IT 276 Exam #1

How does an SPF work and what does it do?

A Sender Policy Framework (SPF) record is used to confirm the IP addresses that can legitimately send email for a particular domain.

What are three primary features of TCP error control?

1) Checksum
2) Acknowledgement
3) Retransmission of data

What does an application layer-address look like?

URL, email address

How many layers are in the TCP/IP hybrid model?

five

How many layers is a switch involved in?

two

What does SYN, FIN, and ACK mean?

SYN - SYNchronize sequence numbers, used to open a new connection

FIN - Finishes the connection

ACK - Indicates that the segment is ACKnowledging a previously-sent segment

What are 5 important application layer protocols?

HTTP, SSH, SMS, SMTP, Telnet

What is SSH?

A modern application layer protocol used to securely access a CLI, complete with encryption of the transmitted data. This protocol can also be used to securely send files between two machines.

Which application layer protocol is often used to transfer files between computers?

FTP

Which application layer protocol can be used to set the correct time and keep it synchronized between network connected devices?

NTP

What are some important transport layer protocols?

TCP, UDP

List the five layers in order

1) Physical layer
2) Data link
3) Network
4) Transport
5) Application

What is the basic function of layer 1?

The physical layer:

Converting messages to signals, also physical and electrical cabling and connector specifications

What does a layer 4 address look like?

port numbers

What layer do we interact with for email, websites, etc.?

The application layer

How many layers are in the OSI suite?

7

How many layers is a router involved in?

three

How many layers is a computer or server involved in?

All five

What is the basic function of layer 2?

Data-link layer:

Delivery of messages (frames) within a single LAN

What is the basic function of layer 3?

Network layer:

Routing e.g., Delivery of packets between networks

What is the basic function of layer 4?

Transport layer:

Messages called segments

Session control, error and flow control

What is the basic function of layer 5?

Application layer:

Messages

Interaction with user through websites and email
Software encryption, software to software interaction

One of the main duties of the transport layer is to provide _______ _______

process-to-process communication

What is encapsulation?

The process of a higher layer adding its own header and passing it down to the stack is called

What is decapsulation?

The process that takes place at the receiving end, and begins at the lowest layer and passes the header up the stack

Data from the application layer is encapsulated at what layer?

The layer right below it

Data from the transport layer is decapsulated at what layer?

The layer right above it

What are the different types of DNS servers?

1) Recursive
2) Root
3) TLD
4) Authoritative

What does each DNS server do? (Can split this one up once #23 is answered)

Authoritative - Know about their domain (Apple.com)
Root - Know about all TLD servers
TLD - Ultimate autho

What is the difference between a client-server and peer-to-peer model?

Client-server: One machine does the bulk of the work
Peer-to-peer: All machines share the load of work

What is a domain?

A domain is a name that defines a certain administrative authority on the Internet

What is the difference between a circuit-switched network and a packet-switched network?

Circuit-switched maintains a point-to-point connection over the duration of the call

Packet switched move data in small blocks called packets according to the destination address

What is the difference between iterative and recursive for DNS lookups?

Iterative DNS queries are ones in which a DNS server is queried and returns an answer without querying other DNS servers, even if it cannot provide a definitive answer

Recursive DNS queries occur when a DNS client requests information from a DNS server that is set to query subsequent DNS servers until a definitive answer is returned to the client

What is the SMTP protocol and what layer is it found in?

Found in the application layer, the SMTP protocol is used as the "delivery" service for the client to send mail to the mail server

How is the IMAP server used?

IMAP temporarily downloads emails from the server and stores them locally

How is the POP server used?

POP downloads emails from the server for permanent storage

Flow Control is a feature of what?

TCP

What are the goals/features of Flow Control?

TCP will ensure that a sender is not overwhelming a receiver by sending packets faster than it can consume.

List four important DNS record types

1) Host record
2) Alias record
3) SPF record
4) MX record

What is the MX record?

Mail exchange address, lists where email should be delivered

What are the functions of DNS records?

