Home AS values in the PRDB -- update

Mon Nov 7 20:24:06 UTC 1994

Hi.

  As you all know, the concept of Home AS is central to the expression
of AS policies in RIPE-181 and the Global Routing Registry.  The NSFNET
Policy Routing Database (PRDB) has been collecting Home AS values for a
year now, though those values have not been required for AS690 routing.  
As part of the transition from the to the Routing Arbiter Database and 
the Global Routing Registry (RADB/GRR), we are in the process of updating 
the database Home AS information.

There are three steps to the plan to update this information:

  1) On November 1st, some missing Home AS values were filled in from
	AS-path information from BGP sessions with origin "IGP".  (RIPE
	database values were also used to update Home AS values for
	European nets in the PRDB).  A report on Home AS (and related)
	values before this was done is contained in the file
	nic.merit.edu:nsfnet/announced.networks/home_as.Nov_1_1994 .

	This operation updated 1592 Home As values, and corrected the
	Home AS values for 365 European nets.  Unfortunately, it still
	left PRDB 7,227 nets without Home As values.

  2) Between now and November 25, we encourage all NSPs to determine the
	Home ASs for nets that they originate or route, and to send
	that information to nsfnet-admin at merit.edu.  (Just send net
	lists and ASs; don't bother with NACRs for this process).

  3) On November 25, we will update any remaining missing Home AS values
	using the following algorithm for each net:

	- If BGP paths have origin "IGP" and show only a single value
	    for the end (Home) AS, use that AS.
	- Else if BGP paths have origin "IGP" and show multiple values
	    for the end (Home) AS, use one of those ASs.
	- Else if BGP paths have origin "EGP", use that AS. 
	- Else if BGP paths have origin "INCOMPLETE", use that AS. 
	- Else use the primary announcing AS from the AS690 Metric:AS list.

To see what this algorithm would do to your nets if we ran it today, look
at the file nic.merit.edu:nsfnet/announced.networks/home_as.now :

> IP/len           Net Name    AS  Src (IGP) ----- Metric:AS(NSS) List ----
> ----------    -----------  ----  ---  ---- ------------------------------
> 6/8               YPG-NET    19  INC    - 1:568 2:19  
> 7/8              EDN-TEMP    35  now    - 1:701(136) 2:701(134)  
> 8/8              BBNCCNET   560  INC    - 1:560 2:701(136) 3:701(134)  
> 13/8            XEROX-NET   200  now    - 1:200(128) 2:200(144)  
> 15/8          HP-INTERNET    71  now    - 1:200(128) 2:200(144) 3:2149 4:174
> 16/8         DEC-INTERNET    33  now    - 1:200(128) 2:200(144) 3:701(136) 4
> 17/8          APPLE-WWNET   714  now    - 1:200(128) 2:200(144) 3:1740  
> 18/8                  MIT     3  now    - 1:3 2:560 3:701(136) 4:701(134)  
> 20/8                  CSC   701  now    - 1:701(136) 2:701(134)  
> 26/8               MILNET    19  now  568 1:568 2:19  
> 28/8             WIDEBAND  2699  EGP    - 1:2699(145) 2:2699(144)  
> 29/8          MILX25-TEMP    19  PRI    - 1:19 2:568  
> 31/8            UCDLA-NET  1740  PRI    - 1:1740 2:200(128) 3:200(144) 4:195
> 32/8           NORGESNETT  2120  now    - 1:1800 2:1879 3:1133 4:1240  
> 33/8                 DCMC    19  INC    - 1:19 2:568  
> 34/8          HALLIBURTON  1328  INC    - 1:1328  
> 35/8                MERIT   237  now    - 1:237 2:233 3:266 4:267 5:1225  
> 36/8          SU-NET-TEMP    32  now    - 1:200(128) 2:200(144)  
> 38/8              PSINETA   174  now MULT 1:2149 2:174  
> 40/8            LILLY-NET    17  now    - 1:17  
> ..

The "AS" column shows the AS that the algorithm will choose if the net
is not otherwise updated by November 25.  The "Src" column shows the
reason for that value:  "now" means there is a current PRDB Home AS
value, "EPG", "INC", and "PRI" indicate that an AS path "EGP" or
"Incomplete" value would be used, or that the Primary announcing AS
would be used.  The "(IGP)" column show were AS path "IGP" values show
a different Home AS than the one registered in the PRDB.  "MULT" in
this column indicates that our BGP dump showed multiple AS paths were 
specifying different IGP ASs were concurrently being announced for this net.

A more complete explantion of the columns is indcluded at the head of
the report file.  The report format is designed for easy grep'ing:
grep for ' 237 ' to find all nets relevant to AS237, or for ' :237 '
to find all nets with AS237 somewhere in the Metric:AS list.

							--Dale Johnson