Interim Policy proposal for IPv6 Address Assignment Policy for Internet Exchange Points

One of the points that has been raised a couple of times is...

  There is a lot of IPv6 address space - why not just give IXP's a sub TLA.

The argument against this seems to be - if IXP's are treated as a
special case then there is a precedent for every other 'special case'
to justify their case.

... but there is still *lots* [1] of address space so why not give
everyone who wants one a sub TLA?

AIUI the reason for restricting who gets sub TLAs is...

  In the current IPv4 world (multiprovider) multihomed customers have
  their own address space and AS number this fills the default-free
  routing table and won't scale.

  In IPv6, addressing is hierarchical and multihomed customers have
  multiple addresses, this keeps the default-free routing table small
  and scalable.

  If everyone (multihomed customers) gets a sub TLA then the
  default-free routing table fills up with multihomed customer sub
  TLAs and IPv6 routing tables are as cluttered and unscalable as IPv4.

Is this the issue? If not, why not give out sub TLAs to all who want them?

Chris - LINX

[1] There are 2^32 (~ 4,000,000,000) /35s available...

    +--+-----+-----+---+-----+------+------------------+
    |-3|--13-|--13-|-6-|--13-|--16--|------64 bits-----|
    +--+-----+-----+---+-----+------+------------------+
    |FP|-TLA-|-sub-|Res|-NLA-|--SLA-|---Interface ID---|
    |--|-ID--|-TLA-|---|--ID-|--ID--|------------------|
    +--+-----+-----+---+-----+------+------------------+