IP Version 6 over PPP
draft-ietf-ipngwg-ipv6-over-ppp-05
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 2472.
|
|
|---|---|---|---|
| Authors | Dimitry L. Haskin , Edward C. Allen | ||
| Last updated | 2013-03-02 (Latest revision 1998-01-29) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 2472 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-ipngwg-ipv6-over-ppp-05
Internet-Draft IP Version 6 over PPP February 1998
Internet Engineering Task Force
INTERNET-DRAFT Dimitry Haskin
Expires August 1998 Ed Allen
<draft-ietf-ipngwg-ipv6-over-ppp-05.txt> Bay Networks, Inc.
February 1998
IP Version 6 over PPP
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months.
Internet-Drafts may be updated, replaced, or obsoleted by other
documents at any time. It is not appropriate to use Internet-Drafts
as reference material or to cite them other than as a ``working
draft'' or ``work in progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
Abstract
The Point-to-Point Protocol (PPP) [1] provides a standard method of
encapsulating Network Layer protocol information over point-to-point
links. PPP also defines an extensible Link Control Protocol, and
proposes a family of Network Control Protocols (NCPs) for establishing
and configuring different network-layer protocols.
This document defines the method for transmission of IP Version 6 [2]
packets over PPP links as well as the Network Control Protocol (NCP)
for establishing and configuring the IPv6 over PPP. It also specifies
the method of forming IPv6 link-local addresses on PPP links.
Expires August 1998 [Page 1]
Internet-Draft IP Version 6 over PPP February 1998
Table of Contents
1. Introduction .......................................... 3
1.1. Specification of Requirements ...................... 3
2. Sending IPv6 Datagrams ................................ 3
3. A PPP Network Control Protocol for IPv6 ............... 4
4. IPV6CP Configuration Options .......................... 5
4.1. Interface-Identifier .............................. 5
5. Stateless Autoconfiguration and Link-Local Addresses .. 11
6 Security Considerations ............................... 12
7 Acknowledgments ....................................... 12
8 Changes from RFC-2023 ................................. 12
9 References ............................................ 13
10 Authors' Addresses .................................... 13
Expires August 1998 [Page 2]
Internet-Draft IP Version 6 over PPP February 1998
1. Introduction
PPP has three main components:
1. A method for encapsulating datagrams over serial links.
2. A Link Control Protocol (LCP) for establishing, configuring, and
testing the data-link connection.
3. A family of Network Control Protocols (NCPs) for establishing and
configuring different network-layer protocols.
In order to establish communications over a point-to-point link, each
end of the PPP link must first send LCP packets to configure and test
the data link. After the link has been established and optional
facilities have been negotiated as needed by the LCP, PPP must send
NCP packets to choose and configure one or more network-layer
protocols. Once each of the chosen network-layer protocols has been
configured, datagrams from each network-layer protocol can be sent
over the link.
In this document, the NCP for establishing and configuring the IPv6
over PPP is referred as the IPv6 Control Protocol (IPV6CP).
The link will remain configured for communications until explicit LCP
or NCP packets close the link down, or until some external event
occurs (power failure at the other end, carrier drop, etc.).
1.1. Specification of Requirements
In this document, several words are used to signify the requirements
of the specification.
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 [7].
2. Sending IPv6 Datagrams
Before any IPv6 packets may be communicated, PPP MUST reach the
Network-Layer Protocol phase, and the IPv6 Control Protocol MUST reach
the Opened state.
Expires August 1998 [Page 3]
Internet-Draft IP Version 6 over PPP February 1998
Exactly one IPv6 packet is encapsulated in the Information field of
PPP Data Link Layer frames where the Protocol field indicates type hex
0057 (Internet Protocol Version 6).
The maximum length of an IPv6 packet transmitted over a PPP link is
the same as the maximum length of the Information field of a PPP data
link layer frame. PPP links supporting IPv6 MUST allow the
information field at least as large as the minimum link MTU size
required for IPv6 [2].
3. A PPP Network Control Protocol for IPv6
The IPv6 Control Protocol (IPV6CP) is responsible for configuring,
enabling, and disabling the IPv6 protocol modules on both ends of the
point-to-point link. IPV6CP uses the same packet exchange mechanism
as the Link Control Protocol (LCP). IPV6CP packets may not be
exchanged until PPP has reached the Network-Layer Protocol phase.
