U. Black. Computer Networks. Prentice-Hall International, New York, 1987.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....2200Hz space for Bell 202, and 1300Hz mark, 2100Hz space for CCITT V.23. These two standards are only to some extent interoperable. 3. 4 Multiaccess Channel Protocols Networks are often divided into two categories: networks using point to point connections and networks using broadcast channels [Tan89]. In broadcast networks, several users share the same communication channel. Protocols are therefore needed to determine who should be allowed to use the channel. The two main approaches to channel allocation are static channel allocation and dynamic channel allocation. 3.4.1 Static Channel ....

....If the load of traffic is changing, or the number of users is large and varying, much bandwidth is wasted. Another static channel allocation scheme, Asynchronous Time Division Multiplexing, ATDM, is also inefficient when there are many uncoordinated, dispersed user trying to allocate the channel [Tan89]. 3.4.2 Dynamic Channel Allocation A better approach when the load of traffic is bursty and the number of users is large, is to use a dynamic channel allocation method. Some of the most common are the ALOHA and the CSMA protocols. Pure ALOHA [Abr85] permits a terminal to transmit at any time. ....

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Tanenbaum, A. 1989: Computer Networks, 2.edition, Prentice-Hall International.

....links, such as a wireless mobile link. 4.1 TCP IP TCP is a reliable transport protocol for the Internet. TCP is designed to ensure that the transmitted data reaches its destination without error. It also controls the transmission rate, based on feedback signals from the destination host [2, 49, 55, 58]. The common re ection one makes about TCP in a wireless environment, is that TCP was designed for high bandwidth, short delay, congestion limited networks, and is not well suited for high loss, high delay, error limited links. The meaning of this is that the ow control mechanisms in TCP react ....

....reduced to the minimum. This is not a desirable reaction in this narrow band environment. We would like to avoid the repeated transmission of TCP segments, since they add to the bandwidth waste. Several methods have been proposed to enhance the performance of TCP over error prone wireless links [3, 6, 27, 41, 58]. Some require changes of the current implementations of TCP on either side, and some improvements can be done without such changes. Improvements that do not require changes at the end points, will in some way interfere with the philosophy of end to end connectivity. Di erent approaches to TCP ....

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A. S. Tanenbaum. Computer Networks. Prentice Hall International, Upper Saddle River, New Jersey, 3 edition, 1996.

....both reorder and duplicate messages [23] In [18] unbounded sequence numbers are assumed for verification of the SW protocol for transport channels. This makes the verification rather simple, because it is known that the repetition of sequence numbers is the main source of errors for SW protocols [22]. Unfortunately, transmission protocols that use unbounded sequence numbers are usually not practical. Because of the impossibility results mentioned above, a SW protocol for transport channels with bounded sequence numbers can only be designed for systems, in which each message in a channel has ....

....of his protocol, depends on the maximum transmission rate of the sender. In the case of TCP, his protocol would only work correctly if the sender did not send into the channel more than some 30 megabytes of data per second (if we take 120 seconds for the maximum packet lifetime in TCP, as in [22]) Such restriction may not be practical for modern networks, which are getting Such protocols can also be designed for untimed systems which limit the reordering of messages in a channel [13] but such systems seem to be only of theoretical interest. faster every year. Indeed, the range of ....

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A.S. Tanenbaum. Computer Networks. Prentice-Hall International, Inc., 1996.

....MODEL FOR A VIRTUAL LABORATORY As can be seen in figure 6, the model consists of four different big blocks: the client (or user) the laboratory server, the measurement server i and the instruments with the devices under test and other setup connected. It is a layered model joining the OSI model [10] with instrument model and client server architecture. Client The user needs a computer with internet connection and a web browser. The layer structure defined by OSI, with the modification of Arpanet [10] network, applies to the model. There are different possibilities in the transport layer ....

....devices under test and other setup connected. It is a layered model joining the OSI model [10] with instrument model and client server architecture. Client The user needs a computer with internet connection and a web browser. The layer structure defined by OSI, with the modification of Arpanet [10] network, applies to the model. There are different possibilities in the transport layer [9, 11] TCP, UDP, Datasocket, The only application needed for the client is a web browser. Laboratory server A laboratory server is needed in each laboratory. It consists of a computer with a web server, ....

Tanenbaum, A. S., Computer Networks, Second edition, Prentice-Hall International, Inc., 1988, ISBN 0131668366.

....Control (UPC) prorating techniques need to be jointly adopted to guarantee di#erent Quality of Service (QoS) levels to competing tra#cs. Several MAC schemes have been proposed in the literature for managing multimedia tra#cs in BWASs [2] Moreover, some examples of UPC techniques can be found in [3]. Aim of this paper is proposing a new Radio Resource Management (RRM) scheme integrating a MAC protocol and a UPC policer both operated by the Access Point (AP) to achieve good QoS levels and high resource utilization. In Dr. Giovanni Giambene (corresponding author) is with Dipartimento di ....

....to a time division duplexing air interface. We consider real time video (streaming class) and Web browsing (interactive class) as two challenging tra#c classes in BWASs. The UPC policer decides the tra#c admitted for the di#erent sources on a frame basis by adopting a tokenbucket approach [3] for Web sources and a fuzzy logic based regulator for video sources. The management of competing video tra#cs is a complex task, since a video stream exhibits unpredictable bitrate fluctuations and complex time correlation. We propose the adoption of a policer based on Fuzzy Logic Controllers ....

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A. S. Tanenbaum. Computer Networks. Prentice-Hall International, Inc., New Jersey, 1996.

