draft-ietf-ipv6-over-ppp-v2-03.txt   rfc5072.txt 
IPv6 Working Group S.Varada (Editor) Network Working Group S. Varada, Ed.
Internet-Draft Transwitch Request for Comments: 5072 Transwitch
Obsoletes: RFC 2472 (if approved) D.Haskins Obsoletes: 2472 D. Haskins
Category: Standards track Ed Allen Category: Standards Track E. Allen
IP Version 6 over PPP September 2007
<draft-ietf-ipv6-over-ppp-v2-03.txt>
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Copyright (C) The IETF Trust (2007). This document specifies an Internet standards track protocol for the
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Abstract Abstract
The Point-to-Point Protocol (PPP) provides a standard method of The Point-to-Point Protocol (PPP) provides a standard method of
encapsulating Network Layer protocol information over encapsulating network-layer protocol information over point-to-point
point-to-point links. PPP also defines an extensible Link Control links. PPP also defines an extensible Link Control Protocol, and
Protocol, and proposes a family of Network Control Protocols proposes a family of Network Control Protocols (NCPs) for
(NCPs) for establishing and configuring different network-layer establishing and configuring different network-layer protocols.
protocols.
This document defines the method for sending IPv6 packets over PPP This document defines the method for sending IPv6 packets over PPP
links, the NCP for establishing and configuring the IPv6 over PPP links, the NCP for establishing and configuring the IPv6 over PPP,
and the method for forming IPv6 link-local addresses on PPP links. and the method for forming IPv6 link-local addresses on PPP links.
It also specifies the conditions for performing Duplicate Address It also specifies the conditions for performing Duplicate Address
Detection on IPv6 global unicast addresses configured for PPP Detection on IPv6 global unicast addresses configured for PPP links
links either through stateful or stateless address either through stateful or stateless address autoconfiguration.
autoconfiguration.
This document obsoletes RFC 2472. This document obsoletes RFC 2472.
Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction ....................................................2
1.1 Specification of Requirements..............................3 1.1. Specification of Requirements ..............................3
2. Sending IPv6 Datagrams.........................................3 2. Sending IPv6 Datagrams ..........................................3
3. A PPP Network Control Protocol for IPv6........................3 3. A PPP Network Control Protocol for IPv6 .........................3
4. IPV6CP Configuration Options...................................4 4. IPV6CP Configuration Options ....................................4
4.1 Interface-Identifier.......................................5 4.1. Interface Identifier .......................................4
5. Stateless Autoconfiguration and Link-Local Addresses..........10 5. Stateless Autoconfiguration and Link-Local Addresses ............9
6. Security Considerations.......................................11 6. Security Considerations ........................................11
7. IANA Considerations...........................................12 7. IANA Considerations ............................................11
8. Acknowledgments...............................................12 8. Acknowledgments ................................................11
9. References....................................................12 9. References .....................................................12
9.1 Normative References......................................12 9.1. Normative References ......................................12
9.2 Informative references....................................13 9.2. Informative references ....................................12
Appendix A: Global Scope Addresses..............................13 Appendix A: Global Scope Addresses................................14
Appendix B: Changes from RFC-2472...............................14 Appendix B: Changes from RFC-2472.................................14
Authors' Addresses...............................................14
IPR Notice .....................................................14
Copyright Notice and Disclaimer..................................15
1. Introduction 1. Introduction
PPP has three main components: PPP has three main components:
1) A method for encapsulating datagrams over serial links. 1) A method for encapsulating datagrams over serial links.
2) A Link Control Protocol (LCP) for establishing, configuring, 2) A Link Control Protocol (LCP) for establishing, configuring, and
and testing the data-link connection. testing the data-link connection.
3) A family of Network Control Protocols (NCPs) for establishing 3) A family of Network Control Protocols (NCPs) for establishing and
and configuring different network-layer protocols. configuring different network-layer protocols.
In order to establish communications over a point-to-point link, In order to establish communications over a point-to-point link, each
each end of the PPP link must first send LCP packets to end of the PPP link must first send LCP packets to configure and test
configure and test the data link. After the link has been the data link. After the link has been established and optional
established and optional facilities have been negotiated as facilities have been negotiated as needed by the LCP, PPP must send
needed by the LCP, PPP must send NCP packets to choose and NCP packets to choose and configure one or more network-layer
configure one or more network-layer protocols. Once each of the protocols. Once each of the chosen network-layer protocols has been
chosen network-layer protocols has been configured, datagrams configured, datagrams from each network-layer protocol can be sent
from each network-layer protocol can be sent over the link. over the link.
In this document, the NCP for establishing and configuring the In this document, the NCP for establishing and configuring the IPv6
IPv6 over PPP is referred as the IPv6 Control Protocol (IPV6CP). over PPP is referred to as the IPv6 Control Protocol (IPV6CP).
The link will remain configured for communications until The link will remain configured for communications until explicit LCP
explicit LCP or NCP packets close the link down, or until some or NCP packets close the link down, or until some external event
external event occurs (power failure at the other end, carrier occurs (power failure at the other end, carrier drop, etc.).
drop, etc.).
This document obsoletes the earlier specification from RFC 2472 This document obsoletes the earlier specification from RFC 2472 [7].
[8]. Changes from RFC 2472 are listed in Appendix B. Changes from RFC 2472 are listed in Appendix B.
