--- 1/draft-ietf-6man-text-addr-representation-03.txt 2010-01-14 13:12:09.000000000 +0100 +++ 2/draft-ietf-6man-text-addr-representation-04.txt 2010-01-14 13:12:09.000000000 +0100 @@ -1,19 +1,19 @@ IPv6 Maintenance Working Group S. Kawamura Internet-Draft NEC BIGLOBE, Ltd. Intended status: Standards Track M. Kawashima -Expires: May 29, 2010 NEC AccessTechnica, Ltd. - November 25, 2009 +Expires: July 18, 2010 NEC AccessTechnica, Ltd. + January 14, 2010 A Recommendation for IPv6 Address Text Representation - draft-ietf-6man-text-addr-representation-03 + draft-ietf-6man-text-addr-representation-04 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 @@ -37,25 +37,25 @@ 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 http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on May 29, 2010. + This Internet-Draft will expire on July 18, 2010. Copyright Notice - Copyright (c) 2009 IETF Trust and the persons identified as the + Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as @@ -77,45 +77,45 @@ 3.1.4. Searching for an Address in a Network Diagram . . . . 7 3.2. Parsing and Modifying . . . . . . . . . . . . . . . . . . 7 3.2.1. General Summary . . . . . . . . . . . . . . . . . . . 7 3.2.2. Logging . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.3. Auditing: Case 1 . . . . . . . . . . . . . . . . . . . 7 3.2.4. Auditing: Case 2 . . . . . . . . . . . . . . . . . . . 8 3.2.5. Verification . . . . . . . . . . . . . . . . . . . . . 8 3.2.6. Unexpected Modifying . . . . . . . . . . . . . . . . . 8 3.3. Operating . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3.1. General Summary . . . . . . . . . . . . . . . . . . . 8 - 3.3.2. Customer Calls . . . . . . . . . . . . . . . . . . . . 9 + 3.3.2. Customer Calls . . . . . . . . . . . . . . . . . . . . 8 3.3.3. Abuse . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4. Other Minor Problems . . . . . . . . . . . . . . . . . . . 9 3.4.1. Changing Platforms . . . . . . . . . . . . . . . . . . 9 3.4.2. Preference in Documentation . . . . . . . . . . . . . 9 3.4.3. Legibility . . . . . . . . . . . . . . . . . . . . . . 9 - 4. A Recommendation for IPv6 Text Representation . . . . . . . . 10 + 4. A Recommendation for IPv6 Text Representation . . . . . . . . 9 4.1. Handling Leading Zeros in a 16 Bit Field . . . . . . . . . 10 4.2. "::" Usage . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2.1. Shorten As Much As Possible . . . . . . . . . . . . . 10 4.2.2. Handling One 16 Bit 0 Field . . . . . . . . . . . . . 10 4.2.3. Choice in Placement of "::" . . . . . . . . . . . . . 10 4.3. Lower Case . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5. Text Representation of Special Addresses . . . . . . . . . . . 11 + 5. Text Representation of Special Addresses . . . . . . . . . . . 10 6. Notes on Combining IPv6 Addresses with Port Numbers . . . . . 11 - 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 - 11.2. Informative References . . . . . . . . . . . . . . . . . . 13 + 7. Prefix Representation . . . . . . . . . . . . . . . . . . . . 11 + 8. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 + 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 12.1. Normative References . . . . . . . . . . . . . . . . . . . 13 + 12.2. Informative References . . . . . . . . . . . . . . . . . . 13 Appendix A. For Developers . . . . . . . . . . . . . . . . . . . 13 - Appendix B. Prefix Issues . . . . . . . . . . . . . . . . . . . . 13 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction A single IPv6 address can be text represented in many ways. Examples are shown below. 2001:db8:0:0:1:0:0:1 2001:0db8:0:0:1:0:0:1 @@ -306,61 +306,61 @@ it was better, a simple diff will tell you that a different address was 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 real auditing. Lots of tools are just plain 'diff's that do not take into account address representation rules. 3.2.4. Auditing: Case 2 Node configurations will be matched against an information system that manages IP addresses. If output notation is different, there - 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 - written text file is highly unlikely to match on first try. + 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 + textual address written by a human is highly unlikely to match on + first try. 3.2.5. Verification Some protocols require certain data fields to be verified. One - example of this is X.509 certificates. If an IPv6 address was - embedded in one of the fields in a certificate, and the verification - was done by just a simple textual comparison, the certificate may be - mistakenly shown as being invalid due to a difference in text - representation methods. + example of this is X.509 certificates. If an IPv6 address field in a + certificate was incorrectly verified by converting it to text and + making a simple textual comparison to some other address, the + certificate may be mistakenly shown as being invalid due to a + difference in text representation methods. 