#4 Add link type to interface information

[Ian Lister]

Each link (well, interface) should have a field specifying what type
of link it is. Although the database was originally created to record
only radio links it is now being used to record VPN links across
existing wired networks, as well as links that are only proposed
(and do not and have not existed). In some cases links may
actually be a dedicated wired connection. There is also a desire by
some to designate some links as having some "special" status and
label them as "backbone" links (although the criteria for what
makes a link "special" in this way are not yet defined).

There are cases where it is useful to be able to filter out links that
are not of interest (for example to filter out links that do not exist
by default, or to look at only the "backbone"), which requires some
classification of links. The obvious categories are:

1) Radio
2) Laser (just in case Jon Kloske et al get anywhere, or we ever
use commercial laser gear :-)
3) Wired
4) VPN
5) Other

It would seem that the "backbone"/"special" attribute and the
"proposed" attribute are each orthogonal issues that should
probably each be in their own separate boolean field.

Other than that, there are a few ways to approach this problem.
One is to try to expand the existing "protocol" (802.11a/b/g/etc)
field. By expanding the categories above to give more detail about
the protocol in use we could have a list such as:

1) 802.11a
2) 802.11b
3) 802.11g
4) 802.3
5) Other Radio
6) Laser (this can be further expanded if somebody puts forward
likely specific protocols)
7) IPSec
8) PPTP
9) CIPE
10) Other VPN
11) Other
etc

In this case it would seem sensible to allow a free text field to
provide more detail where required such as the IPsec setup or the
nature of any of the "Other" options. Possibly this could just be the
existing comments field.

An alternative approach would be to have a hierarchy of fields e.g.
"link type" and "protocol":

1) Radio
a) 802.11a
b) 802.11b
c) 802.11g
d) Other
2) Laser
??
3) Wired
a) 802.3
b) Other
4) VPN
a) IPSec
b) PPTP
c) CIPE
d) Other
5) Other

Ideally the fields would be presented as popup menus, but this
would add some complications to the UI and its implementation
e.g. JavaScript to change the values in the second level menu,
complementary text fields to hold a description of "Other" options
(perhaps?), and even making various of the fields conditional (for
example the "channel" field and most of the fields in the "config"
table apply only to radio links, and VPN links should have
information about ciphers used, etc).

There are probably other approaches but it seems that none of the
options are going to be particularly clean or simple.

Ian