CODEWITHSUNDEEP
tcptcpclientnetwork-protocols
user975343
user975343

Reputation:

TCP And Data Validity

I know what TCP implements in-order data transmission,but does it actually validates the data that arrived from A to B is the actual data that was sent from A ? If it does , how exactly does it happen?

Upvotes: 0

Views: 84

Answers (2)

through-the-ether
through-the-ether

Reputation: 71

does it actually validates the data that arrived from A to B is the actual data that was sent from A ?

Frankly, no. It tries to make sure receiver gets the same number of bytes sender sent during session (using ack and syn numbers). It also makes sure every segment has correct checksum, which, I think doesn't guarantee much. If your host has faulty memory, it could be that you send one stream of bytes, then, a few buffers later some another stream of bytes (due to bit-flapping) is used to calculate checksum. The checksum will be correct, but the sent and received messages will differ. If you want reliability, always implement your own checksumming/hashing/signing of application-level messages.

Some relevant reading explaining a cost of a single bit error: http://status.aws.amazon.com/s3-20080720.html.

Upvotes: 1

Joe
Joe

Reputation: 28366

I believe this excert from RFC 793 answers your question:

The TCP must recover from data that is damaged, lost, duplicated, or
delivered out of order by the internet communication system.  This
is achieved by assigning a sequence number to each octet
transmitted, and requiring a positive acknowledgment (ACK) from the
receiving TCP.  If the ACK is not received within a timeout
interval, the data is retransmitted.  At the receiver, the sequence
numbers are used to correctly order segments that may be received
out of order and to eliminate duplicates.  Damage is handled by
adding a checksum to each segment transmitted, checking it at the
receiver, and discarding damaged segments.

Upvotes: 0

Related Questions