Hutchinson, N. and Peterson, L. "Design of the xkernel. " ACM Symposium proceedings on Comm. Architectures and Protocols, 1988, pp 65-75.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....Framework Protocol composition must be supported by a number of abstractions, tools and run time mechanisms. Relevant run time mechanisms include memory management for message structures, timeout management, thread management, etc. A classical example of work in this area is the x kernel [10], which provides a powerful set of features to develop communication stacks. From the point of view of protocol composition, the function of the protocol kernel is to support the exchange of events between adjacent layers. This paper focus exclusively on the layer composition aspects of protocol ....

....indication and con rmations. Examples of layers are datagram transport , positive acknowledgment , total order , checksum , etc. Good examples of relevant layers and events in the context of fault tolerant applications can be found in [9] We de ne a session as an instance of a layer [10]. The session maintains state that is used by the layer code to process events. A layer that implements ordering may keep a sequence number or a vector clock as part of the session state. In connection oriented protocols, the session also maintains information about the endpoints of the ....

N. Hutchinson and L. Peterson. Design of the xKernel. In Proceedings of the SIGCOMM'88: Communications Architectures and Protocols, Stanford, USA, Aug. 1988. ACM.

....layering to the terminal and network subsystems of research versions of AT T Unix. Such work has since been adopted by a number of Unix flavors. 1 In fact, commercial systems such as Novell s Netware 386 have adopted the Streams framework, presumably for similar reasons. 4 The x kernel [HP88, HPAO89] is a new kernel designed originally to provide customized network protocols. Using a symmetric interface for all kernel services ( everything is a protocol ) great flexibility in protocol selection and combination is provided. Run time protocol selection also allows use of the most ....

....while MachObjects must remain a general purpose interface. For example, all vnodes share a common set of possible operations. This would be undesirable with a general purpose interface because only a small fraction of operations would be needed by any one class. 7. 4 The x kernel The x kernel [HP88, HPAO89] is an operating system kernel designed to simplify network protocol implementations. Designed to provide easy configuration and efficient execution, an original goal was to provide unobtrusive customized kernels for several distributed languages. Since then, the x kernel has used as a ....

Norman C. Hutchinson and Larry L. Peterson. "Design of the x- Kernel." In Proceedings of the 1988 Symposium on Commmunications Architectures and Protocols, pp. 65--75. ACM, August 1988.

....input. Specified packets received on a channel can be routed as input to other channels. For example, packets received on an IP channel with the IP protocol number equal to 17 (UDP) may be input to an UDP channel. In this manner, Bowman supports hierarchical protocol graphs similar to the x kernel [6]. Bowman protocol graphs are run time configurable. A flow processing is determined by the code specified when the a flow is created. Using the Bowman extension mechanism, a flow code can be dynamically introduced into a node; this mechanism is also used for dynamic code loading (as is required ....

Norman C. Hutchinson and Larry L. Peterson, "Design of the x-kernel," in Proceedings of the SIGCOMM '88 Symposium, Stanford, California, 16--19 August 1988, pp. 65--75, ACM Press.

....of high or low level, e.g. applications like a debugger or system services like a transaction manager. 4. 1 Basic principles The K i t L o g model breaks down logging mechanisms into elementary logging functions like the way Ficus does for file systems [11] the x Kernel does for communications [12], and System V does for streams [13] Each function is encapsulated in a distinct object class, called a building block class or just block class. All block classes have the same interface since they all implement the same log semantics. In object terms, all building block classes conform to a ....

N. C. Hutchinson and L. L. Peterson, "Design of the x- Kernel," in Proc. of the SIGCOMM'88 Symp., (Stanford, CA (USA)), pp. 65--71, Aug. 1988.

....well defined ways. Applications that need not run concurrently can be supported by separate operating systems. Building these systems from scratch would involve enormous expense and duplication of effort, but the development of customizable operating systems (such as Choices [10] or the x Kernel [15]) may make their construction practical. It may even prove practical to customize operating systems at run time, so that models can be changed without rebooting. Even so, it is unlikely that applications will be able to communicate across models supported by disjoint portions of the kernel ....

N. C. Hutchinson and L. L. Peterson, "Design of the x- Kernel," Proceedings of the SIGCOMM '88 Symposium, August 1988, pp. 65-75.

....in the degree and nature of support provided by host systems for communication protocols. This diversity appears in both the available hardware (e.g. CPU, network interface, memory hierarchy) and the supporting system software. Software related issues such as scheduling mechanisms (e.g. x kernel[1] lightweight processes vs. STREAMS[2] service routines) user kernel data delivery mechanisms (e.g. BSD socket layer [3] vs. x kernel upcall mechanism) buffer management schemes (e.g. BSD mbufs vs. STREAMS mblk ts) and protocol composition and demultiplexing mechanisms (e.g. STREAMS modules ....

....for protocol development and operation. The services required from the operating environment include scheduling, buffer management, multiplexing demultiplexing and context management. Most existing systems provide some subset of these services (e.g. BSD UNIX[3] UNIX System V STREAMS[2] x kernel[1]) but with very little consistency across environments. For example, all three of the previously mentioned systems provide some form of buffer management (e.g. BSD mbuf, STREAMS mblk, x kernel Msg) but each has somewhat different semantics and interfaces for the basic set of operations (e.g. ....

N. C. Hutchinson and L. L. Peterson, "Design of the x- Kernel," in Proceedings of the SIGCOMM '88 Symposium, (Stanford, Calif.), pp. 65--75, August 1988.

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Hutchinson, N. and Peterson, L. "Design of the xkernel. " ACM Symposium proceedings on Comm. Architectures and Protocols, 1988, pp 65-75.

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