IPV6CP packets received before this phase is reached should be
silently discarded.
The IPv6 Control Protocol is exactly the same as the Link Control
Protocol [1] with the following exceptions:
Data Link Layer Protocol Field
Exactly one IPV6CP packet is encapsulated in the Information
field of PPP Data Link Layer frames where the Protocol field
indicates type hex 8057 (IPv6 Control Protocol).
Code field
Only Codes 1 through 7 (Configure-Request, Configure-Ack,
Configure-Nak, Configure-Reject, Terminate-Request, Terminate-
Ack and Code-Reject) are used. Other Codes should be treated
as unrecognized and should result in Code-Rejects.
Timeouts
IPV6CP packets may not be exchanged until PPP has reached the
Network-Layer Protocol phase. An implementation should be
prepared to wait for Authentication and Link Quality
Determination to finish before timing out waiting for a
Configure-Ack or other response. It is suggested that an
implementation give up only after user intervention or a
Expires August 1998 [Page 4]
Internet-Draft IP Version 6 over PPP February 1998
configurable amount of time.
Configuration Option Types
IPV6CP has a distinct set of Configuration Options.
4. IPV6CP Configuration Options
IPV6CP Configuration Options allow negotiation of desirable IPv6
parameters. IPV6CP uses the same Configuration Option format defined
for LCP [1], with a separate set of Options. If a Configuration
Option is not included in a Configure-Request packet, the default
value for that Configuration Option is assumed.
Up-to-date values of the IPV6CP Option Type field are specified in the
most recent "Assigned Numbers" RFC [4].
The only IPV6CP option defined in this document is the Interface-
Identifier option (Option Type 1). Any other IPV6CP configuration
options that can be defined over time are to be defined in separate
documents.
4.1. Interface-Identifier
Description
This Configuration Option provides a way to negotiate a unique 64-
bit interface identifier to be used for the address
autoconfiguration [3] at the local end of the link (see section 5).
A Configure-Request MUST contain exactly one instance of the
Interface-Identifier option [1]. The interface identifier MUST be
unique within the PPP link; i.e. upon completion of the negotiation
different Interface-Identifier values are to be selected for the
ends of the PPP link. The interface identifier MAY also be unique
over a broader scope.
Before this Configuration Option is requested, an implementation
chooses its tentative Interface-Identifier. The non-zero value of
the tentative Interface-Identifier SHOULD be chosen such that the
value is both unique to the link and, if possible, consistently
reproducible across initializations of the IPV6CP finite state
machine (administrative Close and reOpen, reboots, etc). The
rationale for preferring a consistently reproducible unique
Expires August 1998 [Page 5]
Internet-Draft IP Version 6 over PPP February 1998
interface identifier to a completely random interface identifier is
to provide stability to global scope addresses that can be formed
from the interface identifier.
Assuming that interface identifier bits are numbered from 0 to 63 in
canonical bit order where the most significant bit is the bit number
0, the bit number 6 is the "u" bit (universal/local bit in IEEE
EUI-64 [5] terminology) which indicates whether or not the interface
identifier is based on a globally unique IEEE identifier (EUI-48 or
EUI-64 [5]) (see the case 1 below). It is set to one (1) if a
globally unique IEEE identifier is used to derive the interface
identifier, and it is set to zero (0) otherwise.
The following are methods for choosing the tentative Interface
Identifier in the preference order:
1) If an IEEE global identifier (EUI-48 or EUI-64) is available
anywhere on the node, it should be used to construct the
tentative Interface-Identifier due to its uniqueness properties.
When extracting an IEEE global identifier from another device on
the node, care should be taken to that the extracted identifier
is presented in canonical ordering [8].
The only transformation from an EUI-64 identifier is to invert
the "u" bit (universal/local bit in IEEE EUI-64 terminology).
For example, for a globally unique EUI-64 identifier of the form:
most-significant least-significant
bit bit
|0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+
|cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+
where "c" are the bits of the assigned company_id, "0" is the
value of the universal/local bit to indicate global scope, "g" is
group/individual bit, and "e" are the bits of the extension
identifier, the IPv6 interface identifier would be of the form:
Expires August 1998 [Page 6]
Internet-Draft IP Version 6 over PPP February 1998
most-significant least-significant
bit bit
|0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+
|cccccc1gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+
The only change is inverting the value of the universal/local
bit.
