RFC 4332
Cisco's Mobile IPv4 Host Configuration Extensions
RFC 4332 is Cisco's Mobile IPv4 Host Configuration Extensions 🎀 It's dated December 2005 and its category is Informational, so it's sharing info, not a standard 🌸 The authors are K. Leung (Cisco Systems), A. Patel (Cisco Systems), G. Tsirtsis (Flarion Technologies), and E. Klovning (Birdstep Technology ASA) 🫶 It came from the Network Working Group, and the header doesn't list anything it obsoletes or updates ✨
Status of This Memo ✨
This memo is just here to give the Internet community some info 💅 It is not an Internet standard of any kind, and it can be distributed with no limits 🦋
Copyright Notice 🌈
Copyright (C) The Internet Society (2005).
IESG Note 🙈
This RFC is not a candidate for any level of Internet Standard 💀 The IETF has no idea whether this RFC is fit for any purpose, and publishing it was not based on IETF review for things like security, congestion control, or inappropriate interaction with deployed protocols 😭 The RFC Editor chose to publish it at their own discretion, so readers should be careful about how much they trust it for implementation and deployment 🧚 See RFC 3932 for more info.
This RFC doesn't offer any security mechanisms for data origin authentication and integrity, and those security services are vitally important in this context 🚨
Abstract 🍓
An IP device needs basic host configuration before it can talk to anything 💖 Usually that means an IP address and the address of a DNS server 🧚 That info can be set statically, or grabbed dynamically with Dynamic Host Configuration Protocol (DHCP) or Point-to-Point Protocol/IP Control Protocol (PPP/IPCP) 🌸 The catch is that both DHCP and PPP/IPCP base the config on the access network 😭 In Mobile IPv4, the registration process boots a Mobile Node up on an access network, also called a foreign network ✨ But the config really needs to come from the home network 💅 This document describes the Cisco vendor-specific extensions to Mobile IPv4 that provide that base host config in Registration Request and Reply messages 🎀
Table of Contents 🦋
1. Introduction ....................................................2
2. Host Configuration Extensions Summary ...........................3
3. Host Configuration Extensions ...................................4
3.1. Host Configuration Request Extension .......................5
3.2. Home Network Length Prefix Extension .......................5
3.3. DNS Server Extension .......................................6
3.4. DHCP Server Extension ......................................6
3.5. DHCP Client ID Extension ...................................7
3.6. Default Gateway Extension ..................................7
3.7. DNS Suffix Extension .......................................8
3.8. Configuration URL Extension ................................8
4. Security Considerations .........................................9
5. Acknowledgements ................................................9
6. Informative References ..........................................91. Introduction 💖
An IPv4 device needs some basic config before it can talk to other nodes 🫶 Usually it has an IP address for an interface, plus a DNS server's IP address so it can turn the peer's hostname into an IP address 🌸 DHCP [RFC2131] and PPP/IPCP [RFC1332] give host config info on the access network interface, but that's not enough in a Mobile IPv4 environment 😭 In Mobile IPv4 [RFC3344], a Mobile Node has a virtual network interface on the home network, anchored by the Home Agent 🦋 The IP address, home subnet prefix, default gateway, and the home network's DNS servers are all essential for booting up a network interface ✨ Sometimes those are the only pieces of info the Mobile Node needs 💅
The Mobile IPv4 registration process is how a Mobile Node boots up on a foreign network 🧚 Once registration succeeds, the Mobile Node can talk to the Correspondent Node 🎀 There's a real need for an efficient way to get the host config 😤 If the Mobile Node is a DHCP client, it can get config parameters from the DHCP server on the home network after the initial registration 🍓
This document introduces the Cisco vendor-specific extensions (VSEs) [RFC3115] 🌈 They let a Mobile Node download some fundamental config tied to the home network through the Home Agent 💜 These extensions carry info about the home subnet prefix, DNS server, DHCP server, DHCP client identifier, default gateway, DNS suffix, and configuration URL 👑
2. Host Configuration Extensions Summary ✨
The following Cisco vendor-specific extensions provide the host config for a Mobile Node 💅 The "Host Configuration Request" extension is allowed only in the Registration Request 🙈 The rest are appended in the Registration Reply 🦋
- Host Configuration Request
- Request for host configuration information from the Mobile Node to the Home Agent.
- Home Network Prefix Length
- The length of the subnet prefix on the home network.
- Default Gateway
- The default gateway's IP address on the home network.
- DNS Server
- The DNS server's IP address in the home network.
- DNS Suffix
- The DNS suffix for hostname resolution in the home network.
- DHCP Client ID
- DHCP Server
- The DHCP server's IP address in the home network.
- Configuration URL
- The URL for the Mobile Node to download configuration parameters from a server.
