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Motivation and Overview

Figure 1 illustrates the Anypoint abstraction. An Anypoint connection allows communication between two logical endpoints: an ensemble of end nodes and another peer IP site. In a typical use, the ensemble is a server cluster and the peer is a client interacting with it through some request/response service protocol. Many connections may be active to the same ensemble. The current ensemble membership for a connection is its active set. Anypoint switches direct the traffic flow between each peer and its active set under the control of the ALRM plugins. This serves four related purposes:

This paper focuses on the first three goals, i.e., the role of Anypoint as a basis for virtualized, manageable, scalable Internet services.

Redirecting switches are controversial because the Internet architecture implicitly assumes that each IP datagram is addressed and delivered to a uniquely defined end host, running a single instance of its operating system (cf. RFC 1122 [12]). Anypoint provides a rich set of capabilities enabling an ensemble operating system and its applications to manage the ensemble as a coordinated virtual ``host''--effectively a multicomputer with internal policies for handling network traffic addressed to it. Crucially, the indirection hides the ensemble's internal structure from the connection peer: the peer addresses inbound traffic to a virtual IP address (VIP) for the ensemble and receives outbound traffic with that VIP as the source address. This use of network address translation (NAT)--which may be damaging in other contexts--is done with the guidance and consent of the ensemble applications, and is transparent to the peer. The switch does not obscure the identity of the peer from the ensemble members.



 
next up previous
Next: Anypoint and the Transport Up: Anypoint: Extensible Transport Switching Previous: Introduction
Kenneth G. Yocum
2003-01-20