draft-ietf-6man-text-addr-representation-07.txt		rfc5952.txt
	IPv6 Maintenance Working Group S. Kawamura		Internet Engineering Task Force (IETF) S. Kawamura
	Internet-Draft NEC BIGLOBE, Ltd.		Request for Comments: 5952 NEC BIGLOBE, Ltd.
	Updates: 4291 (if approved) M. Kawashima		Updates: 4291 M. Kawashima
	Intended status: Standards Track NEC AccessTechnica, Ltd.		Category: Standards Track NEC AccessTechnica, Ltd.
	Expires: August 29, 2010 February 25, 2010		ISSN: 2070-1721 August 2010
	A Recommendation for IPv6 Address Text Representation		A Recommendation for IPv6 Address Text Representation
	draft-ietf-6man-text-addr-representation-07
	Abstract		Abstract
	As IPv6 deployment increases there will be a dramatic increase in the		As IPv6 deployment increases, there will be a dramatic increase in
	need to use IPv6 addresses in text. While the IPv6 address		the need to use IPv6 addresses in text. While the IPv6 address
	architecture in RFC 4291 section 2.2 describes a flexible model for		architecture in Section 2.2 of RFC 4291 describes a flexible model
	text representation of an IPv6 address this flexibility has been		for text representation of an IPv6 address, this flexibility has been
	causing problems for operators, system engineers, and users. This		causing problems for operators, system engineers, and users. This
	document defines a canonical textual representation format. It does		document defines a canonical textual representation format. It does
	not define a format for internal storage, such as within an		not define a format for internal storage, such as within an
	application or database. It is expected that the canonical format is		application or database. It is expected that the canonical format
	followed by humans and systems when representing IPv6 addresses as		will be followed by humans and systems when representing IPv6
	text, but all implementations must accept and be able to handle any		addresses as text, but all implementations must accept and be able to
	legitimate RFC 4291 format.		handle any legitimate RFC 4291 format.
	Status of this Memo
	This Internet-Draft is submitted to IETF in full conformance with the
	provisions of BCP 78 and BCP 79.
	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		Status of This Memo
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		This is an Internet Standards Track document.
	http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		This document is a product of the Internet Engineering Task Force
	http://www.ietf.org/shadow.html.		(IETF). It represents the consensus of the IETF community. It has
			received public review and has been approved for publication by the
			Internet Engineering Steering Group (IESG). Further information on
			Internet Standards is available in Section 2 of RFC 5741.
	This Internet-Draft will expire on August 29, 2010.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			http://www.rfc-editor.org/info/rfc5952.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2010 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		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	skipping to change at page 2, line 15		skipping to change at page 2, line 18
	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		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the BSD License.		described in the Simplified BSD License.
	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 RFC 4291 . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . 6
	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 . . . . . . . . . . . . . . . . . . . 7		3.2.3. Auditing: Case 1 . . . . . . . . . . . . . . . . . . . 8
	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 . . . . . . . . . . . . . . . . . . . . 8		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 . . . . . . . . . . . . . . . . . . . . . . 9		3.4.3. Legibility . . . . . . . . . . . . . . . . . . . . . . 9
	4. A Recommendation for IPv6 Text Representation . . . . . . . . 9		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 . . . . . . . . . . . . . . . . . . . . . . . . 10		4.3. Lowercase . . . . . . . . . . . . . . . . . . . . . . . . 10
	5. Text Representation of Special Addresses . . . . . . . . . . . 10		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. Prefix Representation . . . . . . . . . . . . . . . . . . . . 12		7. Prefix Representation . . . . . . . . . . . . . . . . . . . . 12
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 12		8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
	10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12		10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12		10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
	11.1. Normative References . . . . . . . . . . . . . . . . . . . 12		10.2. Informative References . . . . . . . . . . . . . . . . . . 13
	11.2. Informative References . . . . . . . . . . . . . . . . . . 13		Appendix A. For Developers . . . . . . . . . . . . . . . . . . . 14
	Appendix A. For Developers . . . . . . . . . . . . . . . . . . . 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.
