use. These devices are the next generation of the Cisco MCM/Proxy offering support for H.239 (duo-video) and encryption. They are used to route calls to neighboring video networks, and to Internet2 video systems and MCUs. RSVP is still used between these devices for traffic flow.
The DSCP model marks packets only between systems residing in MNET video IP address space. General Internet and Internet2 networks we send video to reside outside this address space. The Cisco CUBEs (which reside in the MNET video IP range) allow MN.IT to provide QoS to the edge of the MNET cloud, ensuring we hand-off a clean signal to the other networks.
Systems provide for real-time, two-way audio/video communications. Typically, H.323 video systems are either computers running H.323-compliant software with specialized hardware, or group conferencing systems using H.323 systems. PC-based personal H.323 systems are not well suited for production conferencing and are not considered in this document nor will MN.IT certify them for use as such. Such devices may be used as part of the general data service. Their communications will not receive quality-of-service handling.
Customers considering implementing H.323 video should consider the various choices of H.323 systems. There are a number of native H.323 systems to choose from. Be aware that some systems claiming to be H.323 video systems are not in full compliance with the ITU standards and should be avoided. Video systems not in full H.323 compliance will not be fully certified and may not be able to participate in some or all conferences. Be sure any system under consideration at your location is in compliance with H.323 specifications.
Polycom and Tandberg video systems underwent extensive testing and were individually evaluated for their reliability and quality.
In addition, MN.IT tested a number of systems from other vendors for interoperability with each other and for performance on the network. Here is a recap of the test results for the systems listed above. The last section of this document contains MN.IT's recommendations for H.323 systems.
These units should be manually set for 100Mbps full duplex, which provides good quality at 384Kbps. 384Kbps is MN.IT's recommended speed for H.323 systems. All models provide simple setup and ease of operation. The EX and FX models have more A/V inputs and outputs, an analog phone add-in, VCR record support and multipoint conferencing capability, while the SP model does not support VCR recording or multipoint. Newer (since November 2003) SP units now support VCR recording. If you want the capability to tape your conferences, be sure to check with your vendor for the most up-to-date and accurate information. Recent testing has shown that newer Polycom models with software revisions above 8.x may need to be set to auto-negotiate.
Polycom systems have a built-in web control interface, as do all room systems. This interface can be set to require a password to gain access to critical setup areas (to receive optimal support, MN.IT recommends you set a password and let MN.IT know what it is). The default password is the last 6 digits of the serial number (or full s/n in newer models) as shown on the bar code sticker.
The EX/FX/SP/VSX Polycom models are geared toward addressing the set-top market, but only the EX/FX and VSX models can be enhanced with second monitors and dual channel motion (not H.329), where the graphics and participants are "live." The VS series (no longer manufactured but can be found at some suppliers) have the same features as the EX/FX/VSX models but are stand-alone systems. Stand alone systems require you to furnish cameras, amplifiers and optionally, additional microphones, either with or without a mixer.
SP software version 7.2 and above (SP) and FX/VS version 6.0.5 are the only certified revisions. If your system is not on one of these software revisions, contact MN.IT for an upgrade. Upgrades to these releases are free.
Polycom also has three VSX models which need to be at least at version 7.53, but work best at the more recent versions (verseion 9.0.6 as of April 2010). Some VSX models have some known issues running at speeds greater than 512Kbps. The more recent (8.03 or later) software revisions will fix this if you're eligible. All VSX and HD models require an active service contract to update the system software. Some Polycom models offer a Telnet-based Open Captions (manually entered) option when connected to other VSX units. All Tandberg systems have Telnet-based Open Captions. Cross platform compatibility is on a trial and error basis.
No information available.
All of these units performed well and have a dual stream mode (except the model 1000), allowing full-motion graphics and video at the same time. When using the dual motion mode, both motion channels are something less than the connected rate. Tandberg 2500 and 6000s are aimed more at the telemedicine or distance learning markets. The 6000s and MXPs are the most feature-rich and can be equipped with many options to enhance videoconferences.
