rfc2622.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   A route set name can also be followed by one of the operators '^-',
   '^+', example, { 5.0.0.0/8, 6.0.0.0/8 }^+ equals { 5.0.0.0/8^+,
   6.0.0.0/8^+ }, and AS1^- equals all the exclusive more specifics of
   routes originated by AS1.

   AS Path Regular Expressions
      An AS-path regular expression can be used as a policy filter by
      enclosing the expression in `<' and `>'.  An AS-path policy filter
      matches the set of routes which traverses a sequence of ASes
      matched by the AS-path regular expression.  A router can check
      this using the AS_PATH attribute in the Border Gateway Protocol
      [19], or the RD_PATH attribute in the Inter-Domain Routing
      Protocol [18].

      AS-path Regular Expressions are POSIX compliant regular
      expressions over the alphabet of AS numbers.  The regular
      expression constructs are as follows:

   ASN
      where ASN is an AS number.  ASN matches the AS-path that is of
      length 1 and contains the corresponding AS number (e.g.  AS-path
      regular expression AS1 matches the AS-path "1").

      The keyword PeerAS can be used instead of the AS number of the
      peer AS.

   AS-set
      where AS-set is an AS set name.  AS-set matches the AS-paths that
      is matched by one of the ASes in the AS-set.

   .
      matches the AS-paths matched by any AS number.



Alaettinoglu, et al.        Standards Track                    [Page 19]

RFC 2622                          RPSL                         June 1999


   [...]
      is an AS number set.  It matches the AS-paths matched by the AS
      numbers listed between the brackets.  The AS numbers in the set
      are separated by white space characters.  If a `-' is used between
      two AS numbers in this set, all AS numbers between the two AS
      numbers are included in the set.  If an as-set name is listed, all
      AS numbers in the as-set are included.

   [^...]
      is a complemented AS number set.  It matches any AS-path which is
      not matched by the AS numbers in the set.

   ^
      Matches the empty string at the beginning of an AS-path.

   $
      Matches the empty string at the end of an AS-path.

   We next list the regular expression operators in the decreasing order
   of evaluation.  These operators are left associative, i.e. performed
   left to right.

   Unary postfix operators * + ?  {m} {m,n} {m,}
      For a regular expression A, A* matches zero or more occurrences of
      A; A+ matches one or more occurrences of A; A?  matches zero or
      one occurrence of A; A{m} matches m occurrence of A; A{m,n}
      matches m to n occurrence of A; A{m,} matches m or more occurrence
      of A. For example, [AS1 AS2]{2} matches AS1 AS1, AS1 AS2, AS2 AS1,
      and AS2 AS2.

   Unary postfix operators ~* ~+ ~{m} ~{m,n} ~{m,}
      These operators have similar functionality as the corresponding
      operators listed above, but all occurrences of the regular
      expression has to match the same pattern.  For example, [AS1
      AS2]~{2} matches AS1 AS1 and AS2 AS2, but it does not match AS1
      AS2 and AS2 AS1.

   Binary catenation operator
      This is an implicit operator and exists between two regular
      expressions A and B when no other explicit operator is specified.
      The resulting expression A B matches an AS-path if A matches some
      prefix of the AS-path and B matches the rest of the AS-path.

   Binary alternative (or) operator |
      For a regular expressions A and B, A | B matches any AS-path that
      is matched by A or B.





Alaettinoglu, et al.        Standards Track                    [Page 20]

RFC 2622                          RPSL                         June 1999


   Parenthesis can be used to override the default order of evaluation.
   White spaces can be used to increase readability.

   The following are examples of AS-path filters:

   <AS3>
   <^AS1>
   <AS2$>
   <^AS1 AS2 AS3$>
   <^AS1 .* AS2$>.

   The first example matches any route whose AS-path contains AS3, the
   second matches routes whose AS-path starts with AS1, the third
   matches routes whose AS-path ends with AS2, the fourth matches routes
   whose AS-path is exactly "1 2 3", and the fifth matches routes whose
   AS-path starts with AS1 and ends in AS2 with any number of AS numbers
   in between.

   Composite Policy Filters The following operators (in decreasing order
   of evaluation) can be used to form composite policy filters:


   NOT Given a policy filter x, NOT x matches the set of routes that
       are not matched by x.  That is it is the negation of policy
       filter x.

   AND Given two policy filters x and y, x AND y matches the intersection
       of the routes that are matched by x and that are matched by y.

   OR  Given two policy filters x and y, x OR y matches the union of the
       routes that are matched by x and that are matched by y.

   Note that an OR operator can be implicit, that is `x y' is equivalent
   to `x OR y'.

  E.g.
    NOT {128.9.0.0/16, 128.8.0.0/16}
    AS226 AS227 OR AS228
    AS226 AND NOT {128.9.0.0/16}
    AS226 AND {0.0.0.0/0^0-18}

   The first example matches any route except 128.9.0.0/16 and
   128.8.0.0/16.  The second example matches the routes of AS226, AS227
   and AS228.  The third example matches the routes of AS226 except
   128.9.0.0/16.  The fourth example matches the routes of AS226 whose
   length are not longer than 18.





