The Communications Alliance is set to revise the industry’s Quality of Service (QoS) guidelines to enhance consumer experience when using the NBN. Paul Skelton reports.

The Communications Alliance has announced it will revise the telecommunications industry’s Quality of Service (QoS) guidelines for internet protocol (IP)-based networks, to help ensure that consumers can enjoy a high quality experience when using the National Broadband Network (NBN).

Chief executive John Stanton says the advent of the NBN makes it timely to revise two key guidelines, introduced in 2007, that service providers use to minimise quality-degrading factors such as delay, jitter and packet loss on IP-based services.

“Most IP services used by Australian consumers until now have run on copperbased networks. The existing guidelines have worked well to help deliver the best available service quality over copper, but the shift to fibre-based services via the NBN will change the classes of traffic being carried and a number of parameters within the access network,” John says.

“Therefore, we need to ensure that the industry guidelines fully reflect the gamechanging aspects of the shift to fibre and continue to foster the best possible endto- end service quality for everyone using services carried over the NBN.”

Specifically, the Comms Alliance Network Reference Panel made the decision to revise G632:2007 Quality of Service parameters for networks using the Internet Protocol and G633:2007 Quality of Service for networks using the Internet Protocol – Test Methods, which cover quality of service parameters and testing arrangements for IP-based services.

According to the documents, traditionally the TCP/IP protocol suite and networks have been built to a principle that “networks will operate on a ‘best efforts packet delivery, with no guarantees’ basis.

“This principle assigns the responsibility for detecting and correcting transmission problems to the customer equipment (CE) and higher-level protocols that require better network conditions. Retransmission (to correct for lost packets), sequence numbering (to correct for duplicated and out-of-order packet delivery) and buffering (to correct for IP packet delay variation, IPDV) are all implemented at the endpoints, permitting the networks between the end-points to function over the widest range of transmission systems with variable reliability, latency, transmission capacity and other characteristics.”

Increasingly, though, end-user applications that are more sensitive to network impairments and delays are being deployed, including streaming audio and video, VoIP, and distributed client/server databases. These applications work best across networks that can deliver ‘better than best-efforts’ for various characteristics.

“These documents were created in 2007, when there was a growing interest in VoIP,” says project manager James Duck. “The technology had been around for a while but there was a growing need to put some industry guidelines together. Now, with the introduction of the NBN, it was decided that QoS needed to be addressed.

“It’s too early to say what the exact changes will be, but something that is in the terms of reference for the working committee to look at is traffic classes.” Just prior to Christmas, NBN Co released a discussion paper on traffic class performance, a document that Comms Alliance will draw from in the development of its guidelines. The document defines the classes (see Table 2) as:

TRAFFIC CLASS 1 (TC-1)

TC-1 is offered as committed information rate (CIR) only, and is designed for applications that require strict performance characteristics, with low bit-rates (between 150kbps and a planned 5Mbps) and small frames (for example 250 bytes). This is typically characteristic of IP-based telephony applications and network control. The CIR performance commitments for NFAS TC-1 are shown in Table 3. ?

TRAFFIC CLASS 2 (TC-2)

TC-2 is not currently offered by NBN Co; however, NBN Co expects to offer TC-2 as CIR only, designed for applications that require strict performance characteristics with high bit-rates (between 5Mbps and 40Mbps) and large frames (up to 1,526 bytes). This is typically characteristic of interactive streaming applications and conversational real-time video. (See Table 4.)

TRAFFIC CLASS MULTI-CAST (TC-MC)

Traffic Class Multi-Cast (MC) is not currently offered by NBN Co; however, NBN Co expects to offer TC-MC as CIR only, designed specifically for NBN Co’s Layer 2 multicast feature. This performance is expected to be similar to TC-2, but operating with additional functionality (Layer 2 replication in the downstream direction and IGMP snooping in the upstream direction). (See Table 5.)

TRAFFIC CLASS 3 (TC-3)

TC- 3 is not currently offered by NBN Co; however, NBN Co expects that it will be designed for applications that require data-oriented performance characteristics, with high bit-rates (between 10Mbps and 100Mbps) and large frames (up to 1,526 bytes). This is typically characteristic of premium data services and business VPN applications. TC-3 will offer capacity in both CIR and peak information rate (PIR), to suit ‘bursty’ applications that require some degree of throughput determinism. (See Table 6.)

TRAFFIC CLASS 4 (TC-4)

TC-4 is designed for applications that require a peak capacity and can tolerate variable throughput. This is characteristic of internet access services. TC-4 offers capacity as a PIR only and will be implemented using shared network capacity that is managed in aggregate, across a number of access seekers (and their end-users). With this in mind, the Comms Alliance working committee will work closely with NBN Co and other relevant stakeholders in revising their guidelines and will also take into account recent international developments (e.g. changes to relevant International Telecommunications Union (ITU) recommendations.)

“Now that we have set-up our working committee, it’s a case of working through the existing documents, looking at new information that’s come up internationally and the NBN Co paper on traffic classes, and seeing how that information changes our guidelines,” James says.

“Once we have a stable draft we will release it for public comment, because there may be people interested in the topic that can’t dedicate the time or resources to actually participate in the meetings, and we look to them for a broader input. Once we have the public’s comments, the working committee reviews them and makes any necessary changes to the draft, and then we move to a sign-off process and publication.”

The revision is anticipated to be completed by mid-2012. John says the QoS guideline revision was one of several activities underway through Comms Alliance on behalf of the industry to enhance the consumer experience when using the NBN.

“Comms Alliance is also developing an Operations Code in cooperation with NBN Co to ensure appropriate intra-industry coordination, so that processes such as customer transfer between services providers is smooth, user-friendly and pro-competitive,” he says.