Jato

Jato, we intellection rs gold we had preserved you." He wow gold shook his brain. "She was nfl jerseys wholesale confident. An unguarded nowadays nfl wholesale jerseys and you were able to secure NFL jerseys her." Lifting the observe, he said.

CSMA / CD
CSMA / CD (Carrier Sense Multiple Access / Collision Detect) is Carrier Sense Multiple Access / Collision Detection in Ethernet, all nodes share the transmission medium. How to ensure the transmission medium orderly and efficient manner to provide transmission services for many nodes, that is, the Ethernet media access control protocol to solve the problem.
directory
First, the Basics: Second, Advanced papers: CSMA / CD control procedures: a few concepts: the three algorithms and features: Third, the application of a chapter, basic articles: CSMA / CD is a contention-based medium access control protocol. It originated in the University of Hawaii used in the development of the ALOHA network contention-based protocol, and has been improved so that it has a higher than the ALOHA protocol media utilization. Another improvement is that, for each station, once it detects a conflict, send it to abandon its current task. In other words, if two stations detect the channel is idle and start sending data at the same time, they will be detected almost immediately conflict. They should not continue to send their frames,air force 1 high, as this will only waste it produces; contrary, after a conflict is detected once, they should immediately stop sending data. Quick end to the damaged frame can save time and bandwidth. CSMA / CD control advantages are: the principle is relatively simple, technically easy to achieve, the network status of each workstation is equal, without centralized control, does not provide priority control. However, the network load increases, the transmission time increases, the transmission efficiency dropped sharply. CSMA / CD used in the second layer of OSI Data Link Layer of its working principle is: listen before sending data channel is idle, if idle data is sent immediately. In sending data, send a side to side listening. If listening to conflict immediately stop sending data. wait a random time, and then try again. CSMA / CD with IEEE 802.3 standard. Its main objectives are: to provide address and media access control, so different devices or network nodes can communicate over the network more than conflict. CSMA / CD can only be used for bus-based network topology. Second, Advanced papers: CSMA / CD control procedures: control procedures of the core issues: addressing the public channel to broadcast data transmission problems may occur (mainly data collision) control process consists of four processing elements: listening , send, detection, conflict management (1) listening: through specialized testing organizations, preparing the site before sending on the bus listening about whether data is being transmitted (line is busy)? If the If (2) Send: When it is determined to be sent, by sending agencies, sending data to the bus. (3) detection: the data sent,air force one high, data collision may occur. Therefore, to send the data side, edge detection, to determine whether the conflict. (See Figure 5P127) (4) conflict resolution: When a conflict is recognized, the access to the conflict process. There are two conflicts: ① ② listener found the line is busy sending data found during the collision ① found if the line is busy listening,air force 1 shoes, then listening again after waiting for a delay, if still busy, continue to delay in waiting, has been that can be sent up. Time differences between each delay, the backoff algorithm to determine the delay value. ② If the collision sent the data found during the first block of information sent to strengthen the conflict, and then work to listen to until the next re-sent (the same method ①) several concepts: the two conflicts are related to a common algorithm - backoff algorithm. ① backoff algorithm: When a circuit conflict, if the conflict of the sites using the same backoff interval, it is very easy to produce second and third collision. Therefore, the requirements of each site with a difference backoff interval. This requires to achieve through the backoff algorithm. Truncated binary exponential backoff algorithm (Backoff Algorithm for one): When a site that the line is busy, you should wait for a delay time M, and then listen for further work. M delay time determined by the following algorithm: M = 0 ~ 2k th power minus one multiplied by a random number between 512 bit times (for example, 10Mbps Ethernet,air force one shoes, 51.2 microseconds), k is the conflict (collision) is number, M the maximum value of 1023, that is, when k = 10 and beyond 1023 M is always between 0 and 51.2, a product of random values,nike air force 1, when k increased to 16,nike air force one high, to send the wrong message. ② special blocking messages: It is a special set of data. Send data found in the conflict, immediately send a special block of information (full-1 successive bytes, usually 32-48 bits) to strengthen the conflict signal to the site as soon as possible on the line by the conflict detection signal, thereby reducing create new potential for conflict. ③ conflict detection time> = 2α: α indicates that the network of transmission lines two sites furthest delay. Expressed as the detection time of the furthest site to issue the data must be guaranteed after the other perceived conflicts shortest time. There is no perception of time in the 2α conflict, to ensure that data is not sent into conflict. (2α time as long as the guarantee test is not necessary to detect both the sending process) ④ X-insist CSMA algorithm: When the line is found in the listener idle, do not send data, while the use of X-insist CSMA algorithm to decide how to for data transmission: the three algorithms and features: - Non-insist CSMA: the line is busy, wait a period of time, and then listen; not busy, he immediately sent; reduce conflict, reduce channel utilization: - 1 adhere to the CSMA: the line is busy continue to listen; not busy, he immediately sent; improve channel utilization, increased conflict: - p insist CSMA: the line is busy, continue to listen; not busy, according to the probability of transmission p, the probability of another 1-p To continue listening (p is the probability of a specified value); effective balance, but the complex: (5) flow chart (top right figure): (6) CSMA control procedures of the characteristics of a broadcasting function ① ② ③ simple average bandwidth: f = F / n ④ absolute equality, non-priority ⑤ low-load high efficiency, high load inefficient ⑥ ⑦ unpredictable delay transmission rate and transmission distance is a constant c, the application papers CSMA / CD used for a variety of bus structure Ethernet (bus topology Ethernet) and twisted-pair Ethernet (twisted-pair Ethernet) in earlier versions. Modern Ethernet switches and full duplex connection is established based on, will not have collisions, so no need to use CSMA / CD. CSMA / CD network transmission must be carried out according to the following five steps (1) transmission before the listener (2) If the busy then wait (3) transmission and detection of conflict (4) If conflict occurs, to wait before retransmission ( 5) re-entry pass, or die Atlas Atlas more extended reading: 1
CSMA / CD algorithm: http://pre.visualland.net/csmacd/ind...title=6.CSMACD 2
Hangzhou University of Electronic Science and Technology
3
basic knowledge of computer networks, training materials
4
Computer Networks (Fourth Edition) Andrew S. Tanenbaum
open Category: Computer network to improve my