GUIDELINES ON IPV4 ADDRESSING AND AUTONOMOUS SYSTEM NUMBERING FOR THE GPRS NETWORK INFRASTRUCTURE

Jarnail Malra, BT Cellnet

?Copyright of the GSM MoU Association 2000

1. References

2. Abbreviations

3. Introduction

3.1 In-scope

This document provides guidelines for IPv4 addressing of the GPRS network infrastructure by GSM mobile network operators to enable GPRS roaming services to be supported.

This document also provides guidelines on the use of Autonomous System (AS) Numbering scheme in the GPRS network infrastructure.

The details defined in this document will enable all GSM mobile network operators to request public IPv4 addresses and AS Numbers for assignment to their GPRS networks in accordance with the requirements and procedures defined by the Internet Registry System.

Note 1. This document does not act as a guarantee that an operator will be assigned public address space. Address space assignment will be assessed on an individual request basis as per the standard request procedures defined by the Internet Registry System.

Note 2. Although the guideline procedures and processes presented in this document associated with requesting public IP addresses/AS Numbers from the RIRs may be new to the GSM Association members, they are considered 'business as usual' for the Internet Registry community.

Note 3. An RIR can submit comments or changes to this document by notifying the editor at the following email address: jarnail.malra@btcellnet.net. GSM-A members will submit changes directly to the GSM-A (i.e. ireg-gprswp@infocentre.gsm.org) using existing Change Request procedures.

3.2 Out of scope

The following items are considered out of the scope of this document:

• IP addressing requirements for mobile terminals.
• IPv6 Addressing.
• Non-GSM/GPRS-based mobile data systems, e.g. Third generation mobile systems (e.g. CDMA-based), D-AMPS, etc.

3.3 Background

In order for mobile network operators to support GPRS roaming services, GPRS network elements in the network of one operator need to communicate with GPRS network elements in the network of another operator. An inter-PLMN backbone network is used to interconnect the networks of each operator. Each GPRS network element involved in the roaming process that interacts across this backbone network must be uniquely addressed. This activity must be co-ordinated on a global basis to ensure the associated GPRS roaming network elements are uniquely addressed for all the GPRS mobile operators across the world. Initial investigations by the GSM Association indicated the most practical method to implement this requirement was to address the network elements using public address space.

The GSM Association subsequently initiated discussions with the European Regional Internet Registry, RIPE NCC in early-2000 to seek clarification and approval of a policy for the use of public IP addresses in the GPRS network infrastructure. Initial proposals were presented by the GSM Association at the RIPE-35 meeting ^[17]. A "GPRS infrastructure IP Addressing Working Party" task force was subsequently set up and a meeting ^[9] held at which the GSM Association's members clarified their needs, ISPs raised their concerns and the RIPE NCC clarified its existing IP address allocation policies and procedures. The outcome of this meeting were presented to the RIPE community at RIPE-36 ^[18], the result of which are described in the following section.

3.4 Current status

A joint press release ^[10] from the GSM Association and the RIPE NCC reported the principal results of the RIPE-36 meeting as follows:

• Public IPv4 address space can be used in parts of the GPRS network infrastructure
• Existing IP address allocation policies and procedures apply
• Requests from mobile network operators can be sent directly to the RIPE NCC or their data network backbone providers

This document has been subsequently reviewed by the other RIRs, i.e. ARIN and APNIC and their comments included in this document. It is intended that these RIRs will present this document at their next 'Public/Open Policy' meetings for review/acceptance by their respective members as follows:

• ARIN: 2-4 October, 2000 (http://www.arin.net/announcements/memmeet.html)
• APNIC: 25-27 October, 2000 (http://www.apnic.net/meetings)

4. Internet Registry System

4.1 Overview

The Internet Registry system has been established to primarily administer and manage the available public Internet address space on a worldwide basis. It is comprised of various hierarchically organised bodies, including an overall co-ordinating body (ICANN), and Internet Registries (IR). IRs are classified according to their primary function and territorial scope within the hierarchical structure and can be organised as Regional IRs (RIR), National IRs (NIR), Delegated Registries (DR) and Local IRs (LIR) as depicted in Figure 1.

4.2 ICANN

The Internet Corporation for Assigned Names and Numbers (ICANN) ^[2] is a technical co-ordination body for the Internet and has authority over all number and domain name spaces used in the Internet. ICANN was created in October 1998 by a broad coalition of the Internet's business, technical, academic and user communities, and assumed responsibility for a set of technical functions that were previously performed under US government contract by IANA and other groups. ICANN co-ordinates the assignment of the three identifiers listed below that must be globally unique for the Internet to function.

