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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 6431

Network Working Group                                  M. Boucadair, Ed.
Internet-Draft                                                  P. Levis
Intended status: Standards Track                           J-L. Grimault
Expires: August 9, 2009                                  A. Villefranque
                                                          France Telecom
                                                        February 5, 2009


             Port Range Configuration Options for PPP IPCP
               draft-boucadair-pppext-portrange-option-00

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 9, 2009.

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   Copyright (c) 2009 IETF Trust and the persons identified as the
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Abstract

   This memo defines two IPCP (IP Configuration Protocol, [RFC1332])
   Options to be used in the context of Port Range solutions.  IPCP is
   the configuration protocol used when PPP (Point-to-Point Protocol,
   [RFC1548]) is deployed.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Port Range Options . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2.  Description  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .  6
       2.3.1.  Successful  Flow: Port Range Options supported by
               both the Client and the Server . . . . . . . . . . . .  7
       2.3.2.  Port Range Options not supported by the Server . . . .  8
       2.3.3.  Port Range Options not supported by the Client . . . . 10
   3.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13



















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1.  Introduction

   Recently, within the context of IPv4 address depletion, several
   solutions have been submitted to the IETF to propose viable
   alternative solutions to Carrier Grade NAT (CGN).

   [ID.boucadair] is an example of these solutions which propose to
   share the same IP address among several devices and to constraint the
   values used as port sources to a limited set of values.  These
   solutions does not require an additional NAT level in the service
   provider's domain.  Several means may be used to convey Port Range
   information.

   This memo defines new IPCP options to be used to carry Port Range
   information.  IPCP has been widely used to convey configuration
   information such as IP Compression Protocol [RFC3241][RFC3544] or IP-
   Address [RFC1332].

   Concretely, this memo defines the notion of Port Mask which is
   generic and flexible.  Several allocation schemes may be implemented
   when using a Port Mask.  This draft proposes a basic mechanism that
   allows the allocation of a unique Port Mask.

   IP exhaustion is only provided as an example of the usage of the PPP
   IPCP option defined in this memo.  Other usages may be considered.


2.  Port Range Options

   This section defines the Port Range IPCP Options.

2.1.  Terminology

   To differentiate between a Port Range containing a contiguous span of
   port numbers and a Port Range with non contiguous port numbers, the
   following denominations are used:

      - Contiguous Port Range: a set of port values which form a
      contiguous sequence.

      - Non Contiguous Port Range: a set of port values which does not
      form a contiguous sequence.

   Moreover, unless explicitly mentioned, Port Mask refers to the couple
   (Port Range Value, Port Range Mask).

   This memo uses the same terminology as per [RFC1548].  Peer and
   client terms are used interchangeably.



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2.2.  Description

   The port range options are used to specify one range of ports
   (contiguous or not contiguous) pertaining to a given IP address.
   Concretely, these options are used to notify a remote peer about the
   Port Mask to be applied when selecting a port value as a source port.
   The Port Range option is used to infer a set of allowed port values.
   A Port Mask defines a set of ports that all have in common a subset
   of pre-positioned bits.  This set of ports is also called Port Range.
   Two port numbers are said to belong to the same Port Range if and
   only if, they have the same Port Mask.

   A Port Mask is composed of a Port Range Value and a Port Range Mask.

   o  The Port Range Value indicates the value of the significant bits
      of the Port Mask.  The Port Range Value is coded as follows:

      *  The significant bits may take a value of "0" or "1".

      *  All the other bits (non significant ones) are set to "0".

   o  The Port Range Mask indicates, by the bit(s) set to "1", the
      position of the significant bits of the Port Range Value.

   These IPCP Configuration Options provide a way to negotiate the port
   range to be used on the local end of the link.  It allows the sender
   of the Configure-Request message to state which port range associated
   with a given IP-address is desired, or to request the peer to provide
   the configuration.  The peer can provide this information by NAKing
   the options, and returning a valid port range (i.e.  (Port Range
   Value, Port Range Mask)).

   IPCP Port Range Value and Port Range Mask MUST be supported
   simultaneously.

   When the server assigns only shared IP addresses, the peer must
   include Port Range Options in its request.  If not, 0.0.0.0 is
   assigned by the server to that peer.

