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2. Network Configuration Profile (NCP)

Version 0.6, 2008-Oct-21

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. We also need to describe conditional relationships between NCUs, for example an IP NCU depends on the underlying link NCU.

2.1.1 Properties

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

property: activation mode
type: enum
value: MANUAL, PRIORITIZED, CONDITIONAL_ANY, CONDITIONAL_ALL
The meaning of each value is:
- MANUAL: The NCU activation is managed by the administrator; NWAM will not automatically remove or change it. The default state is reflected by the "enabled" boolean property. The values in "priority group", "priority group mode", and "condition" will be ignored.
- PRIORITIZED: The NCU should be activated according to the settings in "priority group" and "priority group mode". The values in "enabled" and "condition" will be ignored.
- CONDITIONAL_ANY: The NCU should be activated only when at least one of the conditions set in "condition" is satisfied. Values in "enabled", "priority group", and "priority group mode" will be ignored.
- CONDITIONAL_ALL: The NCU should be activated only when all of the conditions set in "condition" are satisfied. Values in "enabled", "priority group", and "priority group mode" will be ignored.
Note that regardless of the activation mode or other activation policy settings, an IP NCU of class IP will always implicitly depend on the link NCU of the same name, i.e. the underlying link must be active in order for IP to be plumbed. That condition may be explicitly called out in the activation policy settings (as in the examples in section 2.1.2), but will be enforced whether it is called out or not.
property: enabled (activation mode == MANUAL)
type: boolean
value: true or false
Specifies what should be done to a manually activated NCU on startup; if enabled is true, the NCU will be activated; if enabled is false, the NCU will not be activated.
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 will not be seen by end users and is subject to change when the NCP repository is updated. But the priority order will be strictly enforced.
property: priority group 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.
property: condition (activation mode == CONDITIONAL_ANY or CONDITIONAL_ALL)
type: list of strings
value: String(s) identifying the NCU(s) upon which this NCU depends.
Each condition string should be formatted as "ncu is|is-not active", where identifies the NCU by type and name, e.g. 'link:bge0'. Multiple conditions may be specified by additional strings formatted in the same way; the logical relationship between multiple conditions is determined by the activation mode. If NWAM fails to bring up this NCU for any reason, the conditional NCU(s) will be left as-is.

2.1.2 Sample Policies

One link active at a time; prefer wired over wireless
For all physical links:
Include an IP interface plumbed on each active link:

All available wired links active; if no wired available, use one wireless
For all physical links:
Include an IP interface plumbed on each active link:

Always bring up bge0; if bge0 is active, bring up tun0; if bge0 is not active, use any other available link (but only one at a time)
For link bge0:
For link tun0:
For all other links:
Include an IP interface plumbed on each active link:

2.2 GUI representation of Policy Preferences

We need to determine how to represent policy choices derived from this model to the GUI user. To keep things simple, it might be best to simply allow users to select a preferred type of link - wired, wireless, or none, - and a preferred mode of operation - one link active or all links active. In other words the properties editor would have a dropdown list labeled "Prefer active links that are (wired | wireless | "no preference"). In addition we need a way of specifying the link activity policy, which we split into wired and wireless activation. This we could represent as a dropdown labeled "Use (no | all | one) wired link(s)", and another labeled "Use (no | all | one) wireless link(s)".

In addition to these manipulations, link icons can be moved up or down in the list of links, and these changes represent priority changes (initially all links of a given type, wired or wireless, will have the same priority). Link activation can also be disabled/enabled explicitly via clicking on the link.

2.3 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 enabled, 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.

2.4 GUI representation of NCP switching

In terms of GUI representation, we will probably do something like the following:

Properties Editor
- Network Status View
  
  Add some text like "Active Profile: Automatic / User Config" above the list of NCUs.
- Network Configuration View
  
  Add a drop-down list that allows users to select from Automatic/User Config. When Automatic is selected things will need to be in a "view only" mode
Panel presence would mainly operate in "view only" mode, apart from WiFi networks where we the "preferred list" will be editable.

So switching NCP would be done by selecting the active profile from the dropdown list.

Revision History

Revision	Date	Changes
0.1	2008-Apr-17	initial draft
0.2	2008-Apr-21	added UI switching approach suggested by Darren
0.3	2008-Apr-24	added initial thoughts on GUI representation of policy
0.4	2008-Apr-25	editorial/formatting updates
0.5	2008-Sep-09	update property names/values
0.6	2008-Oct-21	update property details