....We decided to study an additional MAP, the 0.001 Persistent. The way were asked to investigate these protocols was using simulations written in the C programming language. What these simulators should demonstrate is load vs. channel utilization. The algorithms for these protocols were taken from [1] and a simulator for slotted ALOHA was given by Dr. Yaun. However, we modified this slotted ALOHA simulator to make it easier to test and display a wide range of results using gnuplot. All of the MAP simulators use the same basic algorithm and data structures. The algorithm generates packets ....

....FL. E mail: marrotte cs.fsu.edu. 0.05 0.1 0.15 0.2 0.25 0 1 2 3 4 5 6 7 8 9 pap.p Fig. 1. Comparison of the channel utilization versus load for the Pure Aloha. II. Aloha The ALOHA method was original proposed by Norman Abramson et al. at the University of Hawaii in the 1970 s [1] and first appeared in [2] Since, then it has been studied in depth and extended in several ways [3] We simulated and studied two of the ALOHA protocols, the Pure ALOHA and the Slotted ALOHA. The main di#erence between the two is that Slotted uses discrete time slots as where Pure does not. ....

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A. Tanenbaum, Computer Networks, Prentice-hall International, Inc., 1996.

....RTO is backed off exponentially at each unsuccessful retransmit of the segment [22] When RTO expires, data transmission is controlled by the slow start algorithm described below. To prevent a fast sender from overflowing a slow receiver, TCP implements the flow control based on a sliding window [28]. When the total size of outstanding segments, segments in flight (FlightSize) exceeds the window advertised by the receiver, further transmission of new segments is blocked until ACK that opens the window arrives. Early in its evolution, TCP was enhanced by congestion control mechanisms to ....

A. S. Tanenbaum. Computer Networks. Prentice-Hall International, 1996.

....communication mechanism between interacting systems. Hence, it is useful to have such a mechanism available when designing parallel and distributed systems. Remote procedure calls is a concept found in many programming languages and operating systems especially in client server architectures [11, 19]. However, there seems to exist very little work on the formal derivation of systems with this communication mechanism in the literature [20] In this paper we give a formal treatment of the remote procedure call mechanism and develop the needed proof rules for reasoning about the correctness and ....

A. S. Tanenbaum. Modern Operating Systems. Prentice--Hall International, 1992. 29

....RTO is backed off exponentially at each unsuccessful retransmit of the segment [21] When RTO expires, data transmis sion is controlled by the slow start algorithm described below. To prevent a fast sender from overflowing a slow receiver, TCP implements the flow control based on a sliding window [29]. When the total size of outstanding I Congestion Avoidance I (linear growth) Window halving i Juponcongestion l lSlFmission Slow Start (exponential growth) Windo.w = l upon ttmeout Time Figure 1: Congestion control in TCP [6] segments, segments in flight (FlightSize) exceeds the ....

A. S. Tanenbaum. Computer Networks. Prentice-Hall International, 1996.

....is backed off exponentially at each unsuccessful retransmit of the segment [PA00] When RTO expires, data transmission is controlled by the slow start algorithm described below. To prevent a fast sender from overflowing a slow receiver, TCP implements the flow control based on a sliding window [Tan96] In every acknowledgment, the receiver advertises to the sender the receiver window, the number of bytes allowed for transmission. The receiver window is always relative to the acknowledgment number. An arriving ACK allows more data to be sent by advancing the edge of the sliding window to the ....

A. S. Tanenbaum. Computer Networks. Prentice-Hall International, 1996.

....messages onto a single virtual logical connection from the SGSN to the MS. The SNDCP also provides the encryption, segmentation, and compression of user data. Between the MS and the BSC, the data link layer has been separated into two distinct sublayers: the logical link control (LLC) GSM0464] [Tane96], pages 302 304) and radio link control medium access control (RLC MAC, GSM0460] sublayers. The LLC layer is the higher sublayer of the data link layer. It provides a highly reliable logical link between the MS and the SGSN. Its functionality includes both acknowledged and unacknowledged data ....

....in order to get some understanding of how a TCP data transfer, running through GPRS, is aoeected by GPRS functionalities. The problems of TCP over wireless networks will be discussed in Section 4. For further information, the interested reader is encouraged to see references [Post81] AlPS99] [Tane96], and [Hals96] 3.1 TCP Overview TCP ooeers to end users usually through applications a reliable byte stream transport service. The TCP protocol is designed to transfer the data associated with two peers in a reliable way, that is to say, error free with no losses or duplicates and in the same ....

Tanenbaum, A. S., Computer Networks (Third Edition). Prentice-Hall International, 1996, pp. 243 - 335. REFERENCES 76

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A.S. Tanenbaum. Computer Networks (second edition). Prentice-Hall International, 1988.

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....are equal and the wrap flags are different then the FIFO is full, otherwise (with identical wrap flags) the FIFO is empty. The wrap flag increases the range of the counters to twice the size of the maximum number of tokens in the FIFO, akin the sliding window protocol for data communication [8]. We choose option 3 since with this option no consistency problem arises 4.2 Implementations of the primitives When a claim data call is executed and a full token is available in the FIFO, a pointer to the token is returned. The token pointer is calculated from the readc value and some static ....

Tanenbaum, A. S., Computer Networks, Prentice/Hall International, Inc., The Netherlands, 1981.

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U. Black. Computer Networks. Prentice-Hall International, New York, 1987.

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A. Tanenbaum. Computer Networks. Prentice--Hall International, 1996. 142

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