They point to different servers on the domain

What are the basics of TCP Window?

How much data (in bytes) the receiving device is willing to receive at any point in time. The receiving device can use this value to control the flow of data, or as a flow control mechanism

What are the three TCP / UDP port ranges and what do they stand for?

Lower range - well known
Mid-range - registered
Upper range - dynamic private random ephemeral (DPRE)

What are the specific numeric ranges for the three port ranges?

Lower: 0 -1023
Middle: 1024 - 49151
Upper: 49152 - 65535

A client program normally uses ____________ port number. A server program normally uses __________ port number.

An ephemeral, a well known

What is a socket address?

The IP address and a port number for the local node, and there is a corresponding socket address at the foreign node

How many addresses does the physical layer have?

zero

What is the difference between SSH and Telnet protocols?

SSH is modern and widely used, Telnet is outdated and typically a security threat today to have

ADD MORE HERE FROM SLIDES

Is CheckSum optional for TCP or UDP?

UDP

Why is CheckSum optional for UDP?

For UDP, packets with differing CheckSum values are detected and discarded for security

What is CheckSum used for in TCP?

Packets with differing CheckSum values are detected and discarded for security, but are sent again in order for the original packet to be recovered

Does UDP use error detection or error recovery?

Error detection

What is TCP?

Transmission Control Protocol is a bidirectional, connection-based protocol that transfers data

What is UDP?

UDP, User Datagram Protocol is a protocol that transfers data without a connection

Is TCP or UDP used more often?

TCP

Protocols using protocols:

HTTP is to _______

as

DNS is to _______

TCP

UDP

What are the primary advantages of TCP?

1) Requires acknowledgment for all packets sent
2)Error detection and correction
3)No data loss

What are three primary disadvantages of TCP?

1) Requires a connection

What are three primary advantages of UDP?

1) Smaller overhead means less bytes equalling less processing time
2) Does not require a connection
3) Fast

What are four primary disadvantages of UDP?

1) No corruption detection
2) Corrupt data is dropped and not recovered
3) Data is unordered
4) No error control

Why is UDP considered unreliable?

It is connectionless and lacks the SYN/ACK flags like TCP

What is a header vs an overhead?

A header is the extra information on top of the payload to ensure data gets to its destination

Overhead is the amount of wasted bandwidth required to transmit the payload

Does TCP or UDP have a higher overhead?

TCP

What layer is TCP and UDP found in?

The transport layer

How does TCP know how to reassemble data?

The sequence number

In _______ switched networks, a single connection is established for the duration of the communication

circuit

What is the goal of DNS?

Phone book

They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses

What is Error correction vs Error detection?

Error detection is the detection of errors

Error correction is the detection of errors and reconstruction of the original, error-free data.

The application layer on the sending side logically talks to the ______ layer on the receiving end.

application

In the __________model, machines have dedicated roles, and one machine does the bulk of the work.

client-server

___________ is a legacy application layer protocol that can be used to access a CLI, but lacks any encryption.

Telnet

A (An) ___________DNS server will only respond to queries for the domain it is responsible for

authoritative only

A standard switched LAN environment, as you'll find in most homes and businesses, is an example a ____________ topology

star

The source port number on the UDP or TCP user datagram header defines _______

The process running on the sending computer

The Application layer is responsible for:

A. Data encryption
B. Presenting data to the user
C. Speaking to the corresponding software at the receiving end
D. All of the above

D: All the above

The bytes of data being transferred in each connection are numbered by TCP. The numbering starts with a __________________.

randomly generated number

______________ means combining multiple data sources onto a single network connection. ______________ means processing/delivering multiple data streams arriving over a single connection.

Multiplexing, demultiplexing

A DNS server receives a request from a client, but doesn't have the answer. The server responds with the next DNS server in the hierarchy for the client to query in order to find the answer. This process may be repeated throughout the entire DNS hierarchy until the client receives the answer. This describes the ___________ method of DNS.

iterative