3.2.6. Unexpected Modifying Sometimes, a system will take an address and modify it as a 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 - RIR databases). If the zeros were input for a reason, the outcome - may be somewhat unexpected. + 2001:0db8:0::1 and make the output 2001:db8::1. If the zeros were + input for a reason, the outcome may be somewhat unexpected. 3.3. Operating 3.3.1. General Summary 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 - 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 - communicating with the operator to solve a problem, is usually not as - distinguished as we would like. + result as 2001:DB8::1:0:0:1. Someone familiar with IPv6 address + representation will know that the right address is set, but not + everyone may understand this. 3.3.2. Customer Calls When a customer calls to inquire about a suspected outage, IPv6 address representation should be handled with care. Not all 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 - 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 - happen in IPv4 because IPv4 address cannot be abbreviated. + The network operations center 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 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. 3.3.3. Abuse Network abuse is reported along with the abusing IP address. This 'reporting' could take any shape or form of the flexible model. A 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 placement of the "::" will result in a critical situation. A system that handles these incidents should be able to handle any type of input and parse it in a correct manner. Also, incidents are reported @@ -370,22 +370,22 @@ information. 3.4. Other Minor Problems 3.4.1. Changing Platforms 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 address text representation. Usually, a change in a platform (e.g. Unix to Windows, Cisco to Juniper) will result in a major change of - code, but flexibility in address representation will increase the - work load. + code anyway, but flexibility in address representation will increase + the work load. 3.4.2. Preference in Documentation A document that is edited by more than one author, may become harder to read. 3.4.3. Legibility Capital case D and 0 can be quite often misread. Capital B and 8 can also be misread. @@ -398,21 +398,21 @@ by various operating systems, and is human friendly. The recommendation in this document SHOULD be followed by systems when generating an address to represent as text, but all implementations 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 Leading zeros should be chopped for human legibility and easier searching. Also, a single 16 bit 0000 field should be represented as - just 0. Place holder zeros are often cause of misreading. + just 0. 4.2. "::" Usage 4.2.1. Shorten As Much As Possible The use of "::" should be used to its maximum capability (i.e. 2001: db8::0:1 is not considered as clean representation). 4.2.2. Handling One 16 Bit 0 Field @@ -437,122 +437,124 @@ Recent implementations tend to represent IPv6 address as lower case. It is better to use lower case to avoid problems such as described in section 3.3.3 and 3.4.3. 5. Text Representation of Special Addresses Addresses such as IPv4-Mapped IPv6 addresses, ISATAP [RFC5214], and IPv4-translatable addresses [I-D.ietf-behave-address-format] have IPv4 addresses embedded in the low-order 32 bits of the address. These addresses have special representation that may mix hexadecimal - and decimal notations. The decimal notation may be used only for the - last 32 bits of the address. For these addresses, mixed notation is - recommended if either of the below conditions are met. - - (1) The address can be distinguished as having IPv4 addresses - embedded in the lower 32 bits solely from the address field. (e.g. - Well Known Prefixes) - - (2) An external mechanism such as prefix learning or pre- - configuration helps in recognizing the address as having IPv4 - addresses embedded in the lower 32 bits. + and dot decimal notations. The decimal notation may be used only for + the last 32 bits of the address. For these addresses, mixed notation + is recommended if the following condition is met: The address can be + distinguished as having IPv4 addresses embedded in the lower 32 bits + solely from the address field through the use of a well known prefix. + If it is known by some external method that a given prefix includes + an IPv4 address, it MAY be represented as mixed notation. Tools that + provide options to specify prefixes that is (or is not) to be + represented as mixed notation may be useful. - However, there may be situations where full hexadecimal - representation is chosen to meet certain needs. Addressing those - needs is out of the scope of this document. 