The 880 model is a set-top model with features and functionality comparable to the Polycom FX.
The 1000 model is a set-top unit not designed for group conferencing, but is more aimed and the executive desktop market.
The Tandberg units come equipped with a web interface. By default, the Telnet interface has no password set but can be secured via the ippassword Telnet command. Users connecting with the web interface have full access to the system including all administrative functions. When first enabled, the default password is TANDBERG. We strongly suggest setting a password and informing MN.IT of the password for best support.
All Tandberg models above (except MXP) work best when running version E5.3 or B10.3 (system dependent) but will work acceptably at some earlier releases. Tandberg classic models (systems with no letter designations) are at their final revision and no more releases will be forthcoming. For MXP units, use F6.x or above for best results (F8.2 as of Jan 2010). Tandberg Classic software versions E4.1, E5.1, and E2.3 exhibited some interoperability issues and should be avoided. Tandberg publishes a hardware/software compatibility grid in the release notes of all their current software. All Tandberg classic units should be at E5.3 or B10.3 for best results. If you do not have an active service contract you will not be able to upgrade. Contact MN.IT for options.
A Multipoint Control Unit (MCU) is a video bridging or switching device used to host multipoint videoconferencing. MCUs perform two major functions: The handling of negotiation between all terminals to determine common capabilities. The other function is the mixing, switching, and other processing for audio, video, and (optionally) content. MN.IT has moved exclusively to the Codian (owned by Tandberg (now Cisco)) MCU platform. MN.IT has 200 MCU ports available for use. Some room systems have integrated MCU functions that allow you to call up to three or five sites. Your ability to use the MCU feature of your system will be heavily dependent on your contracted QoS bandwidth. Locations with connectivity at 3 Mbps or less will be unable to make full use (or cannot connect to capacity) of the integrated MCU feature.
This unit performs well. It does not use a prefix, but rather E.164 identifiers. The Tandberg MCU line (not including Codian) has some limitations as to the number of simultaneous conferences depending on the hardware platform. It is simple to use through its web-based control interface. The web interface also provides snapshots on screen when monitoring. These units support full duplex (which should be set for best results) and are MN.IT-certified. The MPS, when connected to one or more PRI lines can act as a standalone phone bridge or can be used to add voice-only participants into a video conference.
This platform was released in July 2004 and has been tested by MN.IT. The MXP enhancement has been added to Tandberg's entire line and the 2500 series has been replaced with the 3000 model. These units can be optioned for multi-site capabilities and can host 4 or 6-way conferences depending on model and installed options.
The Polycom MGC has proven itself to be a carrier class MCU and interoperates quite well with all platforms. Some newer systems need to have some features turned off to join some conferences. MN.IT no longer uses this platform, but there are some on our network.
It can also act as a stand-alone gateway to allow direct mapping of incoming ISDN calls to H.323 systems as well as allowing direct dialing of ISDN systems from H.323 systems. MN.IT stopped using the MGC platform for several reasons. If you want more information as to why MN.IT moved away from this platform contact MN.IT.
The Polycom MGC has a built-in scheduling interface capable of storing up to 2000 conferences. With the current certified software releases (Version 8 or 9) it supports "Drag & Drop" functions to move participants between like conferences. It can also connect voice-only systems via ISDN or Switched 56k lines.
Codian was purchased by Tandberg in August 2007 and Tandberg is in the process of being purchased by Cisco. The Codian MCU is highly recommended by MN.IT.
This is an IP only box with many nice features like Auto Attendant that allows callers to select conferences from list using their Far End Camera Control. Several Codian models are available with port availabilities from 12 to 80 per system. Unlike the Tandberg MCUs or Polycom MCGs, the number of usable ports does not decrease as the connection rate increases. It features a browser based interface that will work on most platforms. It can either be configured to stream conferences (200 maximum simultaneous streaming viewers per system), or for the ConferenceMe feature allowing webcam equipped PC's to join as well (MAC is not yet supported).
