Peterson, L., Hutchinson, N., O'Malley, S., and Rao, H. (1990). The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23--33. 184  Home/Search   Document Not in Database   Summary   Related Articles   Check

....flexible operating systems. Its focus is on integration of components and on modification rather than specific algorithms for subsystems. Existing algorithms and implementation strategies for subsystems can be used in the verification of these two goals. X kernel communication subsystem [16] and Coda file system for disconnected operation [12] are two such well developed implementation technologies. Incrementality and protection are the two main challenges in producing flexible operating systems as discussed in [11] The p project intends to address these challenges by choosing ....

L. Peterson, et al, The x-kernel: A Platform for Accessing Internet Resources, Computer, IEEE, May 1990, pp. 23-35.

....GVAs in their own data structures. Finally passwords effectively increase the sparseness of the address space and allow addresses to be reused. 7 Current Status The page migration and replication system is currently being designed, and a prototype will shortly be developed using the x kernel [22]. We have commenced modifications of the Choices [8] operating system. A group of students are instrumenting a Unix system to obtain data for our simulations of page size, address space management and page migration. We are also building specialised network hardware which is a locally developed ....

L. L. Peterson, N. C. Hutchinson, and S. W. O. H. Rao. The x -kernel: A platform for accessing internet resources. Computer, 23(5):23--33, 1990.

....and user space protocols. We have used them as example applications to study the impact on overall performance. The Mach system also has a user space protocol for communication between different machines, but this protocol is implemented by separate servers and consequently has a high overhead [13]. Protocol decomposition is studied in the x kernel [13] which allows protocols to be connected in a graph, depending on the needs of the application. Userspace group communication protocols are studied in the Horus project [18] Horus uses a multicast transport service (MUTS) that can run in ....

....applications to study the impact on overall performance. The Mach system also has a user space protocol for communication between different machines, but this protocol is implemented by separate servers and consequently has a high overhead [13] Protocol decomposition is studied in the x kernel [13], which allows protocols to be connected in a graph, depending on the needs of the application. Userspace group communication protocols are studied in the Horus project [18] Horus uses a multicast transport service (MUTS) that can run in kernel space or in user space. Application specific ....

L.L. Peterson, N. Hutchinson, S. O'Malley, and H. Rao. The x-kernel: A platform for accessing internet resources. IEEE Computer, 23(5):23--33, May 1990.

....more gradual interface evolution permitted by our extensible design provides a much more flexible alternative. 4.3 The x kernel The x kernel [4] is designed around the concept of layered protocols. Although originally focused on network protocols, recent work has addressed file systems as well [8]. The scope of the x kernel work is quite different from that of this paper. The x kernel seeks to provide a complete new kernel environment, while our work is targeted specifically at the file system portion of existing Unix systems. Because the x kernel provides the entire computing ....

Larry L. Peterson, Norman C. Hutchinson, Sean W. O'Malley, and Herman C. Rao. The x-Kernel: A platform for accessing Internet resources. IEEE Computer, 23(5):23--33, May 1990.

....globalStoreManager, processStoreManager and localProcessStoreManager, instances of which constituted the storeManager subsystem. had a small kernel 39 and several virtual machines (processes) running operating system tasks. The x kernel is an operating system kernel for networks of machines (Peterson et al. 1990). It supports a library of protocols so that it can access different network resources (such as RPC and file access) with different protocol combinations. The xkernel has a fixed process manager and store manager, whose designs support the needs of communications. The primary feature of the ....

....new protocols that provide exactly the communication support they need (Hutchinson and Peterson, 1988) The version of x kernel described in 1990 statically loaded all protocols to be configured into a given kernel. Howver, it was intended to enhance the system for dynamic loading of protocols (Peterson et al. 1990). 39 18K, half of which was paged, and half resident. Choices achieves code reuse and customisation using both inheritance and by building new object collections from existing classes. However, inheritance fixes the behaviour of an object at creation time (Micallef, 1988) and is essentially ....

