February 1, 2010

Bullpen: Leveraging Broadband Forum Standards

By Chris Busch

The cable community has come to rely upon CableLabs-based specifications. In many cases, CableLabs specifies the operation of customer devices, including the headend-based provisioning of these devices.

Spanning all edges of the cable network, this model has helped contain the overall costs associated with new service and product rollouts to customers.

However, cable has expanded its access network architecture. The question becomes: Will the CableLabs specs of today define and enable all services that could be sold to subscribers of the cable network?

Who is the Broadband Forum?

Similar to CableLabs, the Broadband Forum is an organization that defines the specs of technical requirement (TR) documents. Broadband Forum traditionally serves the carrier community.

Originally known as the DSL Forum, the body has expanded its work to include residential gateway devices, VoIP terminals and IP video set-top boxes, to name a few.

"If (it) is an IP set-top, cost-effective depoyment requires provisioning and remote management controls."

The Broadband Forum has specified TR-069 WAN management protocol, TR-098 Internet gateway device, TR-104 provisioning parameters for VoIP CPE, and TR-135 data model for TR-069-enabled set-top box. Its specs cover an array of devices and configurations, including the provisioning application known as the Auto Configuration Server (ACS).

TR-069 enables a series of specs that span nearly any form of access network enabling remote discovery, provisioning, and operations of these devices.

Networks that have adopted Broadband Forum specs include the various forms of digital subscriber line (DSL) networks, as well as PON, WiMAX and native Ethernet applications, such those enabled over Metro Ethernet Forum (MEF) products.

Broadband Forum residential and commercial gateways can use the DOCSIS network as a pipe to deliver the products they enable.

A Broadband Forum gateway can exist purely on the Ethernet side of a cable modem, using an IP address from the same dynamic host configuration protocol (DHCP) provisioning platform responsible for dynamic IP address assignment to cable modem CPE hosts. It will then interact with an ACS for the provisioning portion of the device, anywhere on the cable operator network, or even register with an ACS entirely outside of the cable network.

A full comparison of the two approaches is beyond the scope of this essay, but here is a brief summary:

Identification. A cable modem will describe itself to the network as a DOCSIS device including the DOCSIS version within its DHCP discover packet; provisioning services then use this information to generate the required configuration file using trivial file transfer protocol (TFTP).

A Broadband Forum gateway will identify itself as a Broadband Forum device in its DHCP discover packet and be instructed by DHCP to register with an ACS in the network. It will use hypertext transfer protocol (HTTP) to identify itself to the ACS, describing all its supported parameters, such as VoIP or IP video settings.

Extensibility. DOCSIS devices are fixed to the cable operator network. Essentially a Cablelabs-based terminal works strictly within DOCSIS cable access networks. Broadband Forum-compliant devices, however, while originally conceived in DSL networks, have evolved to become access network-agnostic, in that Broadband Forum supports many WAN interfaces including DSL, PON and Ethernet.

Customer-side. Cablelabs offers functionality for the provisioning of set-top box and visibility of devices using CableHome specs. Broadband Forum goes further into the CPE provisioning and visibility, enabling discovery of devices and flow through provisioning to support gaming, network storage, VoIP, femto cell, and end-to-end IPTV delivery.

Net ops. Cablelabs devices offer a complete view of modem, MTA and set-top based primarily on the use of SNMP. Broadband Forum relies on an XML data model, which by comparison is heavier on both the terminal and the network systems, but guarantees visibility of Broadband Forum terminals over virtually any access network.

Multi-service access

At the moment, CableLabs does not cover all access networks that the industry has embraced. Take the commercial customer served by fiber using a MEF native Ethernet service.

Without an Ethernet gateway implementing the TR-069 WAN specs for gateway discovery, provisioning and reporting, an MSO must install a manually configured, dedicated router.

This is required even when the Ethernet service is MEF-based.

Another example could be IPTV service over DOCSIS. If an MSO were to deploy an IP set-top box using Ethernet and not an embedded cable modem, the set-top would exist on the CPE Ethernet LAN side of the DOCSIS 3.0 cable modem delivering service to the home.

When a device is deployed to the LAN side of a cable modem in the customer premise today, generally it becomes impossible to guarantee ongoing remote access, much less ensure the device contacts the headend upon boot up.

A gateway implementing TR-069 WAN can serve as a proxy to an IP set-top box inside the customer home network for provisioning and discovery of the IP set-top box device. This assures video service delivery to an authorized set-top, and set-top visibility to the headend.

To be effective in any access network, IPTV requires an end-to-end QoE strategy. Cable has such an application in PacketCable Multimedia (PCMM).

Broadband Forum establishes its baseline QoE requirements in TR-126. While this spec does much to highlight traffic and user application engineering cases, the application control plane for setup and tear down of bandwidth reservation by traffic profile is not present.

Broadband Forum working text (WT) 134 works to address a policy management framework, which will depend on deep packet and deep flow inspection.

Also relying on deep packet inspection, PCMM offers the ability to classify traffic, take a policy-based decision, reserve network resources at the policy enforcement point layer, and tear those resources down as required.

NG IPTV?

Then there is IMS-based IPTV, or next-generation network (NGN) IPTV. In such a scenario, the video assets become integrated within the IMS core as part of the application server infrastructure.

A policy and charging rules function (PCRF) would enable such service, as part of the end-to-end, SIP-based control plane. PCRF is tasked with policy control in the IMS core network, and is aware of each resource conversation.

PacketCable 2.0 standards enable cable to leverage this approach, and within PacketCable 2.0 is the ability to lean on PCMM to guarantee QoE in a cable access network. This solution is directly supported within the DOCSIS access network today, underpinned by the services enabled with DOCSIS 3.0.

Yet no matter which architectural approach is rallied behind, if the set-top box is an IP set-top, cost-effective deployment requires provisioning and remote management controls. These are functions currently available from Broadband Forum standards.

Best of breed

In sum, to remain competitive, MSOs need to offer services over an ever-increasing variety of access technologies. To deliver new services profitably, a cable operator must deploy devices that can be remotely provisioned and managed.

It is possible today to combine the efforts of both groups creating a best-of-breed solution, for any access network.

Chris Busch is vice president broadband technologies for Incognito Software.