There is a range of possible models for performing O&M functions on a router. At one extreme is the local-only model, under which the O&M functions can only be executed locally (e.g., from a terminal plugged into the router machine). At the other extreme, the fully remote model allows only an absolute minimum of functions to be performed locally (e.g., forcing a boot), with most O&M being done remotely from the NOC. There are intermediate models, such as one in which NOC personnel can log into the router as a host, using the Telnet protocol, to perform functions that can also be invoked locally. The local-only model may be adequate in a few router installations, but remote operation from a NOC is normally required, and therefore remote O&M provisions are required for most routers.
Remote O&M functions may be exercised through a control agent (program). In the direct approach, the router would support remote O&M functions directly from the NOC using standard Internet protocols (e.g., SNMP, UDP or TCP); in the indirect approach, the control agent would support these protocols and control the router itself using proprietary protocols. The direct approach is preferred, although either approach is acceptable. The use of specialized host hardware and/or software requiring significant additional investment is discouraged; nevertheless, some vendors may elect to provide the control agent as an integrated part of the network in which the routers are a part. If this is the case, it is required that a means be available to operate the control agent from a remote site using Internet protocols and paths and with equivalent functionality with respect to a local agent terminal.
It is desirable that a control agent and any other NOC software tools that a vendor provides operate as user programs in a standard operating system. The use of the standard Internet protocols UDP and TCP for communicating with the routers should facilitate this.
Remote router monitoring and (especially) remote router control present important access control problems that must be addressed. Care must also be taken to ensure control of the use of router resources for these functions. It is not desirable to let router monitoring take more than some limited fraction of the router CPU time, for example. On the other hand, O&M functions must receive priority so they can be exercised when the router is congested, since often that is when O&M is most needed.