An Active Approach to Measuring Routing Dynamics Induced by Autonomous Systems
|
Figure 1. The active measurement infrastructure deployed in
the RIPE NCC RIS network. |
|
Abstract
We present an active measurement study of the routing dynamics
induced by AS-path prepending, a common method for controlling the inbound
traffic of a multi-homed ISP. Unlike other inter-domain inbound traffic
engineering methods, AS-path prepending not only provides network resilience
but does not increase routing table size. Unfortunately, ISPs often perform
prepending on a trail-and-error basis, which can lead to suboptimal results and
to a large amount of network churn. We study these effects by actively
injecting prepended routes into the Internet routing system using the RIPE NCC
RIS route collectors and observing the result- ing changes from almost 200
publicly-accessible sources of BGP information. Our results show that our
prepending methods are simple and effective and that a small number of ASes is
often responsible for large amounts of the route changes caused by prepending.
Furthermore, we show that our methods are able to reveal hidden prepending
policies to prepending and tie-breaking decisions made by ASes; this is useful
for further predicting the behavior of prepending.
Methodology
The
active measurement infrastructure deployed in the RIPE NCC RIS network.
1.
Inside the RIS network (the lower cloud), we use the announcer
software on a Linux PC (moo.ripe.net) to announce the beacon prefixes to the
three RRCs over IBGP with community values encoding the desired prepending.
2.
Each RRC decodes the community values using a route-map and
announces the prefix with the specified prepending lengths to the upstream
ASes.
3.
We observe AS-level route changes from the set of VPs (the upper
cloud).
Dataset
|
RRC |
Upstreams |
Beacon Prefix (Control Prefix) |
Time of announcement |
|
RRC07 |
AS16150 AS13237 + |
84.205.73.0/24 (84.205.88.0/24) |
8th May 2006 Starting from 01:10 UTC every 2
hrs, we increased prepending length by 1 until total prepending length equals
to 6. |
|
RRC14 |
AS6939 + AS6762 |
84.205.89.0/24
(84.205.95.0/24) |
|
|
RRC10 |
AS1299 AS12779 + |
84.205.88.0/24 (84.205.73.0/24) |
13th May 2006 Starting from 18:00 UTC every 3
hrs, we increased prepending length by 1 until total prepending length equals
to 10. |
"+" indicates prepending on that link.
The data
also has been indexed on DatCat RRC07,
RRC14
and RRC10.