1.1 Specification of Requirements 1.1. Specification of Requirements
In this document, several words are used to signify the In this document, several words are used to signify the requirements
requirements of the specification. of the specification.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
"OPTIONAL" in this document are to be interpreted as described document are to be interpreted as described in [6].
in [7].
2. Sending IPv6 Datagrams 2. Sending IPv6 Datagrams
Before any IPv6 packets may be communicated, PPP MUST reach the Before any IPv6 packets may be communicated, PPP MUST reach the
Network-Layer Protocol phase, and the IPv6 Control Protocol MUST network-layer protocol phase, and the IPv6 Control Protocol MUST
reach the Opened state. reach the Opened state.
Exactly one IPv6 packet is encapsulated in the Information field Exactly one IPv6 packet is encapsulated in the Information field of
of PPP Data Link Layer frames where the Protocol field indicates PPP Data Link Layer frames where the Protocol field indicates Type
Type hex 0057 (Internet Protocol Version 6). hex 0057 (Internet Protocol Version 6).
The maximum length of an IPv6 packet transmitted over a PPP link The maximum length of an IPv6 packet transmitted over a PPP link is
is the same as the maximum length of the Information field of a the same as the maximum length of the Information field of a PPP data
PPP data link layer frame. PPP links supporting IPv6 MUST allow link layer frame. PPP links supporting IPv6 MUST allow the
the information field at least as large as the minimum link MTU information field to be at least as large as the minimum link MTU
size required for IPv6 [2]. size required for IPv6 [2].
3. A PPP Network Control Protocol for IPv6 3. A PPP Network Control Protocol for IPv6
The IPv6 Control Protocol (IPV6CP) is responsible for The IPv6 Control Protocol (IPV6CP) is responsible for configuring,
configuring, enabling, and disabling the IPv6 protocol modules enabling, and disabling the IPv6 protocol modules on both ends of the
on both ends of the point-to-point link. IPV6CP uses the same point-to-point link. IPV6CP uses the same packet exchange mechanism
packet exchange mechanism as the LCP. IPV6CP packets may not be as the LCP. IPV6CP packets may not be exchanged until PPP has
exchanged until PPP has reached the Network-Layer Protocol phase. reached the network-layer protocol phase. IPV6CP packets that are
IPV6CP packets received before this phase is reached should be received before this phase is reached should be silently discarded.
silently discarded.
The IPv6 Control Protocol is exactly the same as the LCP [1] with The IPv6 Control Protocol is exactly the same as the LCP [1] with the
the following exceptions: following exceptions:
Data Link Layer Protocol Field Data Link Layer Protocol Field
Exactly one IPV6CP packet is encapsulated in the Exactly one IPV6CP packet is encapsulated in the Information
Information field of PPP Data Link Layer frames where the field of PPP Data Link Layer frames where the Protocol field
Protocol field indicates type hex 8057 (IPv6 Control indicates type hex 8057 (IPv6 Control Protocol).
Protocol).
Code field Code field
Only Codes 1 through 7 (Configure-Request, Configure-Ack, Only Codes 1 through 7 (Configure-Request, Configure-Ack,
Configure-Nak, Configure-Reject, Terminate-Request, Configure-Nak, Configure-Reject, Terminate-Request, Terminate-
Terminate-Ack and Code-Reject) are used. Other Codes Ack and Code-Reject) are used. Other Codes should be treated
should be treated as unrecognized and should result in as unrecognized and should result in Code-Rejects.
Code-Rejects.
Timeouts Timeouts
IPV6CP packets may not be exchanged until PPP has reached IPV6CP packets may not be exchanged until PPP has reached the
the Network-Layer Protocol phase. An implementation network-layer protocol phase. An implementation should be
should be prepared to wait for Authentication and Link prepared to wait for Authentication and Link Quality
Quality Determination to finish before timing out waiting Determination to finish before timing out waiting for a
for a Configure-Ack or other response. It is suggested Configure-Ack or other response. It is suggested that an
that an implementation give up only after user implementation give up only after user intervention or a
intervention or a configurable amount of time. configurable amount of time.
Configuration Option Types Configuration Option Types
IPV6CP has a distinct set of Configuration Options. IPV6CP has a distinct set of Configuration Options.
4. IPV6CP Configuration Options 4. IPV6CP Configuration Options
IPV6CP Configuration Options allow negotiation of desirable IPv6 IPV6CP Configuration Options allow negotiation of desirable IPv6
parameters. IPV6CP uses the same Configuration Option format parameters. IPV6CP uses the same Configuration Option format defined
defined for LCP [1] but with a separate set of Options. If a for LCP [1] but with a separate set of Options. If a Configuration
Configuration Option is not included in a Configure-Request Option is not included in a Configure-Request packet, the default
packet, the default value for that Configuration Option is value for that Configuration Option is assumed.
assumed.
Up-to-date values of the IPV6CP Option Type field are specified Up-to-date values of the IPV6CP Option Type field are specified in
in the on-line database of "Assigned Numbers" maintained at the online database of "Assigned Numbers" maintained at IANA [9].
IANA [4]. Current value is assigned as follows: The current value assignment is as follows:
1 Interface-Identifier 1 Interface-Identifier
The only IPV6CP option defined in this document is the Interface The only IPV6CP option defined in this document is the interface
Identifier. Any other IPV6CP configuration options that can be identifier. Any other IPV6CP configuration options that can be
defined over time are to be defined in separate documents. defined over time are to be defined in separate documents.
