In IP packet has arrived with datagram of size 700 bytes. The size of ...
Maximum transmission unit = 185 bytes
Size of the IP header = 20 bytes
Number of fragments =
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In IP packet has arrived with datagram of size 700 bytes. The size of ...
IP Datagram Fragmentation
IP datagram fragmentation is the process of dividing a large IP datagram into smaller fragments to fit the Maximum Transmission Unit (MTU) of a network link. Each fragment is then reassembled at the destination to reconstruct the original datagram.
Given Information:
- Datagram size: 700 bytes
- IP header size: 20 bytes
- Link MTU: 185 bytes
Calculation:
To calculate the number of fragments required, we need to consider the following:
Total Datagram Size:
The total size of the IP datagram includes both the data and the IP header. So, the total datagram size is 700 + 20 = 720 bytes.
Fragmentation Offset:
Each fragment has a field called the Fragmentation Offset, which indicates the position of the fragment within the original datagram. The offset is measured in units of 8 bytes.
Maximum Data Length per Fragment:
To determine the maximum data length per fragment, we subtract the IP header size from the link MTU: 185 - 20 = 165 bytes.
Number of Fragments:
To calculate the number of fragments, we divide the total datagram size by the maximum data length per fragment and round up to the nearest whole number.
Number of fragments = ceil(total datagram size / maximum data length per fragment)
= ceil(720 / 165)
= 4.3636363636
≈ 5 (rounded up)
Therefore, the IP datagram will be divided into 5 fragments.
Note:
The last fragment may have less than the maximum data length if the remaining data is less than the maximum. In this case, the last fragment will contain the remaining data and the "More Fragments" flag will be set to 0 to indicate the end of the datagram.