Tussle in Routing: Who Determines Internet Paths?
Zhuoqing Mao2008
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Abstract
As pointed out by Lakshminarayana et al. [3], there is a tussle between end-users and the ISPs in wanting to control the routes on the Internet. We reexamine the tussle among senders, receivers, and ISPs in light of a few new proposals in routing architectures and propose several directions for future work. End-users or edge networks have limited control over routes. End-users today have little control over how traffic reaches the intended destination. Most end-users residing in edge networks just rely on their upstream provider to deliver outgoing traffic to the destination networks. Even Multihoming provides only limited control in the form of choosing the first hop AS among limited choices for outgoing packets. Such decision is often made based on perceived performance and network cost to select the upstream provider to use for traffic for a given destination. Similarly, for incoming traffic, end-users today do not have much control in terms of the paths traversed by packets. Multi-homed customers can advertise different prefixes across different provider links, use AS path prepending, or advertise specific MED values across links to the same provider in an attempt to perform inbound traffic engineering. To overcome these limitations, overlay routing [1] enables end-hosts to select desired application-layer path traversing through intermediate end-hosts. Such overlay paths, however, cannot avoid the first hop AS as determined the immediate upstream providers. Furthermore, the paths between end-hosts serving as overlay nodes are still controlled by the network. Sender-based control: Given the existing limitations imposed by the networks, end-users have little flexibility in managing both outbound and inbound traffic. There are several proposals to increase route diversity by allowing multi-path BGP [8] and enabling source routing for end-hosts [9]. If end-hosts are exposed multiple paths, they can achieve more flexible control over their paths to arbitrary destination networks for purposes such as load-balancing traffic and gaining better fault-tolerance. Receiver-based control: To perform receiver-based admission control or traffic management, proposals such as capability-based scheme [10] or "off by default" [2] attempt to enable receivers to decide which sender is permitted to send traffic to them. The recent work of FastPass [7] enhances the capability-based approach by imposing traffic rate-limiting along the path from specific senders. To summarize, end-hosts today have limited control over routes for reaching external destinations and for external destinations to reach themselves. The control desired by end-hosts can be generalized as follows. (1) Sender: the endto-end route used to reach a destination. (2) Receiver: the end-to-end route used by a sender host. Note that clearly there can be a conflict between receiver-based and sender-based control; however, some balance can be reached. In terms of detailed control, end-hosts often desire control in the form of permitting certain hosts to send traffic to them, the number of routes the end-host has access to, the ability to bypass a particular network along a path, traffic differentiation among different destinations or senders sharing the same links, the performance characteristics, e.g., fault-tolerance, delay, loss, jitter of the path. Despite potential conflict between sender-based and receiver-based control, receiver should have priority to determine the access control of which senders are allowed to send traffic to it. Ideally, this control should be implemented within the network, close to the sender. Next, we discuss the control over routes from network's perspective.