	2001:db8:0:0:1:0:0:1		2001:db8:0:0:1:0:0:1
	2001:0db8:0:0:1:0:0:1		2001:0db8:0:0:1:0:0:1
	skipping to change at page 4, line 28		skipping to change at page 4, line 28
	2001:0db8::1:0:0:1		2001:0db8::1:0:0:1
	2001:db8:0:0:1::1		2001:db8:0:0:1::1
	2001:db8:0000:0:1::1		2001:db8:0000:0:1::1
	2001:DB8:0:0:1::1		2001:DB8:0:0:1::1
	All of the above examples represent the same IPv6 address. This		All of the above examples represent the same IPv6 address. This
	flexibility has caused many problems for operators, systems		flexibility has caused many problems for operators, systems
	engineers, and customers. The problems are noted in Section 3.		engineers, and customers. The problems are noted in Section 3. A
	Also, a canonical representation format to avoid problems is		canonical representation format to avoid problems is introduced in
	introduced in Section 4.		Section 4.
	1.1. Requirements Language		1.1. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Text Representation Flexibility of RFC4291		2. Text Representation Flexibility of RFC 4291
	Examples of flexibility in Section 2.2 of [RFC4291] are described		Examples of flexibility in Section 2.2 of [RFC4291] are described
	below.		below.
	2.1. Leading Zeros in a 16 Bit Field		2.1. Leading Zeros in a 16-Bit Field
	'It is not necessary to write the leading zeros in an individual		'It is not necessary to write the leading zeros in an individual
	field.'		field.'
	Conversely it is also not necessary to omit leading zeros. This		Conversely, it is also not necessary to omit leading zeros. This
	means that, it is possible to select from such as the following		means that it is possible to select from representations such as
	example. The final 16 bit field is different, but all these		those in the following example. The final 16-bit field is different,
	addresses represent the same address.		but all of these addresses represent the same address.
	2001:db8:aaaa:bbbb:cccc:dddd:eeee:0001		2001:db8:aaaa:bbbb:cccc:dddd:eeee:0001
	2001:db8:aaaa:bbbb:cccc:dddd:eeee:001		2001:db8:aaaa:bbbb:cccc:dddd:eeee:001
	2001:db8:aaaa:bbbb:cccc:dddd:eeee:01		2001:db8:aaaa:bbbb:cccc:dddd:eeee:01
	2001:db8:aaaa:bbbb:cccc:dddd:eeee:1		2001:db8:aaaa:bbbb:cccc:dddd:eeee:1
	2.2. Zero Compression		2.2. Zero Compression
	'A special syntax is available to compress the zeros. The use of		'A special syntax is available to compress the zeros. The use of
	"::" indicates one or more groups of 16 bits of zeros.'		"::" indicates one or more groups of 16 bits of zeros.'
	It is possible to select whether or not to omit just one 16 bits of		It is possible to select whether or not to omit just one 16-bit 0
	zeros.		field.
	2001:db8:aaaa:bbbb:cccc:dddd::1		2001:db8:aaaa:bbbb:cccc:dddd::1
	2001:db8:aaaa:bbbb:cccc:dddd:0:1		2001:db8:aaaa:bbbb:cccc:dddd:0:1
	In case where there is more than one zero fields, there is a choice		In cases where there is more than one field of only zeros, there is a
	of how many fields can be shortened.		choice of how many fields can be shortened.
	2001:db8:0:0:0::1		2001:db8:0:0:0::1
	2001:db8:0:0::1		2001:db8:0:0::1
	2001:db8:0::1		2001:db8:0::1
	2001:db8::1		2001:db8::1
	In addition, [RFC4291] in section 2.2 notes,		In addition, Section 2.2 of [RFC4291] notes,
	'The "::" can only appear once in an address.'		'The "::" can only appear once in an address.'
	This gives a choice on where in a single address to compress the		This gives a choice on where in a single address to compress the
	zero.		zero.
	2001:db8::aaaa:0:0:1		2001:db8::aaaa:0:0:1
	2001:db8:0:0:aaaa::1		2001:db8:0:0:aaaa::1
	skipping to change at page 6, line 18		skipping to change at page 6, line 22
	2001:db8:aaaa:bbbb:cccc:dddd:eeee:AaAa		2001:db8:aaaa:bbbb:cccc:dddd:eeee:AaAa
	3. Problems Encountered with the Flexible Model		3. Problems Encountered with the Flexible Model
	3.1. Searching		3.1. Searching
	3.1.1. General Summary		3.1.1. General Summary
	A search of an IPv6 address if conducted through a UNIX system is		A search of an IPv6 address if conducted through a UNIX system is
	usually case sensitive and extended options to allow for regular		usually case sensitive and extended options that allow for regular
	expression use will come in handy. However, there are many		expression use will come in handy. However, there are many
	applications in the Internet today that do not provide this		applications in the Internet today that do not provide this
	capability. When searching for an IPv6 address in such systems, the		capability. When searching for an IPv6 address in such systems, the
	system engineer will have to try each and every possibility to search		system engineer will have to try each and every possibility to search
	for an address. This has critical impacts especially when trying to		for an address. This has critical impacts, especially when trying to
	deploy IPv6 over an enterprise network.		deploy IPv6 over an enterprise network.