• Internet domain names
• IP Address numbers - ICANN allocates public Internet address space to RIRs
• Protocol parameters and port numbers

In addition, ICANN co-ordinates the stable operation of the Internet's root server system.

4.3 Regional Internet Registries

Regional Internet Registries (RIRs) have operated for some years under the authority of IANA, but are now recognised within the ICANN framework. There are currently three RIRs: RIPE NCC, ARIN, and APNIC. Each RIR will serve and represent its members for specific geographic areas as identified in the table below. Additional RIRs may be established in the future, e.g. AfriNIC and LACNIC

Each RIR may have different local structures organised to serve the Internet community. For example, APNIC supports NIRs in addition to LIRs, and similarly ARIN supports DRs.

The RIR will be responsible for the allocation of IP address space to all the LIRs/NIRs it serves, and registering those allocations and subsequent assignments in a publicly-available "who-is" database.

Table 1. RIRs and their served areas
RIR		Areas served	Links for further information
1. RIPE NCC Réseaux IP Européens Network Co-ordination Centre		Europe The Middle East Central Asia African countries located north of the Equator	http://www.ripe.net/
2. ARIN American Registry for Internet Numbers		North America South America Caribbean African countries located south of the Equator	http://www.arin.net/
3. APNIC Asia Pacific Network Information Centre		Entire Asia Pacific region, including 62 economies/countries/regions in South and Central Asia, South-East Asia, Indochina and Oceania	http://www.apnic.net/
Future RIRs currently in the process of being established:
4. AfriNIC African Network Information Centre	To serve the African region Operations start date not yet known			http://www.afrinic.org/ http://www.apnic.net/mailing-lists/pagan/9706/msg00081.html: Proposal document
5. LACNIC Latin American Continent Network Information Centre	To serve the Latin American region. Expected to start operations by Sept/Oct 2000, but no agreed date yet set.			http://www.lacnic.org/

4.4 National Internet Registries

NIRs are only operated and supported in the APNIC organisational structure.

NIRs provide registration and allocation services for members (generally ISPs) organised on a national basis. NIRs operate in Japan (JPNIC), Korea (KRNIC), China (CNNIC), Taiwan (TWNIC) and in Indonesia (APJII). All of these NIRs operate within the APNIC policy framework and receive their resources directly from APNIC.

4.5 Delegated Registries

Delegated Registries are only operated and supported in the ARIN organisational structure, and are equivalent in functionality to the NIRs for APNIC.

There are two Delegated Registries in the ARIN region, which are as follows:

• RNP - Brazillian Registry
• NIC-Mexico - Mexican Registry

4.6 Local Internet Registries

LIRs are established under the authority of an RIR.

The LIR holds allocations of address space for assignment to end-users. LIRs are typically operated by Internet Service Providers (ISP) and serve the customers of those ISPs as well as the customers of smaller ISPs who are connected to the rest of Internet through the larger ISP. Other organisations such as large international Enterprises can also operate as an LIR.

In the ARIN region, the term ISP is used in place of the term "LIR".

4.7 End Users

End users are part of the IR system to the extent that they need to conform to the policies and processes associated with this system. Addressing and deployment plans must be documented and submitted by the end user to their applicable LIR/NIR/DR in accordance with the respective address request policy/process of that LIR/NIR. Additional information may be required from the end user in order for the IR to make any necessary address assignment decisions.

An appropriate LIR or NIR/DR should be selected by the end user to permit aggregation of routing information to be optimised and most efficiently deployed. End users will be expected to plan their networks to use a minimum amount of address space.

Note 1. LIRs are typically operated by ISPs, with each ISP allocated a specific range of addresses for assignment to its end users. Hence, changing ISPs will require the end user to renumber their networks into the address space of the new ISP.

Note 2. Address assignments are made for specific purposes and should not be sub-allocated or sub-assigned other than as documented with IR by the end user. Any change to the registered deployment plans must be notified by the end user to their assigning IR.

Note 3. End users should adopt techniques such as Variable Length Subnet Masking (VLSM) and use appropriate technologies that ensure their assigned address space is used efficiently.

5. IPv4 Addressing policy guidelines for Mobile Network Operators

5.1 Overview

The following sections will describe the policy guidelines and provide guidance notes for mobile network operators to request and use public IPv4 addresses in the GPRS inter-PLMN backbone infrastructure. It is essential that all GSM network operators adopt these guidelines and adhere to the procedures and processes of the Internet Registry System in order for GPRS roaming services to be globally supported.

Note 1. The following policy guidelines do not guarantee that an operator will be assigned public address space. Address space assignment will be assessed on an individual request basis as per the standard request procedures defined by the Internet Registry System.

