Exam 1 Review

Question 1

Hosts

Answer 1

equals end systems which are devices that connect to the internet (PC’s, Linux workstations, Laptops, Smartphones, tablets, TV’s, gaming consoles, webcams, automobiles, etc….)

Question 2

Communication links

Answer 2

Are made up of different types of physical media. End systems are connected together by a network of communication links. Different links can transmit data at different rates.

Question 3

Packet switches

Answer 3

describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network.

Question 4

Transmission rate

Answer 4

link measured in bits/seconds, the speed at which a network device communicates within the network.

Question 5

Packets

Answer 5

A collection of binary digits sent between computers over a network.

Question 6

Routers

Answer 6

A network connection device which contains software that connects network systems and controls traffic flow between them.

Question 7

Link layer switches

Answer 7

used in access networks, forwards packets towards their ultimate destination

Question 8

ISP

Answer 8

Internet Service Provider

Question 9

Protocol

Answer 9

controls the sending and receiving of information within the internet. Rules which govern data communication, including error detection, message length, and transmission speed.

Question 10

IP

Answer 10

internet protocol specifies the format of the packets that are sent and received among routers and end systems

Question 11

RFC

Answer 11

A Request for Comments (RFC) is a formal document from the Internet Engineering Task Force ( IETF ) that is the result of committee drafting and subsequent review by interested parties. Some RFCs are informational in nature. Of those that are intended to become Internet standards, the final version of the RFC becomes the standard and no further comments or changes are permitted. Change can occur, however, through subsequent RFCs that supersede or elaborate on all or parts of previous RFCs.

Question 12

Intranet

Answer 12

An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. The main purpose of an intranet is to share company information and computing resources among employees. An intranet can also be used to facilitate working in groups and for teleconferences.

Question 13

Distributed applications

Answer 13

they involved multiple end systems that exchange data with each other.

Question 14

API(Application Program Interface)

Answer 14

specifies how a program running on one end system asks the internet infrastructure to deliver data to a specific destination program running on another end system.

Question 15

Client

Answer 15

A node, usually a microcomputer, which is used by end users; uses but usually does not supply network resources.

Question 16

Server

Answer 16

Computer or other device on a network which only provides resources to the network and is not available (normally) to individual users; examples include print servers, file servers, and communications servers. Contrast with a workstation.

Question 17

Edge router

Answer 17

A term used in asynchronous transfer mode (ATM) networks, an edge router is a device that routes data packets between one or more local area networks (LANs) and an ATM backbone network, whether a campus network or a wide area network (WAN). An edge router is an example of an edge device and is sometimes referred to as a boundary router.

Question 18

DSL – “Digital Subscriber Line.”

Answer 18

It is medium for transferring data over regular phone lines and can be used to connect to the Internet. However, like a cable modem, a DSL circuit is much faster than a regular phone connection, even though the wires it uses are copper like a typical phone line.

Question 19

HFC

Answer 19

A hybrid fiber coaxial network is a telecommunication technology in which optical fiber cable and coaxial cable are used in different portions of a network to carry broadband content (such as video, data, and voice).

Question 20

Cable modem

Answer 20

A cable modem is used for connecting to the Internet and is much faster than a typical dial-up modem. While a 56K modem can receive data at about 53 Kbps, cable modems support data transfer rates of up to 30 Mbps. That’s over 500 times faster. However, most ISPs limit their subscribers’ transfer rates to less than 6 Mbps to conserve bandwidth.
Another important way that a cable modem is different than a dial-up modem is that it doesn’t connect to a phone line. Instead, the cable modem connects to a local cable TV line, hence the term “cable modem.” This allows cable modems to have a continuous connection to the Internet. Therefore, there is no need to dial your ISP every time you want to check your e-mail.

Question 21

Wireless LAN

Answer 21

A type of local-area network that uses high-frequency radio waves rather than wires to communicate between nodes.

Question 22

Wide Area Access networks

Answer 22

network in which separate areas of coverage or cells are connected wirelessly to provide service to a large geographic area.

