Enabling remote and safe configuration of network devices

TR-069 refers to the Technical Report published by the Broadband Forum that defines the CPE WAN Management Protocol, or CWMP. CWMP was developed to allow providers of broadband services to deploy and manage customer premises equipment in home and business networks.

Every TR-069 session is initiated by a CWMP Endpoint on a CPE. These sessions always occur for a specific reason, called an “Event”. All of the Events that have yet to be delivered to the ACS are contained as arguments in the Inform RPC at the start of every TR-069 session.

In TR-069, the CPE always initiates a session. When making first contact with an ACS, how does it know the ACS URL it is supposed to contact?

Though every TR-069 session is initiated by the CPE endpoint, sometimes it’s necessary for the ACS to request that the CPE contact it immediately. To do this, TR-069 defines a Connection Request mechanism in CWMP, which allows the ACS to stimulate the CPE to begin a session.

There’s one caveat to ConnectionRequests - they require that the CPE can be reached by the ACS over HTTP. For endpoints that may reside behind a Gateway, this is not the case, thanks to Network Address Translation or Firewall rules.

While XML is used most often to define and describe information, TR-069 also uses it directly over the wire when transmitting messages. This means that the ACS and CPE pass XML documents back and forth over HTTP during a TR-069 session.

In TR-069, the 4 Value Change event code is used when a parameter set for notification is changed by any mechanism other than the ACS. These conditions are set using the SetParameterAttributes RPC.

Every TR-069 session is initiated by a CWMP endpoint that is looking to deliver an event. These events have different delivery requirements, using language such as “must not discard”, “must retry until reboot”, “may retry” and “must not retry”.

TR-069 uses several remote procedure calls whose definition determine the types of TR-069 messages that are sent and received by an ACS or CPE. Every RPC is defined in the TR-069 base XML schema which can be found on the Broadband Forum website.

The GetRPCMethods argument is used by both the CPE and the ACS to request a list of the RPCs supported by either endpoint to better understand the endpoint’s capabilities. It’s one of the simpler RPCs in that it contains no arguments.

When an ACS wants to learn what objects exist on a CPE and what parameters they support, it can use the GetParameterNames RPC. Like other RPCs, GetParameterNames makes use of the ParameterPaths argument, so let’s take a minute to understand parameter paths.

The fundamental purpose of TR-069 is to allow an ACS to interact with the CPE’s instantiated data model, that is, the representation of its current state. The RPCs that form the basis of this include the Get and Set Parameter Values methods.

Every parameter a CPE’s CWMP data model contains metadata known as “attributes”. These attributes include the “Notification” attribute and “AccessList” attribute. The access attribute was defined early on in TR-069 to provide a method for assigning an access control rule identifier to each individual parameter.

An “object” in a CPE data model is an element of functionality that can be configured by an ACS. While an object’s parameters are configured using the SetParameterValues RPC, Objects that are able to be created by the ACS can be added to a device using the AddObject RPC, and removed using the DeleteObject RPC.

The Reboot RPC is used by the ACS to explicitly cause the device hardware to restart. This could be for any number of reasons, though should never be used as a means to force the CPE to upgrade itself.

Perhaps the biggest use case for TR-069 is managing a CPE’s firmware, allowing service providers to remotely upgrade their install base without needing to send the firmware to the customer or send an engineer.

Every data model in TR-069 contains the objects and parameters that represent the functions of a broadband CPE or other device. This includes their addressable name, syntax, data types, and a normative description of how they are to be used.

Most objects contain a set of elements containing sub-objects and parameters. Parameters are defined using the parameter element, and, like Objects, have a set of attributes and elements that describe how the parameter is to be used and its requirements.

CDRouter is the official self-test platform of the certification program for TR-069, called BBF.069.

Looking to get certified?

There’s many use cases for TR-069 from a service provider’s perspective. Beyond onboarding, firmware upgrades, and service configuration, however, is the ability to monitor various statistics on devices and network interfaces to help troubleshoot an end-user’s service.

The widely deployed TR-069 protocol and its successor, the User Services Platform (TR-369) are complex and powerful technologies that have successfully brought real value to operators, application vendors, and CE manufacturers. The key to that success is the standardization that can be tested and validated through certification programs.