5.2 IPv4 Policy guideline details

5.2.1 Public IPv4 addresses shall be used for the GPRS inter-PLMN backbone infrastructure.

5.2.2 Address type for GPRS network elements

5.2.2.1 Public addresses must be assigned to all network elements that will be presented to and addressed by the networks of other GSM network operators across the inter-PLMN backbone during the roaming interaction process, e.g. SGSN, GGSN, DNS server and border gateway.

5.2.2.2 Private address space ^[16] can and should be used wherever possible within the operator's internal network to address non-GPRS network elements whose addresses do not need to be presented across the inter-PLMN backbone, e.g. internal network routers.

5.2.3 Initial utilisation of existing public address space

5.2.3.1 Operators should initially utilise any public address space already assigned to them before any new address space is requested from an Internet Registry.

5.2.3.2 If an operator's existing address space is re-used for this purpose, then details of this change of address usage should be notified by the operator to the organisation which made the original address allocation. This could be the LIR, NIR, DR, RIR, or an ISP. In case of any doubt, the RIR should be informed.

5.2.4 Requesting new public address space

5.2.4.1 New address space assignment shall be requested by the operator from the appropriate LIR/NIR/DR using existing procedures supported by its respective serving RIR.

5.2.4.2 The LIR/NIR/DR selected should be one that is served by one of the three RIRs that is responsible for serving the country of the requesting GSM network operator.

5.2.4.3 The address space request procedures can be obtained from the respective RIR's home web site as defined in the table below.

Table 2. RIR home web sites
RIR	Web site address
RIPE NCC	http://www.ripe.net/
ARIN	http://www.arin.net/
APNIC	http://www.apnic.net/

5.2.5 Notification of address assignment to GSM-A

5.2.5.1 The GSM network operator will notify the GSM Association of the assigned public address range it will use for addressing the GPRS network elements that it will present across the inter-PLMN backbone. Document IR.21 ^[8] will be used for this purpose.

5.3 Guidance notes

5.3.1 LIR registration

5.3.1.1 Inter-PLMN backbone providers are usually already established as LIRs. Hence, the administration processes are already in place to assign address space for operators requesting a network backbone service from them.

5.3.1.2 A GSM network operator typically belongs to an organisation that already has an ISP as part of its constituent, and this ISP is likely to be registered as an LIR (or member) of the RIR in its region. In this case, the ISP may be in a position to satisfy the addressing requirements of its associated network operator. This may be a preferable option for larger operators, whilst other operators may elect to request their address space requirements from their inter-PLMN backbone provider or from the ISP associated with another operator that is registered as a LIR.

5.3.2 Requesting address space

Each RIR will have defined procedures and guidelines associated with address space allocation and assignment to their LIRs/NIRs/DRs and corresponding end users. The following tables provide some useful web links on this subject for each respective RIR.

Table 3. Useful RIPE NCC IP address space request web links
Reference	Notes
http://www.ripe.net/ripencc/new-mem/	Contains useful information on how to become a member of the RIPE NCC and how to request address space
http://www.ripe.net/ripencc/mem-services/registration/index.html	RIPE registration services/templates (e.g. ripe-141) associated with submitting address space requirements to a LIR. Note: LIRs do not have to use ripe-141 for their internal operations, but if a significant amount of addresses is required, then the LIR will have to submit the request to the NCC for a second opinion. In this case the request needs to be in a specific format that is described in document ripe-141.
http://ripe.net/ripe/docs/ripe-141.html	European IP Address Space Request Form. Identifies the information that will be required by the LIR when address space is requested by the end user. Further details on these requirements can be found in [1]
http://ripe.net/ripe/docs/ripe-185.html	European Internet Registry Policies and Procedures. Describes the European Internet registry system for the distribution of globally unique Internet address space and its operation. Describes all IP address allocation and assignment policies.

Table 4. Useful ARIN IP address space request web links
Reference	Notes
http://www.arin.net/regserv.html	Registration Services
http://www.arin.net/regserv/initial-isp.html	ISP Guidelines for Requesting Initial IP Address Space
http://www.arin.net/regserv/ip-assignment.html	Internet Protocol (IP) Assignment Guidelines for End Users Note 1. In the ARIN region, end users may request IP address space directly from the RIR if they meet the criteria outlined at http://www.arin.net/regserv/ip-assignment.html. If an end user does not meet the outlined criteria, they would then need to contact an ISP to satisfy their IP address space needs.

