draft-ietf-6man-text-addr-representation-01.txt   draft-ietf-6man-text-addr-representation-02.txt 
IPv6 Maintenance Working Group S. Kawamura IPv6 Maintenance Working Group S. Kawamura
Internet-Draft NEC BIGLOBE, Ltd. Internet-Draft NEC BIGLOBE, Ltd.
Intended status: Informational M. Kawashima Intended status: Standards Track M. Kawashima
Expires: April 21, 2010 NEC AccessTechnica, Ltd. Expires: May 14, 2010 NEC AccessTechnica, Ltd.
October 18, 2009 November 10, 2009
A Recommendation for IPv6 Address Text Representation A Recommendation for IPv6 Address Text Representation
draft-ietf-6man-text-addr-representation-01 draft-ietf-6man-text-addr-representation-02
Abstract
As IPv6 network grows, there will be more engineers and also non-
engineers who will have the need to use an IPv6 address in text.
While the IPv6 address architecture RFC 4291 section 2.2 depicts a
flexible model for text representation of an IPv6 address, this
flexibility has been causing problems for operators, system
engineers, and users. This document will describe the problems that
a flexible text representation has been causing. This document also
recommends a canonical representation format that best avoids
confusion. It is expected that the canonical format is followed by
humans and systems when representing IPv6 addresses as text, but all
implementations must accept and be able to handle any legitimate
RFC4291 format.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 21, 2010. This Internet-Draft will expire on May 14, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
As IPv6 network grows, there will be more engineers and also non- described in the BSD License.
engineers who will have the need to use an IPv6 address in text.
While the IPv6 address architecture RFC 4291 section 2.2 depicts a
flexible model for text representation of an IPv6 address, this
flexibility has been causing problems for operators, system
engineers, and users. This document will describe the problems that
a flexible text representation has been causing. This document also
recommends a canonical representation format that best avoids
confusion. It is expected that the canonical format is followed by
humans and systems when representing IPv6 addresses as text, but all
implementations must accept and be able to handle any legitimate
RFC4291 format.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Text Representation Flexibility of RFC4291 . . . . . . . . . . 4 2. Text Representation Flexibility of RFC4291 . . . . . . . . . . 4
2.1. Leading Zeros in a 16 Bit Field . . . . . . . . . . . . . 4 2.1. Leading Zeros in a 16 Bit Field . . . . . . . . . . . . . 4
2.2. Zero Compression . . . . . . . . . . . . . . . . . . . . . 5 2.2. Zero Compression . . . . . . . . . . . . . . . . . . . . . 5
2.3. Uppercase or Lowercase . . . . . . . . . . . . . . . . . . 5 2.3. Uppercase or Lowercase . . . . . . . . . . . . . . . . . . 5
3. Problems Encountered with the Flexible Model . . . . . . . . . 6 3. Problems Encountered with the Flexible Model . . . . . . . . . 6
3.1. Searching . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Searching . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1.1. General Summary . . . . . . . . . . . . . . . . . . . 6 3.1.1. General Summary . . . . . . . . . . . . . . . . . . . 6
3.1.2. Searching Spreadsheets and Text Files . . . . . . . . 6 3.1.2. Searching Spreadsheets and Text Files . . . . . . . . 6
3.1.3. Searching with Whois . . . . . . . . . . . . . . . . . 6 3.1.3. Searching with Whois . . . . . . . . . . . . . . . . . 6
3.1.4. Searching for an Address in a Network Diagram . . . . 7 3.1.4. Searching for an Address in a Network Diagram . . . . 7
3.2. Parsing and Modifying . . . . . . . . . . . . . . . . . . 7 3.2. Parsing and Modifying . . . . . . . . . . . . . . . . . . 7
3.2.1. General Summary . . . . . . . . . . . . . . . . . . . 7 3.2.1. General Summary . . . . . . . . . . . . . . . . . . . 7
3.2.2. Logging . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.2. Logging . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.3. Auditing: Case 1 . . . . . . . . . . . . . . . . . . . 8 3.2.3. Auditing: Case 1 . . . . . . . . . . . . . . . . . . . 7
3.2.4. Auditing: Case 2 . . . . . . . . . . . . . . . . . . . 8 3.2.4. Auditing: Case 2 . . . . . . . . . . . . . . . . . . . 8
3.2.5. Verification . . . . . . . . . . . . . . . . . . . . . 8 3.2.5. Verification . . . . . . . . . . . . . . . . . . . . . 8
3.2.6. Unexpected Modifying . . . . . . . . . . . . . . . . . 8 3.2.6. Unexpected Modifying . . . . . . . . . . . . . . . . . 8
