A New Internet-Draft is available from the on-line Internet-Drafts
directories.
Title : SRAM-based IP Forwarding Eliminates the Need for Route Aggregation
Author(s) : R. Whittle
Filename : draft-whittle-sram-ip-forwarding-01.txt
Pages : 41
Date : 2007-4-2
I propose a simple, low-cost, low-power, Static RAM (SRAM) based
architecture for the Forwarding Information Base (FIB) function of
transit and border routers in the Default Free Zone (DFZ) of the
Internet. This will provide direct hardware forwarding irrespective
of the size of the "global BGP routing table", within the current
IPv4 convention of limiting advertised prefixes to no longer than
/24. Routers with this or a similar architecture provide the only
elegant hardware solution to the problem of route disaggregation,
which is unavoidable due to increasing numbers of ISPs and Autonomous
System (AS) end-users who need to advertise their prefixes on
topologically diverse parts of the network, for purposes including
multihoming and traffic engineering.
Router hardware limitations with respect to route disaggregation
could also be eliminated for IPv6, by adding further SRAMs or, on a
more limited basis, by using spare space in the SRAM which is
required for IPv4. Two additional SRAMs and a reallocation of the
existing 2000::/3 global unicast allocations to a smaller range - for
instance 2000::/10 - would provide for Provider Independent (PI) /32
allocations to 4 million ISPs and multihomed end-users. Each /32
assignment could be advertised as up to eight /35 prefixes - each of
which provides 8192 /48 user networks. A less disruptive alternative
to reallocating existing IPv6 global unicast addresses would be to
define a /10 prefix - inside or outside 2000::/3 - for new PI
assignments to ISPs and AS end-users with the long-term assurance of
rapid SRAM-based forwarding for prefixes as short as /35, without
concern for route aggregation or network topology. It may be
feasible, for a decade or more, to handle IPv6 without an addition
SRAM chip. Unused space in the IPv4 chip (or two chips for larger
routers) would map 2,097,152 /35 prefixes - for instance to support
PI assignments of /32 prefixes to 262,144 ISPs and AS end-users.
This would provide 17 billion /48 prefixes - the standard assignment
for non-AS end-users.
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