4.1 Interface-Identifier 4.1. Interface Identifier
Description Description
This Configuration Option provides a way to negotiate an unique This Configuration Option provides a way to negotiate a unique, 64-
64-bit interface identifier to be used for the address bit interface identifier to be used for the address autoconfiguration
autoconfiguration [3] at the local end of the link (see [3] at the local end of the link (see Section 5). A Configure-
section 5). A Configure-Request MUST contain exactly one Request MUST contain exactly one instance of the interface-identifier
instance of the Interface-Identifier option [1]. The interface option [1]. The interface identifier MUST be unique within the PPP
identifier MUST be unique within the PPP link; i.e. upon link; i.e., upon completion of the negotiation, different interface-
completion of the negotiation different Interface-Identifier identifier values are to be selected for the ends of the PPP link.
values are to be selected for the ends of the PPP link. The The interface identifier may also be unique over a broader scope.
interface identifier may also be unique over a broader scope.
Before this Configuration Option is requested, an implementation Before this Configuration Option is requested, an implementation
chooses its tentative Interface-Identifier. The non-zero value of chooses its tentative interface identifier. The non-zero value of
the tentative Interface-Identifier SHOULD be chosen such that the the tentative interface identifier SHOULD be chosen such that the
value is unique to the link and, preferably, consistently value is unique to the link and, preferably, consistently
reproducible across initializations of the IPV6CP finite state reproducible across initializations of the IPV6CP finite state
machine (administrative Close and reOpen, reboots, etc). The machine (administrative Close and reOpen, reboots, etc.). The
rationale for preferring a consistently reproducible unique rationale for preferring a consistently reproducible unique interface
interface identifier to a completely random interface identifier identifier to a completely random interface identifier is to provide
is to provide stability to global scope addresses (see Appendix A) stability to global scope addresses (see Appendix A) that can be
that can be formed from the interface identifier formed from the interface identifier.
Assuming that interface identifier bits are numbered from 0 to Assuming that interface identifier bits are numbered from 0 to 63 in
63 in canonical bit order where the most significant bit is canonical bit order, where the most significant bit is the bit number
the bit number 0, the bit number 6 is the "u" bit (universal/local 0, the bit number 6 is the "u" bit (universal/local bit in IEEE
bit in IEEE EUI-64 [5] terminology) which indicates whether or EUI-64 [4] terminology), which indicates whether or not the interface
not the interface identifier is based on a globally unique IEEE identifier is based on a globally unique IEEE identifier (EUI-48 or
identifier (EUI-48 or EUI-64[5])(see the case 1 below). It is set EUI-64 [4])(see case 1 below). It is set to one (1) if a globally
to one (1) if a globally unique IEEE identifier is used to derive unique IEEE identifier is used to derive the interface identifier,
the interface-identifier, and it is set to zero (0) otherwise. and it is set to zero (0) otherwise.
The following are methods for choosing the tentative Interface The following are methods for choosing the tentative interface
Identifier in the preference order: identifier in the preference order:
1)If an IEEE global identifier (EUI-48 or EUI-64) is 1) If an IEEE global identifier (EUI-48 or EUI-64) is available
available anywhere on the node, it should be used to anywhere on the node, it should be used to construct the tentative
construct the tentative Interface-Identifier due to its interface identifier due to its uniqueness properties. When
uniqueness properties. When extracting an IEEE global extracting an IEEE global identifier from another device on the
identifier from another device on the node, care should be node, care should be taken that the extracted identifier is
taken that the extracted identifier is presented in presented in canonical ordering [14].
canonical ordering [14].
The only transformation from an EUI-64 identifier is to invert The only transformation from an EUI-64 identifier is to invert the
the "u" bit (universal/local bit in IEEE EUI-64 terminology). "u" bit (universal/local bit in IEEE EUI-64 terminology).
For example, for a globally unique EUI-64 identifier of the For example, for a globally unique EUI-64 identifier of the form:
form:
most-significant least significant most-significant least-significant
bit bit bit bit
|0 1|1 3|3 4|4 6| |0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3| |0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
|cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee| |cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
where "c" are the bits of the assigned company_id, "0" is the
where "c" are the bits of the assigned company_id, "0" is value of the universal/local bit to indicate global scope, "g" is
the value of the universal/local bit to indicate global the group/individual bit, and "e" are the bits of the extension
scope, "g" is group/individual bit, and "e" are the bits identifier, the IPv6 interface identifier would be of the form:
of the extension identifier, the IPv6 interface identifier
would be of the form:
most-significant least-significant most-significant least-significant
bit bit bit bit
|0 1|1 3|3 4|4 6| |0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3| |0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
|cccccc1gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee| |cccccc1gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
The only change is inverting the value of the The only change is inverting the value of the universal/local bit.
universal/local bit.
