access requirements for subscribers

Every computer that accesses the internet has an internet protocol (IP) address, which consists of four numbers separated by dots (e.g. Access to the full texts of articles in Crystallography Journals Online by subscribers to IUCr journals requires the use of a computer whose IP address can be recognized and validated as one of those registered by the subscriber.

All subscribers must register their IP addresses in order to access the journals. These IP addresses can also be updated at any time. However, please note that it may take up to 24 hours for changes to IP addresses to take effect.

Personal subscribers

Personal subscribers to IUCr journals are permitted to register a single IP address per subscription held, i.e. to access the service from a single computer.

If you are a personal subscriber whose IP address is dynamically assigned by your Internet Service Provider (this is often the case for dial-up accounts), then you will be unable to specify the required single fixed IP address for accessing the service. However, your provider may be able to give you a fixed IP address if you request it. In addition, we will soon be offering an alternative method of accessing the journals for subscribers without fixed IP addresses. (For more information please contact

Institutional subscribers

Institutional subscribers to IUCr journals are permitted to register as many IP addresses as are necessary to describe the (sub)network(s) in use at a single geographical site. All of the subscriptions held by a single institution may then be accessed from any of those IP addresses.

Computers on the same (sub)network will in general have IP addresses that begin with the same two or three numbers. For instance, computers with IP addresses in the range are all on the same subnet (in this case a class C network). A specific (sub)network is identified by a combination of a network address and a subnet mask; for instance, the class C network above would be specified as, where is the subnet mask for a class C network.

To find out the correct way to identify the (sub)network(s) in use at your site, consult your network administrator. You may specify individual IP addresses, e.g., or ranges, e.g. 128.135.*.* (equivalent to or 128.135.1-20.* (equivalent to 128.135.1-20.0). Our registration system will try to identify full class C and class B addresses and assign the appropriate subnet masks. All other subnet masks must be explicitly identified.

Access from multiple sites

Access to the service from multiple sites is possible for institutional subscribers under certain conditions. For more information on this, please see the Terms and Conditions of Use for institutional subscribers and the subscription policy forCrystallography Journals Online. If you are permitted to access the service from multiple sites, then you must register the details of each additional geographical site separately.

The IP addresses of all computers used for distance learning by a single institution should be treated collectively as a single additional site, which should be given the site name `Distance learning'.

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