   When a peer issues a request enclosing IPCP Port Range Options, and
   if the server does not support these options, Port Range Options are
   rejected by the server.

   The format of these IPCP options are provided hereafter:







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   The format of Port Range Value IPCP option is illustrated in the
   figure 1:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     |      Port Range Value         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 1: Format of the PRV IPCP Option

   o  Type: To be assigned.

   o  Length: This field includes the length of the overall option
      including the Type, Length and the PRV.  It must be set to 4 bytes

   o  Port Range Value (PRV): PRV indicates the value of the significant
      bits of the Port Mask.  By default, no PRV is assigned.

   The format of Port Range Mask IPCP option is illustrated in the
   figure 2:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     |      Port Range Mask          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 2: Format of the PRM IPCP Option

   o  Type: To be assigned.

   o  Length: This field includes the lent of the overall option
      including the Type, Length and the PRV.  It must be set to 4 bytes

   o  Port Range Mask (PRM): Port Range Mask indicates the position of
      the bits which are used to build the Port Range Value.  By
      default, no PRM is assigned.  The "1" values in the Port Range
      Mask indicate by their position the significant bits of the Port
      Range Value.

   The following figure provides an example of the resulting Port Range
   when:

   - Port Range Mask is set to 0001010000000000 (5120) and




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   - Port Range Value is set to 0000010000000000 (1024).


       0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0|  Port Range Mask
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |   |
             |   | (two significant bits)
             v   v
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0|  Port Range Value
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |x x x 0 x 1 x x x x x x x x x x|  Usable ports (x may take a value of 0 or 1).
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Figure 3: Example of Port Range Mask and Port Range Value

   Ports belonging to this port range must have the 4th bit (resp. the
   sixth one), from the left, set to 0 (resp. 1).  Only these ports will
   be used by the peer when enforcing the configuration conveyed by PPP
   IPCP.

2.3.  Examples

   The following flows provide examples of the usage of IPCP to convey
   port mask options.  As illustrated in figure 4, IPCP messages are
   exchanged between a Host and a BAS (Broadband Access Server).

      - 1st example: illustrates a successful IPCP exchange;

      - 2nd example: shows the IPCP exchange that occurs when Port Range
      Options are not supported by the server side;

      - 3rd example: shows the IPCP exchange that occurs when Port Range
      Options are not supported by the client side;

      - 4th example: shows the IPCP exchange that occurs when Port Range
      Options are not supported by the client side and a non null IP
      (i.e. an address different from 0.0.0.0) address is enclosed in
      the first configuration request issued by the peer.






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2.3.1.  Successful  Flow: Port Range Options supported by both the
        Client and the Server

   The following message exchange (i.e. figure 4) provides an example of
   successful IPCP configuration operation when port range options are
   used.


     +-----+                                          +-----+
     | Host|                                          | BAS |
     +-----+                                          +-----+
        |                                                |
        |              (1) IPCP Configure-Request        |
        |                IP ADDRESS=0.0.0.0              |
        |                PORT RANGE VALUE=0              |
        |                PORT RANGE MASK=0               |
        |===============================================>|
        |                                                |
        |              (2) IPCP Configure-Nak            |
        |                IP ADDRESS=a.b.c.d              |
        |                PORT RANGE VALUE=80             |
        |                PORT RANGE MASK=496             |
        |<===============================================|
        |                                                |
        |              (3) IPCP Configure-Request        |
        |                IP ADDRESS=a.b.c.d              |
        |                PORT RANGE VALUE=80             |
        |                PORT RANGE MASK=496             |
        |===============================================>|
        |                                                |
        |              (4) IPCP Configure-Ack            |
        |                IP ADDRESS=a.b.c.d              |
        |                PORT RANGE VALUE=80             |
        |                PORT RANGE MASK=496             |
        |<===============================================|
        |                                                |


                        Figure 4: Successful  flow

   The main steps of this flow are:

      (1) The Host sends a first Configure-Request which includes the
      set of options it desires to negotiate.  All these Configuration
      Options are negotiated simultaneously.  In this example,
      Configure-Request carries information about IP-address, Port Range
      Value and Port Range Mask options.  In this example, IP-address
      option is set to "0.0.0.0", Port Range Value is set to "0" and



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      Port Range Mask is set to "0".

