functions of data link layer ppt

... www.bkacad.com Connecting Upper Layer Services to the Media 11 • To support a wide variety of network functions, the Data Link layer is often divided into two sublayers: an upper sublayer and an lower sublayer. – ... www.bkacad.com Overview Upon completion of this chapter, you will be able to: • Explain the role of Data Link layer protocols in data transmission. • Describe how the Data Link layer prepares data for transmission ... Data Link Layer Protocols- The Frame 31 • Remember that although there are many different Data Link layer protocols that describe Data Link layer frames, each frame...

Ngày tải lên: 22/12/2013, 13:17

... 900 Figure 14.8.1. Top: Synthetic noisy data consisting of a sequence of progressively narrower bumps, and additive Gaussian white noise. Center: Result of smoothing the data by a simple moving window average. ... synthetic data. Bottom: Result of smoothing the data by a Savitzky-Golay smoothing filter (of degree 4) using the same 33 points. While there is less smoothing of the broadest feature, narrower ... panels.) The widths of the bumps (full width at half of maximum, or FWHM) are 140, 43, 24, 17, 13, and 10, respectively. The middle panel of Figure 14.8.1 shows the result of smoothing by a moving...

Ngày tải lên: 15/12/2013, 04:15

... measure of goodness -of- fit. When the third item suggests that the model is an unlikely match to the data, then items (i) and (ii) are probably worthless. Unfortunately, many practitioners of parameter ... graph of data and model “looks good.” This approach is known as chi-by-eye. Luckily, its practitioners get what they deserve. CITED REFERENCES AND FURTHER READING: Bevington, P.R. 1969, Data Reduction ... based on? The answer to these questions takes us into the subject of maximum likelihood estimators. Given a particular data set of x i ’s and y i ’s, we have the intuitive feeling that some parameter...

Ngày tải lên: 15/12/2013, 04:15

... float *xx,*yy,*sx,*sy,*ww,aa,offs; float chixy(float bang) Captive function of fitexy , returns the value of (χ 2 − offs ) for the slope b=tan(bang) . Scaled data and offs are communicated via the ... variance of the linear combination y i − a − bx i of two random variables x i and y i , Var(y i − a − bx i )=Var(y i )+b 2 Var(x i )=σ 2 yi +b 2 σ 2 xi ≡1/w i (15.3.3) The sum of the square of N ... large that the data are consistent with a vertical (infinite b) line. If siga and sigb are returned as BIG , then the data are consistent with all values of b. { void avevar(float data[ ], unsigned...

Ngày tải lên: 15/12/2013, 04:15

... value of a measured quantity, or the mean of some function of the measured quantities. The bootstrap method [1] uses the actual data set D S (0) , with its N data points, to generate any number of ... or different data reduction techniques, and seek to minimize the uncertainty of the result according to any desired criteria. Offered the choice between mastery of a five-foot shelf of analytical ... even when they must be offered without proof. Figure 15.6.1 shows the conceptual scheme of an experiment that “measures” a set of parameters. There is some underlying true set of parameters a true that...

Ngày tải lên: 15/12/2013, 04:15

... *arr,d,sum=0.0; arr=vector(1,ndatat); for (j=1;j<=ndatat;j++) arr[j]=yt[j]-b*xt[j]; if (ndatat & 1) { aa=select((ndatat+1)>>1,ndatat,arr); } else { j=ndatat >> 1; aa=0.5*(select(j,ndatat,arr)+select(j+1,ndatat,arr)); } abdevt=0.0; for ... on the following fact: The median c M of a set of numbers c i is also that value which minimizes the sum of the absolute deviations  i |c i − c M | (Proof: Differentiate the above expression ... fractionally small departures for all data points, or else fractionally large departures for a small number of data points. It is the latter interpretation, leading to the notion of outlier points, that is...

Ngày tải lên: 15/12/2013, 04:15

... same data access technologies as that of the nontransactional DAL. The following data access technologies were covered in Module 8, “The Nontransactional Data Access Layer : ! Microsoft Data ... data services layer. The transactional DAL can return to the business logic layer either success or failure. If the transaction also involved retrieving data as a result of updates to the data, ... DAL: Module 8, “The Nontransactional Data Access Layer and Module 9, “The Transactional Data Access Layer. ” The DAL is an application’s means of access to data services. After completing this...

Ngày tải lên: 17/01/2014, 09:20

... frame i+1 out of sequence  Receiver send reject i  Transmitter goes back to frame i and retransmits William Stallings Data and Computer Communications Chapter 7 Data Link Control Cyclic ... Access Procedure, Balanced (LAPB)  Part of X.25 (ITU-T)  Subset of HDLC - ABM  Point to point link between system and packet switching network node  Link Access Procedure, D-Channel  ISDN ... code  Parity  Value of parity bit is such that character has even (even parity) or odd (odd parity) number of ones  Even number of bit errors goes undetected HDLC Operation  Exchange of information,...