Question 23

LEO satellites

Answer 23

Short for low earth orbit, a satellite system used in telecommunications. LEO satellites orbit the earth between 400 and 1,000 miles above the earth’s surface. LEOs are mostly used for data communication such as e-mail, paging and videoconferencing. Because LEOs are not fixed in space in relation to the rotation of the earth, they move at very high speeds and therefore data being transmitted via LEOs must be handed off from one satellite to the next as the satellites move in and out of range of the earth-bound transmitting stations that are sending the signals into space.

Question 24

Circuit

Answer 24

(specific) path between two or more points along which signals can be carried. Unless otherwise qualified, a circuit is a physical path, consisting of one or more wires (or wireless paths) and possibly intermediate switching points. A network is an arrangement of circuits. In a dial-up (switched) connection, a circuit is reserved for use by one user for the duration of the calling session. In a dedicated or leased line arrangement, a circuit is reserved in advance and can only be used by the owner or renter of the circuit.

Question 25

TDM(Time-division Multiplexing)

Answer 25

a communication channel is divided into discrete TIME SLOTS. Each node is assigned a time slot and each sender is given a specific period of time. Uses a multiplex

Question 26

FDM(Frequency-Division Multiplexing)

Answer 26

Data from multiple nodes are sent over multiple frequencies or channels over the network medium. The mux puts each nodes signal into its own channel

Question 27

Store and forward transmission

Answer 27

A technique common in messaging services where a data transmission is sent from one device to a receiving device but first passes through a “message center”. The message center is typically a server that is used by the message service to store the transmitted message only until the receiving device can be located, and it then forwards the transmission to the intended recipient and deletes the message from the server. A common type of store-and-forward messaging is that used between mobile phones.

Question 28

Output buffer or queue

Answer 28

is the location in memory or cache where data ready to be displayed is held until the device used to display the data is ready.

Question 29

Packet loss

Answer 29

occurs when one or more packets of data traveling across a computer network fail to reach their destination. Packet loss is distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.

Question 30

Statistical multiplexing

Answer 30

is one method for transmitting several types of data simultaneously across a single transmission cable or line (such as a T1 or T3 line). STDM is often used for managing data being transmitted via a local area network (LAN) or a wide area network (WAN). In these situations, the data is often simultaneously transmitted from any number of input devices attached to the network, including computers, printers, or fax machine

Question 31

Tier 1 ISP

Answer 31

is an Internet Protocol (IP) network that participates in the Internet solely via settlement-free interconnection, also known as settlement-free peering.

Question 32

Nodal processing delay

Answer 32

The time it takes to process a packet in a network node (router, switch, hub, etc.), which is dependent on the speed of the device and congestion in the network.

Question 33

Queuing delay

Answer 33

is the time a job waits in a queue until it can be executed. It is a key component of network delay. In a switched network, the time between the completion of signaling by the call originator and the arrival of a ringing signal at the call receiver. Queues may be caused by delays at the originating switch, intermediate switches, or the call receiver servicing switch. In a data network, the sum of the delays between the request for service and the establishment of a circuit to the called data terminal equipment (DTE). In a packet-switched network, the sum of the delays encountered by a packet between the time of insertion into the network and the time of delivery to the addressee.

Question 34

Transmission delay

Answer 34

is the amount of time required to push all of the packet’s bits into the wire. In other words, this is the delay caused by the data-rate of the link.

Question 35

Propagation delay

Answer 35

is the amount of time it takes for the head of the signal to travel from the sender to the receiver. It can be computed as the ratio between the link length and the propagation speed over the specific medium.

Question 36

Datagram

Answer 36

a self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network.

Question 37

Denial of service attack

Answer 37

(is an incident in which a user or organization is deprived of the services of a resource they would normally expect to have. In a distributed denial-of-service, large numbers of compromised systems (sometimes called a botnet) attack a single target.

Question 38

Distributed DOS

Answer 38

A distributed denial-of-service (DDoS) attack is one in which a multitude of compromised systems attack a single target, thereby causing denial of service for users of the targeted system. The flood of incoming messages to the target system essentially forces it to shut down, thereby denying service to the system to legitimate users.

Question 39

Peer

Answer 39

a network entity with which one performs peering operations

Question 40

Client server architecture

Answer 40

A network architecture in which each computer or process on the network is either a client or a server. Servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network servers ). Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power.

