Abstract: Compared with software-only video conferencing systems, hardware-based video conferencing systems are heavily invested, complex in construction, and not flexible enough, but for users, if the high quality and stability of video conferencing is critical, hardware The video conferencing system is still the best choice.
-------------------------------------------------- ------------------------------
Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
Abstract: Compared with software-only video conferencing systems, hardware-based video conferencing systems are heavily invested, complex in construction, and not flexible enough, but for users, if the high quality and stability of video conferencing is critical, hardware The video conferencing system is still the best choice.
-------------------------------------------------- ------------------------------
Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
Abstract: Compared with software-only video conferencing systems, hardware-based video conferencing systems are heavily invested, complex in construction, and not flexible enough, but for users, if the high quality and stability of video conferencing is critical, hardware The video conferencing system is still the best choice.
-------------------------------------------------- ------------------------------
Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
-------------------------------------------------- ------------------------------
Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
Abstract: Compared with software-only video conferencing systems, hardware-based video conferencing systems are heavily invested, complex in construction, and not flexible enough, but for users, if the high quality and stability of video conferencing is critical, hardware The video conferencing system is still the best choice.
-------------------------------------------------- ------------------------------
Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
Abstract: Compared with software-only video conferencing systems, hardware-based video conferencing systems are heavily invested, complex in construction, and not flexible enough, but for users, if the high quality and stability of video conferencing is critical, hardware The video conferencing system is still the best choice.
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Compared with the pure software video conferencing system , the hardware-based video conferencing system has a large investment, complex construction, and insufficient flexibility, but for the user, if the high quality and stability of the video conferencing is critical, the hardware video The conference system is still the best choice.
From a technical point of view the system of video conferencing systems, the current market mature, hardware-based video conferencing systems can be divided into two categories, video conferencing system based on the H.323 standard-based H.320 video conferencing systems and standards. H.320 is an earlier ITU-T video conferencing standard, which is based entirely on a series of video conferencing system- specific technologies. The H.323 standard is based entirely on general, open computer network communications. . Since the issuance of the H.323 standard in 1996, more and more manufacturers have introduced products that comply with the H.323 standard.
Two technical standards
When it comes to hardware-based video conferencing systems , you have to introduce the two standards of H.320 and H.323. The H.320 standard was established in 1990 and is mainly for circuit-switched networks such as ISDN, DDN, PCM, VSAT, etc. Since the circuit-switched network is characterized by connection-oriented, stable transmission rate and delay, small delay, and low bit error rate, the quality of video conferencing is easily guaranteed. However, its shortcomings can also be obvious. The network generally has to make a point-to-point permanent connection, the bandwidth utilization is low, the openness is poor, and the connection is inconvenient.
The H.323 standard was established to allow interoperability of multimedia products and applications from different vendors, covering audio, video and data communications over IP networks, including stand-alone devices, personal computer technologies, and point-to-point and point-to-multipoint Point video conferencing, which addresses issues such as call and session control, multimedia and bandwidth management in video conferencing. At present, the video conferencing system of the H.323 standard can have various options such as ADSL, telecom line, and satellite network.
The video conferencing systems built in China in the early days are mostly based on the H.320 standard. In recent years, they have been affected by the popularity of IP networks. Especially with the stability and reliability of broadband networks, the development of H.323 video conferencing systems based on IP networks. quickly. However, considering compatibility and interoperability, mainstream video conferencing systems generally support both H.320 and H323 modes to protect user investments. At present, with the improvement of computer computing power and the continuous improvement of network bandwidth, pure software video conferencing systems based on MPEG-4 video compression standards are becoming mature, especially among small and medium-sized enterprises, especially those with low video conferencing quality requirements. It is very popular.
Network structure
The network structure of the video conferencing system varies with the participants' participation modes. As a whole, there are two networking structures: a peer-to-peer networking structure and a multipoint conference networking structure.
1. Point-to-point networking structure
The peer-to-peer video conferencing system involves only two conference terminal systems. The networking structure is very simple and does not require an MCU.