Ngày tải lên: 16/02/2014, 08:20

... power of a memory hierarchy comes from its ability to take advantage of patterns of data use that are transient. Repeated requests tend to be made to a given data item over a short period of ... best advantage. The emphasis of the book will be on the practical applications of such results. The focus of the applications examined in this book is on the portion of a computer system’s memory ... vendors, vendors often offer such reporting as a differentiating feature. As befits a work about fractal modeling, the chapters of the book cover events that play out at a wide range of time scales....

Ngày tải lên: 03/07/2014, 08:20

... STRUCTURE OF DATA REFERENCE Figure 1.7. time. CICS storage pools: cache performance as a function of average cache residency Figure 1.8. time. IMS storage pools: cache performance as a function of ... function of cache size. Just as the miss ratio, as a function of the single - reference residency time, takes the form of a simple power law, so does the miss ratio, as a function of cache ... experienced by a wide range of cached data. Figures 1.4 through 1.10 present the performance of a “plain vanilla” cache, relative to average residency time, for a range of application storage pools....

Ngày tải lên: 03/07/2014, 08:20

... CICS storage pools: distribution oftrack interarrival times. Figure 1.14. CICS storage pools: distribution ofrecord interarrival times. 30 THE FRACTAL STRUCTURE OF DATA REFERENCE Figure 1.15. IMS ... storage pools: distribution of track interarrival times. Figure 1. 16. IMS storage pools: distribution of record interarrival times. 28 THE FRACTAL STRUCTURE OF DATA REFERENCE Figure 1.11. DB2 ... pools: distribution oftrack interarrival times. Figure 1.12. DB2 storage pools: distribution ofrecord interarrival times. 26 operating separately [ 18]: THE FRACTAL STRUCTURE OF DATA REFERENCE (1.26) (Note,...

Ngày tải lên: 03/07/2014, 08:20

... well. 42 THE FRACTAL STRUCTURE OF DATA REFERENCE A general - purpose technique exists for generating synthetic patterns of ref - erence, which is also capable of producing references that conform ... concept of stack distance, or the depth at which previously referenced data items appear in the LRU list [8, 21]. The idea is to build a history of previous references (organized in the form of ... variety of individual “daemons”, large numbers of which can run concurrently and independently. This type of benchmark structure is attractive, in that it mirrors, at a high level, the behavior of...

Ngày tải lên: 03/07/2014, 08:20

... FRACTAL STRUCTURE OF DATA REFERENCE Table 4.1. Busiest 20 files (data sets) in the case study. Use of Memory at the I/O Interface 53 meant that all memory deployment strategies of interest could ... manage database files. Databases constructed using DataBase 2 ( DB2) and Information Man - agement System (IMS) database management software were also in heavy use. Most database storage was contained ... ( VSAM) files. Our examination of the installation of the case study is based on a trace of all storage subsystem I/O during 30 minutes of the morning peak. The busiest 20 files (alsocalleddatasets)appearing...

Ngày tải lên: 03/07/2014, 08:20

... determine the best trade - off of memory among the n workloads. The optimal allocation of memory must be the one for which the marginal benefit (reduction of delays), per unit of added cache memory, ... a point of reference. Thus, we normalize the individual partition I/O rates relative to : (5.5) Memory Management in an LRU Cache 63 misses, in units of seconds of delay per second of clock ... management of cache memory is therefore optimal. 1.1 IMPACT OF MEMORY PARTITIONING In the assumptions stated at the beginning of the section, we excluded those cases, such as a complete lack of I/O,...

Ngày tải lên: 03/07/2014, 08:20

... probability of further updates is highest shortly afterward. THE FRACTAL STRUCTURE OF DATA REFERENCE IMPACT OF TRANSIENT DATA ACCESS Figure 6.2. also presented in Figure 1.2. Distribution of time ... reflects how quickly data are written to disk relative to the overall lifetime of the data. We should expect its value to be of the same order as the ratio of “dirty” data items in cache, relative ... overall number of data items on disk. The value of d would typically range from nearly zero (almost no buffering of writes) up to a few tenths of a percent. Since a wide range of this ratio might...

Ngày tải lên: 03/07/2014, 08:20

Ngày tải lên: 03/07/2014, 08:20

Ngày tải lên: 05/07/2014, 06:20

Ngày tải lên: 05/07/2014, 06:20

Ngày tải lên: 05/07/2014, 06:20

Ngày tải lên: 05/07/2014, 06:20