	3.1.2. Searching Spreadsheets and Text Files		3.1.2. Searching Spreadsheets and Text Files
	Spreadsheet applications and text editors on GUI systems, rarely have		Spreadsheet applications and text editors on GUI systems rarely have
	the ability to search for a text using regular expression. Moreover,		the ability to search for text using regular expression. Moreover,
	there are many non-engineers (who are not aware of case sensitivity		there are many non-engineers (who are not aware of case sensitivity
	and regular expression use) that use these application to manage IP		and regular expression use) that use these applications to manage IP
	addresses. This has worked quite well with IPv4 since text		addresses. This has worked quite well with IPv4 since text
	representation in IPv4 has very little flexibility. There is no		representation in IPv4 has very little flexibility. There is no
	incentive to encourage these non-engineers to change their tool or		incentive to encourage these non-engineers to change their tool or
	learn regular expression when they decide to go dual-stack. If the		learn regular expression when they decide to go dual-stack. If the
	entry in the spreadsheet reads, 2001:db8::1:0:0:1, but the search was		entry in the spreadsheet reads, 2001:db8::1:0:0:1, but the search was
	conducted as 2001:db8:0:0:1::1, this will show a result of no match.		conducted as 2001:db8:0:0:1::1, this will show a result of no match.
	One example where this will cause problem is, when the search is		One example where this will cause a problem is, when the search is
	being conducted to assign a new address from a pool, and a check was		being conducted to assign a new address from a pool, and a check is
	being done to see if it was not in use. This may cause problems to		being done to see if it is not in use. This may cause problems for
	the end-hosts or end-users. This type of address management is very		the end-hosts or end-users. This type of address management is very
	often seen in enterprise networks and also in ISPs.		often seen in enterprise networks and ISPs.
	3.1.3. Searching with Whois		3.1.3. Searching with Whois
	The "whois" utility is used by a wide range of people today. When a		The "whois" utility is used by a wide range of people today. When a
	record is set to a database, one will likely check the output to see		record is set to a database, one will likely check the output to see
	if the entry is correct. If an entity was recorded as 2001:db8::/48,		if the entry is correct. If an entity was recorded as 2001:db8::/48,
	but the whois output showed 2001:0db8:0000::/48, most non-engineers		but the whois output showed 2001:0db8:0000::/48, most non-engineers
	would think that their input was wrong and will likely retry several		would think that their input was wrong and will likely retry several
	times or make a frustrated call to the database hostmaster. If there		times or make a frustrated call to the database hostmaster. If there
	was a need to register the same address on different systems, and		was a need to register the same prefix on different systems, and each
	each system showed a different text representation, this would		system showed a different text representation, this would confuse
	confuse people even more. Although this document focuses on		people even more. Although this document focuses on addresses rather
	addresses rather than prefixes, this is worth mentioning since the		than prefixes, it is worth mentioning the prefix problems because the
	problems encountered are mostly equal.		problems encountered with addresses and prefixes are mostly equal.
	3.1.4. Searching for an Address in a Network Diagram		3.1.4. Searching for an Address in a Network Diagram
	Network diagrams and blueprints often show what IP addresses are		Network diagrams and blueprints often show what IP addresses are
	assigned to a system devices. In times of trouble shooting there may		assigned to a system devices. In times of trouble shooting there may
	be a need to search through a diagram to find the point of failure		be a need to search through a diagram to find the point of failure
	(for example, if a traceroute stopped at 2001:db8::1, one would		(for example, if a traceroute stopped at 2001:db8::1, one would
	search the diagram for that address). This is a technique quite		search the diagram for that address). This is a technique quite
	often in use in enterprise networks and managed services. Again, the		often in use in enterprise networks and managed services. Again, the
	different flavors of text representation will result in a time-		different flavors of text representation will result in a time-
	consuming search leading to longer MTTR in times of trouble.		consuming search leading to longer mean times to restoration (MTTR)
			in times of trouble.
