Computer Networks, DNS - Essay Example

The size of the window is controlled by a window field in the TCP header.

In the case of length=140 seq num=1 ack =141 window=260, the receiver acknowledges all bytes that are inclusive but not necessarily inclusive of the sequence number 1. It then sets the new window size 260. The starting point of the sliding window slides to position 1 with size 260. When the size W of the window gets to 0, transmission is stopped. Increasing the size of the windows enhances the bandwidths and makes the connection more efficient. Considering the basic functionality of the window size, that is holding the data by a device from its peer at any one time, increasing the size will then make the device hold more data in the buffer at a time. This will enhance the efficiency of communication. Over-reliance on cumulative acknowledgments can cause data transfer inefficiency due to packet loss.

Selective acknowledgment allows the receiver of the packets to be able to accept packets that are discontinuous but received correctly. This is in addition to the last successful contiguous byte that was received. This is the same situation that happens in a basic acknowledgment. In this mode, the acknowledgment specifies the SACK blocks and they are then conveyed through starting and ending sequence numbers. The SMTP processes the email address of the recipient in the same domain. When the names correspond, the message is directly routed to the POP3 server or the IMAP server.

In this case, it is routed to the SMTP. In the case of the local client who is sending an email over the network, there will be no communication with another domain server. This communication will be from the internal mail server 10.1.0.10 from 10.1.0.10/8. On getting the email address, the SMTP server can connect to the recipient SMTP server. For the local client, this communication is maintained within the same server. For sending an email over the internet, the information is passed over to the border router. b) A DNS lookup occurs when a device supporting an IP asks the DNS server for the IP address that is associated with a certain domain name.

When looking for postmaster@myertor.com, the series of lookups that will take place include; the primary DNS server will be seeking to establish the IP address for postmaster@myertor.com.