In the case of a EUI-48 identifier, it is first converted to the
EUI-64 format by inserting two bytes, with hexadecimal values of
0xFF and 0xFE, in the middle of the 48 bit MAC (between the
company_id and extension-identifier portions of the EUI-48
value). For example, for a globally unique 48 bit EUI-48
identifier of the form:
most-significant least-significant
bit bit
|0 1|1 3|3 4|
|0 5|6 1|2 7|
+----------------+----------------+----------------+
|cccccc0gcccccccc|cccccccceeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+
where "c" are the bits of the assigned company_id, "0" is the
value of the universal/local bit to indicate global scope, "g" is
group/individual bit, and "e" are the bits of the extension
identifier, the IPv6 interface identifier would be of the form:
most-significant least-significant
bit bit
|0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+
|cccccc1gcccccccc|cccccccc11111111|11111110eeeeeeee|eeeeeeeeeeeeeeee|
+----------------+----------------+----------------+----------------+
2) If an IEEE global identifier is not available a different source
of uniqueness should be used. Suggested sources of uniqueness
include link-layer addresses, machine serial numbers, et cetera.
In this case the "u" bit of the interface identifier MUST be set
Expires August 1998 [Page 7]
Internet-Draft IP Version 6 over PPP February 1998
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 the
Interface-Identifier negotiation to succeed. If neither a 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-Identifier
Configuration Option and the receiving peer implements this option,
the received Interface-Identifier is 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
Interface-Identifier is zero, a Configure-Nak is sent with a non-
zero 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
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 different and the received
Interface-Identifier is not zero, the Interface-Identifier MUST be
acknowledged, i.e. a Configure-Ack is sent with the requested
Interface-Identifier, meaning that the responding peer agrees with
the Interface-Identifier requested.
If the two Interface-Identifiers are equal and are not zero, a
Configure-Nak MUST be sent specifying a different non-zero
Expires August 1998 [Page 8]
Internet-Draft IP Version 6 over PPP February 1998
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-
Identifiers negotiation MUST be terminated by transmitting the
Configure-Reject with the Interface-Identifier value set to zero. In
this case a unique Interface-Identifier can not be negotiated.
If a Configure-Request is received with the Interface-Identifier
Configuration Option and the receiving peer does not implement this
option, Configure-Rej is sent.
A new Configure-Request SHOULD NOT be sent to the peer until normal
processing would cause it to be sent (that is, until a Configure-Nak
is received or the Restart timer runs out).
A new Configure-Request MUST NOT contain the Interface-Identifier
option if a valid Interface-Identifier Configure-Reject is received.
Reception of a Configure-Nak with a suggested Interface-Identifier
different from that of the last Configure-Nak sent to the peer
indicates a unique Interface-Identifier. In this case a new
Configure-Request MUST be sent with the identifier value suggested
in the last Configure-Nak from the peer. But if the received
Interface-Identifier is equal to the one sent in the last Configure-
Nak, a new Interface-Identifier MUST be chosen. In this case, a new
Configure-Request SHOULD be sent with the new tentative Interface-
Identifier. This sequence (transmit Configure-Request, receive
Configure-Request, transmit Configure-Nak, receive Configure-Nak)
might occur a few times, but it is extremely unlikely to occur
repeatedly. More likely, the Interface-Identifiers chosen at either
end will quickly diverge, terminating the sequence.
If negotiation of the Interface-Identifier is required, and the peer
did not provide the option in its Configure-Request, the option
SHOULD be appended to a Configure-Nak. The tentative value of the
Interface-Identifier given must be acceptable as the remote
Interface- Identifier; i.e. it should be different from the
identifier value selected for the local end of the PPP link. The
Expires August 1998 [Page 9]
Internet-Draft IP Version 6 over PPP February 1998
next Configure-Request from the peer may include this option. If
the next Configure-Request does not include this option the peer
MUST NOT send another Configure-Nak with this option included. It
should assume that the peer's implementation does not support this
option.
By default, an implementation SHOULD attempt to negotiate the
Interface-Identifier for its end of the PPP connection.
A summary of the Interface-Identifier Configuration Option format is
shown below. The fields are transmitted from left to right.