	3.2. Parsing and Modifying		3.2. Parsing and Modifying
	3.2.1. General Summary		3.2.1. General Summary
	With all the possible methods of text representation each application		With all the possible methods of text representation, each
	must include a module, object, link, etc. to a function that will		application must include a module, object, link, etc. to a function
	parse IPv6 addresses in a manner that no matter how it is		that will parse IPv6 addresses in a manner such that no matter how it
	represented, they will mean the same address. Many system engineers		is represented, they will mean the same address. Many system
	who integrate complex computer systems for corporate customers will		engineers who integrate complex computer systems for corporate
	have difficulties finding that their favorite tool will not have this		customers will have difficulties finding that their favorite tool
	function, or will encounter difficulties such as having to rewrite		will not have this function, or will encounter difficulties such as
	their macros or scripts for their customers.		having to rewrite their macros or scripts for their 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. Sometimes logging for critical systems is done by		for human reading. Sometimes logging for critical systems is done by
	mirroring the same traffic to two different systems. Care must be		mirroring the same traffic to two different systems. Care must be
	taken so that no matter what the log output is the logs should be		taken so that no matter what the log output is, the logs should be
	parsed so they will mean the same.		parsed so they are equivalent.
	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:
	0000:0000:0000:0001 just because the new engineer on the block felt		0000:0000:0000:0001 just because the new engineer on the block felt
	it was better, a simple diff will show that a different address was		it was better, a simple diff will show that a different address was
	configured. If this was done on a wide scale network people will be		configured. If this was done on a wide scale network, people will be
	focusing on 'why the extra zeros were put in' instead of doing any		focusing on 'why the extra zeros were put in' instead of doing any
	real auditing. Lots of tools are just plain diffs that do not take		real auditing. Lots of tools are just plain diffs that do not take
	into account address representation rules.		into account address representation rules.
	3.2.4. Auditing: Case 2		3.2.4. Auditing: Case 2
	Node configurations will be matched against an information system		Node configurations will be matched against an information system
	that manages IP addresses. If output notation is different there		that manages IP addresses. If output notation is different, there
	will need to be a script that is implemented to cover for this. The		will need to be a script that is implemented to cover for this. The
	result of an SNMP GET operation, converted to text and compared to a		result of an SNMP GET operation, converted to text and compared to a
	textual address written by a human is highly unlikely to match on the		textual address written by a human is highly unlikely to match on the
	first try.		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 field in a		example of this is X.509 certificates. If an IPv6 address field in a
	certificate was incorrectly verified by converting it to text and		certificate was incorrectly verified by converting it to text and
	skipping to change at page 8, line 51		skipping to change at page 9, line 9
	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. Someone familiar with IPv6 address		result as 2001:DB8::1:0:0:1. Someone familiar with IPv6 address
	representation will know that the right address is set, but not		representation will know that the right address is set, but not
	everyone may understand this.		everyone may understand this.
	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 do they have a similar skill level in
	The network operations center will have to take extra steps to		IPv6 technology. The network operations center will have to take
	humanly parse the address to avoid having to explain to the customers		extra steps to humanly parse the address to avoid having to explain
	that 2001:db8:0:1::1 is the same as 2001:db8::1:0:0:0:1. This is one		to the customers that 2001:db8:0:1::1 is the same as
	thing that will never happen in IPv4 because IPv4 address cannot be		2001:db8::1:0:0:0:1. This is one thing that will never happen in
	abbreviated.		IPv4 because IPv4 addresses cannot be abbreviated.
	3.3.3. Abuse		3.3.3. Abuse
	Network abuse reports generally include the abusing IP address. This		Network abuse reports generally include the abusing IP address. This
	'reporting' could take any shape or form of the flexible model. A		'reporting' could take any shape or form of the flexible model. A
	team that handles network abuse must be able to tell the difference		team that handles network abuse must be able to tell the difference
	between a 2001:db8::1:0:1 and 2001:db8:1::0:1. Mistakes in the		between a 2001:db8::1:0:1 and 2001:db8:1::0:1. Mistakes in the
	placement of the "::" will result in a critical situation. A system		placement of the "::" will result in a critical situation. A system
	that handles these incidents should be able to handle any type of		that handles these incidents should be able to handle any type of
	input and parse it in a correct manner. Also, incidents are reported		input and parse it in a correct manner. Also, incidents are reported
	over the phone. It is unnecessary to report if the letter is an		over the phone. It is unnecessary to report if the letter is
	uppercase or lowercase. However, when a letter is spelled uppercase,		uppercase or lowercase. However, when a letter is spelled uppercase,
	people tend to clarify that it is uppercase, which is unnecessary		people tend to specify that it is uppercase, which is unnecessary
	information.		information.