      (2) BAS sends back a Configure-Nak and sets the enclosed options
      to its preferred values.  In this example: IP-Address option is
      set to "a.b.c.d", Port Range Value is set to "80" and Port Range
      Mask is set to "496".

      (3) The Host re-sends a Configure-Request requesting IP-address
      option to be set to "a.b.c.d", Port Range Value to be set to "80"
      and Port Range Mask to be set to "496".

      (4) BAS sends a Configure-Ack message

   As a result of this exchange, Host is configured to use as local IP
   address "a.b.c.d" and the following 128 Contiguous Port Ranges
   resulting of the Port Mask (Port Range Value == 0, Port Range Mask ==
   496):

      - from 80 to 95

      - from 592 to 607

      - ...

      - from 65104 to 65119

2.3.2.  Port Range Options not supported by the Server

   This example (figure 5) depicts an exchange of messages when the BAS
   does not support IPCP Port Range Options.





















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     +-----+                                          +-----+
     | Host|                                          | BAS |
     +-----+                                          +-----+
        |                                                |
        |              (1) IPCP Configure-Request        |
        |                IP ADDRESS=0.0.0.0              |
        |                PORT RANGE VALUE=0              |
        |                PORT RANGE MASK=0               |
        |===============================================>|
        |                                                |
        |              (2) IPCP Configure-Reject         |
        |                PORT RANGE VALUE=0              |
        |                PORT RANGE MASK=0               |
        |<===============================================|
        |                                                |
        |              (3) IPCP Configure-Request        |
        |                IP ADDRESS=0.0.0.0              |
        |===============================================>|
        |                                                |
        |              (4) IPCP Configure-Nak            |
        |                IP ADDRESS=a.b.c.d              |
        |<===============================================|
        |                                                |
        |              (5) IPCP Configure-Request        |
        |                IP ADDRESS=a.b.c.d              |
        |===============================================>|
        |                                                |
        |              (6) IPCP Configure-Ack            |
        |                IP ADDRESS=a.b.c.d              |
        |<===============================================|
        |                                                |


      Figure 5: Failed  flow: Port Range Options not supported by the
                                  server

   The main steps of this flow are:

      (1) The Host sends a first Configure-Request which includes the
      set of options it desires to negotiate.  All these Configuration
      Options are negotiated simultaneously.  In this example,
      Configure-Request carries the codes of IP-address, Port Range
      Value and Port Range Mask options.  In this example, IP-address
      option is set to "0.0.0.0", Port Range Value is set to "0" and
      Port Range Mask is set to "0".

      (2) BAS sends back a Configure-Reject to decline Port Range Value
      and Port Range Mask options.



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      (3) The Host sends a Configure-Request which includes only the
      codes of IP-Address option.  In this example, IP-Address option is
      set to "0.0.0.0".

      (4) BAS sends back a Configure-Nak and sets the enclosed option to
      its preferred value.  In this example: IP-Address option is set to
      "a.b.c.d".

      (5) The Host re-sends a Configure-Request requesting IP-Address
      option to be set to "a.b.c.d".

      (6) BAS sends a Configure-Ack message

   As a result of this exchange, Host is configured to use as local IP
   address "a.b.c.d".  This IP address is not a shared IP address.

2.3.3.  Port Range Options not supported by the Client

   This example (figure 6) depicts exchanges when only shared IP
   addresses are assigned to end-user's devices.  The support of IPCP
   Port Range Options is MANDATORY.


     +-----+                                          +-----+
     | Host|                                          | BAS |
     +-----+                                          +-----+
        |                                                |
        |              (1) IPCP Configure-Request        |
        |                IP ADDRESS=0.0.0.0              |
        |===============================================>|
        |                                                |
        |              (2) IPCP Configure-Ack            |
        |                IP ADDRESS=0.0.0.0              |
        |<===============================================|
        |                                                |


         Figure 6: Port Range Options not supported by the Client

   The main steps of this flow are:

      (1) The Host sends a Configure-Request requesting IP-Address
      option to be set to "0.0.0.0" and without enclosing Port Range
      Options.