In the case of a EUI-48 identifier, it is first converted In the case of a EUI-48 identifier, it is first converted to the
to the EUI-64 format by inserting two bytes, with EUI-64 format by inserting two bytes, with hexa-decimal values of
hexa-decimal values of 0xFF and 0xFE, in the middle of the 0xFF and 0xFE, in the middle of the 48-bit MAC (between the
48 bit MAC (between the company_id and extension identifier company_id and extension identifier portions of the EUI-48 value).
portions of the EUI-48 value). For example, for a globally For example, for a globally unique 48-bit EUI-48 identifier of the
unique 48 bit EUI-48 identifier of the
form: form:
most-significant least-significant most-significant least-significant
bit bit bit bit
|0 1|1 3|3 4| |0 1|1 3|3 4|
|0 5|6 1|2 7| |0 5|6 1|2 7|
+----------------+----------------+----------------+ +----------------+----------------+----------------+
|cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee| |cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+ +----------------+----------------+----------------+
where "c" are the bits of the assigned company_id, "0" is where "c" are the bits of the assigned company_id, "0" is the
the value of the universal/local bit to indicate global value of the universal/local bit to indicate global scope, "g" is
scope, "g" is group/individual bit, and "e" are the bits the group/individual bit, and "e" are the bits of the extension
of the extension identifier, the IPv6 interface identifier identifier, the IPv6 interface identifier would be of the form:
would be of the form:
most-significant least-significant most-significant least-significant
bit bit bit bit
|0 1|1 3|3 4|4 6| |0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3| |0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
|cccccc1gcccccccc|cccccccc11111111|11111110eeeeeeee|eeeeeeeeeeeeeeee| |cccccc1gcccccccc|cccccccc11111111|11111110eeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+ +----------------+----------------+----------------+----------------+
2) If an IEEE global identifier is not available, a different 2) If an IEEE global identifier is not available, a different source
source of uniqueness should be used. Suggested sources of of uniqueness should be used. Suggested sources of uniqueness
uniqueness include link-layer addresses, machine serial include link-layer addresses, machine serial numbers, et cetera.
numbers, et cetera. In this case, the "u" bit of the
interface-identifier MUST be set to zero (0).
3) If a good source of uniqueness cannot be found, it is
recommended that a random number be generated. In this
case, the "u" bit of the interface-identifier MUST be set to
zero (0).
Good sources [1] of uniqueness or randomness are required for In this case, the "u" bit of the interface identifier MUST be set
the Interface-Identifier negotiation to succeed. If neither an to zero (0).
unique number or a random number can be generated, it is
recommended that a zero value be used for the Interface
Identifier transmitted in the Configure-Request. In this case
the PPP peer may provide a valid non-zero Interface-Identifier
in its response as described below. Note that if at least one of
the PPP peers is able to generate separate non-zero numbers for
itself and its peer, the identifier negotiation will succeed.
When a Configure-Request is received with the Interface 3) If a good source of uniqueness cannot be found, it is recommended
Identifier Configuration Option and the receiving peer that a random number be generated. In this case, the "u" bit of
implements this option, the received Interface-Identifier is the interface identifier MUST be set to zero (0).
compared with the Interface-Identifier of the last
Configure-Request sent to the peer. Depending on the result of the
comparison an implementation MUST respond in one of the
following ways:
If the two Interface-Identifiers are different but the received Good sources [1] of uniqueness or randomness are required for the
Interface-Identifier is zero, a Configure-Nak is sent with a interface identifier negotiation to succeed. If neither a unique
non-zero Interface-Identifier value suggested for use by the number nor a random number can be generated, it is recommended that a
remote peer. Such a suggested Interface-Identifier MUST be zero value be used for the interface identifier transmitted in the
different from the Interface-Identifier of the last Configure-Request. In this case, the PPP peer may provide a valid
Configure-Request sent to the peer. It is recommended that the non-zero interface identifier in its response as described below.
value suggested be consistently reproducible across Note that if at least one of the PPP peers is able to generate
initializations of the IPV6CP finite state machine (administrative separate non-zero numbers for itself and its peer, the identifier
Close and reOpen, reboots, etc). The "u" (universal/local) bit of negotiation will succeed.
the suggested identifier MUST be set to zero (0) regardless of its
source unless the globally unique EUI-48/EUI-64 derived
identifier is provided for the exclusive use by the remote peer.
If the two Interface-Identifiers are different and the received When a Configure-Request is received with the Interface-Identifier
Interface-Identifier is not zero, the Interface-Identifier MUST be Configuration Option and the receiving peer implements this option,
acknowledged, i.e. a Configure-Ack is sent with the requested the received interface identifier is compared with the interface
Interface-Identifier, meaning that the responding peer agrees with identifier of the last Configure-Request sent to the peer. Depending
the Interface-Identifier requested. on the result of the comparison, an implementation MUST respond in
one of the following ways:
If the two Interface-Identifiers are equal and are not zero, If the two interface identifiers are different but the received
Configure-Nak MUST be sent specifying a different non-zero interface identifier is zero, a Configure-Nak is sent with a non-zero
Interface-Identifier value suggested for use by the remote peer. interface-identifier value suggested for use by the remote peer.
Such a suggested interface identifier MUST be different from the
interface identifier of the last Configure-Request sent to the peer.
It is recommended that the value suggested be consistently It is recommended that the value suggested be consistently
reproducible across initializations of the IPV6CP finite state reproducible across initializations of the IPV6CP finite state
machine (administrative Close and reOpen, reboots, etc). The "u" machine (administrative Close and reOpen, reboots, etc). The "u"
(universal/local) bit of the suggested identifier MUST be set to (universal/local) bit of the suggested identifier MUST be set to zero
zero (0) regardless of its source unless the globally unique (0) regardless of its source unless the globally unique EUI-48/EUI-64
EUI-48/EUI-64 derived identifier is provided for the exclusive use derived identifier is provided for the exclusive use by the remote
by the remote peer. peer.
