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TOPIC: Pseudo header in Checksum calculation in transport layer

Pseudo header in Checksum calculation in transport layer 9 years 8 months ago #20237

  • shreyas
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Actually i have doubt regarding the calculation of pseudo header value in transport layer.Actually the pseudo header uses the destination and source ip address for calculating that value.But in transport layer how it will get the ip address?
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Re: Pseudo header in Checksum calculation in transport layer 9 years 8 months ago #20252

  • Elohim
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It doesn't. By the time a data segment reaches layer 4, the IP Addressing headers have already been stripped off. The transport layer will not know about the IP Addresses. It only knows what port the data segment was sourced from and which port the data segment needs to go to.

Remember your five steps of data encapsulation?
Actually i have doubt regarding the calculation of pseudo header value in transport layer.Actually the pseudo header uses the destination and source ip address for calculating that value.But in transport layer how it will get the ip address?
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Re: Pseudo header in Checksum calculation in transport layer 9 years 8 months ago #20258

  • shreyas
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if it is the case while we are sending the data it goes from transport layer to n/w layer.In this site it is mentioned that in transport layer the pseudo header calculation is done for check sum and for that we need ip address..From where do it get the ip address?
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Re: Pseudo header in Checksum calculation in transport layer 9 years 8 months ago #20274

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What are you reading off? The transport doesn't see the network layer headers. When a packet reaches the transport layer, the network layer headers have been stripped off the segment already and therefore contains no ip addressing information so you cannot obtain the IP addressing at layer 4. The bottom line is you don't.
if it is the case while we are sending the data it goes from transport layer to n/w layer.In this site it is mentioned that in transport layer the pseudo header calculation is done for check sum and for that we need ip address..From where do it get the ip address?
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Re: Pseudo header in Checksum calculation in transport layer 9 years 8 months ago #20358

  • shreyas
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I know that transport layer dosent have ip information.Then how do it calculate the pseudo header value?
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