      (2) BAS sends a Configure-Ack message and sets the IP address to
      "0.0.0.0" since only shared IP addresses are assigned.




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   As a result of this exchange, Host is configured to use as local IP
   address "0.0.0.0".  Host is not able to access the service.

   If in the first Configure-Request, a valid IP address is enclosed,
   the following exchange (figure 7) should be experienced:


     +-----+                                          +-----+
     | Host|                                          | BAS |
     +-----+                                          +-----+
        |                                                |
        |              (1) IPCP Configure-Request        |
        |                IP ADDRESS=a.b.c.d              |
        |===============================================>|
        |                                                |
        |              (2) IPCP Configure-Nak            |
        |                IP ADDRESS=0.0.0.0              |
        |<===============================================|
        |                                                |
        |              (3) IPCP Configure-Request        |
        |                IP ADDRESS=0.0.0.0              |
        |===============================================>|
        |                                                |
        |              (4) IPCP Configure-Ack            |
        |                IP ADDRESS=0.0.0.0              |
        |<===============================================|
        |                                                |


       Figure 7: Port Range Options not supported by the Client (2)

   The main steps of this flow are:

      (1) The Host sends a Configure-Request requesting IP-Address
      option to be set to "a.b.c.d" and without enclosing Port Range
      Options.

      (2) BAS sends a Configure-Nak and sets the enclosed option to its
      preferred value.  In this example: IP-Address option is set to
      "0.0.0.0" since only shared IP addresses are assigned.

      (3) The Host re-sends a Configure-Request requesting IP-Address
      option to be set to "0.0.0.0".

      (4) BAS sends a Configure-Ack message and confirms to set the IP
      address to "0.0.0.0".

   As a result of this exchange, Host is configured to use as local IP



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   address "0.0.0.0".  Host is not able to access the service.


3.  IANA Considerations

   This document requests IANA to assign numbers for these IPCP options:

      - Port Range Value Option;

      - Port Range Mask Option.


4.  Security Considerations

   This document does not introduce any security issue in addition to
   those related to PPP.  Service providers should use authentication
   mechanisms such as CHAP [RFC1994] or PPP link encryption [RFC1968].


5.  Acknowledgements

   The authors would like to thank Christian JACQUENET for his review
   and inputs.


6.  References

6.1.  Normative References

   [RFC1332]  McGregor, G., "The PPP Internet Protocol Control Protocol
              (IPCP)", RFC 1332, May 1992.

   [RFC1548]  Simpson, W., "The Point-to-Point Protocol (PPP)",
              RFC 1548, December 1993.

   [RFC1661]  Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
              RFC 1661, July 1994.

   [RFC1968]  Meyer, G. and K. Fox, "The PPP Encryption Control Protocol
              (ECP)", RFC 1968, June 1996.

   [RFC1994]  Simpson, W., "PPP Challenge Handshake Authentication
              Protocol (CHAP)", RFC 1994, August 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2290]  Solomon, J. and S. Glass, "Mobile-IPv4 Configuration



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              Option for PPP IPCP", RFC 2290, February 1998.

   [RFC3241]  Bormann, C., "Robust Header Compression (ROHC) over PPP",
              RFC 3241, April 2002.

   [RFC3544]  Koren, T., Casner, S., and C. Bormann, "IP Header
              Compression over PPP", RFC 3544, July 2003.

6.2.  Informative References

   [ID.boucadair]
              Boucadair, M., Levis, P., Bajko, G., and T. Savolainen ,
              "IPv4 Connectivity Access in the context of IPv4 Address
              Exhaustion", January 2009.


Authors' Addresses

   Mohamed Boucadair (editor)
   France Telecom
   42 rue des Coutures
   BP 6243
   Caen Cedex 4  14066
   France

   Email: mohamed.boucadair@orange-ftgroup.com


   Pierre Levis
   France Telecom

   Email: pierre.levis@orange-ftgroup.com


   Jean-Luc Grimault
   France Telecom

   Email: jeanluc.grimault@orange-ftgroup.com


   Alain Villefranque
   France Telecom

   Fax:
   Email: alain.villefranque@orange-ftgroup.com






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