Peterson, L., N. Hutchinson, S. O'Malley and H. Rao (1990) The x-kernel: A platform for accessing internet resources. IEEE Computer 23(5), 23-33.

....hand and a typical user level software DSM on the other. An obvious advantage of kernel level handlers is that the time to handle the events related to shared memory management is reduced. For example, in the context of network protocols, experience with the x kernel at the University of Arizona [17] has shown that a kernel level protocol can outperform user level protocols by a factor of 2 to 3. Thus, to compete with a kernel level implementation, a user level implementation must rely on very careful recoding of parts of the kernel; but even in this case message latencies are still larger ....

L.L. Petersen, N.C. Hutchinson, S.W. O'Malley, and H.C. Rao. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23-33, May 1990.

....hand and a typical user level software DSM on the other. An obvious advantage of kernel level handlers is that the time to handle the events related to shared memory management is reduced. For example, in the context of network protocols, experience with the x kernel at the University of Arizona [18] has shown that a kernel level protocol can outperform user level protocols by a factor of 2 to 3. Thus, to compete with a kernel level implementation, a user level implementation must rely on very careful recoding of parts of the kernel; but even in this case message latencies are still larger ....

L.L. Petersen, N.C. Hutchinson, S.W. O'Malley, and H.C. Rao. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23-33, May 1990.

.... Traps Interrupts 37 An obvious advantage of sub kernel handlers is that the latency and overheads to process coherence events is much reduced (the latency is of tens of instructions) For example, in the context of network protocols, experience with the x kernel at the University of Arizona [60] has shown that a kernel level protocol can outperform user level protocols by a factor of 2 to 3. A second advantage is that the protocols are shared by all the processes running on the machine without any overhead. True, in a user level protocol, each user could specify a different protocol ....

L.L. Petersen, N.C. Hutchinson, S.W. O'Malley, and H.C. Rao. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23-33, May 1990.

....the application and to the characteristics of the underlying network. A library of protocol building blocks will be developed, so that protocol implementation is as simple as functor composition. These ideas are similar to the notion of micro protocols in the x kernel at the University of Arizona [29]. Our approach, developed independently, is completely integrated with the Standard ML language and requires no extra linguistic tools. Indeed, the idea simply falls out of good ML programming practice. In contrast, the x kernel designers introduced a graphical module interconnection language, ....

Larry Peterson, Norman Hutchinson, Sean O'Malley, and Herman Rao. The x-kernel: A platform for accessing Internet resources. Computer, 23(5):23--33, May 1990.

....in many communication subsystems, x kernel relies on three primitive communication objects: protocols, sessions and objects. It also provides a symmetric call mechanism between the kernel and the user level; system call for user level to access kernel modules and upcall in the opposite direction [Peterson, 90] Pager Device Drivers IBM Microkernel (IPC, Virtual Memory, Tasks, Threads, Interrupts) Hardware Figure 3.4: Microkernel Approach and Multiple Servers Generic OS Servers (UNIX, OS 2 Warp) Microkernel Servers (Paging, Naming) 36 In addition to an elegant architecture for protocol ....

L. Peterson, N. Hutchinson, S. O'Malley & H. Rao, The x-kernel: A Platform for Accessing Internet Resources, IEEE Computer, 23(5), May 1990, pp. 23-33.

....using this framework. One of the target subsystems, currently under construction is an implementation of a user level communication protocol library. The idea is to provide a dynamic object oriented framework for building communication protocols, a problem similar to that addressed by x kernel [Peterson, 90] The layout of the hierarchies that constitute the framework is shown in Fig 2. RTTI meta ProtocolBase RTTI meta Protocol SecondInterface Implem type Protocol2ndInt Implementation ProtocolBaseMeta RTTI BaseMeta ProtocolRTTI Meta DispatchTable ProtocolRTTI DispatchTable 2IntfMeta ImplSpec ....

L. Peterson, N. Hutchinson, S. O'Malley & H. Rao, The x-kernel: A Platform for Accessing Internet Resources, IEEE Computer, 23(5), May 1990, pp. 23-33.

