rfc2280.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

                       Figure 10:  route-set Objects

   An address prefix or a route-set name in a members attribute can be
   optionally followed by a range operator.  For example, the following
   set




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      route-set: rs-bar
      members: 5.0.0.0/8^+, 30.0.0.0/8^24-32, rs-foo^+

   contains all the more specifics of 5.0.0.0/8 including 5.0.0.0/8, all
   the more specifics of 30.0.0.0/8 which are of length 24 to 32 such as
   30.9.9.96/28, and all the more specifics of address prefixes in route
   set rs-foo.

   The mbrs-by-ref attribute is a list of maintainer names or the
   keyword ANY.  If this attribute is used, the route set also includes
   address prefixes whose route objects are registered by one of these
   maintainers and whose member-of attribute refers to the name of this
   route set.  If the value of a mbrs-by-ref attribute is ANY, any route
   object referring to the route set name is a member.  If the mbrs-by-
   ref attribute is missing, only the address prefixes listed in the
   members attribute are members of the set.

      route-set: rs-foo
      mbrs-by-ref: MNTR-ME, MNTR-YOU

      route-set: rs-bar
      members: 128.7.0.0/16
      mbrs-by-ref: MNTR-YOU

      route: 128.9.0.0/16
      origin: AS1
      member-of: rs-foo
      mnt-by: MNTR-ME

      route: 128.8.0.0/16
      origin: AS2
      member-of: rs-foo, rs-bar
      mnt-by: MNTR-YOU


                      Figure 11:  route-set objects.

   Figure 11 presents example route-set objects that use the mbrs-by-ref
   attribute.  The set rs-foo contains two address prefixes, namely
   128.8.0.0/16 and 128.9.0.0/16 since the route objects for
   128.8.0.0/16 and 128.9.0.0/16 refer to the set name rs-foo in their
   member-of attribute.  The set rs-bar contains the address prefixes
   128.7.0.0/16 and 128.8.0.0/16.  The route 128.7.0.0/16 is explicitly
   listed in the members attribute of rs-bar, and the route object for
   128.8.0.0/16 refer to the set name rs-bar in its member-of attribute.

   Note that, if an address prefix is listed in a members attribute of a
   route set, it is a member of that route set.  The route object



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   corresponding to this address prefix does not need to contain a
   member-of attribute referring to this set name.  The member-of
   attribute of the route class is an additional mechanism for
   specifying the members indirectly.

5.2 as-set Class

   The attributes of the as-set class are shown in Figure 12.  The as-
   set attribute defines the name of the set.  It is an RPSL name that
   starts with "as-".  The members attribute lists the members of the
   set.  The members attribute is a list of AS numbers, or other as-set
   names.

      Attribute    Value                    Type
      as-set       <object-name>            mandatory, single-valued,
                                            class key
      members      list of <as-numbers> or  optional, single-valued
                   <as-set-names>
      mbrs-by-ref  list of <mntner-names>   optional, single-valued


                    Figure 12:  as-set Class Attributes

   Figure 13 presents two as-set objects.  The set as-foo contains two
   ASes, namely AS1 and AS2.  The set as-bar contains the members of the
   set as-foo and AS3, that is it contains AS1, AS2, AS3.

    as-set: as-foo                      as-set: as-bar
    members: AS1, AS2                   members: AS3, as-foo


                    Figure 13:  as-set objects.


   The mbrs-by-ref attribute is a list of maintainer names or the
   keyword ANY.  If this attribute is used, the AS set also includes
   ASes whose aut-num objects are registered by one of these maintainers
   and whose member-of attribute refers to the name of this AS set.  If
   the value of a mbrs-by-ref attribute is ANY, any AS object referring
   to the AS set is a member of the set.  If the mbrs-by-ref attribute
   is missing, only the ASes listed in the members attribute are members
   of the set.

