1.1. Terminology Many contemporary operating systems utilize a system Many contemporary operating systems provide an call interface between the operating system and its clients. interface between user code and the operating system Increasing numbers of systems are providing low-level services based on special "system calls". One can view mechanisms for intercepting and handling system calls in the system interface as simply a special form of structured user code. Nonetheless, they typically provide no higher- communication channel on which messages are sent, level tools or abstractions for effectively utilizing these allowing such operations as interposing programs that mechanisms. Using them has typically required record or modify the communications that take place on reimplementation of a substantial portion of the system this channel. In this paper, such a program that both uses interface from scratch, making the use of such facilities and provides the system interface will be refe...

Interposition agents are a well known device for attaching legacy applications to distributed system.s However, agents are difficult to build and are often large, monolithic pieces of software which are suited only to limited applications or systems. We solve this problem with Bypass, a language

NFS daemon, or lnfsd, which interposes an NFS client and Legion to provide seamless access to the Legion name space from a Unix environment. lnfsd overcomes the insecurities of its NFS heritage and mitigates the performance degradation of interposition through well-known file system techniques

agent. In this paper, we present several lessons learned about interposition agents via a progressive study of design possibilities. Although performance is an important concern, we pay special attention to less tangible issues such as portability, reliability, and compatibility. We begin with a

as an interposition agent. In this paper, we present several lessons learned about interposition agents via a progressive study of design possibilities. Although performance is an important concern, we pay special attention to less tangible issues such as portability, reliability, and compatibility. We begin with a

agent. In this paper, we present several lessons learned about interposition agents via a progressive study of design possibilities. Although performance is an important concern, we pay special attention to less tangible issues such as portability, reliability, and compatibility. We begin with a

Interposition agents are a well-known device for attaching legacy applications to distributed systems. However, agents are difficult to build and are often large, monolithic pieces of software which are suited only to limited applications or systems. We solve this problem with Bypass, a language

as an interposition agent. In this paper, we present several lessons learned about interposition agents via a progressive study of design possibilities. Although performan e is an important on ern, we pay spe ial attention to less tangible issues su h as portability, reliability, and ompatibility. We begin with a

as an interposition agent. In this paper, we present several lessons learned about interposition agents via a progressive study of design possibilities. Although performan e is an important on ern, we pay spe ial attention to less tangible issues su h as portability, reliability, and ompatibility. We begin with a

seamlessly with existing applications through the use of interposition agents [18]. The interposition agents provide a layer of indirection making it possible to implement transparent remote file access and data encryption/decryption without any OS modifications. System performance evaluations show