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Bandwidth utilization for each protocol ( ALOHA - Slotted ALOHA - CSMA/CD - CSMA/CA) Why IS it different
على ماذا يعتمد الاختلاف هل على حجم fram ام طريقة كل بروتوكول في الارسال.
إذا فيه مصدر معين لهذا الموضوع. وشكراً
الحمد لله لقد تمكنت من إيجاد حل لبعض من استفساراتي واتمنى الفائدة تعم
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WHOLA :
o Station send frame any time when it has. So the collision will happen because there is no synchronization that means there is no specific time to send frame.
o Then the frame will damage .if it was destroyed the station wait a random amount then sends it again.
o The maximum throughput or efficiency is about 18.4%.
o This figure is illustrated the relationship between bandwidth ,link efficiency and idle duration
o There is Inverse relationship between the bandwidth and efficiency when the bandwidth is low the efficiency will be increasing until the max efficiency 18.4%.
o On other side when bandwidth growth then the efficiency decline ,that means no frame sent in the network then idle time increase.
o Also, when the bandwidth is high that means it can has more frame the collision will be decrease . On the other hand, when the bandwidth is very low the link experiences a high collision rate and a low idle time rate also.
o This figure is illustrated the relationship between Frame size ,link efficiency and idle duration .
o It seems that the relationship between the efficiency and frame size is inverse similar the relation with bandwidth , When the frame size is small then the efficiency will increase until reach the max efficiency 18.4%, but when the frame size is big then the efficiency will decrease.
o On the other hand, when the frame size is very low the link experiences a low collision rate and a high idle time rate also.
وكذلك وجدت شيئاً مفيداً:
- Slotted WHOLA:
o This is quite to Aloha, differing only in the way transmissions .
o All frame slotted into equal size (L).
o Time in channel divided into uniform slot that means slot is the time to transmit one frame.
o Stations start to transmit frame when slot frame beginnings .
o There is synchronize for all stations , the time divided into slot.
o If two or more frames collide in a slot, then all the stations detect the collision event before the slot ends.
o the number of collisions are reduced and the performance become much better compared to Aloha. collisions may only take place with nodes that are ready to speak at the same time. But nevertheless, this is a substantial reduction.
o The maximum throughput or efficiency is about 37%.
o In Slotted ALOHA the collision will be low when the size of channel (bandwidth) is high , when the bandwidth is low. In such cases the transmission time is high. This increases the number of collisions occurring in the network.
o it is similar the ALOHA in each relation between bandwidth with collision and bandwidth with efficiency and the size of frame.
للأمانه المعلومات جمعت من كذا موقع:
http://www.cse.iitk.ac.in/users/dheeraj/cs425/lec04.html/
http://www.auburn.edu/~benbrah/comp6340/s_csma_cd.php?p=1
http://www.laynetworks.com/protocol.htm
بالإضافة إلى كتاب
Computer Network for Andrew S