	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 anyway, but flexibility in address representation will increase		code anyway, but flexibility in address representation will increase
	the work load.		the work load.
	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
	by various operating systems, and is human friendly. The		various operating systems, and is human friendly. The recommendation
	recommendation in this section SHOULD be followed by systems when		in this section SHOULD be followed by systems when generating an
	generating an address to represent as text, but all implementations		address to be represented as text, but all implementations MUST
	MUST accept and be able to handle any legitimate [RFC4291] format.		accept and be able to handle any legitimate [RFC4291] format. It is
	It is advised that humans also follow these recommendations when		advised that humans also follow these recommendations when spelling
	spelling an address.		an address.
	4.1. Handling Leading Zeros in a 16 Bit Field		4.1. Handling Leading Zeros in a 16-Bit Field
	Leading zeros MUST be suppressed. For example 2001:0db8::0001 is not		Leading zeros MUST be suppressed. For example, 2001:0db8::0001 is
	acceptable and must be represented as 2001:db8::1. A single 16 bit		not acceptable and must be represented as 2001:db8::1. A single 16-
	0000 field MUST be represented as 0.		bit 0000 field MUST be represented as 0.
	4.2. "::" Usage		4.2. "::" Usage
	4.2.1. Shorten As Much As Possible		4.2.1. Shorten as Much as Possible
	The use of symbol "::" MUST be used to its maximum capability. For		The use of the symbol "::" MUST be used to its maximum capability.
	example, 2001:db8::0:1 is not acceptable, because the symbol "::"		For example, 2001:db8:0:0:0:0:2:1 must be shortened to 2001:db8::2:1.
			Likewise, 2001:db8::0:1 is not acceptable, because the symbol "::"
	could have been used to produce a shorter representation 2001:db8::1.		could have been used to produce a shorter representation 2001:db8::1.
	4.2.2. Handling One 16 Bit 0 Field		4.2.2. Handling One 16-Bit 0 Field
	The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.		The symbol "::" MUST NOT be used to shorten just one 16-bit 0 field.
	For example, the representation 2001:db8:0:1:1:1:1:1 is correct, but		For example, the representation 2001:db8:0:1:1:1:1:1 is correct, but
	2001:db8::1:1:1:1:1 is not correct.		2001:db8::1:1:1:1:1 is not correct.
	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 MUST be shortened (i.e.		longest run of consecutive 16-bit 0 fields MUST be shortened (i.e.,
	the sequence with three consecutive zero fields is shortened in 2001:		the sequence with three consecutive zero fields is shortened in 2001:
	0:0:1:0:0:0:1). When the length of the consecutive 16 bit 0 fields		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), the first sequence of zero		are equal (i.e., 2001:db8:0:0:1:0:0:1), the first sequence of zero
	bits MUST be shortened. For example 2001:db8::1:0:0:1 is correct		bits MUST be shortened. For example, 2001:db8::1:0:0:1 is correct
	representation.		representation.
	4.3. Lower Case		4.3. Lowercase
	The characters "a", "b", "c", "d", "e", "f" in an IPv6 address MUST		The characters "a", "b", "c", "d", "e", and "f" in an IPv6 address
	be represented in lower case.		MUST be represented in lowercase.
	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
	IPv4-translatable addresses [I-D.ietf-behave-address-format] have		IPv4-translatable addresses [ADDR-FORMAT] have IPv4 addresses
	IPv4 addresses embedded in the low-order 32 bits of the address.		embedded in the low-order 32 bits of the address. These addresses
	These addresses have special representation that may mix hexadecimal		have a special representation that may mix hexadecimal and dot
	and dot decimal notations. The decimal notation may be used only for		decimal notations. The decimal notation may be used only for the
	the last 32 bits of the address. For these addresses, mixed notation		last 32 bits of the address. For these addresses, mixed notation is
	is RECOMMENDED if the following condition is met: The address can be		RECOMMENDED if the following condition is met: the address can be
	distinguished as having IPv4 addresses embedded in the lower 32 bits		distinguished as having IPv4 addresses embedded in the lower 32 bits
	solely from the address field through the use of a well known prefix.		solely from the address field through the use of a well-known prefix.
