Computer Network Unit 1 q what are the topologies in computer n/w ?

Q 11. Explain Token bucket Algorithm.

Ans : The algorithm can be conceptually understood as follows:

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  A token is added to the bucket every 1 / r seconds.
  
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  The bucket can hold at the most b tokens. If a token arrives when the bucket is full, it is discarded.
  
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  When a packet (network layer PDU) of n bytes arrives, ntokens are removed from the bucket, and the packet is sent to the network.
  
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  If fewer than n tokens are available, no tokens are removed from the bucket, and the packet is considered to be non-conformant.
  

The algorithm allows bursts of up to b bytes, but over the long run the output of conformant packets is limited to the constant rate, r. Non-conformant packets can be treated in various ways:

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  They may be dropped.
  
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  They may be enqueued for subsequent transmission when sufficient tokens have accumulated in the bucket.
  
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  They may be transmitted, but marked as being non-conformant, possibly to be dropped subsequently if the network is overloaded.
  

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How the algorithm works
The algorithm is based on a concept of credit. We begin with an amount of credits calculated from the values specified with the ­­limit and ­­limit­ burst. This amount of credits we start with is also the maximum credit we can have. We also calculate a cost that every packet that pass needs to pay. The only way to get new credit is to wait, that means that only time can give us new credit. It use the jiffies counter because it's more efficient than using a real clock on every packet. It's thus impossible to give new credits every time, we must have a checkpoint. This checkpoint is the jiffy counter which is incremented HZ times per second. As stated above,


Q 12. How the network traffic problem is handled in wireless communication ?
Ans: When you have trouble connecting a wireless client (a desktop, laptop, PDA, or phone) to an office network, these step-by-step debugging tips can help.