3.3. Operating . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3. Operating . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1. General Summary . . . . . . . . . . . . . . . . . . . 8 3.3.1. General Summary . . . . . . . . . . . . . . . . . . . 8
3.3.2. Customer Calls . . . . . . . . . . . . . . . . . . . . 9 3.3.2. Customer Calls . . . . . . . . . . . . . . . . . . . . 9
3.3.3. Abuse . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3.3. Abuse . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Other Minor Problems . . . . . . . . . . . . . . . . . . . 9 3.4. Other Minor Problems . . . . . . . . . . . . . . . . . . . 9
3.4.1. Changing Platforms . . . . . . . . . . . . . . . . . . 9 3.4.1. Changing Platforms . . . . . . . . . . . . . . . . . . 9
3.4.2. Preference in Documentation . . . . . . . . . . . . . 9 3.4.2. Preference in Documentation . . . . . . . . . . . . . 9
3.4.3. Legibility . . . . . . . . . . . . . . . . . . . . . . 10 3.4.3. Legibility . . . . . . . . . . . . . . . . . . . . . . 9
4. A Recommendation for IPv6 Text Representation . . . . . . . . 10 4. A Recommendation for IPv6 Text Representation . . . . . . . . 10
4.1. Handling Leading Zeros in a 16 Bit Field . . . . . . . . . 10 4.1. Handling Leading Zeros in a 16 Bit Field . . . . . . . . . 10
4.2. "::" Usage . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2. "::" Usage . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2.1. Shorten As Much As Possible . . . . . . . . . . . . . 10 4.2.1. Shorten As Much As Possible . . . . . . . . . . . . . 10
4.2.2. Handling One 16 Bit 0 Field . . . . . . . . . . . . . 10 4.2.2. Handling One 16 Bit 0 Field . . . . . . . . . . . . . 10
4.2.3. Choice in Placement of "::" . . . . . . . . . . . . . 10 4.2.3. Choice in Placement of "::" . . . . . . . . . . . . . 10
4.3. Lower Case . . . . . . . . . . . . . . . . . . . . . . . . 11 4.3. Lower Case . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Text Representation of Special Addresses . . . . . . . . . . . 11 5. Text Representation of Special Addresses . . . . . . . . . . . 11
6. Notes on Combining IPv6 Addresses with Port Numbers . . . . . 11 6. Notes on Combining IPv6 Addresses with Port Numbers . . . . . 11
7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. For Developers . . . . . . . . . . . . . . . . . . . 13 Appendix A. For Developers . . . . . . . . . . . . . . . . . . . 13
Appendix B. Prefix Issues . . . . . . . . . . . . . . . . . . . . 13 Appendix B. Prefix Issues . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
A single IPv6 address can be text represented in many ways. Examples A single IPv6 address can be text represented in many ways. Examples
are shown below. are shown below.
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With all the possible text representation ways, each application must With all the possible text representation ways, each application must
include a module, object, link, etc. to a function that will parse include a module, object, link, etc. to a function that will parse
IPv6 addresses in a manner that no matter how it is represented, they IPv6 addresses in a manner that no matter how it is represented, they
will mean the same address. This is not too much a problem if the will mean the same address. This is not too much a problem if the
output is to be just 'read' or 'managed' by a network engineer. output is to be just 'read' or 'managed' by a network engineer.
However, many system engineers who integrate complex computer systems However, many system engineers who integrate complex computer systems
to corporate customers will have difficulties finding that their to corporate customers will have difficulties finding that their
favorite tool will not have this function, or will encounter favorite tool will not have this function, or will encounter
difficulties such as having to rewrite their macro's or scripts for difficulties such as having to rewrite their macro's or scripts for
their customers. It must be noted that each additional line of a their customers.
program will result in increased development fees that will be
charged to the customers.
3.2.2. Logging 3.2.2. Logging
If an application were to output a log summary that represented the If an application were to output a log summary that represented the
address in full (such as 2001:0db8:0000:0000:1111:2222:3333:4444), address in full (such as 2001:0db8:0000:0000:1111:2222:3333:4444),
the output would be highly unreadable compared to the IPv4 output. the output would be highly unreadable compared to the IPv4 output.