	Such prefixes are defined in [RFC4291] and [RFC2765] at the time of		Such prefixes are defined in [RFC4291] and [RFC2765] at the time of
	writing. If it is known by some external method that a given prefix		this writing. If it is known by some external method that a given
	is used to embed IPv4, it MAY be represented as mixed notation.		prefix is used to embed IPv4, it MAY be represented as mixed
	Tools that provide options to specify prefixes that are (or are not)		notation. Tools that provide options to specify prefixes that are
	to be represented as mixed notation may be useful.		(or are not) to be represented as mixed notation may be useful.
	There is a trade-off here where a recommendation to achieve exact		There is a trade-off here where a recommendation to achieve an exact
	match in a search (no dot decimals whatsoever) and recommendation to		match in a search (no dot decimals whatsoever) and a recommendation
	help the readability of an addresses (dot decimal whenever possible)		to help the readability of an address (dot decimal whenever possible)
	does not result in the same solution. The above recommendation is		does not result in the same solution. The above recommendation is
	aimed at fixing the representation as much as possible while leaving		aimed at fixing the representation as much as possible while leaving
	the opportunity for future well known prefixes to be represented in a		the opportunity for future well-known prefixes to be represented in a
	human friendly manner as tools adjust to newly assigned prefixes.		human-friendly manner as tools adjust to newly assigned prefixes.
	The text representation method noted in Section 4 should be applied		The text representation method noted in Section 4 should be applied
	for the leading hexadecimal part (i.e. ::ffff:192.0.2.1 instead of		for the leading hexadecimal part (i.e., ::ffff:192.0.2.1 instead of
	0:0:0:0:0:ffff:192.0.2.1).		0:0:0:0:0:ffff:192.0.2.1).
	6. Notes on Combining IPv6 Addresses with Port Numbers		6. Notes on Combining IPv6 Addresses with Port Numbers
	When IPv6 addresses and port numbers are represented in text combined		There are many different ways to combine IPv6 addresses and port
	together, there are many different ways to do so. Examples are shown		numbers that are represented in text. Examples are shown below.
	below.
	o [2001:db8::1]:80		o [2001:db8::1]:80
	o 2001:db8::1:80		o 2001:db8::1:80
	o 2001:db8::1.80		o 2001:db8::1.80
	o 2001:db8::1 port 80		o 2001:db8::1 port 80
	o 2001:db8::1p80		o 2001:db8::1p80
	o 2001:db8::1#80		o 2001:db8::1#80
	The situation is not much different in IPv4, but the most ambiguous		The situation is not much different in IPv4, but the most ambiguous
	case with IPv6 is the second bullet. This is due to the "::"usage in		case with IPv6 is the second bullet. This is due to the "::"usage in
	IPv6 addresses. This style is NOT RECOMMENDED for its ambiguity.		IPv6 addresses. This style is NOT RECOMMENDED because of its
	The [] style as expressed in [RFC3986] SHOULD be employed, and is the		ambiguity. The [] style as expressed in [RFC3986] SHOULD be
	default unless otherwise specified. Other styles are acceptable when		employed, and is the default unless otherwise specified. Other
	there is exactly one style for the given context and cross-platform		styles are acceptable when there is exactly one style for the given
	portability does not become an issue. For URIs containing IPv6		context and cross-platform portability does not become an issue. For
	address literals, [RFC3986] MUST be followed, as well as the rules in		URIs containing IPv6 address literals, [RFC3986] MUST be followed, as
	this document.		well as the rules defined in this document.
	7. Prefix Representation		7. Prefix Representation
	Problems with prefixes are just the same as problems encountered with		Problems with prefixes are the same as problems encountered with
	addresses. The text representation method of IPv6 prefixes should be		addresses. The text representation method of IPv6 prefixes should be
	no different from that of IPv6 addresses.		no different from that of IPv6 addresses.
	8. Security Considerations		8. Security Considerations
	This document notes some examples where IPv6 addresses are compared		This document notes some examples where IPv6 addresses are compared
	in text format. The example on Section 3.2.5 is one that may cause a		in text format. The example on Section 3.2.5 is one that may cause a
	security risk if used for access control. The common practice of		security risk if used for access control. The common practice of
	comparing X.509 data is done in binary format.		comparing X.509 data is done in binary format.
	9. IANA Considerations		9. Acknowledgements
	None.
