Re: [RRG] Fwd: [Q] draft-farinacci-lisp: IPv4 address depletion
Robin Whittle <rw@firstpr.com.au> Wed, 26 September 2007 01:41 UTC
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Date: Wed, 26 Sep 2007 11:41:25 +1000
From: Robin Whittle <rw@firstpr.com.au>
Organization: First Principles
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To: Routing Research Group list <rrg@psg.com>
Cc: Tony Li <tli@cisco.com>, Satoshi Ogawa <saogawa@cisco.com>
Subject: Re: [RRG] Fwd: [Q] draft-farinacci-lisp: IPv4 address depletion
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Satoshi Ogawa wrote, in part: >> I think, the draft-farinacci-lisp is NOT a method to resolve IPv4 >> address depletion problem. >> >> Is my understanding is correct? >> >> If my understanding is correct, LISP is one of useful solution to >> resolve only routing table scalability. I don't think any of these proposals: LISP-NERD, LISP-CONS, eFIT-APT, Ivip, TRRP is capable of "resolving" the IPv4 address depletion problem. They are all intended to resolve the problem of "routing table scalability" by enabling the BGP routing system to work with a lower number of prefixes and changes to those prefixes than would otherwise be the case, particularly due to the increase in the number of end-user networks which are multihomed. Of these proposals, only my one - Ivip - has an explicit goal of enabling significantly better utilisation of IPv4 address space. I have no clear idea of how much it would help, and I don't think anything can fully "resolve" the problem of growing usage in a finite address space. My idea is that there are many end-user networks which need less than 256 IP addresses and whose owners need or strongly desire their networks to be multihomed and/or to be free to move to another ISP without renumbering. Either of these requirements means that their network needs to keep its IP addresses, which under current arrangements would mean at least one more prefix/route/advertisement in the global BGP system. With Ivip, the idea is that there will be multiple (thousands, tens of thousands perhaps) address blocks each of which is advertised in BGP and which is split up by the Ivip system to serve the needs of more than one end-user network which needs to retain its IP addresses when using a different ISP. In principle, as long as Ivip generally serves more such end-user networks than the number of separately advertised address blocks it is managing, then it facilitates a reduction in the number of advertised BGP routes, thereby contributing to the resolution of the problem of "routing table scalability". The best outcome would be just a few - say 4 - large blocks of addresses, such as some /8s, being split up by Ivip to serve the needs of hundreds of thousands or millions of separate end-user networks. I believe that the same or similar benefits - reducing the impact of IPv4 address shortage by enabling more end-user networks, each with a given number of actively used addresses, to use the IPv4 address space - should be achievable by all the other proposals. It is not a goal of the other proposals, and few if any people other than me seem optimistic about this goal. The principles are: 1 - The current IPv4 BGP granularity of address space division is, in practice 256 IP addresses. This is due to widely implemented filtering of advertisements to reject any which are longer than /24. There is no formal arrangement for this, but unless virtually all ISPs changed their policies to allow /25s etc., at least in some parts of the address space, this restriction will remain indefinitely. 2 - The blocks of address space which are managed by LISP, eFIT-APT, Ivip or TRRP are all similarly chosen with the same granularity - 256 addresses. 3 - All these proposals enable an end-user network to be given address space in smaller increments, including a single IP address. Ivip arbitrarily maps the address space by individual IP addresses, so there is no restriction whatsoever. I think the other protocols specify the space for each end-user network as prefixes, so they can do 1, 2, 4, 8 etc. address divisions. In principle, if more and more end-user networks rely on NAT and so only need one or a few IP addresses, then any one of these systems could be used to greatly extend the use of IPv4. It is possible - I think likely - that for many years to come, it will be unattractive (probably completely unworkable for general Internet communications) to have only an IPv6 address. Therefore, I think it is likely there will be continued pressure for everyone to need an IPv4 address (with the possible exception of some cell-phone and other specialised systems), if only via NAT for non-server machines. In that case, it is possible to imagine more and more end-users, such as home and desktop office machines, being behind NAT. This would enable large numbers of computers (but not servers ) to be accommodated in an end-user network which has only one or a few public IP addresses. At present, any such end-user network which requires portability and/or multihoming has to get at least a /24 and add one more advertisement to the BGP system. With any of these proposals, many such end-user networks could be accommodated from an address block of 256, 512 etc. IP addresses, with either no advertisements in BGP, or just one, for the entire address block, with Ivip and perhaps LISP-NERD. Ivip also intends to provide fast mobility, with optimal or nearly optimal path lengths, for IPv4 and IPv6, with the correspondent host not required to have any new software. In this way, a physically mobile device or entire NAT-based network (such as that of a passenger aircraft) could occupy a single IP address. Note: I haven't read the 02 version of LISP-NERD, or fully read Bill Herrin's TRRP proposal. Please see RRG messages 264 and 288 for why I think LISP-NERD may involve "anycast ITRs" similar to those proposed in Ivip. http://psg.com/lists/rrg/2007/maillist.html http://tools.ietf.org/html/draft-farinacci-lisp-03 http://tools.ietf.org/html/draft-meyer-lisp-cons-02 http://tools.ietf.org/html/draft-lear-lisp-nerd-02 http://tools.ietf.org/html/draft-jen-apt-00 http://www.cs.ucla.edu/~lixia/papers/07SIG_IP6WS.pdf http://www.firstpr.com.au/ip/ivip/ http://bill.herrin.us/network/trrp.html - Robin -- to unsubscribe send a message to rrg-request@psg.com with the word 'unsubscribe' in a single line as the message text body. archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg
- Re: [RRG] Fwd: [Q] draft-farinacci-lisp: IPv4 add… Robin Whittle
- Re: [RRG] Fwd: [Q] draft-farinacci-lisp: IPv4 add… HeinerHummel