The address would have to be parsed and reformed to make it useful The address would have to be parsed and reformed to make it useful
for human reading. This will result in additional code on the for human reading. Sometimes, logging for critical systems is done
applications which will result in extra fees charged to the by mirroring the same traffic to two different systems. Care must be
customers. Sometimes, logging for critical systems is done by
mirroring the same traffic to two different systems. Care must be
taken that no matter what the log output is, the logs should be taken that no matter what the log output is, the logs should be
parsed so they will mean the same. parsed so they will mean the same.
3.2.3. Auditing: Case 1 3.2.3. Auditing: Case 1
When a router or any other network appliance machine configuration is When a router or any other network appliance machine configuration is
audited, there are many methods to compare the configuration audited, there are many methods to compare the configuration
information of a node. Sometimes, auditing will be done by just information of a node. Sometimes, auditing will be done by just
comparing the changes made each day. In this case, if configuration comparing the changes made each day. In this case, if configuration
was done such that 2001:db8::1 was changed to 2001:0db8:0000:0000: was done such that 2001:db8::1 was changed to 2001:0db8:0000:0000:
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will need to be a script that is implemented to cover for this. An will need to be a script that is implemented to cover for this. An
SNMP GET of an interface address and text representation in a humanly SNMP GET of an interface address and text representation in a humanly
written text file is highly unlikely to match on first try. written text file is highly unlikely to match on first try.
3.2.5. Verification 3.2.5. Verification
Some protocols require certain data fields to be verified. One Some protocols require certain data fields to be verified. One
example of this is X.509 certificates. If an IPv6 address was example of this is X.509 certificates. If an IPv6 address was
embedded in one of the fields in a certificate, and the verification embedded in one of the fields in a certificate, and the verification
was done by just a simple textual comparison, the certificate may be was done by just a simple textual comparison, the certificate may be
maistakenly shown as being invalid due to a difference in text mistakenly shown as being invalid due to a difference in text
representation methods. representation methods.
3.2.6. Unexpected Modifying 3.2.6. Unexpected Modifying
Sometimes, a system will take an address and modify it as a Sometimes, a system will take an address and modify it as a
convenience. For example, a system may take an input of convenience. For example, a system may take an input of
2001:0db8:0::1 and make the output 2001:db8::1 (which is seen in some 2001:0db8:0::1 and make the output 2001:db8::1 (which is seen in some
RIR databases). If the zeros were input for a reason, the outcome RIR databases). If the zeros were input for a reason, the outcome
may be somewhat unexpected. may be somewhat unexpected.
3.3. Operating 3.3. Operating
3.3.1. General Summary 3.3.1. General Summary
When an operator sets an IPv6 address of a system as 2001:db8:0:0:1: When an operator sets an IPv6 address of a system as 2001:db8:0:0:1:
0:0:1, the system may take the address and show the configuration 0:0:1, the system may take the address and show the configuration
result as 2001:DB8::1:0:0:1. A distinguished engineer will know that result as 2001:DB8::1:0:0:1. A distinguished engineer will know that
the right address is set, but an operator, or a customer that is the right address is set, but an operator, or a customer that is
communicating with the operator to solve a problem, is usually not as communicating with the operator to solve a problem, is usually not as
distinguished as we would like. Again, the extra load in checking distinguished as we would like.
that the IP address is the same as was intended, will result in fees
that will be charged to the customers.
3.3.2. Customer Calls 3.3.2. Customer Calls
When a customer calls to inquire about a suspected outage, IPv6 When a customer calls to inquire about a suspected outage, IPv6
address representation should be handled with care. Not all address representation should be handled with care. Not all
customers are engineers nor have the same skill in IPv6 technology. customers are engineers nor have the same skill in IPv6 technology.
The NOC will have to take extra steps to humanly parse the address to The NOC will have to take extra steps to humanly parse the address to
avoid having to explain to the customers that 2001:db8:0:1::1 is the avoid having to explain to the customers that 2001:db8:0:1::1 is the
same as 2001:db8::1:0:0:0:1. This is one thing that will never same as 2001:db8::1:0:0:0:1. This is one thing that will never
happen in IPv4 because IPv4 address cannot be abbreviated. happen in IPv4 because IPv4 address cannot be abbreviated.
