ANSI SCTE 173-2-2017 pdf free download – Framework for Implementing Preferential Telecommunications in IPCablecom and IPCablecom2 Networks.
6 Common framework for priority [ANSI/SCTE 173-1] lists a number of requirements to assure priority treatment in IPCablecom and IPCablecom2 networks. Even though architectural differences exist between IPCablecom described in [ANSI/SCTE 24-1] and IPCablecom2 in [ITU-T J.360], this clause discusses the framework that is applicable for both networks. There are three aspects to consider when addressing priority treatment for preferential telecommunications services.
These are classification or labelling of the session or call as requiring priority treatment, signalling for priority and the mechanisms to support the requested priority. The selection of mechanisms and policies, along with their respective implementations, are outside the scope of this Standard. Table 1 categorizes the requirements according to these three aspects: classification, signalling and mechanisms. Some of the requirements are categorized to have more than one aspect because the priority classification of the call is to be maintained and the actual mechanisms to preserve the classification may vary.
Prioritization means obtaining a higher probability for completing a call/session. In other words, once the traffic is identified to be for a preferential telecommunications service, the policies need to provide a higher probability of success relative to call admission, routing and delivery of traffic. This capability should exist on the access link and should also be propagated throughout all relevant network entities such as call management servers (CMSs) and media gateway controllers (MGCs) or the entities in the session initiation protocol (SIP) infrastructure. Even though priority enabling mechanisms and assignment of QoS are not the same, in IPCablecom, DQoS session classes can be used to assign priority treatment to a session.
One of the requirements to allocate resources that can be supported in IPCablecom networks is the concept of multimedia gates described in [ANSI/SCTE 24-4] and [ANSI/SCTE 159-1]. [ANSI/SCTE 24-4] is specific to IPCablecom and is addressed below. The gates are used to control access by an IP flow to enhanced QoS from the DOCSIS network. Gates are installed in the cable modem termination system (CMTS) to allow the creation of service flows with a guaranteed QoS by reserving the required resources. Admission control at the CMTS is used to ensure available resources are greater than committed and reserved resources. In the case of IPCablecom using [ANSI/SCTE 24-4], a client such as embedded media terminal adapter (E-MTA) initiates resource reservation and activation, whereas [ANSI/SCTE 159-1] supporting multimedia allows a proxy to perform these steps on behalf of the endpoint client. Priority signalling is addressed separately for IPCablecom and IPCablecom2 because of the differences in approaches used by an E-MTA or UE to connect to the access network. IPCablecom and IPcablecom2 use real-time transport protocol (RTP) as media transport protocol for audio and video packets.
As discussed in [b-IETF RFC 4190], RTP does not include markings to indicate the priority of the packet with a label. Different methods are discussed which include defining a new per-hop behaviour for preferential traffic, new shim layer protocol over IP or marking an application layer packet.ANSI SCTE 173-2 pdf download.