   Figure 14 presents an example as-set object that uses the mbrs-by-ref
   attribute.  The set as-foo contains AS1, AS2 and AS3.  AS4 is not a
   member of the set as-foo even though the aut-num object references
   as-foo.  This is because MNTR-OTHER is not listed in the as-foo's
   mbrs-by-ref attribute.



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    as-set: as-foo
    members: AS1, AS2
    mbrs-by-ref: MNTR-ME

    aut-num: AS3                          aut-num: AS4
    member-of: as-foo                     member-of: as-foo
    mnt-by: MNTR-ME                       mnt-by: MNTR-OTHER


                        Figure 14:  as-set objects.

5.3 Predefined Set Objects


   In a context that expects a route set (e.g.  members attribute of the
   route-set class), an AS number ASx defines the set of routes that are
   originated by ASx; and an as-set AS-X defines the set of routes that
   are originated by the ASes in AS-X. A route p is said to be
   originated by ASx if there is a route object for p with ASx as the
   value of the origin attribute.  For example, in Figure 15, the route
   set rs-special contains 128.9.0.0/16, routes of AS1 and AS2, and
   routes of the ASes in AS set AS-FOO.

      route-set: rs-special
      members: 128.9.0.0/16, AS1, AS2, AS-FOO


         Figure 15:  Use of AS numbers and AS sets in route sets.

   The set rs-any contains all routes registered in IRR.  The set as-any
   contains all ASes registered in IRR.

5.4 Hierarchical Set Names

   Set names can be hierarchical.  A hierarchical set name is a sequence
   of set names and AS numbers separated by colons ":".  For example,
   the following names are valid: AS1:AS-CUSTOMERS, AS1:RS-EXCEPTIONS,
   AS1:RS-EXPORT:AS2, RS-EXCEPTIONS:RS-BOGUS. All components of an
   hierarchical set name which are not AS numbers should start with
   "as-" or "rs-" for as sets and route sets respectively.

   A set object with name X1:...:Xn-1:Xn can only be created by the
   maintainer of the object with name X1:...:Xn-1.  That is, only the
   maintainer of AS1 can create a set with name AS1:AS-FOO; and only the
   maintainer of AS1:AS-FOO can create a set with name AS1:AS-FOO:AS-
   BAR.





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   The purpose of an hierarchical set name is to partition the set name
   space so that the controllers of the set name X1 controls the whole
   set name space under X1, i.e.  X1:...:Xn-1.  This is important since
   anyone can create a set named AS-MCI-CUSTOMERS but only the people
   created AS3561 can create AS3561:AS-CUSTOMERS. In the former, it is
   not clear if the set AS-MCI-CUSTOMERS has any relationship with MCI.
   In the latter, we can guarantee that AS3561:AS-CUSTOMERS and AS3561
   are created by the same entity.

6 aut-num Class

   ASes are specified using the aut-num class.  The attributes of the
   aut-num class are shown in Figure 16.  The value of the aut-num
   attribute is the AS number of the AS described by this object.  The
   as-name attribute is a symbolic name (in RPSL name syntax) of the AS.
   The import, export and default routing policies of the AS are
   specified using import, export and default attributes respectively.

   Attribute  Value                  Type
   aut-num    <as-number>            mandatory, single-valued, class key
   as-name    <object-name>          mandatory, single-valued
   member-of  list of <as-set-names> optional, single-valued
   import     see Section 6.1        optional, multi valued
   export     see Section 6.2        optional, multi valued
   default    see Section 6.5        optional, multi valued

                    Figure 16:  aut-num Class Attributes

6.1 import Attribute:  Import Policy Specification

   Figure 17 shows a typical interconnection of ASes that we will be
   using in our examples throughout this section.  In this example
   topology, there are three ASes, AS1, AS2, and AS3; two exchange
   points, EX1 and EX2; and six routers.  Routers connected to the same
   exchange point peer with each other, i.e. open a connection for
   exchanging routing information.  Each router would export a subset of
   the routes it has to its peer routers.  Peer routers would import a
   subset of these routes.  A router while importing routes would set
   some route attributes.  For example, AS1 can assign higher preference
   values to the routes it imports from AS2 so that it prefers AS2 over
   AS3.  While exporting routes, a router may also set some route
   attributes in order to affect route selection by its peers.  For
   example, AS2 may set the MULTI-EXIT-DISCRIMINATOR BGP attribute so
   that AS1 prefers to use the router 9.9.9.2.  Most interAS policies
   are specified by specifying what route subsets can be imported or
   exported, and how the various BGP route attributes are set and used.