....In general, solutions based on protocol libraries or architecture provide programmers with a library interface and an architecture for constructing protocols. The interface and the architecture are engineered by factoring out common protocol functionalities and abstractions. HCS HRPC [1] x kernel [20, 21] 14 , and TACT [2] 15 are examples of this type of solution. However, library architectures are restricted by the number of implementations provided in their libraries. Therefore, introducing a new RPC protocol often requires updates to every library on the network, which is not desirable in ....

L. Peterson, N. Hutchinson, S. O'Malley, and H. Rao. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23--33, May 1990.

.... The Choices object oriented operating system uses frameworks to structure the implementation of process management, virtual memory, storage, and other services [Campbell92] The x kernel used a similar idea to combine components form a fast and efficient interprocess communication subsystem [Peterson90]. This mechanism has been used to construct a modular system for building consistent group communication protocols [Mishra92] The Synthesis operating system uses run time code synthesis to combine protocol objects at run time [Massalin89] 1.3 Group communication A group communication mechanism ....

Larry Peterson, Norman Hutchinson, Sean O'Malley, and Herman Rao. The x-kernel: a platform for accessing Internet resources. IEEE Computer, 23(5):23--33, May 1990.

....operating system interface not only would allow us to more easily take full advantage of the resources in a heterogeneous cluster, but it would also reduce the system complexity. To this end, the vnode interfaces have failed miserably. Despite many years of research in extensible file systems [39, 5, 40, 38, 42, 22, 1, 28, 52], the construction of portable file systems has remained a difficult undertaking, especially for the commercial operating systems. We are currently investigating portable and efficient interposition agents as a means of distributing our code [17] In this section, we have seen that the vnode layer ....

Peterson, L., Hutchinson, N., O'Malley, S., and Rao, H. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer 23, 5 (September 1990), 23--33.

....checks across different contexts. For example, a naive network message driver may have a procedure to interpret the headers and trailers of each level in a multi level protocol. The procedure calls may be avoided by integrating different layers into flat code, as apparently is done in the x kernel [6]. The third method is called executable data structures . We omit it here because it has been described in some detail [3] and is not crucial to our example. To illustrate the quaject creation, we use the example of a data channel . In Synthesis, all the data movement is represented as a data ....

L. Peterson, N. Hutchinson, S. O'Malley, and H. Rao. The x-kernel: A platform for accessing internet resources. IEEE Computer, 23(5):23--34, May 1990.

....permits partitioned update, it does not support automatic directory reconciliation. The stackable layers architecture in Ficus is related to several other pieces of work. It is in many ways the file system analog of Ritchie s System V streams [14] and of the x Kernel s notion of protocol stacks [7, 11]. It is compatible with and motivated by the open system and micro kernel philosophy growing out of the Mach work [1] Rosenthal at Sun Microsystems is independently exploring similar approaches to layered filing [15] The Ficus work integrates and substantially extends the referenced concepts. ....

Larry L. Peterson, Norman C. Hutchinson, Sean W. O'Malley, and Herman C. Rao. The x-Kernel: A platform for accessing Internet resources. IEEE Computer, 23(5):23--33, May 1990.

....configuration for parallel processing, a runtime system providing location transparency is necessary. Metacomputing has been promoted by Smarr and Catlett [5] although without attention to massively parallel computing. Two approaches exist that are heading into a similar direction: The x kernel [4] addresses the problem of accessing Internet wide resources on operating system level, although not aiming at parallel computing, and Panda [1] focuses on providing a portable and efficient runtime system with communication abstractions and threads for the development of parallel programming ....

Peterson L., Hutchinson N., et al.: The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer 23(5) (1990) 23--33

....programmers to include their own API, and (e) to devise a flexible design which other people can apply to their own systems. This section focusses on the design of the GTS server, which is implemented in the C programming language. A GTS server is structured in a way similar to the x kernel [13] and to Electra [11] Each GTS server consists of a collection of adaptor objects plugged together to form a protocol tree as depicted in Figure 2. The root object (GTSroot) communicates with the client applications running in its cluster. Leaf Actor Crypt Compress Checksum Encode UUCP EMail TCP ....

