Answer to Question #220732 in Computer Networks for Pierre OLLIER

Question

1. Assuming standard 1500 byte Ethernet max payloads: how many IPv4 fragments will be needed to transfer 2000 bytes of user data with a single UDP send? And, how do the 2000 bytes get split over the frags?
2. Despite its conceptual elegance, RPC (Remote Procedure Call) has a few problems. Discuss any 3 of those in brief.
3. Why is timestamping needed in real-time applications? This is in the context of Real-time Transport Protocol (RTP).
4. Why does UDP exist? Would it not have been enough to just let user processes send raw IP packets?
5. Explain how QUIC eliminates a couple of RTTs usually needed at the start of a secure web connection.

Answer 1

1.Two IPV4 fragments will be needed. The IPV4 header = 20bytes, payload of Ethernet size 1500B

Therefore 1500- 20bytes . In the two fragments data is sent through it, effect is zero.

1496- 20,1496/ 8

= 187

2. (a)Lack of streaming_ the problem involves the fact that when the server constructs the response, it must fully construct the response and then the client is idle for that period.

(b) Single threaded server _ the RCP supports the use of multi-threaded server instead of threaded server.

(c) Security _ RPC is executing code on a remote system so we need to have means to ensure that the person executing the code has the rights to do so.

3.Time stamping is used to synchronize and to discard old invalid packets. As the receiver processes the frames sent, any packets which had older time stamp would obviously mean that those packets were delayed in transmission. Time stamp can also be used to drop packets that no longer have relevance.

4.It exists to support real the applications where data packets are time sensitive and would prefer to drop the data then wait. The segment cannot be delivered to the specified application as a raw IP packet. The UDP supports real time application, application which are time sensitive and wants to discard data before waiting and application that handle error checking and corrections.

5.QUIC allows DAT to be included in the first packet of the connection ( compared to TCP it saves one RTT) and usually eliminates the second RTT during TLS encryption negotiation. However it eliminates a couple of RTTs usually needed at the start of a secure web connection.