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<body> <p> <pre> Regional IRs typically assign address blocks on the basis of an immediate need and projected utilization rate within one year. (If you are in the ARIN region, it is one year for end user organizations and three months for ISPs.) Calculate your address space request accordingly. It is recommended to include the organization chart and network topology diagram referred to in section I.C, number 3 (above). Note that address space is allocated based on CIDR bit boundaries (see next section). The registries will need to understand your network engineering and deployment plans in significant detail before they can allocate address space. Therefore, the more detailed information you can provide, the more likely your request will be processed quickly. If you obtain address space from your ISP, it is very likely that you will need to renumber should you decide to change upstream providers and/or if you grow considerably. As this renumbering may affect your customers (and their customers, etc.) if they are using dedicated lines, you should carefully weigh the cost/benefit involved in obtaining address space from your upstream provider. If you are singly homed, you should obtain your address space from your upstream ISP. If you plan on enlarging but remaining singly homed, you should continue to obtain space this way as it promotes aggregation. If, however, you plan to be multi-homed as part of your growth plan, it would make sense to become a member of an appropriate Regional IR (or, if one exists in your region, a national Network Information Center (NIC) and obtain a /19 or "provider aggregatable" address space. The minimum routable block is often a /19, so if you plan on enlarging, it is better to pay the fees to the Regional IR now and obtain a /19 block so that you will not have to renumber later. Note that if you are an ISP in the ARIN region, ARIN has special requirements before you can do this in terms of the amount of address space you have previously used, which must be a /21. The current policy is that you must have used a /19 previously from your upstream ISP before going to ARIN, or you must be multi-homed and show you have used a /21 and be willing to renumber and ARIN will issue a /20 from a reserved /19. As of February 8, 1999, ARIN lowered the minimum allocation size for IP addresses from a /19 to a /20. ARIN will issue initial allocations of prefixes no longer than /20. If allocations smaller than /20 are needed, ISPs and end users should request address space from their upstream provider. ARIN does not guarantee that addresses will be globally routable. APNIC and RIPE NCC do not have these requirements. For APNIC, new allocations to members will be a /19. Remember that your upstream provider should route you if you ask them. You are a customer of the ISP, so if the service is not what you need you should change ISPs. IF YOU ARE CONNECTED TO ONLY ONE PROVIDER, AND ARE NOT VERY LARGE YET, GET AN ADDRESS RANGE FROM YOUR PROVIDER. SKIP THE REST OF THIS SECTION AND ALL OF SECTION V. C. What is CIDR? CIDR stands for Classless Inter-Domain Routing. Historically, IP addresses were assigned within classes: Class A (8 bits of network address, 24 bits of host address), Class B (16 bits of network address, 16 bits of host address), or Class C (24 bits of network address, 8 bits of host address). With the advent of CIDR, address space is now allocated and assigned on bit boundaries. Using CIDR means you are able to assign addresses corresponding with the number of hosts on the network, thereby conserving address space. The following table illustrates this: Addrs Bits Pref Class Mask 1 0 /32 255.255.255.255 2 1 /31 255.255.255.254 4 2 /30 255.255.255.252 8 3 /29 255.255.255.248 16 4 /28 255.255.255.240 32 5 /27 255.255.255.224 64 6 /26 255.255.255.192 128 7 /25 255.255.255.128 256 8 /24 1C 255.255.255.0 512 9 /23 2C 255.255.254.0 1K 10 /22 4C 255.255.252.0 2K 11 /21 8C 255.255.248.0 4K 12 /20 16C 255.255.240.0 8K 13 /19 32C 255.255.224.0 Wenzel, et al. Informational [Page 9] RFC 2901 Administrative Internet Infrastructure Guide August 2000 Addrs Number of addresses available; note that the number of addressable hosts normally is 2 less than this number because the host parts with all equal bits (all 0s, all 1s) are reserved. Bits Size of the allocation/assignment in bits of address space. Pref Length of the prefix covering this address space. This is sometimes used to indicate the size of an allocation/assignment. Class Size of the address space in terms of class C network numbers. Mask The network mask defining the routing prefix in dotted quad notation. (From http://www.ibm.net.il/~hank/cidr.html) D. How do I request and register address space? You will need to send a database object to the appropriate registry to request and register address space. The registration databases are composed of records that are a series of fields separated by one or more blank lines; each field consists of two parts, the tag and the value. Do not modify the tags in the templates or errors will occur. Values for particular fields are specified in the templates; be careful to enter appropriate information. The first line of a template denotes the record type. For example, an IP address template's first line is inetnum, therefore the record is known as an inetnum object. This first line is also used as the primary key for the record, therefore if you want to modify the first field of the record, the only way to do so is to delete the record entirely and add a new record with the corrected information. For illustration, here is the RIPE inetnum object. inetnum: [IP address range that will be assigned] netname: Network-Name descr: Network-Name Communications Company, Town admin-c: NIC-handle of administrative contact tech-c: NIC-handle of technical contact country: ISO 3166-country-code </pre> </p> </body>