If the two Interface-Identifiers are equal to zero, the Interface If the two interface identifiers are different and the received
Identifiers negotiation MUST be terminated by transmitting the interface identifier is not zero, the interface identifier MUST be
Configure-Reject with the Interface-Identifier value set to zero. acknowledged, i.e., a Configure-Ack is sent with the requested
In this case a unique Interface-Identifier can not be negotiated. interface identifier, meaning that the responding peer agrees with
the interface identifier requested.
If the two interface identifiers are equal and are not zero,
Configure-Nak MUST be sent specifying a different non-zero
interface-identifier value suggested for use by the remote peer. It
is recommended that the value suggested be consistently reproducible
across initializations of the IPV6CP finite state machine
(administrative Close and reOpen, reboots, etc). The "u"
(universal/local) bit of the suggested identifier MUST be set to zero
(0) regardless of its source unless the globally unique EUI-48/EUI-64
derived identifier is provided for the exclusive use by the remote
peer.
If the two interface identifiers are equal to zero, the interface
identifier's negotiation MUST be terminated by transmitting the
Configure-Reject with the interface-identifier value set to zero. In
this case, a unique interface identifier cannot be negotiated.
If a Configure-Request is received with the Interface-Identifier If a Configure-Request is received with the Interface-Identifier
Configuration Option and the receiving peer does not implement Configuration Option and the receiving peer does not implement this
this option, Configure-Rej is sent. option, Configure-Reject is sent.
A new Configure-Request SHOULD NOT be sent to the peer until A new Configure-Request SHOULD NOT be sent to the peer until normal
normal processing would cause it to be sent (that is, until a processing would cause it to be sent (that is, until a Configure-Nak
Configure-Nak is received or the Restart timer runs out [1]). is received or the Restart timer runs out [1]).
A new Configure-Request MUST NOT contain the Interface-Identifier A new Configure-Request MUST NOT contain the interface-identifier
option if a valid Interface-Identifier Configure-Reject is option if a valid Interface-Identifier Configure-Reject is received.
received.
Reception of a Configure-Nak with a suggested Interface-Identifier Reception of a Configure-Nak with a suggested interface identifier
different from that of the last Configure-Nak sent to the peer different from that of the last Configure-Nak sent to the peer
indicates an unique Interface-Identifier. In this case a new indicates a unique interface identifier. In this case, a new
Configure-Request MUST be sent with the identifier value suggested Configure-Request MUST be sent with the identifier value suggested in
in the last Configure-Nak from the peer. But if the received the last Configure-Nak from the peer. But if the received interface
Interface-Identifier is equal to the one sent in the last identifier is equal to the one sent in the last Configure-Nak, a new
Configure-Nak, a new Interface-Identifier MUST be chosen. In this interface identifier MUST be chosen. In this case, a new Configure-
case, a new Configure-Request SHOULD be sent with the new Request SHOULD be sent with the new tentative interface identifier.
tentative Interface-Identifier. This sequence (transmit This sequence (transmit Configure-Request, receive Configure-Request,
Configure-Request, receive Configure-Request, transmit transmit Configure-Nak, receive Configure-Nak) might occur a few
Configure-Nak, receive Configure-Nak) might occur a few times, but times, but it is extremely unlikely to occur repeatedly. More
it is extremely unlikely to occur repeatedly. More likely, the likely, the interface identifiers chosen at either end will quickly
Interface-Identifiers chosen at either end will quickly diverge, diverge, terminating the sequence.
terminating the sequence.
If negotiation of the Interface-Identifier is required, and the If negotiation of the interface identifier is required, and the peer
peer did not provide the option in its Configure-Request, the did not provide the option in its Configure-Request, the option
option SHOULD be appended to a Configure-Nak. The tentative value SHOULD be appended to a Configure-Nak. The tentative value of the
of the Interface-Identifier given must be acceptable as the remote interface identifier given must be acceptable as the remote interface
Interface-Identifier; i.e. it should be different from the identifier; i.e., it should be different from the identifier value
identifier value selected for the local end of the PPP link. The selected for the local end of the PPP link. The next Configure-
next Configure-Request from the peer may include this option. If Request from the peer may include this option. If the next
the next Configure-Request does not include this option the peer Configure-Request does not include this option, the peer MUST NOT
MUST NOT send another Configure-Nak with this option included. It send another Configure-Nak with this option included. It should
should assume that the peer's implementation does not support this assume that the peer's implementation does not support this option.
option.
By default, an implementation SHOULD attempt to negotiate the By default, an implementation SHOULD attempt to negotiate the
Interface-Identifier for its end of the PPP connection. interface identifier for its end of the PPP connection.
A summary of the Interface-Identifier Configuration Option format A summary of the Interface-Identifier Configuration Option format is
is shown below. The fields are transmitted from left to right. shown below. The fields are transmitted from left to right.
0 1 2 3 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 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 | Interface-Identifier (MS Bytes) | Type | Length | Interface-Identifier (MS Bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Interface-Identifier (cont) Interface-Identifier (cont)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Interface-Identifier (LS Bytes) | Interface-Identifier (LS Bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 9, line 44 skipping to change at page 9, line 28
Interface-Identifier (LS Bytes) | Interface-Identifier (LS Bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
1 1
Length Length
10 10
Interface-Identifier Interface-Identifier
The 64-bit Interface-Identifier, which is very likely to be The 64-bit interface identifier, which is very likely to be
unique on the link, or zero if a good source of uniqueness unique on the link, or zero if a good source of uniqueness
can not be found. can not be found.