	10. Acknowledgements
	The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami,		The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami,
	Toshimitsu Matsuura for their generous and helpful comments in kick		and Toshimitsu Matsuura for their generous and helpful comments in
	starting this document. We also would like to thank Brian Carpenter,		kick starting this document. We also would like to thank Brian
	Akira Kato, Juergen Schoenwaelder, Antonio Querubin, Dave Thaler,		Carpenter, Akira Kato, Juergen Schoenwaelder, Antonio Querubin, Dave
	Brian Haley, Suresh Krishnan, Jerry Huang, Roman Donchenko, Heikki		Thaler, Brian Haley, Suresh Krishnan, Jerry Huang, Roman Donchenko,
	Vatiainen ,Dan Wing, and Doug Barton for their input. Also a very		Heikki Vatiainen, Dan Wing, and Doug Barton for their input. Also, a
	special thanks to Ron Bonica, Fred Baker, Brian Haberman, Robert		very special thanks to Ron Bonica, Fred Baker, Brian Haberman, Robert
	Hinden, Jari Arkko, and Kurt Lindqvist for their support in bringing		Hinden, Jari Arkko, and Kurt Lindqvist for their support in bringing
	this document to the light of IETF working groups.		this document to light in IETF working groups.
	11. References		10. References
	11.1. Normative References		10.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm		[RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm
	(SIIT)", RFC 2765, February 2000.		(SIIT)", RFC 2765, February 2000.
	[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform		[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
	Resource Identifier (URI): Generic Syntax", STD 66,		"Uniform Resource Identifier (URI): Generic Syntax",
	RFC 3986, January 2005.		STD 66, RFC 3986, January 2005.
	[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing		[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
	Architecture", RFC 4291, February 2006.		Architecture", RFC 4291, February 2006.
	11.2. Informative References		10.2. Informative References
	[I-D.ietf-behave-address-format]		[ADDR-FORMAT] Bao, C., "IPv6 Addressing of IPv4/IPv6 Translators",
	Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X.		Work in Progress, July 2010.
	Li, "IPv6 Addressing of IPv4/IPv6 Translators",
	draft-ietf-behave-address-format-04 (work in progress),
	January 2010.
	[RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.		[RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.
	Castro, "Application Aspects of IPv6 Transition",		Castro, "Application Aspects of IPv6 Transition",
	RFC 4038, March 2005.		RFC 4038, March 2005.
	[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site		[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
	Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,		Automatic Tunnel Addressing Protocol (ISATAP)",
	March 2008.		RFC 5214, March 2008.
	Appendix A. For Developers		Appendix A. For Developers
	We recommend that developers use display routines that conform to		We recommend that developers use display routines that conform to
	these rules. For example, the usage of getnameinfo() with flags		these rules. For example, the usage of getnameinfo() with flags
	argument NI_NUMERICHOST in FreeBSD 7.0 will give a conforming output,		argument NI_NUMERICHOST in FreeBSD 7.0 will give a conforming output,
	except for the special addresses notes in Section 5. The function		except for the special addresses notes in Section 5. The function
	inet_ntop() of FreeBSD7.0 is a good C code reference, but should not		inet_ntop() of FreeBSD7.0 is a good C code reference, but should not
	be called directly. See [RFC4038] for details.		be called directly. See [RFC4038] for details.
	Authors' Addresses		Authors' Addresses
	Seiichi Kawamura		Seiichi Kawamura
	NEC BIGLOBE, Ltd.		NEC BIGLOBE, Ltd.
	14-22, Shibaura 4-chome		14-22, Shibaura 4-chome
	Minatoku, Tokyo 108-8558		Minatoku, Tokyo 108-8558
	JAPAN		JAPAN
	Phone: +81 3 3798 6085		Phone: +81 3 3798 6085
	Email: kawamucho@mesh.ad.jp		EMail: kawamucho@mesh.ad.jp
	Masanobu Kawashima		Masanobu Kawashima
	NEC AccessTechnica, Ltd.		NEC AccessTechnica, Ltd.
	800, Shimomata		800, Shimomata
	Kakegawa-shi, Shizuoka 436-8501		Kakegawa-shi, Shizuoka 436-8501
	JAPAN		JAPAN
	Phone: +81 537 23 9655		Phone: +81 537 23 9655
	Email: kawashimam@necat.nec.co.jp		EMail: kawashimam@necat.nec.co.jp
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