Question

1.

(a) In circuit-switched networks, the resources needed along a path (buffers, link transmission rate) to provide for communication between the end systems are not reserved for the duration of the communication session between the end systems.

True

False

(b) Consider the minimum time for P2P file distribution, as discussed in Section 2.5. Suppose the upload rate of the server is10 Mbps, the upload rates of all peers is 1 Mbps, and the download rates of all peers is 10 Mbps. Further suppose that there are 100 peers and the file is 100 million bits. The minimum distribution time is ____.

	A.	approximately 100 seconds
	B.	approximately 1000 seconds
	C.	approximately 1 second
	D.	approximately 10 seconds

(c) TCP and UDP protocols provide the same set of transport-layer services to the invoking application.

True

False

(D) Local DNS name servers ____.

	A.	cache resource records, but discard them after a period of time that is on the order of a few days
	B.	never cache resource records
	C.	cache resource records and never discard them
	D.	obtain resource records from Web caches

(e) Which of the following TCP/IP protocols is used to communicate between a Web Browser and a Web Server?

	A.	SMTP
	B.	HTTP
	C.	UDP
	D.	POP3

(f) UDP includes a congestion-control mechanism while TCP does not include a congestion-control mechanism.

True

False

Answer 1

(a)False

Explanation:

There are two approaches to building a network core:

1.circuit switching:The resources needed along a path (buffers, link bandwidth) to provide for communication between the end systems are reserved for the duration of the session.

2.packet switching:The resources needed along a path (buffers, link bandwidth) to provide for communication between the end systems are not reserved for the duration of the session.

(b).approximately 100 seconds

(c).False

TCP and UDP protocols provide the different set of transport-layer services to the invoking application.

(d).cache resource records, but discard them after a period of time that is on the order of a few days.

(e).HTTP (Hyper Text Transfer Protocol) handles the communication between a web server and a web browser.

HTTPS (Secure HTTP) handles secure communication between a web server and a web browser.

(f).False

UDP does not provide congestion control, reliability, or flow control semantics.

TCP provides Congestion Control in three phases- Slow start phase, Congestion Avoidance Phase, Congestion Detection Phase.