Network Services

CHARACTERISTICS OF THE DVS

PRINT PAGE Add This

Some of the characteristics of the DISN Video Services:

Regional Hubs

The network master Hub is located in Virginia with two additional Continental United States (CONUS) Hubs. One is located in Ohio and the other in California. The European area Hub is located in Germany, the Pacific area Hub in Hawaii, and a sixth Hub is in Southwest Asia. All Hub to Hub video traffic will be transported on Government provided T1 circuits. A T1 is a telephone line that can transmit 1.544 mbps (that’s millions of bits of data per second), and it is subdivided into 24 channels of 64kbps (that’s thousands of bits of data per second (kilo means thousand)). The average standard modem on a personal computer works at 33.6kbps. A videoconference under DISN Video Services will typically take from 2 (128 kbps) to 12 (768 kbps) of these 64kbps channels. Inside the US, the Hub to Hub circuits will be provided by the DISN Transmission Systems – CONUS (DTS-C) contractor. Dedicated T1 lines between Germany and Virginia will provide Hub to Hub connections between the DISN Video Services European Hub, CONUS and PAC. There are also dedicated T1 lines between Hawaii and Ohio.

Dedicated Subscriber

A dedicated subscriber is a Video Teleconferencing Facility (VTF) which uses a dedicated circuit (a T1) to connect to the nearest Hub. One of 24 channels within the T1 is used for control of Line Interface Unit (LIU). Dedicated VTFs are usually installed in fixed sites dedicated to conducting VTCs and can be expected to conduct a large number of Video Teleconferences. This type of user has all of their VTC requirements processed through the Hub.

Dial-up (Switched) Subscriber

A dial-up subscriber is a VTF that dials into the network when they need a connection much the same way you would dial into your Internet provider when you desire Web connection. Subscribers can use any of the dial-up transmission services available such as DISN, FTS-2001 (both Government networks), or commercial networks such as AT&T or MCI. Users that are on the same network can conduct point-to-point videoconferences without going through one of the video Hubs. However, users of different transmission networks may not be able to complete a dial-up point-to-point without using a DISN Video Services Hub. Dial-up users may conduct VTC activity through any of the Hubs; however, each dial-up subscriber terminal will be assigned to a specific Hub based on geographic location. DoD Customers must request long-haul connectivity through DISA.

Internet Protocol Subscriber

An Internet Protocol (IP) subscriber is a VTF that accesses the Columbus or SWA Hubs via DISA's Secret Internet Router Protocol Network (SIPRNet). Secret packet switched video conferencing, using the ITU-T H.323 standard is available to customers, albeit on a limited basis.

Multi-point Conferences

DISN Video Services offers three types of multi-point conferences:

  1. Telebroadcast – in this type of conference a video and audio signal is sent from one VTF to two or more VTFs with no signal being sent in return. This is like watching a television broadcast.
  2. Teleseminar – in this type of conference a video and audio signal is sent from one VTF to two or more VTFs and the audio only signal is returned. This allows for fully interactive audio in the conference. This method has often been used for "distance learning" in that all can see the instructor and can hear each other’s questions or comments.
  3. Interactive – in this type of conference video and audio signals are sent and received at all participants in the conference. This type of DISN Video Services multi-point conference can incorporate one of three different types of switching. Switching refers to the way the "control" of the conference is handled. DISN Video Services offers four modes of switching:
  • Voice activated – there is no overall control of the conference and the monitors will change to show the person currently talking
  • Lecture – the Lecturer retains control of the conference. The Lecturer may allow others to brief but will never relinquish control of the videoconference.
  • Chairperson control – in this method the current speaker is in control of the conference. When the current speaker has completed speaking they select the next person to speak and pass them control.
  • Continuous Presence – this method is more commonly referred to as "Hollywood Squares" because the screen is divided to show several participants at once.