This machine performs very well and is very user friendly, from its interface to its CDRs Call Detail Records. The current version is 4.0(1.54). There is a known issue with version 4's interaction with TMS version 12.5 in that TMS cannot provide snapshots.
Other features include FECC (Far End Camera Control) and text messages that can be flashed on one or all screens for various lengths of time. It also supports conference passwords, dynamic screen layouts on a per-site or per-conference basis, and remote access to computers running VNC (http://www.realvnc.com) and many others. This product also comes with an automated attendant operated via TouchTones or far end camera controls.
A gateway is a device that provides the translation services between H.323 or SIP (Session Initiated Protocol) systems on the IP network and other ITU-compliant terminals (for example, old-style H.320 room systems) on circuit switched networks. A gateway is typically a self-contained network component that translates between H.323 or SIP and H.320 protocols. These gateways let users connect IP-based H.323 (or SIP) videoconference systems to legacy circuit-switched H.320 systems and Plain Old Telephone Service (POTS). Gateways convert multimedia information from circuit switch (ISDN) to H.323 or SIP IP packets.
The Codian MSE-8000 owned and operated by MN.IT has a Gateway card with two ISDN PRI lines connected, allowing up to six 384Kbps connects and 10 POTS connections (total 46 x 64Kbps) simultaneously. This Gateway has been very reliable. Almost every issue we've encountered using it has been traced back to the far end ISDN connection.
While the Codian does offer SIP to H.323 gateway functionality, the primary device for this function is Tandberg's VCS (Video Communications Server) which is currently (April 2010) being tested. The VCS acts as a Gatekeeper for H.323 and SIP devices. It will also allow gateway connections between Microsoft Office Communicator (MOC), Tandberg's SIP clients (Movi) and H.323 systems. MN.IT hopes to offer SIP video solutions in the near future.
MN.IT now has nearly ten years of experience with IP video and has developed the following technology recommendations. These recommendations are to assist customers with the implementation of a video system. The recommendations cover issues related to LANs, WANs, Firewalls, H.323 and SIP devices.
Although the H.323 recommendation describes the gatekeeper as an optional component of a functional H.323 system, in practice the gatekeeper is essential.
MN.IT recommends the following systems:
MN.IT does not always have the resources (staff or hardware) to verify all new software releases. As such, new versions may be available that are not certified by MN.IT. You may wish to contact MN.IT before doing any upgrades.
As a reminder, if you upgrade your system's software you will be required to re-certify your system with the MN.IT video support team.
MN.IT recommends the use of the Codian, Tandberg Polycom MGC, or Polycom MGC MCU line.
The main reasons for cascading two H.323 conferences are to increase the number of sites (currently 38) that can be in a single MCU at 384Kbps with H.239 support.
MN.IT recommends avoiding a cascade between H.323 conferences. While cascading is possible, it results in enough delay to be distracting to conference participants. We have also seen that when a conference is cascaded and includes H.239 content, the use of the "make site important" button must not be used. Use of this button on a cascaded conference will result in loss of the content channel to non-H.239 optioned systems and to slave MCU.
MN.IT does not recommend conferences larger than 36 participants due to issues related to cascading. MN.IT strongly recommends that large conferences be connected 60 minutes prior to actual start time to allow everyone to connect, and to fix (or find a workaround) any issues that may arise.
Conferences exceeding 30 sites may be better served by using streaming technologies with electronic mail feedback. MN.IT also offers a hosted webinar service that may be a better fit than a video conference to reach large audiences.
MN.IT will host conferences larger than 30 sites, but does not recommend them.
Our events section has more information on events.
Multipoint Conferences with ISDNISDN locations can be problematic in that many are older systems and BRI lines frequently lose contact with the phone switch they are attached to. Please make sure that any ISDN location you conference with has been certified by MN.IT, or allow a minimum of one hour prior to the start of the conference to get these locations connected properly.