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3.4. Other Minor Problems 3.4. Other Minor Problems
3.4.1. Changing Platforms 3.4.1. Changing Platforms
When an engineer decides to change the platform of a running service, When an engineer decides to change the platform of a running service,
the same code may not work as expected due to the difference in IPv6 the same code may not work as expected due to the difference in IPv6
address text representation. Usually, a change in a platform (e.g. address text representation. Usually, a change in a platform (e.g.
Unix to Windows, Cisco to Juniper) will result in a major change of Unix to Windows, Cisco to Juniper) will result in a major change of
code, but flexibility in address representation will increase the code, but flexibility in address representation will increase the
work load which will again, result in fees that will be charged to work load.
the customers, and also longer down time of systems.
3.4.2. Preference in Documentation 3.4.2. Preference in Documentation
A document that is edited by more than one author, may become harder A document that is edited by more than one author, may become harder
to read. to read.
3.4.3. Legibility 3.4.3. Legibility
Capital case D and 0 can be quite often misread. Capital B and 8 can Capital case D and 0 can be quite often misread. Capital B and 8 can
also be misread. also be misread.
4. A Recommendation for IPv6 Text Representation 4. A Recommendation for IPv6 Text Representation
A recommendation for a canonical text representation format of IPv6 A recommendation for a canonical text representation format of IPv6
addresses is presented in this section. The recommendation in this addresses is presented in this section. The recommendation in this
document is one that, complies fully with [RFC4291], is implemented document is one that, complies fully with [RFC4291], is implemented
by various operating systems, and is human friendly. The by various operating systems, and is human friendly. The
recommendation in this document SHOULD be followed by humans and recommendation in this document SHOULD be followed by systems when
systems when generating an address to represent as text, but all generating an address to represent as text, but all implementations
implementations MUST accept any legitimate [RFC4291] format. MUST accept any legitimate [RFC4291] format. It is advised that
humans also follow these recommendations when spelling an address.
4.1. Handling Leading Zeros in a 16 Bit Field 4.1. Handling Leading Zeros in a 16 Bit Field
Leading zeros should be chopped for human legibility and easier Leading zeros should be chopped for human legibility and easier
searching. Also, a single 16 bit 0000 field should be represented as searching. Also, a single 16 bit 0000 field should be represented as
just 0. Place holder zeros are often cause of misreading. just 0. Place holder zeros are often cause of misreading.
4.2. "::" Usage 4.2. "::" Usage
4.2.1. Shorten As Much As Possible 4.2.1. Shorten As Much As Possible
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4.2.3. Choice in Placement of "::" 4.2.3. Choice in Placement of "::"
When there is an alternative choice in the placement of a "::", the When there is an alternative choice in the placement of a "::", the
longest run of consecutive 16 bit 0 fields should be shortened (i.e. longest run of consecutive 16 bit 0 fields should be shortened (i.e.
latter is shortened in 2001:0:0:1:0:0:0:1). When the length of the latter is shortened in 2001:0:0:1:0:0:0:1). When the length of the
consecutive 16 bit 0 fields are equal (i.e. 2001:db8:0:0:1:0:0:1), consecutive 16 bit 0 fields are equal (i.e. 2001:db8:0:0:1:0:0:1),
the former is shortened. This is consistent with many current the former is shortened. This is consistent with many current
implementations. One idea to avoid any confusion, is for the implementations. One idea to avoid any confusion, is for the
operator to not use 16 bit field 0 in the first 64 bits. By nature operator to not use 16 bit field 0 in the first 64 bits. By nature
IPv6 addresses are usually assigned or allocated to end-users as IPv6 addresses are usually assigned or allocated to end-users from a
longer than 32 bits (typically 48 bits or longer). prefix of 32 bits or longer (typically 48 bits or longer).
4.3. Lower Case 4.3. Lower Case
Recent implementations tend to represent IPv6 address as lower case. Recent implementations tend to represent IPv6 address as lower case.
It is better to use lower case to avoid problems such as described in It is better to use lower case to avoid problems such as described in
section 3.3.3 and 3.4.3. section 3.3.3 and 3.4.3.
5. Text Representation of Special Addresses 5. Text Representation of Special Addresses
Addresses such as IPv4-Mapped IPv6 addresses, ISATAP [RFC5214], and Addresses such as IPv4-Mapped IPv6 addresses, ISATAP [RFC5214], and
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