Chapter 2 final exam

Question 1

Name 3 Characteristics associated with client-server approach to structuring network applications

Answer 1

1.
There is a server with a well known server IP address
2.HTTP uses this application structure.
3.There is a server that is always on.

Question 2

Name 2 Characteristics associated with P2P approach to structuring network applications:

Answer 2

1. There is not a server that is always on
2. A process requests service from those it contacts and will provide service to processes that contact it.

Question 3

Which of the following pieces of information will appear in a server’s application-level HTTP reply message?

Answer 3

A response code
A response phrase associated with a response code

Question 4

When an application uses a TCP socket, what transport services are provided to the application by TCP?

Answer 4

Flow Control, Congestion Control and reliable data transfer

Question 5

What is meant by HTTP being Stateless?

Answer 5

Server maintains no information about clients

Question 6

What is an HTTP cookie used for?

Answer 6

A cookie is a code used by a SERVER, carried on a client’s HTTP request, to access information the server had earlier stored about an earlier interaction with this Web browser. [Think about the distinction between a browser and a person.]

Question 7

What is the purpose of the HTTP GET message?

Answer 7

The HTTP GET request message is used by a web client to request a web server to send the requested object from the server to the client.

Question 8

What is the purpose of the conditional HTTP GET request message?

Answer 8

To allow a server to only send the requested object to the client if this object has changed since the server last sent this object to the client.

Question 9

What are some advantages of using a web cache?

Answer 9

FASTER PAGE LOAD TIME.Caching generally provides for a faster page load time at the client, if the web cache is in the client’s institutional network, because the page is loaded from the nearby cache rather than from the distant server.
2.Caching uses LESS BANDWIDTH coming into an institutional network where the client is located, if the cache is also located in that institutional network.

Question 10

What are some differences between HTTP1.1 and 2?

Answer 10

1) HTTP/2 allows a LARGE OBJECT to be broken down into SMALLER PIECES, and the transmission of those pieces to be interleaved with transmission other smaller objects, thus preventing a large object from forcing many smaller objects to wait their turn for transmission.

2)
HTTP/2 allows objects in a PERSISTENT CONNECTION to be sent in a client-specified PRIORITY ORDER.

Question 11

What is the purpose of the If-Modified-Since field in a HTTP GET request message

Answer 11

To indicate to the SERVER that the CLIENT has cached this object from a previous GET, and the time it was cached.

Question 12

What is the purpose of a cookie value in the HTTP GET request?

Answer 12

The cookie value itself doesn’t mean anything. It is just a value that was returned by a web server to this client during an earlier interaction.

Question 13

name three characteristics that apply to HTTP only

Answer 13

Operates mostly as a “client pull” protocol.
Uses server port 80.
Uses a blank line (CRLF) to indicate end of request header.

Question 14

name three characteristics that apply to SMTP only

Answer 14

Uses server port 25.
Uses CRLF.CRLF to indicate end of message.
Operates mostly as a “client push” protocol.

Question 15

Name 2 characteristics that apply to BOTH HTTP and SMTP

Answer 15

Is able to use a persistent TCP connection to transfer multiple objects.
Has ASCII command/response interaction, status codes.

Question 16

Provides authoritative hostname to IP mappings for organization’s named hosts.

Answer 16

Authoritative DNS server

Question 17

Replies to DNS query by local host, by contacting other DNS servers to answer the query.

Answer 17

Local DNS server

Question 18

Responsible for a domain (e.g., *.com, *.edu); knows how to contact authoritative name servers

Answer 18

Top Level Domain (TLD) servers

Question 19

Highest level of the DNS hierarchy, knows how to reach servers responsible for a given domain (e.g., *.com, *.edu).

Answer 19

DNS root servers

Question 20

What is the value of caching in the local DNS name server?

Answer 20

DNS caching results in LESS LOAD elsewhere in DNS, when the reply to a query is found in the local cache.
DNS caching provides for FASTER REPLIES, if the reply to the query is found in the cache.

Question 21

What information does the type “A” resource record hold in the DNS database?

Answer 21

A hostname and an IP address

Question 22

In which of the forms of caching does a user benefit from its not only from its own recent requests (and cached replies) but also from recent requests made from other users?

Answer 22

HTTP local web caching
Local DNS server caching

Question 23

Check all of the phrases below that state a true property of a local DNS server.

Answer 23

The local DNS server record for a remote host is sometimes different from that of the authoritative server for that host.

The local DNS server can decrease the name-to-IP-address resolution time experienced by a querying local host over the case when a DNS is resolved via querying into the DNS hierarchy.

Question 24

What is the role of an authoritative name server in the DNS?

Answer 24

It provides the DEFINITIVE ANSWER to the query with respect to a name in the authoritative name server’s domain.