2. Network Configuration Profile (NCP)

Version 0.10, 2009-Mar-11

2.1 NCP policy

We need to have a way to specify NCP policy in terms of the individual elements (Network Configuration Units, or NCUs) that comprise it. We would like to be able to specify policy preferences such as "prefer wired over wireless", "one interface at a time", etc.

Activation policy will be described in each Link NCU. As all IP NCUs must be associated with an underlying link, IP NCUs will not have an individual policy; rather, the activation of an IP NCU will happen automatically when the underlying link NCU is activated. Therefore, the properties described in the following section will only be defined for link NCUs.

2.1.1 Properties

Four properties in the NCU data structure will be used to represent the activation policy. They are "activation-mode", "enabled", "priority-group", and "priority-mode". These properties are discussed in more detail in the following sections.

• property: activation-mode
  type: enum
  value: MANUAL, PRIORITIZED

  The meaning of each value is:

  • MANUAL: The NCU activation is managed by the administrator (using either the GUI or the nwamadm(1M) commandline tool); NWAM will not automatically remove or change it. The current state is reflected by the "enabled" boolean property. The values in "priority-group" and "priority-mode" will be ignored.
  • PRIORITIZED: The NCU should be activated according to the settings in "priority-group" and "priority-mode". The value in "enabled" will be ignored.

• property: enabled (activation-mode == MANUAL)
  type: boolean
  value: true or false

  Specifies the current state of a manually activated NCU.

• property: priority-group (activation-mode == PRIORITIZED)
  type: int
  value: An integer, with 0 being the lowest priority. Negative values are invalid.

  Among all the available priority-groups, only the NCU(s) in the highest available priority-group will be activated. Activation behavior when more than one NCU with the same priority is available is defined by "priority group mode" below.

  Note: The priority number should not be viewed as an absolute value; it is subject to change when the NCP repository is updated. But the priority order will be strictly enforced.

• property: priority-mode (activation-mode == PRIORITIZED)
  type: enum
  values: EXCLUSIVE, SHARED, ALL

  The meaning of each value is:

  • EXCLUSIVE: Only 1 NCU in the priority-group may be active; NWAM will randomly activate one that is available within the group and ignore all others.
  • SHARED: Multiple NCUs in the priority-group may be active at the same time.
  • ALL: In order for the priority-group to be considered available (and thus made active), all NCUs in the group must be available.

2.1.2 Sample Policies

• One link active at a time; prefer wired over wireless

  For all physical links:

  NCU Type: LINK
  NCU Class: PHYS
  Activation-mode: PRIORITIZED
  Priority-group: 1 (media type == 802.3) or 0 (media type == 802.11)
  Priority-mode: EXCLUSIVE
  

• All available wired links active; if no wired available, use one wireless

  For all physical links:

  NCU Type: LINK
  NCU Class: PHYS
  Activation-mode: PRIORITIZED
  Priority-group: 1 (media type == 802.3 or 0 (media type == 802.11)
  Priority-mode: SHARED (802.3) or EXCLUSIVE (802.11)
  

2.2 Automatic and User-Configured NCPs

In NWAM phase 1, we will have 2 NCPs: the Automatic and User-Configured NCPs. The former will specify DHCP for address acquisition method, and will default to a policy of one active link at a time, preferring plugged-in, wired links over wireless, and plumbing IP and IPv6 on that link. If network links are hotplug inserted, these will be automatically added to the Automatic NCP, and if the new link is wired and plugged in, a switch of active link is possible.

On a fresh install, the Automatic NCP will be the only NCP available until the user has created an NCP via the UI; NWAM will therefore run with the Automatic NCP active until the user makes a change. In the upgrade case, if a phase 0 /etc/nwam/llp file existed on the previous installation, that file will be used to create the initial User-Configured NCP, and NWAM will run with that NCP by default. If there was no pre-existing NWAM configuration, the behavior on upgrade will be the same as on initial install, with the Automatic NCP being the default active NCP.

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