Autonomous System (AS) Number Assignment Policies and Procedures

   Mirjam K.A��hne
   Nurani Nimpuno
   Sabrina Wilmot
                 
   Document ID: ripe-245
   Date: 14 June 2002
   Obsoletes: ripe-185
     _________________________________________________________________

Abstract
        
   This document provides a description of Autonomous System Numbers
   (ASNs), the assignment procedure of AS Numbers and guidelines on
   how to obtain AS Numbers in the RIPE NCC service region.
   _________________________________________________________________

Contents
        
   1.0 AS Number Assignment Policies and Procedures
   1.1 Requesting an AS Number                     
   1.2 Returning an AS Number 


1.0 AS Number Assignment Policies and Procedures

   An Autonomous System (AS) is a group of IP networks run by one or
   more network operators that has a single and clearly defined
   routing policy.

   Every AS has a unique number associated with it that is used as an
   identifier for the AS in the exchange of exterior routing
   information.  Exterior routing protocols such as BGP, described in
   RFC 1771 "A Border Gateway Protocol 4 (BGP-4)", are used to
   exchange routing information between ASs. More information on RFC
   1771 can be found at:

   ftp://ftp.ripe.net/rfc/rfc1771.txt
                                     
   An AS will normally use some interior gateway protocol to exchange
   routing information on its internal networks.

   In order to help decrease global routing complexity, a new AS
   number should be created only if a new external routing policy is
   required.  Sharing an AS number among a set of networks that do not
   fall under the same organisational umbrella is possible but will
   sometimes require extra co-ordination among the various network
   administrators.  (In some cases, some level of network
   re-engineering may be needed.)  This may be the only way to
   implement the desired routing policy. For more information please
   see RFC 1930 "Guidelines for creation, selection, and registration
   of an Autonomous System (AS)" found at:

   ftp://ftp.ripe.net/rfc/rfc1930.txt

   Current assignment guidelines require a network to be multihomed
   for an AS number to be assigned. When a registry applies for an
   ASN, it needs to submit the routing policy of the Autonomous System
   that requires an AS number. The policy is defined in the following
   attributes as part of the aut-num object: multiple fields of
   "import:" (description of accepted routing information from
   neighbouring ASs.); multiple fields of "export:" (description of
   generated routing information sent to other AS peers); one or more
   fields of "default:" (indication of how default routing is done).

1.1. Requesting an AS Number
   
   The RIPE NCC assigns AS numbers for Autonomous Systems that are
   located in the RIPE NCC service region. As for IP address requests,
   the RIPE NCC only accepts requests for AS numbers from Local
   Internet Registries (LIRs) that are members of the RIPE NCC.

   To obtain an AS number, the RIPE NCC provides a form containing
   contact information and three database templates:
   
     - aut-num (autonomous system number) template,
     - mntner (maintainer) template,               
     - one or more person templates.

   All of the information requested in the form is required. The RIPE
   NCC may also ask for additional information in order to understand
   the planned routing policy and to decide if an AS number is
   needed. The information provided in the templates will be entered
   into the RIPE Whois Database and is publicly accessible. For more
   information on Database templates, please refer to:

   http://www.ripe.net/perl/whois -t aut-num
                                  -t mntner
                                  -t person (or role)
   
   A completed form should be sent to the RIPE NCC Hostmaster mailbox:
   <hostmaster@ripe.net>. After evaluating the requests, the RIPE NCC
   will enter all relevant information in the RIPE Database and will
   notify the LIR of the assignment.
   
   The form for requesting AS Numbers is available from the RIPE
   Document Store at:
   
   http://www.ripe.net/ripe/docs/asnrequestform.html
   
   Supporting notes for the AS Number Request Form is available from
   the RIPE Document Store at:
   
 http://www.ripe.net/ripe/docs/asnsupport.html
   
1.2. Returning an AS Number
   
   If an organisation has an AS number that is no longer in use, it
   can be returned to the public pool of AS numbers by sending a
   message to <hostmaster@ripe.net>. It can then be reassigned to
   another Autonomous System by the RIPE NCC.