Alaettinoglu, et al.        Standards Track                    [Page 21]

RFC 2622                          RPSL                         June 1999


   Routing Policy Attributes Policy filters can also use the values of
   other attributes for comparison.  The attributes whose values can be
   used in policy filters are specified in the RPSL dictionary.  Please
   refer to Section 7 for details.  An example using the the BGP
   community attribute is shown below:

    aut-num: AS1
    export: to AS2 announce AS1 AND NOT community(NO_EXPORT)

   Filters using the routing policy attributes defined in the dictionary
   are evaluated before evaluating the operators AND, OR and NOT.

   Filter Set Name
      A filter set name matches the set of routes that are matched by
      its filter attribute.  Note that the filter attribute of a filter
      set, can recursively refer to other filter set names.  For example
      in Figure 17, fltr-foo matches { 5.0.0.0/8, 6.0.0.0/8 }, and
      fltr-bar matches AS1'S routes or { 5.0.0.0/8, 6.0.0.0/8 } if their
      as path contained AS2.

5.5 rtr-set Class

   The attributes of the rtr-set class are shown in Figure 18.  The
   rtr-set attribute defines the name of the set.  It is an RPSL name
   that starts with "rtrs-".  The members attribute lists the members of
   the set.  The members attribute is a list of inet-rtr names,
   ipv4_addresses or other rtr-set names.

    Attribute    Value                        Type
    rtr-set      <object-name>                mandatory, single-valued,
                                              class key
    members      list of <inet-rtr-names> or  optional, multi-valued
                 <rtr-set-names>
                 or <ipv4_addresses>
    mbrs-by-ref  list of <mntner-names>       optional, multi-valued


                    Figure 18:  rtr-set Class Attributes













Alaettinoglu, et al.        Standards Track                    [Page 22]

RFC 2622                          RPSL                         June 1999


   Figure 19 presents two rtr-set objects.  The set rtrs-foo contains
   two routers, namely rtr1.isp.net and rtr2.isp.net.  The set rtrs-bar
   contains the members of the set rtrs-foo and rtr3.isp.net, that is it
   contains rtr1.isp.net, rtr2.isp.net, rtr3.isp.net.

 rtr-set: rtrs-foo                     rtr-set: rtrs-bar
 members: rtr1.isp.net, rtr2.isp.net   members: rtr3.isp.net, rtrs-foo


                        Figure 19:  rtr-set objects.

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

       rtr-set: rtrs-foo
       members: rtr1.isp.net, rtr2.isp.net
       mbrs-by-ref: MNTR-ME

       inet-rtr: rtr3.isp.net
       local-as: as1
       ifaddr: 1.1.1.1 masklen 30
       member-of: rtrs-foo
       mnt-by: MNTR-ME


                              Figure 20:  rtr-set objects.

   Figure 20 presents an example rtr-set object that uses the mbrs-by-
   ref attribute.  The set rtrs-foo contains rtr1.isp.net, rtr2.isp.net
   and rtr3.isp.net.















Alaettinoglu, et al.        Standards Track                    [Page 23]

RFC 2622                          RPSL                         June 1999


5.6 Peerings and peering-set Class

   The attributes of the peering-set class are shown in Figure 21.  A
   peering-set object defines a set of peerings that are listed in its
   peering attributes.  The peering-set attribute defines the name of
   the set.  It is an RPSL name that starts with "prng-".

      Attribute    Value          Type
      peering-set  <object-name>  mandatory, single-valued, class key
      peering      <peering>      mandatory, multi-valued

                    Figure 21:  filter Class Attributes

   The peering attribute defines a peering that can be used for
   importing or

     ----------------------                   ----------------------
     |            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 22: Example topology consisting of three ASes, AS1, AS2, and
        AS3; two exchange points, EX1 and EX2; and six routers.

   exporting routes.
      In describing peerings, we are going to use the topology of Figure
      22.  In this 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 and
      exchange routing information.  That is, 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.

      The syntax of a peering specification is:

      <as-expression> [<router-expression-1>] [at <router-expression-2>]
     | <peering-set-name>




Alaettinoglu, et al.        Standards Track                    [Page 24]

RFC 2622                          RPSL                         June 1999


      where <as-expression> is an expression over AS numbers and AS sets
      using operators AND, OR, and EXCEPT, and <router-expression-1> and
      <router-expression-2> are expressions over router IP addresses,
      inet-rtr names, and rtr-set names using operators AND, OR, and
      EXCEPT.  The binary "EXCEPT" operator is the set subtraction
      operator and has the same precedence as the operator AND (it is
      semantically equivalent to "AND NOT" combination).  That is "(AS1
      OR AS2) EXCEPT AS2" equals "AS1".

      This form identifies all the peerings between any local router in
      <router-expression-2> to any of their peer routers in <router-
      expression-1> in the ASes in <as-expression>.  If <router-
      expression-2> is not specified, it defaults to all routers of the
      local AS that peer with ASes in <as-expression>.  If <router-
      expression-1> is not specified, it defaults to all routers of the
      peer ASes in <as-expression> that peer with the local AS.

      If a <peering-set-name> is used, the peerings are listed in the
      corresponding peering-set object.  Note that the peering-set
      objects can be recursive.

      Many special forms of this general peering specification is