2. Multipoint conference networking structure
When performing multipoint conferences at multiple conference venues, one or more MCUs must be set up. The multi-point conference networking structure is complex. According to the number of MCUs, it can be divided into two categories: single MCU mode and multiple MCU mode. Multi-MCU methods can be divided into two types: star network structure and tree network structure.
When the number of conference venues is small and the geographical distribution is relatively concentrated, a single MCU mode can be adopted, and the conference control mode of the multipoint video conference system connected by a single MCU is often a voice control mode and a speaker control mode.
A star network structure with multiple MCU connections, where VCT is an abbreviation of VideoConference Terminal. This star structure has lower requirements for the conference terminal system and is easy to expand when adding new conference venues. Because the number of conference sites in the networking mode is large, the conference control mode should adopt the chair control mode.
The tree-type networking structure of multiple MCU connections is most suitable for deployment in the geographical dispersion of conference sites, and can use communication networks such as ISDN, B-ISDN or long-distance digital transmission network (DDN). This tree structure covers a wide range of areas and can also be used for international video conferencing, which is not only easy to expand, but also easier to manage. The conference control modes suitable for this structure are the voice control mode and the chairman control mode.
It should be noted that the MCU networking of the H.323 video conferencing system is somewhat different from that of the H.320. The MCU in H.323 is only a logical network structure, and there is no fixed connection between them. In the more complex H.323 video conferencing system , there is also a component called the gatekeeper. Its function is to provide call control services for H.323 nodes, which can be used to build very complex networks. In a videoconferencing system with a gatekeeper, all H.323 nodes in the area responsible for the gatekeeper must be registered on the gatekeeper. Multiple gatekeepers can form a mesh mechanism and a master-slave structure: each gatekeeper has equal status in the mesh structure, and manages the address resolution and area management of the connected MCUs respectively. The master-slave structure can have one gatekeeper and multiple domains. The gatekeepers form a digital structure, which facilitates the upgrade and expansion of the network.
Bandwidth is a major consideration in the networking of video conferencing systems , especially in galaxy network architectures. If an MCU has 5 terminals, if each terminal uses 128 kbps of bandwidth, at least 640 kbps of bandwidth is required at this MCU. The bandwidth of a video conference is occupied by four parts: image, sound, data, and signaling. Usually the bandwidth occupied by data and signaling is relatively small, and the sound requires about 64K. Video takes up the most bandwidth and changes the most, and it changes because of the amount of motion of the image. Generally, the connection between the terminal and the MCU can be selected from networks such as ISDN and ADSL, but it is often necessary to select a network with more bandwidth between the MCUs and even rent a private network.
QoS is the key
Video conferencing has high requirements for real-time performance, and is sensitive to network transmission delay and jitter. To ensure the quality of the conference, QoS guarantee must be provided. The video conferencing system based on the H.320 standard runs on a circuit-switched network, and uses DDN, satellite circuits, ISDN, ATM, etc., and has a small delay, and is a fixed circuit, and QoS is not a problem. With the development of broadband networks, the stability and reliability of IP networks are constantly improving. The H.323 video conferencing system based on IP networks has developed rapidly in recent years. However, the QoS guarantee based on the IP network is inherently insufficient, and problems such as network jitter, packet disorder, and network congestion may affect the smooth progress of the video conference system . We can take some measures from the two levels of network infrastructure and video conferencing system in the practical application of video conferencing systems to address QoS issues.
The QoS problem is still the limitation of network bandwidth. If there is enough bandwidth guarantee, QoS is not a problem. But bandwidth and cost are directly related. The main concern here is how to reduce the network bandwidth requirements while ensuring that the video conferencing system is properly held.
First, the H.323 standard itself provides a QoS mechanism. H.323 uses protocols such as UDP/IP, RTP, RTCP, and RSVP. The gatekeeper of H.323 can provide functions such as flow control and bandwidth control. You can also use directional routing to route H.323 data to a private network with QoS guarantees to take full advantage of the private network.
Secondly, an enterprise broadband private network can be established by using MPLS VPN to carry a video conference system . MPLS-capable VPNs are connectionless IP networks. They also have the confidentiality of frame relay and multi-level IP services, making MPLS VPN operations more efficient, and service providers can provide cheaper manageable IP services.
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