pref syntax for RIPE-81++

Folks,

Below is a new version to beat at.  The changes are:

a. no multiple 'preference' 
b. '( )' being added to preference (per Laurent's request)
c. changes to the pref in <pref-type> (pretty major change, please read) 

Note, again, the place for <routerid> is not defined here because it is not
settled (re my yeaterday's message).  This is just to present the idea
so the text is not polished).
						--Jessica

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interas-in and interas-out preference definition

1. interas-in

interas-in: [from] neighborAS (preference) [accept] route

where 'preference' here is defined as:

<pref-type> = <value>

The currently supported <pref-type> is "pref". The associated value is

<value> = <numeric value> | MED

When the value is numeric value, the lower the value, the higher the
preference.  When the value is "MED", that means the AS will use the MED
value from its neighbor.

The pref-type could be others such as tos/qos or other type of metric and
will be defined when real application exist.
 	
2. interas-out

	interas-out: [to] neighborAS (metric) [announce] route  

where 'metric' is defined as:

<metric-type> = <value> 

The currently supported <metric-type> is "metric_out". The associated value is

<value> = numeric | IGP 

When the value is a numeric value, that is a pre-configured metric for
outbound routes.  The lower the value, the higher the preference.  In   
the case of value equal IGP, that means the meric here reflects the
the AS's internal topology cost.  The topology is reflected here by
using MED which is a function of IGP metric.


3. Examples:

aut-num: AS237
interas-out: to AS690 <enss128> (metric_out=IGP) announce AS237
interas-out: to AS690 <enss145> (metric_out=IGP) announce AS237

aut-num: AS266 
interas-out: to AS690 <enss131> (pref=1) announce {35/8, 128.14/16}
interas-out: to AS690 <enss129> (pref=2) announce {35/8, 128.14/16}  

aut-num: AS701

interas-out: to AS690 <enss134> (metric_out=2) announce {15/8,192.35.1/24}
interas-out: to AS690 <enss145> (metric_out=4) announce {15/8,192.35.1/24, 193.1.1/24}

aut-num: AS690

interas-in: <enss131> from AS266 (pref = 1) accept {35/8, 128.146/16}
interas-in: <enss129> from AS266 (pref = 2) accept {35/8, 128.146/16}

interas-in: from AS701 (pref = MED) accept ANY 

4. Future Expansion

The preference field by this design could be easily expanded in the future
when other metrics be used for policy decisions without changes to the already
defined ones.  For example, when tos/qos is widely used, one could just add
another keyword for the <pref-type>.



-------- Logged at  Fri Jul 15 20:09:29 MET DST 1994  ---------