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 0:0:0:0:0:ffff: - 192.0.2.1). + 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 + 0:0:0:0:0:ffff:192.0.2.1). 6. Notes on Combining IPv6 Addresses with Port Numbers When IPv6 addresses and port numbers are represented in text combined - together, there seems to be many different ways to do so. Examples - are shown below. + together, there are many different ways to do so. Examples are shown + below. o [2001:db8::1]:80 o 2001:db8::1:80 o 2001:db8::1.80 o 2001:db8::1 port 80 o 2001:db8::1p80 o 2001:db8::1#80 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 IPv6 addresses. This style is not recommended for its ambiguity. - The [] style as expressed in [RFC3986] is recommended. Other styles - are acceptable when cross-platform portability does not become an - issue. + The [] style as expressed in [RFC3986] should be employed, and is the + default unless otherwise specified. Other styles are acceptable when + there is exactly one style for the given context and cross-platform + portability does not become an issue. -7. Conclusion +7. Prefix Representation + + Problems with prefixes are just the same as problems encountered with + addresses. Text representation method of IPv6 prefixes should be no + different from that of IPv6 addresses. + +8. Conclusion The recommended format of text representing an IPv6 address is summarized as follows. (1) omit leading zeros in a 16 bit field (2) when using "::", shorten consecutive zero fields to their maximum extent (leave no zero fields behind). (3) "::" used where shortens address the most (4) "::" used in the former part in case of a tie breaker (5) do not shorten one 16 bit 0 field, but always shorten when there are two or more consecutive 16 bit 0 fields (6) use lower case Hints for developers are written in the Appendix section. -8. Security Considerations +9. Security Considerations None. -9. IANA Considerations +10. IANA Considerations None. -10. Acknowledgements +11. Acknowledgements The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami, Toshimitsu Matsuura for their generous and helpful comments in kick starting this document. We also would like to thank Brian Carpenter, Akira Kato, Juergen Schoenwaelder, Antonio Querubin, Dave Thaler, Brian Haley, Suresh Krishnan, Jerry Huang, Roman Donchenko, Heikki Vatiainen ,Dan Wing for their input. Also a very special thanks to Ron Bonica, Fred Baker, Brian Haberman, Robert Hinden, Jari Arkko, and Kurt Lindqvist for their support in bringing this document to the light of IETF working groups. -11. References +12. References -11.1. Normative References +12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. -11.2. Informative References +12.2. Informative References [I-D.ietf-behave-address-format] Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", - draft-ietf-behave-address-format-01 (work in progress), - October 2009. + draft-ietf-behave-address-format-03 (work in progress), + December 2009. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E. Castro, "Application Aspects of IPv6 Transition", RFC 4038, March 2005. [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site @@ -561,26 +563,20 @@ Appendix A. For Developers We recommend that developers use display routines that conform to these rules. For example, the usage of getnameinfo() with flags argument NI_NUMERICHOST in FreeBSD 7.0 will give a conforming output, 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 be called directly. See [RFC4038] for details. -Appendix B. Prefix Issues - - Problems with prefixes are just the same as problems encountered with - addresses. Text representation method of IPv6 prefixes should be no - different from that of IPv6 addresses. - Authors' Addresses Seiichi Kawamura NEC BIGLOBE, Ltd. 14-22, Shibaura 4-chome Minatoku, Tokyo 108-8558 JAPAN Phone: +81 3 3798 6085 Email: kawamucho@mesh.ad.jp