Default Default
If no valid interface identifier can be successfully If no valid interface identifier can be successfully
negotiated, no default Interface-Identifier value should be negotiated, no default interface-identifier value should be
assumed. The procedures for recovering from such a case are assumed. The procedures for recovering from such a case are
unspecified. One approach is to manually configure the unspecified. One approach is to manually configure the
interface identifier of the interface. interface identifier of the interface.
5. Stateless Autoconfiguration and Link-Local Addresses 5. Stateless Autoconfiguration and Link-Local Addresses
The Interface-Identifier of IPv6 unicast addresses [6] of a PPP The interface identifier of IPv6 unicast addresses [5] of a PPP
interface, SHOULD be negotiated in the IPV6CP phase of the PPP interface SHOULD be negotiated in the IPV6CP phase of the PPP
connection setup (see section 4.1). If no valid Interface connection setup (see Section 4.1). If no valid interface identifier
Identifier has been successfully negotiated, procedures for has been successfully negotiated, procedures for recovering from such
recovering from such a case are unspecified. One approach is to a case are unspecified. One approach is to manually configure the
manually configure the Interface-Identifier of the interface. interface identifier of the interface.
The negotiated Interface-Identifier is used by the local end of The negotiated interface identifier is used by the local end of the
the PPP link to autoconfigure IPv6 link-local unicast address for PPP link to autoconfigure an IPv6 link-local unicast address for the
the PPP interface. However, it SHOULD NOT be assumed that the PPP interface. However, it SHOULD NOT be assumed that the same
same Interface-Identifier is used in configuring global unicast interface identifier is used in configuring global unicast addresses
addresses for the PPP interface using IPv6 stateless address for the PPP interface using IPv6 stateless address autoconfiguration
autoconfiguration [3]. The PPP peer MAY generate one or more [3]. The PPP peer MAY generate one or more interface identifiers,
Interface Identifiers, for instance, using a method described in for instance, using a method described in [8], to autoconfigure one
[9], to autoconfigure one or more global unicast addresses. or more global unicast addresses.
As long as the Interface-Identifier is negotiated in the IPV6CP As long as the interface identifier is negotiated in the IPV6CP phase
phase of the PPP connection setup, it is redundant to perform of the PPP connection setup, it is redundant to perform duplicate
duplicate address detection (DAD) as a part of the IPv6 Stateless address detection (DAD) as a part of the IPv6 Stateless Address
Address Autoconfiguration protocol [3] on the IPv6 link-local Autoconfiguration protocol [3] on the IPv6 link-local address
address generated by the PPP peer. It may also be redundant to generated by the PPP peer. It may also be redundant to perform DAD
perform DAD on any global unicast addresses configured (using an on any global unicast addresses configured (using an interface
Interface-Identifier that is either negotiated during IPV6CP or identifier that is either negotiated during IPV6CP or generated, for
generated, for instance, as per [9]) for the interface as part of instance, as per [8]) for the interface as part of the IPv6 Stateless
the IPv6 Stateless Address Autoconfiguration protocol [3] provided Address Autoconfiguration protocol [3] provided that the following
that the following two conditions are met: two conditions are met:
1) The prefixes advertised, through the Router Advertisement 1) The prefixes advertised through the Router Advertisement
messages, by the access router terminating the PPP link are messages by the access router terminating the PPP link are
exclusive to the PPP link. exclusive to the PPP link.
2) The access router terminating the PPP link does not 2) The access router terminating the PPP link does not
autoconfigure any IPv6 global unicast addresses from the autoconfigure any IPv6 global unicast addresses from the
prefixes that it advertises. prefixes that it advertises.
Therefore, it is RECOMMENDED that for PPP links with the IPV6CP Therefore, it is RECOMMENDED that for PPP links with the IPV6CP
Interface-Identifier option enabled and satisfying the interface-identifier option enabled and satisfying the aforementioned
aforementioned two conditions, the default value of the two conditions, the default value of the DupAddrDetectTransmits
DupAddrDetectTransmits autoconfiguration variable [3] is set to autoconfiguration variable [3] is set to zero by the system
zero by the system management. 3GPP2 networks are an example of a management. 3GPP2 networks are an example of a technology that uses
technology that uses PPP to enable a host to obtain an IPv6 global PPP to enable a host to obtain an IPv6 global unicast address and
unicast address and satisfies the aforementioned two conditions satisfies the aforementioned two conditions [10]. 3GPP networks are
[10]. 3GPP networks are another example [11] & [13]. another example ([11] [13]).
Link-local addresses Link-local addresses
Link-local addresses of PPP interfaces have the following Link-local addresses of PPP interfaces have the following format:
format:
| 10 bits | 54 bits | 64 bits | | 10 bits | 54 bits | 64 bits |
+----------+------------------------+-----------------------------+ +----------+------------------------+-----------------------------+
|1111111010| 0 | Interface-Identifier | |1111111010| 0 | Interface-Identifier |
+----------+------------------------+-----------------------------+ +----------+------------------------+-----------------------------+
The most significant 10 bits of the address is the Link-Local prefix
The most significant 10 bits of the address is the Link-Local FE80::. 54 zero bits pad out the address between the Link-Local
prefix FE80::. 54 zero bits pad out the address between the prefix and the interface-identifier fields.
Link-Local prefix and the Interface-Identifier fields.