Question 41

Application architecture

Answer 41

is the organizational design of an entire software application, including all sub-components and external applications interchanges. There are several design patterns that are used to define this type of architecture, and these patterns help to communicate how an application will complete the necessary business processes as defined in the system requirements.

Question 42

P2P

Answer 42

peer to peer , A network system in which all nodes share in communications management. No central controller (server) is required. These systems are relatively simple and inexpensive to implement; used by LANs.

Question 43

Throughput

Answer 43

The amount of data transferred or process in a specified time, usually one second, similar to band width.

Question 44

Port number

Answer 44

A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server.

Question 45

HTTP

Answer 45

The Hypertext Transfer Protocol - provides a standard for Web browsers and servers to communicate. The definition of HTTP is a technical specification of a network protocol that software must implement. HTTP is an application layer network protocol built on top of TCP. HTTP clients (such as Web browsers) and servers communicate via HTTP request and response messages. The three main HTTP message types are GET, POST, and HEAD.

Question 46

Stateful and stateless

Answer 46

are adjectives that describe whether a computer or computer program is designed to note and remember one or more preceding events in a given sequence of interactions with a user, another computer or program, a device, or other outside element. Stateful means the computer or program keeps track of the state of interaction, usually by setting values in a storage field designated for that purpose. Stateless means there is no record of previous interactions and each interaction request has to be handled based entirely on information that comes with it. Stateful and stateless are derived from the usage of state as a set of conditions at a moment in time. (Computers are inherently stateful in operation, so these terms are used in the context of a particular set of interactions, not of how computers work in general.)

Question 47

SMTP

Answer 47

(Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving e-mail.

Question 48

MIME

Answer 48

(Multi-Purpose Internet Mail Extensions) is an extension of the original Internet e-mail protocol that lets people use the protocol to exchange different kinds of data files on the Internet: audio, video, images, application programs, and other kinds, as well as the ASCII text handled in the original protocol, the Simple Mail Transport Protocol (SMTP)

Question 49

POP3

Answer 49

(Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail, probably using POP3. This standard protocol is built into most popular e-mail products, such as Eudora and Outlook Express. It’s also built into the Netscape and Microsoft Internet Explorer browsers.

Question 50

IMAP

Answer 50

(Internet Message Access Protocol) is a standard protocol for accessing e-mail from your local server. IMAP is a client/server protocol in which e-mail is received and held for you by your Internet server. You (or your e-mail client) can view just the heading and the sender of the letter and then decide whether to download the mail. You can also create and manipulate multiple folders or mailboxes on the server, delete messages, or search for certain parts or an entire note. IMAP requires continual access to the server during the time that you are working with your mail.

Question 51

Root DNS

Answer 51

A root server is any of the small number domain name system (DNS) servers on the Internet that contain the IP addresses of the top level domain (TLD) registry organizations that maintain the global domains (e.g., .com, .org, net, .gov and .edu) and the country code domains (e.g., .uk, .ca, .cn, .dk, .fr, and .jp).

Question 52

TLD

Answer 52

A top-level domain (TLD) is the last segment of the domain name. The TLD is the letters immediately following the final dot in an Internet address. A TLD identifies something about the website associated with it, such as its purpose, the organization that owns it or the geographical area where it originates. Each TLD has a separate registry managed by a designated organization under the direction of the Internet Corporation for Assigned Names and Numbers (ICANN).

Question 53

Authoritative DNS

Answer 53

An authoritative name server provides actual answer to your DNS queries such as – mail server IP address or web site IP address (A resource record). It provides original and definitive answers to DNS queries. It does not provides just cached answers that were obtained from another name server. Therefore it only returns answers to queries about domain names that are installed in its configuration system. There are two types of Authoritative Name Servers:

1. Master server (primary name server) – A master server stores the original master copies of all zone records. A hostmaster only make changes to master server zone records. Each slave server gets updates via special automatic updating mechanism of the DNS protocol. All slave servers maintain an identical copy of the master records.
2. Slave server (secondary name server) – A slave server is exact replica of master server. It is used to share DNS server load and to improve DNS zone availability in case master server fails. It is recommend that you should at least have 2 slave servers and one master server for each domain name.

