RFC 5223

Discovering Location-to-Service Translation (LoST) Servers Using the Dynamic Host Configuration Protocol (DHCP)

📅 published August 2008, from ietf

RFC 5223 💖 Discovering Location-to-Service Translation (LoST) Servers Using the Dynamic Host Configuration Protocol (DHCP)

okay bestie, RFC 5223 is giving main character energy 🎀 here's the title block tea:

Stream: Network Working Group 🌸
Category: Standards Track ✨ (it's an Internet standards track protocol)
Date: August 2008 🦋
Authors: Henning Schulzrinne (Columbia University), James Polk (Cisco), and Hannes Tschofenig (Nokia Siemens Networks) 💜
Obsoletes / Updates: the title block doesn't list anything this RFC obsoletes or updates 🙈

Status of This Memo 🌸

This doc specifies an Internet standards track protocol for the Internet community, and it's asking for discussion and suggestions for improvements 🫶 For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1). Distribution of this memo is unlimited 💅

Abstract 🦋

The Location-to-Service Translation (LoST) Protocol is an XML-based protocol that maps service identifiers and geospatial or civic location information to service contact Uniform Resource Locators (URLs) 🗺️ LoST servers can be located anywhere, but a placement closer to the end host, e.g., in the access network, is desirable 💖 In disaster situations with intermittent network connectivity, that kind of placement helps the resiliency of emergency service communication 🚨

This document describes how a LoST client can discover a LoST server using the Dynamic Host Configuration Protocol (DHCP) 🧚

Table of Contents 📑

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.  Domain Name Encoding  . . . . . . . . . . . . . . . . . . . . . 3
   4.  LoST Server DHCPv4 Option . . . . . . . . . . . . . . . . . . . 3
   5.  LoST Server DHCPv6 Option . . . . . . . . . . . . . . . . . . . 4
   6.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
     7.1.  DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . . 5
     7.2.  DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 6
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 6

1. Introduction ✨

The Location-to-Service Translation (LoST) Protocol [RFC5222] is an XML-based protocol for mapping service identifiers and geospatial or civic location information to service contact Uniform Resource Locators (URLs) 🌈

So, to talk to a LoST server, the LoST client needs to find out the server's IP address 👀 There are a few ways to learn it, including manual configuration. But in environments where the access network either deploys a LoST server or knows a third party that runs one, DHCP can hand the end host a domain name 🎁 That domain name then gets fed into the DNS-based resolution mechanism described in LoST [RFC5222], which reuses the URI-enabled NAPTR specification (see [RFC4848]) 🧠

This document specifies a DHCPv4 option and a DHCPv6 option that let LoST clients discover local LoST servers 💜

Section 2 gives the terminology. Section 3 shows the encoding of the domain name. Section 4 describes the DHCPv4 option, and Section 5 describes the DHCPv6 option, which does the same job 💅 IANA and Security Considerations wrap things up in Sections 7 and 8 🎀

2. Terminology 🧸

In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [RFC2119] 📖

Within this document, we borrow terminology from [RFC5012] and [RFC5222] 🫶

3. Domain Name Encoding 🌷

This section explains how the domain name used in the DHCPv4 option (Section 4) and the DHCPv6 option (Section 5) gets encoded 🧩

The domain name is encoded according to Section 3.1 of RFC 1035 [RFC1035], where each label is written as a one-octet length field followed by that many octets. Since every domain name ends with the null label of the root, a domain name is terminated by a length byte of zero 🛑 The high-order two bits of every length octet MUST be zero, and the remaining six bits of the length field limit the label to 63 octets or less. To keep implementations simple, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less 📏

4. LoST Server DHCPv4 Option 🦋

The LoST server DHCPv4 option carries a DNS (RFC 1035 [RFC1035]) fully-qualified domain name (FQDN) that the LoST client uses to locate a LoST server 🔍

Here's the format for this option 👇

      Code    Len   LoST Server Domain Name
      +-----+-----+-----+-----+-----+-----+-----+----
      | 137 |  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...
      +-----+-----+-----+-----+-----+-----+-----+----

Figure 1: LoST FQDN DHCPv4 Option

The values s1, s2, s3, etc. represent the domain name labels in the domain name encoding. Quick heads up: the length field in the DHCPv4 option is the length of the entire domain name encoding, while the length fields inside the domain name encoding (see Section 3) are the length of a single label 🙌

Code: OPTION_V4_LOST (137)
Len: Length of the 'LoST Server Domain Name' field in octets; variable.
LoST Server Domain Name: The domain name of the LoST server for the client to use.

A DHCPv4 client MAY request a LoST server domain name in a Parameter Request List option, as described in [RFC2131] 💌

The encoding of the domain name is described in Section 3 🧁

This option contains a single domain name and, as such, MUST contain precisely one root label 💀

5. LoST Server DHCPv6 Option 🌸

This section defines a DHCPv6 option that carries a domain name 🎀

The DHCPv6 option has the format shown in Figure 2 ✨

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      OPTION_V6_LOST           |         option-length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                LoST Server Domain Name                        |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code: OPTION_V6_LOST (51)
option-length: Length of the 'LoST Server Domain Name' field in octets; variable.
LoST Server Domain Name: The domain name of the LoST server for the client to use.

Figure 2: DHCPv6 Option for LoST Server Domain Name List

A DHCPv6 client MAY request a LoST server domain name in an Options Request Option (ORO), as described in [RFC3315] 🫧

The encoding of the domain name is described in Section 3 🧁

This option contains a single domain name and, as such, MUST contain precisely one root label 💀

Okay, that's the first half of the protocol with all the DHCP option drama 💜

Full Copyright Statement 💖

Okay bestie, the legal part is here 📜 Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 🦋

This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 😭

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That's the whole document, bestie! 🌈👑

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ietf: rfc5223 2008-08
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