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     ----------------------                   ----------------------
     |            7.7.7.1 |-------|   |-------| 7.7.7.2            |
     |                    |     ========      |                    |
     |   AS1              |      EX1  |-------| 7.7.7.3     AS2    |
     |                    |                   |                    |
     |            9.9.9.1 |------       ------| 9.9.9.2            |
     ----------------------     |       |     ----------------------
                               ===========
                                   |    EX2
     ----------------------        |
     |            9.9.9.3 |---------
     |                    |
     |   AS3              |
     ----------------------

   Figure 17: Example topology consisting of three ASes, AS1, AS2, and
   AS3; two exchange points, EX1 and EX2; and six routers.

   In RPSL, an import policy is divided into import policy expressions.
   Each import policy expression is specified using an import attribute.
   The import attribute has the following syntax (we will extend this
   syntax later in Sections 6.3 and 6.6):

       import: from <peering-1> [action <action-1>]
               . . .
               from <peering-N> [action <action-N>]
               accept <filter>

   The action specification is optional.  The semantics of an import
   attribute is as follows: the set of routes that are matched by
   <filter> are imported from all the peers in <peerings>; while
   importing routes at <peering-M>, <action-M> is executed.


     E.g.
       aut-num: AS1
       import: from AS2 action pref = 1; accept { 128.9.0.0/16 }

   This example states that the route 128.9.0.0/16 is accepted from AS2
   with preference 1.  In the next few subsections, we will describe how
   peerings, actions and filters are specified.

6.1.1 Peering Specification

   Our example above used an AS number to specify peerings.  The
   peerings can be specified at different granularities.  The syntax of
   a peering specification has two forms.  The first one is as follows:




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               <peer-as> [<peer-router>] [at <local-router>]

   where <local-router> and <peer-router> are IP addresses of routers,
   <peer-as> is an AS number.  <peer-as> must be the AS number of
   <peer-router>.  Both <local-router> and <peer-router> are optional.
   If both <local-router> and <peer-router> are specified, this peering
   specification identifies only the peering between these two routers.
   If only <local-router> is specified, this peering specification
   identifies all the peerings between <local-router> and any of its
   peer routers in <peer-as>.  If only <peer-router> is specified, this
   peering specification identifies all the peerings between any router
   in the local AS and <peer-router>.  If neither <local-router> nor
   <peer-router> is specified, this peering specification identifies all
   the peerings between any router in the local AS and any router in
   <peer-as>.

   We next give examples.  Consider the topology of Figure 17 where
   7.7.7.1, 7.7.7.2 and 7.7.7.3 peer with each other; 9.9.9.1, 9.9.9.2
   and 9.9.9.3 peer with each other.  In the following example 7.7.7.1
   imports 128.9.0.0/16 from 7.7.7.2.

    (1) aut-num: AS1
        import: from AS2 7.7.7.2 at 7.7.7.1 accept { 128.9.0.0/16 }

   In the following example 7.7.7.1 imports 128.9.0.0/16 from 7.7.7.2
   and 7.7.7.3.

    (2) aut-num: AS1
        import: from AS2 at 7.7.7.1 accept { 128.9.0.0/16 }

   In the following example 7.7.7.1 imports 128.9.0.0/16 from 7.7.7.2
   and 7.7.7.3, and 9.9.9.1 imports 128.9.0.0/16 from 9.9.9.2.

    (3) aut-num: AS1
        import: from AS2 accept { 128.9.0.0/16 }