Question 54

Query flooding

Answer 54

is a method to search for a resource on a P2P network. It is simple but scales very poorly and thus is rarely used.

Question 55

Bootstrap problem

Answer 55

A bootstrap is a small strap or loop at the back of a leather boot that enables you to pull the entire boot on. In computers, to bootstrap (or “to boot”) is to load a program into a computer using a much smaller initial program to load in the desired program (which is usually an operating system). In general usage, bootstrapping is the leveraging of a small initial effort into something larger and more significant. There is also a common expression, “pulling yourself up by your own bootstraps,” meaning to leverage yourself to success from a small beginning

Question 56

Well Known Ports

Answer 56

20 FTP – Data
21 FTP – Control

80 HTTP

443 HTTPS

546 DHCP Client
547 DHCP Server

Question 57

Edge vs. core

Answer 57

A core router is just that…a router that is very near to the bankbone connection to the internet..or near the “core”..where there is a lot of traffic being exchanged between peers. Edge routers are on the “fringes”…the smaller routes. They have smaller amounts of traffic to route…therefore may be faster than the bigger routers…simply because they have to deal with less traffic and fewer protocols.

Question 58

There are currently three common ways to access the Internet. They are broadband access, WiFi and dial-up. Each type of access has its own benefits and shortcomings:

Answer 58

• Dial-up access is very inexpensive and available anywhere a phone landline can reach. But it’s very slow and has become almost obsolete, except in areas where no other access is available.
• WiFi access is convenient, especially in your home. It allows you to move your wireless laptop away from a desk to a comfortable living room chair or a kitchen counter top. WiFi can also be accessed away from home, such as at hotels and coffee shops.
• Broadband access, typically supplied by a cable or telephone company, is fast and efficient but is also expensive. And it’s sometimes not available to communities in rural areas.

Question 59

FDM Vs. TDM

Answer 59

1. FDM divides the channel into multiple, but smaller frequency ranges to accommodate more users, while TDM divides a channel by allocating a time period for each channel.
2. TDM provides much better flexibility compared to FDM.
3. FDM proves much better latency compared to TDM.
4. TDM and FDM can be used in tandem.

Question 60

What Is a Virus?

What Is a Worm?

What Is a Trojan horse?

Answer 60

What Is a Virus?
A Virus is a program or piece of code that causes an unexpected, usually negative, event. Viruses are often disguised as games or images with clever marketing titles such as “Me, nude”.

What Is a Worm?
Computer Worms are viruses that reside in the active memory of a computer and duplicate themselves. They may send copies of themselves to other computers, such as through email or Internet Relay Chat (IRC).

What Is a Trojan horse?

A Trojan Horse program is a malicious program that pretends to be a benign application; a Trojan horse program purposefully does something the user does not expect. Trojans are not viruses since they do not replicate, but Trojan horse programs can be just as destructive.

Question 61

TCP vs. UDP

Answer 61

UDP – (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP) and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end.

TCP – transmission control protocol, is a set of rules (protocol) used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.

Question 62

TCP vs UDP Diagram

Answer 62

Question 63

1. Explain the difference between a port and a socket

Answer 63

A port is a software address on a computer on the network–for instance, the News server is a piece of software that is normally addressed through port 119, the POP server through port 110, the SMTP server through port 25, and so on.

A socket is a communication path to a port. When you want your program to communicate over the network, you have given it a way of addressing the port and this is done by creating a socket and attaching it to the port.

Basically, socket = IP + ports Sockets provide access to the port+ip

Question 64

2. Describe how web caching works

Answer 64

The web cache is designed to store any web-based XBRL documents that use an http://scheme in the hierarchical order discovered from the web.

Question 65

3. Describe how Skype works

Answer 65

Skype uses VoIP, a novel technology related to the Internet. Normally, signals are sent via PSTN, either analog or digital. In case of VoIP, SIP is used to create data packets that are sent on the same network one uses for mailing and surfing. These data packets can carry more than the standard voice on a telephone. They can carry text messages, offer live video and stereo quality sound. VoIP also gives ‘screen sharing’ depending on the speed of the Internet connectivity. You can even use Skype conference calls for video conference calling with different clients.

Question 66

TCP/IP Model

Answer 66