RFC 6153

DHCPv4 and DHCPv6 Options for Access Network Discovery and Selection Function (ANDSF) Discovery

📅 published February 2011, from ietf

RFC 6153: DHCPv4 and DHCPv6 Options for ANDSF Discovery ✨

Internet Engineering Task Force (IETF) 🌸 Request for Comments: 6153 Category: Standards Track ISSN: 2070-1721 Date: February 2011

okay bestie, the title block first 🎀 this one was written by S. Das (Telcordia Technologies) and G. Bajko (Nokia). It's on the Standards Track, which means it's an official Internet standard, not just an idea floating around. It came out in February 2011. The header doesn't list any RFCs it obsoletes or updates, so there's no drama with older versions 💅

Abstract

okay so this doc adds new DHCPv4 and DHCPv6 options 🦋 that let a mobile node find an Access Network Discovery and Selection Function (ANDSF) entity on an IP network. ANDSF is being built in the Third Generation Partnership Project (3GPP), and it hands out inter-system mobility policies and access-network-specific info to mobile nodes (MNs). the whole point is helping phones pick the right network 📶✨

Status of This Memo

This is an Internet Standards Track document. ✨

It's a product of the Internet Engineering Task Force (IETF), so it reflects consensus across the IETF community. It went through public review and got approved for publication by the Internet Engineering Steering Group (IESG). If you want more about Internet Standards, check Section 2 of RFC 5741.

Want the latest on this document's status, any errata, or where to send feedback? Head to http://www.rfc-editor.org/info/rfc6153 🌈

Copyright (c) 2011 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) as they stand on the publication date. please read these carefully, because they spell out your rights and restrictions for this document 🧾

Code components pulled out of this document must include the Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, same as the Simplified BSD License says 💜

Table of Contents 🍓

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................3
      1.2. Terminology and Abbreviations Used in This Document ........3
   2. ANDSF IPv4 Address Option for DHCPv4 ............................3
   3. ANDSF IPv6 Address Option for DHCPv6 ............................4
   4. Option Usage ....................................................4
      4.1. Usage of ANDSF Options for DHCPv4 ..........................4
           4.1.1. Mobile Node Behavior ................................4
      4.2. Usage of ANDSF Options for DHCPv6 ..........................5
           4.2.1. Mobile Node Behavior ................................5
   5. Security Considerations .........................................5
   6. IANA Considerations .............................................5
   7. Acknowledgments .................................................6
   8. References ......................................................6
      8.1. Normative References .......................................6
      8.2. Informative References .....................................6

1. Introduction ✨

okay so ANDSF is being defined in 3GPP [3GPPTS23.402] to give mobile nodes the network discovery and selection help they need 🧚 this matters most in multi-access scenarios where 3GPP access-network-level solutions aren't enough for a mobile node to discover and select non-3GPP networks.

the info ANDSF provides includes inter-system mobility policies and access-network-specific data that help the mobile node do an inter-system handover 🦋 the home operator can preload this info onto the mobile node, or ANDSF can send it dynamically over the S14 reference point, as defined in [3GPPTS23.402] and [3GPPTS24.302].

in 3GPP, ANDSF can live in the subscriber's home operator network or the visited network. the MN needs to know about it, or find it on its own. according to [3GPPTS23.402] and [3GPPTS24.302], the MN discovers ANDSF by talking to the Domain Name Service function or the DHCP server function 💅

so this document defines new DHCPv4 and DHCPv6 options, called the ANDSF IP Address Options, which let the MN locate an ANDSF server 🎀

1.1. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 🌸

1.2. Terminology and Abbreviations Used in This Document

here's the vocab you need 📚

  • ANDSF (Access Network Discovery and Selection Function): an entity that provides network discovery and selection assistance data to the user entity (UE) as per operator policy [3GPPTS23.402].
  • Access Network: a network that is accessed by the UE.
  • 3GPP Network: a radio access network specified by Third Generation Partnership Project.
  • Non-3GPP Network: a radio access network specified outside 3GPP by other projects or standards organizations.

2. ANDSF IPv4 Address Option for DHCPv4 🦋

this section is all about the ANDSF IPv4 Address Option for DHCPv4. here's the layout, bestie:

      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 Code   |    Length     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     IP Address                                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     +---------------------------------------------------------------+

Option Code 💜 the value is OPTION-IPv4_Address-ANDSF (142).

Length 🌷 this is the length in bytes of the option, not counting the 'Option Code' and 'Length' fields. the 'Length' field is set to 4N, where N is the number of IPv4 addresses carried in the option.

IP Address 🍓 these are the IPv4 address(es) of the ANDSF server(s).

ANDSF servers MUST be listed in order of preference, and the client SHOULD process them in decreasing order of preference. 👑

3. ANDSF IPv6 Address Option for DHCPv6 🌈

this section is the IPv6 version, the ANDSF IPv6 Address Option for DHCPv6. quick heads up: all values in this option are written in network byte order 🧚 here's the layout:

      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 Code              |         Length                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         IP Address                            |
     .                                                               .
     +---------------------------------------------------------------+

Option Code 🦋 the value is OPTION-IPv6_Address-ANDSF (143).

Length 💅 this is the length in bytes of the option, not counting the 'Option Code' and 'Length' fields. the 'Length' field is set to 16N, where N is the number of IPv6 addresses carried in the option.

IP Address ✨ these are the IPv6 address(es) of the ANDSF server(s).

ANDSF servers MUST be listed in order of preference, and the client SHOULD process them in decreasing order of preference. 🫶

8.2. Informative References ✨

okay wait, this is the bit where the RFC lists its "extra reading" sources, and they're all about the 3GPP specs that the whole ANDSF thing leans on 📚💅

Authors' Addresses 🎀

okay so here are the people who wrote it, and how to reach them if you're feeling brave 💖

Subir Das 🧚 Telcordia Technologies Inc. EMail: subir@research.telcordia.com

Gabor Bajko 👑 Nokia EMail: gabor@bajko.nokia.com

literally the whole RFC, start to finish, bestie 🫶 periodt ✨

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