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 | Interface-Identifier (MS Bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Interface-Identifier (cont)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Interface-Identifier (LS Bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
1
Length
10
Interface-Identifier
The 64-bit Interface-Identifier which is very likely to be unique
on the link or zero if a good source of uniqueness can not be
found.
Default Interface-Identifier Value
If no valid interface identifier can be successfully negotiated,
no default Interface-Identifier value should be assumed. The
procedures for recovering from such a case are unspecified. One
approach is to manually configure the interface identifier of the
interface.
Expires August 1998 [Page 10]
Internet-Draft IP Version 6 over PPP February 1998
5. Stateless Autoconfiguration and Link-Local Addresses
The Interface Identifier of IPv6 unicast addresses [6] of a PPP
interface, SHOULD be negotiated in the IPV6CP phase of the PPP
connection setup (see section 4.1). If no valid Interface Identifier
has been successfully negotiated, procedures for recovering from such
a case are unspecified. One approach is to manually configure the
Interface Identifier of the interface.
As long as the Interface Identifier is negotiated in the IPV6CP phase
of the PPP connection setup, it is redundant to perform duplicate
address detection as a part of the IPv6 Stateless Autoconfiguration
protocol [3]. Therefore it is recommended that for PPP links with the
IPV6CP Interface-Identifier option enabled the default value of the
DupAddrDetectTransmits autoconfiguration variable [3] be zero.
Link-local addresses of PPP interfaces have the following format:
| 10 bits | 54 bits | 64 bits |
+----------+------------------------+-----------------------------+
|1111111010| 0 | Interface Identifier |
+----------+------------------------+-----------------------------+
The most significant 10 bits of the address is the Link-Local prefix
FE80::. 54 zero bits pad out the address between the Link-Local
prefix and the Interface Identifier fields.
Expires August 1998 [Page 11]
Internet-Draft IP Version 6 over PPP February 1998
6. Security Considerations
The IPv6 Control Protocol extension to PPP can be used with all
defined PPP authentication and encryption mechanisms.
7. Acknowledgments
This document borrows from the Magic-Number LCP option and as such is
partially based on previous work done by the PPP working group.
8. Changes from RFC-2023
The following changes were made from RFC-2023 "IP Version 6 over PPP":
- Changed to use "Interface Identifier" instead of the "Interface
Token" term according to the terminology adopted in [6].
- Increased the size of Interface Identifier to 64 bits according
to the newly adopted IPv6 addressing architecture [6].
- Added methods for selection of an interface identifier that is
consistently reproducible across initializations of the IPV6CP
finite state machine.
- Added the interface identifier selection methods for generating
globally unique interface identifier from an unique an IEEE
global identifier when it is available anywhere on the node.
- Changed to send a Configure-Nak instead a Configure-Ack in
response to receiving a Configure-Request with a zero Interface-
Identifier value.
- Removed the IPv6 Configuration option definition and added text
stating that other than the Interface-Identifier IP6CP
configuration options are to be defined in separate documents.
- Added new and updated references.
- Minor text clarifications and improvements.
Expires August 1998 [Page 12]
Internet-Draft IP Version 6 over PPP February 1998
9. References
[1] Simpson, W., "The Point-to-Point Protocol", STD 51, RFC 1661,
July 1994.
[2] Deering, S., and R. Hinden, Editors, "Internet Protocol, Version
6 (IPv6) Specification", currently draft-ietf-ipngwg-ipv6-spec-
v2-01.txt
[3] Thomson, S., and T. Narten, "IPv6 Stateless Address
Autoconfiguration", currently draft-ietf-ipngwg-addrconfv2-00.txt
[4] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
October 1994.
[5] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority",
http://standards.ieee.org/db/oui/tutorials/EUI64.html, March
1997.
[6] Hinden, R., and S. Deering, "IP Version 6 Addressing
Architecture", currently draft-ietf-ipngwg-addr-arch-v2-02.txt
[7] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels," RFC 2119.
[8] Narten T., and C. Burton, "A Caution On The Canonical Ordering Of
Link-Layer Addresses", currently draft-narten-canonical-
ordering-00.txt.
10. Authors' Addresses
Dimitry Haskin
Bay Networks, Inc.
600 Technology Park
Billerica, MA 01821
email: dhaskin@baynetworks.com
Ed Allen
Bay Networks, Inc.
600 Technology Park
Billerica, MA 01821
email: eallen@baynetworks.com
Expires August 1998 [Page 13]