Re: Addr: Re: BGP-4 - revised I-D

[Jessica Yu <[e-mail]>]

>If we (as a working group) agree that we should not compare MED values
>from different neighbor ASes, then we should at least document a MED
>election algorithm somewhere.

I personally prefer NOT to compare MED values from different neighbor ASs.
The usage of MED is to distinguish multiple exit points to a particular
external AS.  If the WG decides to compare MED values from different ASs
then I suggest the definition of the MEDs and the reference to MEDs in
the bgp4 spec needs to be changed as well.

Below is one of the places in bgp4 spec refering to MEDs. 
 

5.1.4   MULTI_EXIT_DISC
 
 
   The MULTI_EXIT_DISC attribute may be used on external (inter-AS)
   links to discriminate among multiple exit or entry points to the same
								^^^ ^^^^
   neighboring AS.  The value of the MULTI_EXIT_DISC attribute is a four
   ^^^^^^^^^^^^^^
   octet unsigned number which is called a metric.  All other factors
   being equal, the exit or entry point with lower metric should be
   preferred.  If received over external links, the MULTI_EXIT_DISC
   attribute may be propagated over internal links to other BGP speakers
   within the same AS.  The MULTI_EXIT_DISC attribute is never
   propagated to other BGP speakers in neighboring AS's.
 


							--Jessica