[arin-ppml] Routing Research Group is about to decide its scalable routing recommendation

William Herrin bill at herrin.us
Fri Dec 18 01:24:57 EST 2009

On Thu, Dec 17, 2009 at 9:00 PM, Leo Bicknell <bicknell at ufp.org> wrote:
> What I haven't seen is anything that makes the leap from "BGP is
> broken" to "the whole architecture must be changed".  More specifically,
> I haven't seen anyone look at BGPv5, or a brand new replacement
> routing protocol.

Hi Leo,

Here's a clip from the intro to an internet draft I'm preparing which
may explain it:

   Efficient Internet routing is all about aggregation.  Combine
   multiple downstream routes into a single CIDR prefix sent upstream
   and all is well in the world.  Fail and the routing table grows, the
   cost of routers rises and the general stability of the Internet falls.

   Because of how TCP and the various UDP-based transport protocols
   interact with the IP address, multihoming and mobility can defeat
   aggregation.  These protocols require the IP address to remain the
   same throughout their operation.  Any time a host changes its
   location within the network without also changing its IP address,
   knowledge about that address becomes disaggregate with its neighbors.
   The change must be propagated throughout the entire network.

   Routing researchers believe that if the host could readily change its
   IP addresses to match its attachment to the network then the network
   wouldn't have to change its routing to match the host's movement.
   This would improve aggregation and reduce the frequency of routing
   updates needed to keep the network operating.  They call this concept
   "locator/identifier separation."

   Locator/identifier separation's premise is simple: don't use the IP
   address for both forwarding packets through the network and
   associating those packets with their respective endpoints.  Instead,
   separate this overloaded functionality into distinct elements within
   each packet: locators used solely for forwarding packets and
   identifiers used to associate those packets with specific hosts,
   services and sessions.

   Practically speaking, this means we can either treat the IP address
   as a host identifier and build an overlay to the routing system with
   a new locator field somewhere in the packet or we can treat the IP
   address as a locator and introduce new elements into the transport
   protocols to figure out which packets belong to who.

>  It seems that improving the system and fixing
> some of the known issues may be useful if nothing else as a stopgap,
> and yet no one seems to be working seriously on the issue.

That would be the IETF GROW working group. They're plenty serious but
they've run short on ideas. Hence the RRG's exploration of potential
next-generation architectures.

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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