When the Mobile Node needs its host config, the Host Configuration Request VSE gets appended to the Registration Request 🌸 That VSE tells the Home Agent that either all or selected host config VSEs should be appended to the Registration Reply 🧚 If the Home Agent got the info from a DHCP server (in Proxy DHCP mode), then the DHCP Client ID and DHCP Server extensions get appended to the Registration Reply 🫶 Those DHCP-related extensions carry values that were used in the DHCP messages exchanged between the Home Agent and the DHCP server 🔥
The VSEs get authenticated as part of the registration message, using any of the authentication mechanisms defined for Mobile IP ([RFC3344], [RFC3012]) 🔐
This message MAY contain extensions defined in Mobile IP, including vendor-specific extensions [RFC3115] 💖
3. Host Configuration Extensions 🌈
Cisco's host config extensions to Mobile IPv4 are based on the vendor-specific extensions defined in [RFC3115] 💜 Here's the format of the VSE TLV (Type-Length-Value) 👀
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor/Org-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-NVSE-Type | Vendor-NVSE-Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 134
Length:
Indicates the length (in bytes) of the data field within this
extension, excluding the Type and Length fields.
Reserved:
Reserved for future use. To be set to 0 while sending, ignored
on reception.
Vendor/Org-ID:
9 (Cisco Systems)
Vendor-NVSE-Type:
14 (Host Configuration)
Vendor-NVSE-Value:
Format is shown below for each subtype. The Sub-Type field is
an integer from 0 to 255.3.1. Host Configuration Request Extension 💅
Here's the format of the Host Configuration Request extension 🎀
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Selector |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Sub-Type:
0 - Selector:
0means the Mobile Node is requesting all host config that's available to the Home Agent (HA) 🦋
3.2. Home Network Length Prefix Extension 🌸
Here's the format of the Home Network Prefix Length extension 💖
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Sub-Type:
1 - Prefix Length: the number of bits in the home subnet prefix 🧚
3.3. DNS Server Extension 🌈
Here's the format of the DNS Server extension ✨
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Primary DNS Server
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . | Secondary DNS Server
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Sub-Type:
2 - Primary DNS Server: the IP address of the primary DNS server 💜
- Secondary DNS Server: the IP address of the secondary DNS server 🫶
3.4. DHCP Server Extension 🔥
Here's the format of the DHCP Server extension 💅
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | DHCP Server
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Sub-Type:
3 - DHCP Server: the IP address of the DHCP server 🎀
3.5. DHCP Client ID Extension
Okay so here's what the DHCP Client ID extension looks like 🎀
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Client ID . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Sub-Type: 4
Client ID: DHCP servers use this value to index their database of address bindings 🗂️ The value is expected to be unique for all clients in an administrative domain 🔑 The size of the field is between 2 and 255 octets ✨
3.6. Default Gateway Extension
This is the Default Gateway extension, and it's giving "tell me where to go" 🧭 Here's the layout:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Default Gateway
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Sub-Type: 5
Default Gateway: This is the IP address of the default gateway for the Mobile Node on the home network 🏠💖
3.7. DNS Suffix Extension
Next up is the DNS Suffix extension 🌸 Check out the shape:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | DNS Suffix . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Sub-Type: 6
DNS Suffix: This is the DNS suffix that gets appended to the name of the Mobile Node when it's completing its fully qualified domain name (FQDN) 🧚 The size of the field is between 1 and 246 octets 💅
3.8. Configuration URL Extension
Last one in this group: the Configuration URL extension 🦋 Here it is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | URL String . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Sub-Type: 7
URL String: The Mobile Node can retrieve configuration parameters via the URL 📥 The URL is at most 246 bytes in length 🍓
4. Security Considerations 🔐
Bestie, this part is serious, so read it closely 👀
The host configuration extensions follow the same rules for Mobile IP extensions in registration messages 🫶 See the Security Considerations section in RFC 3344 for the full picture.
⚠️ The Configuration URL extension may trigger the Mobile Node to download the configuration parameters from a server. The protection of that data transfer is outside the scope of this document 😭 Possible options include encryption of the data before transfer, or using HTTPS.
5. Acknowledgements 🌈
The authors would like to thank Jayshree Bharatia, Kuntal Chowdhury, Avi Lior, and Lila Madour for their contributions to the work in progress titled "Mobile IPv4 Extension for Configuration Options Exchange" 💜
6. Informative References 📚
Here's the reading list, with every reference and all its details:
[RFC1332] McGregor, G., "The PPP Internet Protocol Control Protocol
(IPCP)", RFC 1332, May 1992.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC3012] Perkins, C. and P. Calhoun, "Mobile IPv4 Challenge/
Response Extensions", RFC 3012, November 2000.
[RFC3115] Dommety, G. and K. Leung, "Mobile IP Vendor/
Organization-Specific Extensions", RFC 3115, April 2001.
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.Authors' Addresses 🎀
Meet the squad behind this spec 💖
Kent Leung
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Phone: +1 408-526-5030
EMail: kleung@cisco.com
Alpesh Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Phone: +1 408-853-9580
EMail: alpesh@cisco.com
George Tsirtsis
Flarion Technologies
Bedminster One
135 Route 202/206 South
Bedminster, NJ 07921
US
Phone: +1 908-947-7059
EMail: g.tsirtsis@flarion.com
Espen Klovning
Birdstep Technology ASA
Bryggegata 7
Oslo, 0250
Norway
Phone: +47 95 20 26 29
EMail: espen@birdstep.comFull Copyright Statement ⭐
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions contained in BCP 78 and at www.rfc-editor.org/copyright.html, and except as set forth therein, the authors retain all their rights.
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Acknowledgement 🌸
Funding for the RFC Editor function is currently provided by the Internet Society 💅✨
📦 where this page comes from
- ietf: rfc4332 2005-12
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