6. Security Considerations 6. Security Considerations
Lack of link security, such as authentication, trigger the Lack of link security, such as authentication, trigger the security
security concerns raised in [3] when stateless address auto- concerns raised in [3] when the stateless address autoconfiguration
configuration method is employed for the generation of global method is employed for the generation of global unicast IPv6
unicast IPv6 addresses out of interface identifiers that are addresses out of interface identifiers that are either negotiated
either negotiated through the IPV6CP or generated, for instance, through the IPV6CP or generated, for instance, using a method
using a method described in [9]. Thus, the mechanisms that are described in [8]. Thus, the mechanisms that are appropriate for
appropriate for ensuring PPP link security are addressed below ensuring PPP link security are addressed below, together with the
together with the reference to a generic threat model. reference to a generic threat model.
The mechanisms that are appropriate for ensuring PPP link The mechanisms that are appropriate for ensuring PPP link Security
Security are: 1) Access Control Lists that apply filters on are: 1) Access Control Lists that apply filters on traffic received
traffic received over the link for enforcing admission policy, 2) over the link for enforcing admission policy, 2) an Authentication
an Authentication protocol that facilitates negotiations between protocol that facilitates negotiations between peers [15] to select
peers [15] to select an authentication method (e.g., MD5 [16]) an authentication method (e.g., MD5 [16]) for validation of the peer,
for validation of the peer, and 3) an Encryption protocol that and 3) an Encryption protocol that facilitates negotiations between
facilitates negotiations between peers to select encryption peers to select encryption algorithms (or crypto-suites) to ensure
algorithms (or, crypto-suites) to ensure data confidentiality data confidentiality [17].
[17]).
There are certain threats associated with peer interactions on a There are certain threats associated with peer interactions on a PPP
PPP link even with one or more of the above security measures in link even with one or more of the above security measures in place.
place. For instance, using MD5 authentication method [16] exposes For instance, using the MD5 authentication method [16] exposes one to
one to replay attack, where in which, an attacker could intercept replay attack, where an attacker could intercept and replay a
and replay a station's identity and password hash to get access to station's identity and password hash to get access to a network. The
a network. The user of this specification is advised to refer to user of this specification is advised to refer to [15], which
[15], which presents a generic threat model, for an understanding presents a generic threat model, for an understanding of the threats
of the threats posed to the security of a link. The reference posed to the security of a link. The reference [15] also gives a
[15] also gives framework to specify requirements for the framework to specify requirements for the selection of an
selection of an authentication method for a given application. authentication method for a given application.
7. IANA Considerations 7. IANA Considerations
The editor has no specific recommendations for the IANA on the The IANA has assigned value 1 for the Type field of the IPv6 datagram
assignment of a value for the Type field of IPv6 datagram interface-identifier option specified in this document. The current
Interface-Identifier option specified in this specification. The assignment is up-to-date at [9].
current assignment is up-to-date at [4]. However, the reference
to the RFC number needs to be updated.
8. Acknowledgments 8. Acknowledgments
This document borrows from the Magic-Number LCP option and as such This document borrows from the Magic-Number LCP option and as such is
is partially based on previous work done by the PPP working group. partially based on previous work done by the PPP working group.
The editor is grateful for the input provided by members of the The editor is grateful for the input provided by members of the IPv6
IPv6 community in the spirit of updating the RFC 2472. Thanks, in community in the spirit of updating RFC 2472. Thanks, in particular,
particular, go to Pete Barany and Karim El-malki for their go to Pete Barany and Karim El Malki for their technical
technical contributions. Also, thanks to Alex Conta, for a contributions. Also, thanks to Alex Conta for a thorough review,
thorough reviewing, Stephen Kent, for helping with security Stephen Kent for helping with security aspects, and Spencer Dawkins
aspects, Spencer Dawkins and Pekka Savola for the nits. Finally, and Pekka Savola for the nits. Finally, the author is grateful to
the author is grateful to Jari Arkko, for his initiation to bring Jari Arkko for his initiation to bring closure to this specification.
closure to this specification.
9. References 9. References
9.1 Normative References 9.1. Normative References
[1] Simpson, W., "The Point-to-Point Protocol," STD 51, RFC
1661, July 1994.
[2] Deering, S., and R. Hinden, Editors, "Internet Protocol, [1] Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD 51,
Version 6 (IPv6) Specification," RFC 2460, December 1998. RFC 1661, July 1994.
[3] Thomson, S., and T. Narten, "IPv6 Stateless Address [2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Autoconfiguration," RFC 2462, December 1998. Specification", RFC 2460, December 1998.
[4] IANA, "Assigned Numbers," http://www.iana.org/numbers.html [3] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address
Autoconfiguration", RFC 4862, September 2007.
[5] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64) [4] IEEE, "Guidelines For 64-bit Global Identifier (EUI-64)",
Registration Authority", April 2004. http://standards.ieee.org/regauth/oui/tutorials/EUI64.html
[6] Hinden, R., and S. Deering, "IP Version 6 Addressing [5] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
[7] Bradner, S., "Key words for use in RFCs to Indicate Requirement [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels," BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[8] Haskin D., and E. Allen, "IP Version 6 over PPP," RFC 2472, [7] Haskin, D. and E. Allen, "IP Version 6 over PPP", RFC 2472,
December 1998. December 1998.
[9] Narten T., et. al., " Privacy Extensions for Stateless Address [8] Narten T., Draves, R., and S. Krishnan, "Privacy Extensions for
Autoconfiguration in IPv6," draft-ietf-ipv6-privacy-addrs-v2- Stateless Address Autoconfiguration in IPv6", RFC 4941,
05, August 2006. September 2007.
