From Voice Video Services Policy STIG
Part of Deficient Design: Access Circuit Call Budgets
The DISN NIPRNet IPVS PMO has developed a method to provide Assured Service voice and video communications over the bandwidth constrained portion of the DISN. This method includes or supports providing precedence and priority capabilities for C2 users similar to the MLPP service provided by the traditional TDM based DSN. The enclave’s internal LAN is required to be designed to be non-blocking. That is it must provide ample bandwidth for all the traffic that it is expected to carry. This is controllable by DoD. On the other hand, the DISN Core is designed to have ample bandwidth and expandability to support what ever traffic the DoD enclaves throw at it. As such it is considered to be bandwidth rich. Due to issues surrounding the ability for an attached enclave to determine the bandwidth availability or congestion conditions within the core in real time, an assumption has to be made that the DISN Core is also non-blocking. The DISN Core bandwidth is also controllable by DoD. The portion of the overall DISN network that is bandwidth constrained is the TDM or optical OCx access circuits between the local enclave and the DISN Core. This is the portion of the network where we have the least control over bandwidth availability, primarily due to the cost of these circuits. The cost factor is an issue since many DISN access circuits must rely on commercial carriers for some portion of the overall circuit. This is typically the portion that delivers the DISN service to the B/C/P/S. Access circuit issues are less of an issue if the B/C/P/S also provides a home for one of the DISN Core SDNs. This is because a direct connection can be made between the CER and the SDN, however, the circuit capacity may still be an issue if the SDN is a small one that does not have an AR or PE. Due to the nature of digital transmission over these bandwidth constrained circuits, the quality and availability of the communications is degraded as these circuits become congested. “Data” packets can wait until processed without negatively affecting the delivery of a message. This is not the case for VVoIP due to its time sensitive nature (it is a real time service). If VVoIP packets have to wait for transmission, the quality of the call suffers. In IA terms, this relates to the availability of the service and quality communications. To overcome the bandwidth constraints inherent in WAN access circuits, an engineered bandwidth budget must be developed for each service (voice, video, and data) using the circuit. Voice and video budgets are developed in terms of call or session counts. For example, the UCR defines a voice call as follows: “One voice session budget unit shall be equivalent to 110 kilobits per second (kbps) of access circuit bandwidth independent of the EI codec used. This includes ITUT Recommendation G.711 encoding rate plus Internet Protocol Version 6 (IPv6) packet overhead plus ASLAN Ethernet overhead. IPv6 overhead, not IPv4 overhead, is used to determine bandwidth equivalents here.”
Inspect the documentation related to the size of the access circuits and the SAC budgets used in its sizing to determine compliance with the requirement. This is a finding in the event access circuit sizing does not take the required ASAC budgets into account.
In the event the VVoIP system connects to the DISN WAN for VVoIP transport between enclaves AND the system is intended to provide assured service communications to any level of C2 user (Special C2, C2, C2(R)), ensure Session Admission Control (SAC) for the DISN Core access circuit(s) is supported by engineered bandwidth budgets for VoIP and Video calls/sessions in support of Assured Service. NOTE: SAC in support of Assured Service is also referred to as Assured Service Admission Control (ASAC) NOTE: The VoIP budget covers the following types of services: Voice VoIP, FoIP, MoIP, or SCIP over IP calls NOTE: Per call/session units are defined in the UCR and are unidirectional. They must be doubled to support bi-directional communications between users which is the typical phone call. NOTE: Instructions for determining voice call budgets for a DISN WAN access circuit can be found in the UCR section 5.3.3.11 Provisioning
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