Subject: [RADIR] Section 5 outline

From: Jason Schiller <[email-masked]>
Date: Tue, 12 Jun 2007 16:45:56 -0400 (EDT)

Below are some notes from the RADIR meeting on June 12, 2007.  We took
this opportunity to discuss section 5 "Pressures on Routing Update
Rate" in an attempt to put together a loose out line, or topics to be
addressed in the strawman text.  Strawman text is pending.

5.1 Interconnection Richness
- As the degree of interconnection goes up, the number of paths increases
- When a failure occurs, there is more path hunting, and thus more updates

5.2 Multihoming
- Multihoming causes greater interconnection richness on the edge
- Multihoming results in the advertising of additional prefixes for 2
  reasons:
   1. PI addresses used for multihoming must be leaked to the DFZ to
      create reachability
   2. PA more specifics must be leaked to the DFZ to allow for multiple
      provides to transit traffic equally as well.
- An outage affecting reachability to one of these addresses (such as
  failure of the access circuit) will be seen in the DFZ.  This differs
  from a static customer using a PA address.  

5.3 Traffic Engineering
- Traffic engineering is a multiplier effect on multihoming
- A network will advertise multiple more specifics instead of advertising
  a single aggregate per location in order to gain more granular control
  over inbound traffic 
- A single failure may cause multiple updates as multiple more specific
  routes may be sharing one path. 

5.4 Questionable Practices

5.4.1 Rapid shuffling of prefixes
- Some networks try to assert highly granular control of inbound traffic
  by continuously modifying route announcements.  This is a pulse width
  modulation approach to squeezing the maximum bandwidth out of multiple
  links.
- Some route selection boxes take forwarding plane measurements and
  optimize inbound traffic by withholding or depreferencing certain
  prefixes to some set of upstream providers. 
 
5.4.2 Anti-Route Hijacking 
- Some network advertise all of their space as multiple small
  prefixes.  This prevents another network from advertising a more
  specific route and stealing their traffic.

5.4.3 Operational Ignorance
- Default behavior is to leak routes
- It takes additional work to restrict routes from being leaked
  -- no-export, route aggregation, etc
- It is easier to redistribute all routes into BGP, then figure out how to
  aggregate
- Implementing extra configuration to reduce unneeded routes increases
  complexity, and some operators may have fear that the new configuration
  may break current routing
- Leaking unneeded routes generally do not hurt those with the
  misconfiguration

(Operational ignorance) + (default behavior) + (fear of breaking something
that works) + (tragedy of the commons) = extra updates.

5.5 RIR IPv6 Policy is Not Balanced 
Marla sent out some strawman text

__Jason
==========================================================================
Jason Schiller                                               (703)886.6648
Senior Internet Network Engineer                         fax:(703)886.0512
Public IP Global Network Engineering                       [email-masked]
UUNET / Verizon                         [email-masked]

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