On the Effects of the Wide-Spread Deployment of Route Control Products
and Overlay Routing Services (Aditya Akella, CMU)
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Recent years have seen route control and overlay routing products that
allow users and end-networks to select wide-area paths for their
transfers in a more informed manner. For example, multihomed
subscribers at the edge of the network are increasingly employing
route control products (e.g., RouteScience's "Path
Control"). Similarly, customers of Akamai's SureRoute service receive
access to a large, diverse overlay network to route traffic on. The
primary motivation for these products is to provide end-network-based
mechanisms for optimizing wide-area performance and reliability. While
the deployment of these products and services is not very widespread
today, we expect it to grow rapidly over the coming years.
At the same time, the deployment of such route control mechanisms has
given rise to concerns about their impact on the general well-being
(e.g. the stability of routing and network load) of the network. For
this reason, the questions below are critical to our understanding of
where the state-of-the-art in end-to-end routing and route selection
lies today and where it is headed in the foreseeable future:
- What is the impact of the deployment of route control mechanisms and
services on the operation of ISP networks and on the efficient
functioning of the Internet as a whole?
- Would these products cause route or traffic instability in the
Internet and if so, to what extent?
- What new mechanisms do we need to put in place to counter the
potential ill-effects?
These questions can be addressed via a combination of measurement and
analysis. The first step here is to accurately measure prevalent
end-network practices for achieving intelligent route control and then
build models for such end-network behavior. It is also crucial to
understand, in general, what the best end-network strategies are for
improving performance and resilience. This may help influence (and
possibly, model) future product design too.
The next step is to study the impact that both limited and wide-spread
deployment of route control products can have on network
operation. Since these products are not overly popular amongst
end-networks today, this question cannot be answered using traditional
measurement-based approaches. However, modeling, simulation and
analysis could give us the answers we are looking for. One useful tool
is game theory. The interaction between various intelligent
end-networks and the Internet can be modeled as a game in which the
end-networks are selfish agents trying to individually maximize a
local goal, such as observed performance. The models for end-network
behavior constructed above could prove very useful in such an
analysis.
If the above analysis shows that deployment of route control does not
impact the stability of routes in a negative manner, network traffic
and the efficient operation of the network as a whole, then we need
not be too concerned about the proliferation of route control
products. If, on the other hand, the analysis shows that these
products can have a negative impact on how well the network functions,
then we may have to work on measures to counter the
ill-effects. Stated otherwise, "aggressive" end-network behavior must
be sufficiently penalized and thereby discouraged.
One way to achieve the negative incentives described above is to
design novel pricing schemes (which may involve rewriting SLAs) to
ensure that end-networks offer somewhat fixed, predictable load to
their provider networks. The SLAs could be coupled with policing
schemes at the ingresses of ISP networks which could, for example,
rate-limit traffic or drop packets to discourage a particular choice
of routes made by the end-network. Such schemes could help strike the
right balance between the end-networks' attempts to improve
performance and resilience, and the carriers' goal of ensuring stable
traffic and routes, by factoring in economic benefit as the key
incentive for socially conformant behavior.
To summarize, it is unclear yet whether widespread use of route
control products will disturb the stability of the operation of the
Internet. This issue should be further explored by first identifying
the various ways in which end networks can impact stability, then
understanding the extent of the ill-effects, and finally designing
pricing-based mechanisms to contain the ill-effects.