Janos, You raise an excellent point with respect to using nibble boundaries. If one uses a partitioning scheme like that in RFC 3531 AND require that partitions (sets of prefixes) be on nibble boundaries, a /32 allocation with a 64-bit prefix length contains only 8 partitions of 4 bits each. This yields just 16 possible subnets per partition. If one allows a 96-bit prefix length, the number of nibble partitions jumps to 16 or, alternately, the size of the 8 partitions grows to 8 bits (256 subnets).
In addition to simplifying reverse DNS lookup, nibble boundary partitioning makes it far easier to identify subnets belonging to the same partition. This reduces IP address management complexity. Best Regards, Jeffrey Dunn Info Systems Eng., Lead MITRE Corporation. (301) 448-6965 (mobile) -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mohacsi Janos Sent: Wednesday, October 01, 2008 9:08 AM To: Alexandru Petrescu Cc: Sherman, Kurt T.; ipv6@ietf.org; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Martin, Cynthia E. Subject: Re: what problem is solved by proscribing non-64 bit prefixes? On Wed, 1 Oct 2008, Alexandru Petrescu wrote: > [EMAIL PROTECTED] wrote: >>> In a typical IPv6 ADSL household landscape... >>> >>> An ADSL IPv6 operational deployment offers a /64 prefix at home. >>> With that, I can't subnet _and_ use IPv6 stateless auto-configuration. >> >> In a typical IPv6 ADSL household landscape the ISP will assign you a >> /48 with plenty of subnetting space. > > Not sure, FWIW, in the IPv6 ADSL household I live in gives me a /64 and not > /48 (see draft-despres-v6ops-6rd-ipv6-rapid-deployment-01.txt). > > That's typical for me but I don't know about the other deployed IPv6 ADSL, do > they give /64 or shorter prefixes? The draft-despres-v6ops-6rd-ipv6-rapid-deployment-01.txt is largely irrelevant in this discussion, This draft describing a particular solution that can be implemented by the ISPs if: 1. they have complete operational control over the CPEs installed users 2. They want to implement IPv6 quickly 3. They users are using only one subnets which is the allocated /64. In general - my recommendation when I giving tutorials about IPv6: - /48 to /128 is delegated to end users - /48 general case, /47 if justified for bigger networks - /64 if one and only one network is required - /128 if it is sure that one and only one device is going to be connected between /48 - /64 up to you if you are cautious about address conservation: - but use nibble boundary for easier reverse DNS delegation. Regards, Janos Mohacsi: -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
