QA stands for QUALITY ASSURANCE. QA team assures the quality by monitor the whole development process. QA tracks the outcomes and adjusting process to meet the expectation.

The role of Quality Assurance is discussed below:

- QA team is responsible for monitoring the process to be carried out for development.

- Responsibilities of QA team are planning testing execution process.

- QA Lead creates the time tables and agrees on a Quality Assurance plan for the product.

- QA team communicated QA process to the team members.

- QA team ensures traceability of test cases to requirements.

The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. 

In networking and in other areas, a task is often begun before the previous task has ended. This is known as pipelining.

The protocol specifies that frames need to be numbered. This is done by using sequence numbers. A field is added to the data frame to hold the sequence number of that frame. Since we want to minimize the frame size, the smallest range that provides unambiguous communication. The sequence numbers can wrap around.

In Stop and wait protocol, sender sends one frame, waits until it receives confirmation from the receiver (okay to go ahead), and then sends the next frame.

RIP is a is an interior gateway protocol that was often used in interior networks and in some degree in internet networks. It helps the router adapt to the modifications that are made in a network regarding connections. Now it become less used since more efficient protocols were implemented like OSPF or IS-IS. It is limited to a lower number of routers, a maximum of fifteen router.

The LMHOSTS file is a static method of resolving NetBIOS names to IP addresses in the same way that the HOSTS file is a static method of resolving domain names into IP addresses. An LMHOSTS file is a text file that maps NetBIOS names to IP addresses; it must be manually configured and updated.

- Divide the data into sections

- Add the sections together using 1's complement arithmetic

- Take the complement of the final sum, this is the check sum