Table 5. Useful APNIC IP address space request web links
Reference	Notes
http://www.apnic.net/services/index.html	APNIC Registration Services
http://www.apnic.net/apnic-bin/isp-address-request.pl	To request address space allocation as an APNIC member
ftp://ftp.apnic.net/apnic/docs/isp-address-request	Text version of above, i.e. APNIC-065 - APNIC Internet Service Provider Internet Address Request Form
http://www.apnic.net/member/index.html	Step by step guide to the membership application procedure
http://www.apnic.net/docs/add-manage-policy.htm	APNIC-076: Policies for address space management in the Asia Pacific region
http://www.apnic.net/apnic-bin/second-opinion-request.pl	Second opinion request form for customer assignments.
http://www.apnic.net/faq/awfaq.html	Assignment Window Q&A

6. AS Number Guidelines for Mobile Network Operators

6.1 Overview

Autonomous System Numbers (ASN) are used to uniquely identify Autonomous Systems (AS), and which enable an AS to exchange exterior routing information between neighbouring Autonomous Systems.

Each GSM network operator will be required to assign an Autonomous System Number (ASN) that will be associated with the total GPRS IP network that is under their control.

An Autonomous System (AS) is a connected group of IP networks that adhere to a single and clearly defined routing policy. To further elaborate this definition, an AS has ALL of the following attributes:

• Comprised of a set of routers under a single technical administration
• Uses an Interior Gateway Protocol (IGP) and common metrics to route packets within the AS
• Note: An AS can use one or more IGPs when exchanging reachability information within its own AS.
• Uses an Exterior Gateway Protocol (EGP) to route packets to other ASs.

An AS is sometimes referred to as a Routing Domain.

Hence, the total GPRS IP network that is controlled by a GSM PLMN operator can be considered as an AS, and each AS will be required to have a unique AS Number.

6.2 AS Numbers

ASNs are used for the following purposes:

• Exchange of exterior routing information, i.e. network reachability information between neighbouring Autonomous Systems, using an exterior gateway routing protocol, such as BGP-4
• Identifier of the AS itself

The AS number is defined as a 16 bit integer, hence limited to 65535 unique values.

The Internet Registry System has divided the AS number space for public and private use as follows:

• Public AS number range: 0 through to 64511
• Each RIR is allocated a range of AS numbers by ICANN
• The RIR assigns a unique AS number to the AS for its members
• Private AS number range: 64512 through to 65535 (i.e. 1,024 values)

Note: AS numbers for private use must not be advertised on the global Internet.

6.3 AS Number Policy guideline details

The policy guidelines for mobile network operators to use AS numbers in the GPRS inter-PLMN backbone infrastructure are provided below.

6.3.1. Each GSM network operator shall assign an Autonomous System Number (ASN) that is unique within the GPRS inter-PLMN backbone infrastructure to represent their respective GPRS IP network.

6.3.2. BGP-4 will be used as the inter-Autonomous System routing protocol between the Border Gateways of each operator's network across the inter-PLMN backbone.

6.3.3. An operator can elect to use either a Public AS number or a Private/Reserved ^[6] AS number in association with their GPRS network. It has been previously proposed by the GSM Association [7] that Private AS numbers should be initially used as the default AS numbering scheme for this purpose.

Note 1. There is no technical reason why Private AS numbers have been selected in favour of Public AS numbers as the 'default' choice by the GSM Association. The main benefit is seen as simplifying administration procedures, i.e. simpler processes to acquire a Private AS number from the GSM Association than a Public AS Number from the Internet Registry.

Note 2. Private AS numbers must not be advertised on the global Internet.

Note 3. An Operator can change their assigned Private AS number to a Public AS number (or vice-a-versa) at a later stage if necessary.

Note 4. There is no dependency for an Operator to use a Public AS number if Public IP addressing scheme has been deployed in its network, i.e. a Private AS number can be assigned to an Operator's network even though its network elements have been assigned public addresses.

6.3.4. The GSM Association will administer the assignment of Private AS numbers to its members. Private AS numbers can be requested from the GSM Association using the following email address:

as_number@gsm.org

6.3.5. A new entry point to record the AS number (Private or Public) assigned to each operator will be added to IR.21 ^[8] in the "GPRS information" section.

6.3.6.If an operator wishes to use a Public AS Number for their network, then it will be the operator's responsibility to request it from their RIR. Details for an operator to acquire a Public AS number can be obtained from the home web site of their respective RIR. Some useful links are provided below.

Note 5. It will be the operator's responsibility to notify the GSM Association of the Public AS Number assigned to them using the procedures associated with IR.21 ^[8].

Table 6. Useful links to acquire Public AS numbers
RIR	AS Number links
RIPE NCC	http://www.ripe.net/ripe/docs/ripe-147.html
ARIN	http://www.arin.net/regserv/asnguide.htm
APNIC	http://www.apnic.net/db/aut-num.html

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