Lesson 3

Question 1

Application Layer

Answer 1

Layer 7 of the OSI Model and the top layer of the TCP/IP Model. Protocols such as DNS, DHCP, and SMTP operate on the Application layer. Proxy servers and advanced firewalls operate on the Application layer.

Question 2

Data Link layer

Answer 2

Layer 2 of the OSI Model. It has two sublayers: Logical Link Control (LLC) and Media Access Control (MAC).

Question 3

File Transfer Protocol (FTP)

Answer 3

A protocol used to transfer files over the Internet using TCP. Many operating systems such as Windows 7 include an FTP command-line tool. FTP uses ports 20 and 21.

Question 4

Hypertext Transfer Protocol (HTTP)

Answer 4

The primary protocol used to transfer web pages and web elements such as pictures and audio files over the Internet. HTTP commonly transfers HTML files that are displayed in web browsers. HTTP uses port 80. HTTPS is a secure version of HTTP using port 443.

Question 5

Internet Group Management Protocol (IGMP)

Answer 5

A protocol used to multicast data to a group of computers. This is in contrast to unicast, which sends data from one computer to one computer, and broadcast, which sends data from one computer to all other computers in a subnet.

Question 6

Internet layer

Answer 6

One of the layers on the TCP/IP Model that maps to the Network layer of the OSI Model. Routers operate on this layer.

Question 7

Internet Message Access Protocol (IMAP)

Answer 7

A mail protocol used to store email messages and download them to clients when requested. Users can view email message headers and choose whether to download the email messages or not. This differs from POP servers which download the messages as soon as the client connects. Clients use SMTP to send email. IMAP4 uses port 143.

Question 8

Internet Protocol (IP)

Answer 8

IP is a logical addressing scheme used with networking. IPv4 has been around since the 1980s, and IPv6 is the newer version. Both are currently being used on the Internet and in internal networks. Eventually, IPv6 will replace IPv4.

Question 9

Internet Protocol Security (IPSec)

Answer 9

An encryption protocol that includes an Authentication Header (AH) for authentication and Encapsulating Security Payload (ESP) for encryption. IPSec is used with L2TP/IPSec for VPNs.

Question 10

Internet Control Message Protocol (ICMP)

Answer 10

A protocol used to carry error messages and messages about the availability of services. Troubleshooting tools such as Ping, PathPing, and tracert use ICMP. ICMP uses IP directly and doesn’t use either TCP or UDP.

Question 11

ipconfig

Answer 11

A command-line tool that can display TCP/IP configuration information for a system. It can also change some of the configuration settings.

Question 12

Layer 2 Tunneling Protocol (L2TP)

Answer 12

A tunneling protocol used for VPNs. L2TP is commonly used with IPSec (as L2TP/IPSec) when used in a VPN. L2TP uses port 1723.

Question 13

Layer 3 switch

Answer 13

An advanced switch that can operate on layer 3 similar to a router. Layer 3 switches function just like a router but perform routing using internal hardware instead of software.

Question 14

Lightweight Directory Access Protocol (LDAP)

Answer 14

A protocol used to query directories such as Microsoft’s Active Directory Domain Services. LDAP uses port 389. LDAP can be secured with either SSL or TLS. Secure LDAP uses port 636.

Question 15

Link aggregation control protocol (LACP)

Answer 15

LACP is defined by IEEE 802.3ax and is responsible for allowing bundled links on switches to linked devices. Bundled links allows higher throughput between devices.

Question 16

Link layer

Answer 16

The lowest layer of the TCP/IP Model. It maps to the Data Link and Physical layers of the OSI Model.

Question 17

MAC address

Answer 17

The MAC address is a 48-bit hardware address that is required by every device on a LAN to communicate on that segment. The switch uses the MAC address in the MAC table.

Question 18

Network layer

Answer 18

Layer 3 of the OSI Model. It maps to the Internet layer of the TCP/IP Model. The Network layer of the OSI is responsible for routing and selecting the best path to another network. Routers and layer 3 switches operate on this layer. IPv4, IPv6, ARP, and ICPM operate on this layer.

Question 19

Open Shortest Path First (OSPF)

Answer 19

A routing protocol added to a router. Routing protocols allow routers to exchange routing information between each other. OSPF is used in place of RIPv2 on many hardware routers.

Question 20

Open Systems Interconnect (OSI) model

Answer 20

The Open Systems Interconnection (OSI) model is a framework for network communication. It includes seven layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical.

Question 21

Physical layer

Answer 21

Layer 1 of the OSI Model. Hubs and repeaters are examples of devices at this layer. Ethernet and Token Rink are examples of protocols on this layer.

Question 22

Post Office Protocol version 3 (POP3)

Answer 22

An email protocol used to download email to clients as soon as the client connects to the email server. Clients use SMTP to send email. POP3 uses port 110.

Question 23

Presentation layer

Answer 23

Layer 6 of OSI Model. It is responsible for translation between different formats, encryption, decryption, compression, and decompression.

Question 24

Routing Information Protocol

Answer 24

A routing protocol added to a router. Routing protocols allow routers to exchange routing information between each other. RIPv2 is the current version and has replaced RIPv1 in most applications.

Question 25

Segment

Answer 25

On the physical network, a segment is a common connection between multiple computers. On the OSI Model, a segment is the name of data traveling on the Transport layer. Packets travel on the Network layer and frames travel on the Data Link layer.

Question 26

Session layer

Answer 26

Layer 5 of the OSI Model. The Session layer establishes, maintains, and terminates the session between two devices.

Question 27

Simple Mail Transfer Protocol (SMTP)

Answer 27

A primary protocol used to send email on the Internet and internal networks. Clients use SMTP to send email to email servers. Email servers use SMTP to send and receive email between other email servers. SMTP uses port 25.

Question 28

Simple Network Management Protocol (SNMP)

Answer 28

A management protocol used to query and manage network devices such as routers and switches. SNMP uses ports 161 and 162.

Question 29

TCP/IP

Answer 29

A suite of protocols used on the Internet and Microsoft networks. It includes TCP, IP, and many other protocols.

Question 30

TCP/IP Model

Answer 30

The TCP/IP Model describes a virtual networking model that was created by the U.S. Department of Defense in the 1970s. It includes four layers known as Application, Transport, Internet, and Link.

Question 31

Transmission Control Protocol (TCP)

Answer 31

A connection-oriented protocol that provides guaranteed delivery. TCP uses a three-way handshake to begin a session, uses sequence numbers to track packets, and includes regular acknowledgments. The alternative is UDP, which is a connectionless protocol that provides best-effort delivery.

Question 32

Transport layer

Answer 32

Layer 4 of the OSI Model and one of the layers of the TCP/IP Model. The Transport layer is responsible for flow control, reliability, and error checking. TCP and UDP protocols operate here.

Question 33

Trivial File Transfer Protocol (TFTP)

Answer 33

A scaled-down version of File Transfer Protocol (FTP). TFTP uses UDP as the transport protocol and can’t be used on the Internet.

Question 34

User Datagram Protocol (UDP)

Answer 34

A connectionless protocol that provides a best-effort delivery. The alternative is TCP, which is a connection-oriented protocol that provides guaranteed delivery.