Peterson, L., Hutchinson, N., O'Malley, S., and Rao, H. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer 23, 5 (May 1990).

....Sprite Sun 3 75 2.8 720 2.0 Measured kernel to kernel Mach Sun 3 60 11.0 3.0 Throughput not reported Fig. 6. Latency and throughput for some systems reported in the literature. The RPC numbers for the other systems listed in Fig. 6. are taken from the following publications: Cedar [5] x Kernel [19], Sprite [18] V [6] Topaz [22] and Mach [19] The numbers shown here cannot be compared without knowing about the systems from which they were taken, as the speed of the hardware on which the tests were made varies by about a factor of 3. On all distributed systems of this type running on fast ....

....Mach Sun 3 60 11.0 3.0 Throughput not reported Fig. 6. Latency and throughput for some systems reported in the literature. The RPC numbers for the other systems listed in Fig. 6. are taken from the following publications: Cedar [5] x Kernel [19] Sprite [18] V [6] Topaz [22] and Mach [19]. The numbers shown here cannot be compared without knowing about the systems from which they were taken, as the speed of the hardware on which the tests were made varies by about a factor of 3. On all distributed systems of this type running on fast LANs, the protocols are largely CPU bound. ....

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Peterson, L., Hutchinson, N., O'Malley, S., and Rao, H. The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer 23 (May 1990), pp. 23-33.

....as with an increase in the complexity of assuring that the combination of modules enforces a given policy. In principle, Escort does not impose granularity restrictions as long as each module exports well defined interfaces and provides well defined functionality. However, it has been shown in [46, 37, 54] that the granularity of one network protocol e.g. 37 IP or TCP per module is a useful tradeoff, especially for Information Appliances that mainly contain network protocols. Network protocols can be easily reused and provide a well defined interface and functionality. Compared to more ....

....advantage of access control lists, which are no migration of access rights, easy access revocation, and tight resource control of kernel data structure. Another group of similar operating systems are modular systems that can be configured for specific appliances like, for example, the x kernel [54], Inferno [66, 72] MMLite [36] or GEOS SC [31] of which none provides a path abstraction and the associated benefits. The only other project with a path abstraction is CORDS [79] which uses paths for resource allocation. CORDS is a real time networking architecture derived from the x kernel. ....

Larry L. Peterson. The X-kernel: a platform for accessing Internet resources. Technical report TR 89-23, University of Arizona, Dept. of Computer Science, Tucson, AZ, USA, October 1989.

....protocols. We have used the x kernel as a vehicle for experimenting with the decomposition of large protocols into primitive building block pieces [15 ] as a workbench for designing and evaluating new protocols [22] and as a platform for accessing heterogeneous collections of network services [23]. Many operating systems support abstractions for encapsulating protocols; examples include Berkeley Unix sockets [17] and System V Unix streams [28] Such abstractions are useful because they provide a common interface to a collection of dissimilar protocols, thereby simplifying the task of ....

L. L. Peterson, N. C. Hutchinson, S. W. O`Malley, and H. C. Rao. The x-Kernel: A platform for accessing internet resources. IEEE Computer, 23(5):23--33, May 1990.

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Peterson, L., Hutchinson, N., O'Malley, S., and Rao, H. (1990). The x-kernel: A Platform for Accessing Internet Resources. IEEE Computer, 23(5):23--33. 184

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L. Peterson, N. Hutchinson, S. O'Malley, and H. Rao. The X-kernel: A platform for accessing Internet resources. Computer, 23(5):23--33, May 1990.

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L. L. Peterson and et al, The x-kernel: A Platform for Accessing Internet Resources, IEEE Computer, 23(5): 23-33, May 1990

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Peterson, L., Hutchinson, N., O'Malley, S. and Rao, H. The x-kernel: A platform for accessing internet resources. IEEE Computer 23 (5): 23-33, 1990.

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