9.2 Informative references 9.2. Informative references
[9] IANA, "Assigned Numbers," http://www.iana.org/numbers.html
[10] 3GPP2 X.S0011-002-C v1.0, "cdma2000 Wireless IP Network [10] 3GPP2 X.S0011-002-C v1.0, "cdma2000 Wireless IP Network
Standard: Simple IP and Mobile IP Access Services," September Standard: Simple IP and Mobile IP Access Services," September
2003. 2003.
[11] 3GPP TS 29.061 V6.4.0, "Interworking between the Public Land [11] 3GPP TS 29.061 V6.4.0, "Interworking between the Public Land
Mobile Network (PLMN) Supporting packet based services and Mobile Network (PLMN) Supporting packet based services and
Packet Data Networks (PDN) (Release 6)," April 2005. Packet Data Networks (PDN) (Release 6)," April 2005.
[12] Droms, E., et al., "Dynamic Host Configuration Protocol for [12] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C.,
IPv6 (DHCPv6)," RFC 3315, July 2003. and M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[13] 3GPP TS 23.060 v6.8.0, "General Packet Radio Service (GPRS); [13] 3GPP TS 23.060 v6.8.0, "General Packet Radio Service (GPRS);
Service description; Stage 2 (Release 6)," March 2005. Service description; Stage 2 (Release 6)," March 2005.
[14] Narten T., and C. Burton, "A Caution On The Canonical Ordering [14] Narten, T. and C. Burton, "A Caution On The Canonical Ordering
Of Link-Layer Addresses," RFC 2469, December 1998. Of Link-Layer Addresses", RFC 2469, December 1998.
[15] Aboba, R., et. al., "Extensible Authentication Protocol," RFC [15] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol (EAP)", RFC
3748, June 2004. 3748, June 2004.
[16] Rivest, R., "The MD5 Message-Digest Algorithm," RFC 1321, April [16] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
1992. 1992.
[17] Meyer, G., "The PPP Encryption Control Protocol (ECP)," RFC [17] Meyer, G., "The PPP Encryption Control Protocol (ECP)", RFC
1968, June 1996. 1968, June 1996.
Appendix A: Global Scope Addresses Appendix A: Global Scope Addresses
A node on the PPP link MUST create global unicast addresses either A node on the PPP link creates global unicast addresses either
through stateless or stateful address auto-configuration through stateless or stateful address autoconfiguration mechanisms.
mechanisms. In the stateless address auto-configuration [3], the In the stateless address autoconfiguration [3], the node relies on
node relies on sub-net prefixes advertised by the router via the sub-net prefixes advertised by the router via the Router
Router Advertisement messages to obtain global unicast addresses Advertisement messages to obtain global unicast addresses from an
from an interface identifier. In the stateful address auto- interface identifier. In the stateful address autoconfiguration, the
configuration, the host relies on a Stateful Server, like, DHCPv6 host relies on a Stateful Server, like DHCPv6 [12], to obtain global
[12], to obtain global unicast addresses. unicast addresses.
Appendix B: Changes from RFC-2472 Appendix B: Changes from RFC 2472
The following changes were made from RFC-2472 "IPv6 over PPP": The following changes were made from RFC 2472 "IPv6 over PPP":
- Minor updates to sections 3 and 4 - Minor updates to Sections 3 and 4
- Updated the text in section 4.1 to include the reference to - Updated the text in Section 4.1 to include the reference to
Appendix A and minor text clarifications. Appendix A and minor text clarifications.
- Removed the section 4.2 on IPv6-Compression-Protocol, based on - Removed Section 4.2 on IPv6-Compression-Protocol based on IESG
the IESG recommendation, and created a new standards track recommendation, and created a new standards-track document to
draft to cover the negotiation of IPv6 datagram compression cover negotiation of the IPv6 datagram compression protocol using
protocol using IPV6CP. IPV6CP.
- Updated the text in Section 5 to: (a) allow the use of one or - Updated the text in Section 5 to: (a) allow the use of one or more
more Interface-Identifiers generated by a peer, in addition to interface identifiers generated by a peer, in addition to the use
the use of Interface-identifier negotiated between peers of the of interface identifier negotiated between peers of the link, in
link, in the creation of global unicast addresses for the local the creation of global unicast addresses for the local PPP
PPP interface, and (b) identify cases against the DAD of interface, and (b) identify cases against the DAD of created non-
created non-link-local addresses. link-local addresses.
- Added new and updated references. - Added new and updated references.
- Added the Appendix A - Added Appendix A
Authors' Addresses Authors' Addresses
Dimitry Haskin Dimitry Haskin
Ed Allen Ed Allen
Srihari Varada (Editor) Srihari Varada (Editor)
TranSwitch Corporation TranSwitch Corporation
3 Enterprise Dr. 3 Enterprise Dr.
Shelton, CT 06484. US. Shelton, CT 06484. US.
Phone: +1 203 929 8810 Phone: +1 203 929 8810
EMail: varada@txc.com EMail: varada@ieee.org
IPR Notice Full Copyright Statement
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Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to rights
in RFC documents can be found in BCP 78 and BCP 79.
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found in BCP 78 and BCP 79.
This document and the information contained herein are provided Copies of IPR disclosures made to the IETF Secretariat and any
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 End of changes. 105 change blocks. 
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