Teleconferencing & Video Implementation Analysis
...s an existing Local Area Network (LAN) in place? If so, then the network required for videoconferencing (VC) is already in place. It is a networking issue that determines how the participating platforms are going to be connected together and hence which is the applicable standard that should be considered. In the case of the law firm of C.P.M.J.D. & A, they only want to communicate within their organization and already have a LAN installed between the two offices. There are two main standards used in video conferencing; H.320 or H.323. H.320 conferences can occur between just two participants as ISDN is essentially a point-to-point connection. This would work well for C.P.M.J.D. & A. A crucial area in selecting a system is to discuss the expectations levels of the users. What is a realistic frame rate and window size for the available bandwidth? We fund that is was much lower than that expected by the users. However, for the users to get the most out of a video conferencing system, they must be content when using it. Their expectation levels must be aligned to what is realistic from the available systems. (Cost vs Wants). H.320 conferences are essentially a point-to-point connection and need to use a form of Multipoint Control Unit (MCU) to link and manage all the ISDN lines in order to hold a conference with three or more participants. The MCU's basic function is to maintain the communications between all the participants in the conference. H.320 MCU's are usually a separate piece of hardware dedicated to their function as they need to connect to all of the ISDN lines from each participant. For example, to manage a conference between four H.320 systems, each at 384kbps (3xBRI), the H.320 MCU needs to connect the twelve BRI's. This is typically done as 24 x 64kbps channels within a Primary Rate Interface, (PRI). A dedicated H.320 MCU can represent a large capital investment. There is an initial investment of installing ISDN lines to each of the sites involved and this is probably the most common reason for not going H.320. For C.P.M.J.D. & A., because they only have two sites involved, the cost will run approximately $4,095.00 per location. After deciding which standard to adhere too, the platform, price and performance equation can be determined. ADSL, ISDN or the Internet The decision on which of the above networks to use is essentially a trade between quality, cost and topology. At the high performance, high cost end there is ISDN, at the high performance, medium cost end there is ADSL, while at the low performance, low cost end there is the Internet option. They are all effectively standalone systems, but adhere to different standards. There are both Desktop and Group systems that support 384kbps ISDN connections and offer the highest performance within the H.320 standard. The question of what is an acceptable frame rate and window size needs to be considered. If it is 2-6 fps at QCIF, then the Internet option and low cost H.323 systems will provide a solution. However, most professional people will demand much higher frame rates at CIF size and as such, ISDN linked H.320 compliant Desktop or Group systems are the solution. These systems can achieve 25 fps at CIF size with low-bit rates, especially if they use H.264 video compression. H.261 was the original ITU-T developed standard used in Video Conferencing. This was quickly followed by H.263 in 1995. After this, the ITU-T Video Coding Experts Group (VCEG) started work on a short-term effort to add extra features, (H.263 v2) and a long-term effort to develop a new standard that offers higher video compression efficiency and better resilience from packet and data loss. In 2001, the ISO Motion Picture Experts Group (MPEG) recognized the potential of this ITU-T development and formed the Joint Video Team (JVT) that included people from MPEG and VCEG. The result is two identical standards: ISO MPEG4 Part 10 and ITU-T H.264, with the official name Advanced Video Coding (AVC). The H.261, H.263 and H.264 algorithms are all designed for use with low bandwidth communications and incorporate motion prediction as well as Lossy Compression, also known as Lossless Compression, to further reduce the amount of information to be transmitted. Whilst H.261 and H.263 images are also limited to CIF and QCIF sizes, H.264 can support graphics at XGA resolution when used in H.239 data streaming. The basic technique of motion prediction works by sending a full frame followed by a sequence of frames that only contain the parts of the image that have changed. Full frames are also known as 'key frames' or 'I-frames' and the predicted frames are known as 'P-frames'. Since a lost or dropped frame can cause a sequence of frames sent after it to be illegible, new 'I-frames' are sent after a predetermined number of 'P-frames'. It is the combination of both Lossy Compression and motion prediction that allows H.261, H.263 and H.264 systems to achieve the required reduction in data whilst still providing an acceptable image quality. There is little difference between the functional elements of H.264 and those of the earlier H.261 and H.263 standards. The changes that do make the difference lie mainly in the detail within each element, how well the algorithm is implemented and whether it is performed in hardware or software. Be cautious of systems that claim to achieve high frame rates over low bandwidths using software implemented compression. These codes still need computational power and it is unlikely that H.264 can be satisfactorily achieved in software with anything less than a 1.4GHz Centrino or 2.8 GHz Pentium IV based system H.320 MCU's are usually a separate piece of hardware dedicated to their function as they need to connect to all of the ISDN lines from each participant. For example, to manage a conference between four H.320 systems, each at 384kbps (3xBRI), the H.320 MCU needs to connect the twelve BRI's. This is typically done as 24 x 64kbps channels within a Primary Rate Interface, (PRI). A dedicated H.320 MCU can represent a large capital investment that maybe difficult to justify. Location of Participants H.323, H.320 and H.324M (3G-324M) systems can interoperate with the use of a Gateway. Essentially, the Gateway provides translation and trans-coding between different circuit-switched networks (ISDN & Cellular) and packet-based networks (LAN), enabling the endpoints to communicate. Installations and Usage Costs For H.320 based systems, the costs need to cover installation of the ISDN lines and the on-going line rental as well as the initial purchase of the H.320 equipment and a Wide Screen TV. With regards to multi-party H.320 conferences, the costs would have to cover the purchase of an MCU. However, as these can be very expensive and there usage unknown, it is probably more cost-effective to either use a Bureau Service until the exact requirements are known or use the Polycom VSX 7000 with ISDN and Multipoint options that will allow mixed-mode calls involving itself and up to 3 other sites over ISDN and IP. Products Required Associated Cost Sony Plasma 42" TV $3,295.00 Polycom VSX7000 H.323 System $4,795.00 Polycom Multipoint Software $2,795.00 Total Equipment Cost $10,885.00 Service Required Associated Cost USA ISDN (1 hour @ 384K) $103.14 Security Issues One of the most important things for us to consider when implementing out ISDN video-conferencing solution is how to ensure that our network is not compromised and all transmissions are secure. In a law firm, very sensitive legal issues are discussed which could have many negative effects if obtained by the wrong people. Clients must reveal to us proprietary company information, confidential details of possible litigation, and confidential employee information. If proprietary or trade secrets are leaked, a company’s market advantage could be lost or competitors could benefit from the knowledge. In highly visible or large-scale litigation, evidence is leaked before the trial could be very costly, possibly even compromising our case. There are many ways to help ensure security in a video conferencing network. The following are some methods available for securing ISDN networks. Using SS7, the ISDN can deliver end-to-end Information Elements such as Caller-ID and Dialed Number Information Service (DNIS). This information can be used to provide additional security when designing ISDN solutions. It is recommended that PPP authentication always be implemented. PPP authentication PPP authentication is used to provide primary security on ISDN and other PPP encapsulated links. The authenticated username is also used by MultiLink PPP to maintain bundles and by DDR to determine which dialer sites are currently connected. PPP authentication is enabled with the ppp authentication interface command. PAP and/or CHAP can be used to authenticate the remote connectio...