In the realm of computer networking, especially when dealing with routing and network protocols, the concept of a Family Identifier is crucial. These identifiers, specifically known as Address Family Numbers (AFNs) in the context of network addresses, act as a fundamental mechanism for categorizing and differentiating various types of network addresses. This article delves into the world of Address Family Numbers, as officially maintained by the Internet Assigned Numbers Authority (IANA), providing a comprehensive guide to their purpose and significance in modern networking.
Address Family Numbers are numerical identifiers assigned to different address families. Think of them as labels that tell network devices and protocols what kind of address they are dealing with. This is essential because networks today handle a multitude of protocols and address formats, from the ubiquitous IPv4 and IPv6 to more specialized or legacy systems. Without a clear way to identify these different address families, network communication would be chaotic and inefficient.
The IANA maintains the definitive registry of Address Family Numbers, ensuring a standardized and globally recognized system. This registry is critical for interoperability and consistent operation of network devices and software across the internet. The official registry is publicly accessible and serves as the authoritative source for these identifiers.
| Number | Description | Reference |
|---|---|---|
| 0 | Reserved | |
| 1 | IP (IP version 4) | |
| 2 | IP6 (IP version 6) | |
| 3 | NSAP | |
| 4 | HDLC (8-bit multidrop) | |
| 5 | BBN 1822 | |
| 6 | 802 (includes all 802 media plus Ethernet “canonical format”) | |
| 7 | E.163 | |
| 8 | E.164 (SMDS, Frame Relay, ATM) | |
| 9 | F.69 (Telex) | |
| 10 | X.121 (X.25, Frame Relay) | |
| 11 | IPX | |
| 12 | Appletalk | |
| 13 | Decnet IV | |
| 14 | Banyan Vines | |
| 15 | E.164 with NSAP format subaddress | [ATM Forum UNI 3.1. October 1995.][Andy_Malis] |
| 16 | DNS (Domain Name System) | |
| 17 | Distinguished Name | [Charles_Lynn] |
| 18 | AS Number | [Charles_Lynn] |
| 19 | XTP over IP version 4 | [Mike_Saul] |
| 20 | XTP over IP version 6 | [Mike_Saul] |
| 21 | XTP native mode XTP | [Mike_Saul] |
| 22 | Fibre Channel World-Wide Port Name | [Mark_Bakke] |
| 23 | Fibre Channel World-Wide Node Name | [Mark_Bakke] |
| 24 | GWID | [Subra_Hegde] |
| 25 | AFI for L2VPN information | [RFC4761][RFC6074] |
| 26 | MPLS-TP Section Endpoint Identifier | [RFC7212] |
| 27 | MPLS-TP LSP Endpoint Identifier | [RFC7212] |
| 28 | MPLS-TP Pseudowire Endpoint Identifier | [RFC7212] |
| 29 | MT IP: Multi-Topology IP version 4 | [RFC7307] |
| 30 | MT IPv6: Multi-Topology IP version 6 | [RFC7307] |
| 31 | BGP SFC | [RFC9015] |
Table: A selection of registered Address Family Numbers. For the complete and most up-to-date list, refer to the official IANA registry.
The Role of Address Family Numbers in Networking Protocols
Address Family Numbers are utilized in various networking protocols, most notably in Border Gateway Protocol (BGP), a critical protocol for routing internet traffic. In BGP, AFNs are used to specify the address family for which routing information is being exchanged. This allows BGP to carry routes for multiple address families, such as IPv4 and IPv6, within the same peering session.
For instance, when BGP peers negotiate capabilities, they indicate the address families they support using these numbers. This ensures that routers understand the type of network addresses being advertised and can process them correctly. Without AFNs, BGP and other similar protocols would struggle to handle the diverse range of network address types prevalent in modern networks.
Understanding the IANA Registry and Range Allocation
The IANA registry for Address Family Numbers is organized and managed to ensure that assignments are unique and follow a defined process. The registry includes a range of numbers, each with a specific allocation policy:
- 1-16383: Standards Action: This range is designated for address families that are standardized through formal standards development organizations like the Internet Engineering Task Force (IETF). Assignments in this range require a “Standards Action,” meaning they must be documented in a published standard (RFC).
- 16384-32767: First Come First Served: This range operates on a “First Come First Served” basis. This allows for more rapid assignment for new address families that may not yet have a formal standard but are still needed for operational purposes.
This two-tiered approach balances the need for both standardized, well-vetted address families and the flexibility to accommodate newer, emerging networking technologies.
Key Address Family Identifiers to Know
While the IANA registry contains a comprehensive list, some Address Family Numbers are more commonly encountered than others, particularly in contemporary networking. These include:
- 1 (IPv4): Representing the Internet Protocol version 4, the foundational protocol of the internet.
- 2 (IPv6): Representing Internet Protocol version 6, the successor to IPv4, designed to address IPv4 address exhaustion and provide enhanced capabilities.
- 25 (AFI for L2VPN information): Used in the context of Layer 2 Virtual Private Networks (VPNs), indicating address family information related to L2VPNs.
Understanding these key identifiers is essential for network professionals working with routing protocols, network configuration, and protocol analysis.
Conclusion: The Importance of Standardized Family Identifiers
Address Family Numbers, as managed by IANA, are a seemingly simple yet profoundly important element of network infrastructure. They provide a standardized method for identifying and categorizing different types of network addresses, enabling the seamless operation of complex networking protocols and ensuring interoperability across diverse network environments. By providing a clear and universally recognized system of family identifiers, IANA facilitates the smooth functioning and continued evolution of the internet and modern computer networks.
Contact Information
| ID | Name | Contact URI | Last Updated |
|---|---|---|---|
| [Andy_Malis] | Andy Malis | mailto:agmalis&gmail.com | 2013-05-28 |
| [Charles_Lynn] | Charles Lynn | mailto:clynn&bbn.com | 2000-03 |
| [David_Meyer] | David Meyer | mailto:dmm&1-4-5.net | 2009-11-12 |
| [Donnie_Savage] | Donnie Savage | mailto:dsavage&cisco.com | 2008-05-13 |
| [Mark_Bakke] | Mark Bakke | mailto:mbakke&cisco.com | 2002-03 |
| [Mike_Saul] | Mike Saul | mailto:mike&nentat.com | 2000-09 |
| [Nischal_Sheth] | Nischal Sheth | mailto:nischal.sheth&gmail.com | 2019-11-04 |
| [Subra_Hegde] | Subra Hegde | mailto:subrah&cisco.com | 2002-03 |
RFC2453
RFC2677
RFC2858
RFC4761
RFC6074
RFC7212
RFC7307
RFC9015
RFC9552
RFC7042
RFC7961
RFC7455
draft-ietf-idr-rpd-02
draft-kaliraj-bess-bgp-sig-private-mpls-labels-03
Alt texts for images (if any were present in the original and deemed relevant to re-include):
(There were no images in the original text that were directly content-related. The icons were for file format downloads and are not essential to the understanding of “family identifier” or “Address Family Numbers”. Therefore, no images from the original were re-included in this rewritten article.)
