Network Working Group M. Boucadair, Ed.
Internet-Draft P. Levis
Intended status: Standards Track J-L. Grimault
Expires: January 3, 2010 A. Villefranque
France Telecom
July 2, 2009
Port Range Configuration Options for PPP IPCP
draft-boucadair-pppext-portrange-option-01
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Abstract
This memo defines two IPCP (IP Configuration Protocol, [RFC1332])
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Options to be used in the context of Port Range solutions. IPCP is
the configuration protocol used when PPP (Point-to-Point Protocol,
[RFC1661]) 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. Illustration Examples . . . . . . . . . . . . . . . . . . 6
2.3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . 6
2.3.2. Successful Flow: Port Range Options supported by
both the Client and the Server . . . . . . . . . . . . 7
2.3.3. Port Range Options not supported by the Server . . . . 8
2.3.4. 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).
[I-D.boucadair-port-range] is an example of these solutions which
propose to share the same (public) IP address among several devices
and to constrain the values used as port sources to a limited set of
values. These solutions do 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.
IPv4 address exhaustion is only provided as an example of the usage
of the PPP IPCP Options defined in this memo. Other usages may be
considered in the future.
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 [RFC1661].
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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 (a.k.a., 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 formats of these IPCP Options are provided in Figure 1 and
Figure 2.
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The format of Port Range Value IPCP Option is illustrated in 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 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 length of the overall option
including Type, Length and PRV fields. 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 value is assigned. The 1 values in the Port Range
Mask indicate by their position the significant bits of the Port
Range Value.
Figure 3 provides an example of the resulting Port Range:
- Port Range Mask is set to 0001010000000000 (5120) and
- Port Range Value is set to 0000010000000000 (1024).
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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
Port values belonging to this Port Range must have the 4th bit (resp.
the sixth one), from the left, set to 0 (resp. 1). Only these port
values will be used by the peer when enforcing the configuration
conveyed by PPP IPCP.
2.3. Illustration Examples
2.3.1. Overview
These flows provide examples of the usage of IPCP to convey Port
Range Options. As illustrated in Figure 4, IPCP messages are
exchanged between a Host and a BRAS (Broadband Access Server).
1. The first example illustrates a successful IPCP exchange;
2. The second example shows the IPCP exchange that occurs when Port
Range Options are not supported by the server;
3. The third example shows the IPCP exchange that occurs when Port
Range Options are not supported by the client;
4. The fourth example shows the IPCP exchange that occurs when Port
Range Options are not supported by the client 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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2.3.2. 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 IPCP
Options are used.
+-----+ +-----+
| Host| | BRAS|
+-----+ +-----+
| |
| (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 listed below:
(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 Port
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Range Mask is set to 0.
(2) BRAS 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) BRAS 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
2.3.3. Port Range Options not supported by the Server
This example (Figure 5) depicts an exchange of messages when the BRAS
does not support IPCP Port Range Options.
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+-----+ +-----+
| Host| | BRAS|
+-----+ +-----+
| |
| (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 listed hereafter:
(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) BRAS 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) BRAS 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) BRAS 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.
2.3.4. 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| | BRAS|
+-----+ +-----+
| |
| (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) BRAS 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| | BRAS|
+-----+ +-----+
| |
| (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 described below:
(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) BRAS 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) BRAS 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 the following 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.
[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
Option for PPP IPCP", RFC 2290, February 1998.
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[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
[I-D.boucadair-port-range]
Boucadair, M., Levis, P., Bajko, G., and T. Savolainen,
"IPv4 Connectivity Access in the Context of IPv4 Address
Exhaustion", draft-boucadair-port-range-01 (work in
progress), January 2009.
Authors' Addresses
Mohamed Boucadair (editor)
France Telecom
3, Av Francois Chateau
Rennes 35000
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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