# A CSMA/CD QUESTION

CSMA/CD (Carrier Sense Multiple Access / Collision Detection) is the protocol used in Ethernet networks to ensure that only one network node is transmitting on the network wire at any one time. In this protocol, if one host sending a message collides with someone, the host will wait a random number of slot-time before trying to re-send the message. The random waiting slot time is calculated by binary exponential back-off algorithm. Now, please explain how the binary exponential back-off algorithm works? Besides, if the host experiences the second collision, what would be the range of the possible number of slot-time for this host to wait before the third trial?

### 4 個解答

• 9 年前
最佳解答

Collision in multiple access medium probably is non-issue nowadays, especially most layer 2 devices are store and forward. This design makes collision impossible.

2012-02-28 01:59:34 補充：

Now, please explain how the binary exponential back-off algorithm works?

When a colision is detected, the sending device who detects the colision shall wait for a random amount of time then restart the transmission procedure. The binary exponential back-off algorithm is to double the window size of the "possible" random wait. See also the details below.

Besides, if the host experiences the second collision, what would be the range of the possible number of slot-time for this host to wait before the third trial?

binary exponential back-off algorithm is AKA truncated binary exponential backoff. It uses time slot t and randomly choose a backoff time between 0 through 2^c-1 time slots for collision c. For example, after collision 0 (ie, no collision), the random wait time is 0 time slot. After collision 1, random backoff is between 0 and 1 slot. After collision 2, backoff is 0..3, collision 3, backoff at 0..7.

However, if you have collisions this bad, your random access domain is probably too big. That means you need to reduce the size of your access domain.

• 匿名使用者
6 年前

推薦您前往黃金俱樂部遊戲網！

提供您詳盡的說明

您可以先進行遊戲下載：

誠心服務！會員溫馨！永久服務！

第一：全程直播遊戲的公平與公正性【亞洲唯一直屬會員代理】

第二：點數儲值和託售皆在十分鐘之內完成【全台娛樂城速度最快24小時不分周末】

第三：二十四小時專業客服務線上服務全年無休【大大小小問題都可以馬上做詳細解答喔】

電子機台．真人遊戲和你一同玩樂

麻將 百家樂 5PK 德州撲克 水果盤 賓果

輪盤 21點 10點半 骰盅 牌九 鬥地主 13支

全年網站優惠活動不間斷！

快去註冊會員！免費：http://99點5888th點net

• 匿名使用者
7 年前

線上遊戲天堂 http://ts999.tw

運動遊戲

實況棒球、籃球、足球、冰球、網球等多種經典賽事

即時遊戲

百家、21點、牌九、二八杠、骰寶、龍虎、輪盤、牛牛、番攤

對戰遊戲

麻將、德州撲克、二八杠、吹牛、鬥地主、13支、暗棋、接龍

電子遊戲

5PK、7PK、水果盤遊戲、5輪遊戲、極限飆速、趙雲救主、西遊戲、金瓶梅、中國美人、英雄

彩球遊戲

大樂透、六合、時時彩、今彩539、3星彩、4星彩

最新優惠活動

1. 運動遊戲連過5關,彩今再加碼10%

2. 新會員加入,有機會獲得500元禮券與精美讀卡機

3. 遊戲積分可兌換汽機車、3C、精品等多種大獎

免費線上體驗試玩喔~!

線上遊戲天堂 http://ts999.tw

• 阿昌
Lv 7
9 年前

CSMA/ CD（載波偵聽多路訪問/衝突檢測）是在以太網網絡中使用，以確保在任何一個時間只有一個網絡節點上網絡線傳輸的協議。在這個協議中，如果一台主機發送消息與他人串通，主機將試圖重新發送消息之前等待的時間槽的隨機數。計算二進制指數回退算法的隨機等待時間槽。現在，請解釋如何二進制指數回退算法的工作嗎？此外，如果主機遇到的第二次碰撞，將是這之前等待第三次試驗的主機盡可能多的時間槽範圍？