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Class A assignments used only the first 8 bits to identify the class and the network, providing for a relatively small number (126) of very large networks accommodating up to 16.7 million hosts. Class B assignments used the first 16 bits to identify the class and the network prefix, providing for 16,384 intermediatesized networks accommodating up to 65,536 hosts. Class C assignments provided for a very large number of small networks with only 256 unique identifiers for hosts. There were also two additional classes, D and E, one for multicasting and the other for experimental uses.
Class C networks, with room for only 256 hosts, were too small for most organizations, and few applications were received for them; The huge class A assignments were massively underutilized by those lucky enough to get them. Class B assignments began to run out rapidly.
RFC 950 (1985). Subnetting allowed organizations with larger enterprise networks to turn the two-part IP address structure into a three-level hierarchy. This facilitated route aggregation at the organizational level.
RFCs 1517, 1518, 1519, and 1520 (1993).
Email to author from Karl Auerbach, May 18, 2000.
Office of the Manager, National Communications System, 'Internet Protocol Next Generation (IPv6): A Tutorial for IT Managers.' Technical Information Bulletin 97-1, January 1997.
Currently, only the letters A-Z, numerals 0-9, and the hyphen character (-) can be used in a domain name, and the hyphen cannot be used as the first or last character in a domain name. Efforts are underway to internationalize domain names so that they can utilize non-Roman characters such as Chinese characters or various European alphabets. Domain names can be a maximum of 67 characters long, including the top-level domain.
Of course, not all of them are meaningful, and as was noted in chapter 2, the value attributed by users to different names will vary greatly.
ISO-3166-1. Maintained by DIN in Germany.
BIND stands for Berkeley Internet Name Domain. It is a software implementation of DNS protocols that includes a DNS server, a DNS library resolver, and tools for verifying the proper operation of the DNS server. BIND is currently maintained and distributed by the Internet Software Consortium, <http://www.isc.org/>.
On August 23, 2000, four root name servers- b.root-servers.net, g. rootservers.net, j.root-servers.net, and m.root-servers.net -had no name server records for the entire .com zone. The problem occurred because the BIND software interacted with Network Solutions' zone generation procedures in an unexpected way, causing the name server to remove the .com zone delegation information from the root zone held in memory. This means that the entire .com zone did not exist for about 4/13 of all the resolvers in the world that needed to refresh their .com pointers during the interval in question.
RFC 2826 (2000), 'IAB Technical Comment on the Unique DNS Root,' is often cited in the policy debates over alternative roots as if it were the last word on the subject. The basic point of the statement is simply that 'there must be a generally agreed single set of rules for the root.' This is a good starting point for policy discussion. However, to assert that the root zone needs to be coordinated is both uncontroversial and not dispositive of the policy problem posed by competing roots. Advocates of a 'single authoritative root' need to face the reality that portions of the Internet community can and do defect from or supplement the so-called authoritative root. Asserting that a particular root server system 'should be' authoritative and singular does not make it so. One can agree on the need for coordination at the root level without necessarily agreeing on who is the sole or proper source of those rules. Nor does the general need for a single set of rules eliminate the legitimacy and benefit of competition over what those rules should be.
But I will give my personal opinion. The value added by alternative roots that only offer new top-level domains is minimal relative to the compatibility risks unless some other innovative functionalities are added. Large providers with the ability to overcome the critical mass problem are more likely to choose strategies that work over or around DNS rather than replacing it.
Joe Baptista, 2000, root server estimates.
Karen Kaplan, 'Start-up Offers Alternative System for Net Addresses,' Los Angeles Times, March 6, 2001.
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