Two stations running TCP/IP are engaged in transferring a file. This file is 1000MB long, the payload size is 100 bytes, and the negotiated window size is 1000 bytes. The sender receives an ACK 1200 from the receiver. Requried:
a. Which bytes will be sent next?
b. What is the last byte number that can be sent without an ACK being sent by the receiver?

a. 2100

b. 2199

Explanation:

GIven that:

The file size = 1000 MB

The  payload size is  = 100 bytes

The negotiated window size is = 1000 bytes.

This implies that the sliding window can accommodate maximum number of 10 packets

The sender receives an ACK 1200 from the receiver.

Total byte of the file is :

1000 MB = 1024000000 bytes

a.

Sender receives an ACK 1200 from the receiver but still two packets are still unacknowledged

=1200 + 9 * 100

= 1200 +  900

= 2100

b. What is the last byte number that can be sent without an ACK being sent by the receiver?

b. Usually byte number starts from zero, in the first packet, the last byte will be 99 because it is in 1000th place.

Thus; the last byte number send is :

= 1200 + 10 *100 -1

= 1200 + 1000-1

= 1200 + 999

= 2199