MIS561 Exam 1

What is the OSI model?

It is a seven-layer conceptual model that describes the standards for inter-computer communication

What is the application layer? What is it's datagram?

(7) Network applications such as email, file transfer, client/server, remote connections, and web.
Datagrams: Upper layer data

What is the presentation layer? What is it's datagram?

(6) Provides a context for communication between layers. (ex. ASCII characters), encryption and decryption, compression, BCD to binary, data conversion

Datagrams: Upper layer data

What is the session layer? What is it's datagrams?

(5) Controls the dialogs between computers. It controls duplexing, termination, and restarts. Starts, stops session. Maintains order.
Datagrams: Upper layer data

What is the transport layer?

(4) It provides a transparent transfer of data (TCP and UDP). Ensures delivery of entire file or message.
Segments

What is TCP? What is the data called?

It has a slower but reliable transfer, and it typical applications are: email and web-browsing (Unicast)

Data: segments

What is UDP? What is the data called?

Fast but non-guaranteed transfers ("best efforts")
Typical applications: volP
(unicast, multicast, broadcasts)

Data: datagrams

TCP Transport?
Syn?
Ack?
Fin?

communicates between applications

Syn: indicates the start of TCP session
Ack: bit used to indicate that the ack number if the TCP header is acknowledging data.
Fin: indicates the termination of a TCP session

What is the network Layer? Data?

(3) provides connections to hosts and different networks (IPv4 and IPv6). Routes data to different LANs and WANs based on network addresses.
Datagrams: packets

What is the data link layer? Datagrams?

(2) provides connections between hosts on the same network (ethernet and mac addresses). Transmits packets from node to node based on station address.
Datagrams: frames

What is the physical layer? Datagrams?

(1) describes the electrical and physical specifications for devices (cables, connectors, hubs, and repeaters). Electrical signals and cabling.
datagrams: bits

What is a subnet mask?

A mechanism that allows a network device to divide an IP address into a network and host number.

default gateway

The first IP address of the device that a client computer will look for when attempting to gain access outside the local network.
(pathway to the local network)

Internal/private

non-routable IP addresses

External/public

Routable IP addresses

Switch

A computer networking device that connects network segments, used to create networks, data directly connected to port

Hubs

Simple devices that connect network components, sending a packet of data to all other connected devices A device connecting computers.

Router

a device that connects two or more networks together

ipconfig

internet protocol configuration, shows IP addresses,

tracert

A command that determines the route data takes to get to a particular destination. Also, tells you hops.

ping

send a message from one computer to another to check whether it is reachable and active (ex. ping yahoo.com), sends packets

UDP

User Datagram Protocol. Used instead of TCP when guaranteed delivery of each packet is not necessary. UDP uses a best-effort delivery mechanism.

TCP

Transmission Control Protocol - provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and is usually seen as TCP/IP in writing.

localhost

A reserved name that corresponds to the loopback address, 127.0.0.1.

managed switch

A switch can be configured via a command-line interface and sometimes can be configured in groups. Usually, they are assigned their own IP addresses. VLANs can only be implemented through managed switches.

unmanaged switch

A basic Layer 2 switch. This will work simply by plugging it in and connecting it. It is not configurable.

TCP Handshake

The protocol by which a client and server machine establish communication for the transfer of data.

What are these ports for and what protocol? 25/ 2525/ 465/ 587

Email
protocol: SMPT (Simple Mail Transfer Protocol)

What are these ports for and what protocol? 23

used to log on remotely to a system, popular with network administrators
Protocol: Telnet Protocol (terminal emulation program)

What are these ports for and what protocol? 80/443

display webpages and encrypts HTTP
protocol: HTTP (hyper text protocol)/HTTPS

What are these ports for and what protocol? 110/995

retrieves email and encrypts POP3
protocol: POP3(Post Office Protocol version 3)

What are these ports for and what protocol? 20/21

used to transfer files between computers
Protocol: FTP (File transfer protocol)

What are these ports for and what protocol? 53

translates URLs into web addresses
Protocol: DNS (domain name system)

What are these ports for and what protocol? 3389

enables remote connections to other computers, typically over TCP
Protocol: RDP (Remote desktop protocol)

Well Known Ports

port numbers in the range of 1-1024 that identify network applications that are well known such as web, email, and remote login applications

registered ports

Ports 1024 - 49151. These ports typically accompany non-system applications associated with vendors and developers.

Dynamic/Private Ports

Port range: 49, 152-65, 535. These ports can be used by applications, but they cannot be registered by vendors.

inbound ports

Ports are used when another computer wants to connect to a service or application running on your computer. Servers primarily use inbound ports so that they can accept incoming connections and serve data.

outbound ports

Used when your computer wants to connect to a service or application running on another computer. Client computers primarily use outbound ports and these are assigned dynamically by the operating system.

DHCP Server

Assigns an IP address to a computer when it first attempts to initiate a connection to the network. (Dynamic Host Configuration Protocol)

Bits vs Bytes

the word bit is an abbreviation for binary digit, it can be further abbreviated, usually as a lowercase b. A group of eight bits is called a byte and is usually abbreviated as an uppercase B

MAC address

Unique address embedded in network-connected devices. The physical address of a network card. It is a 6-byte hexadecimal number. The first bytes define the vendor.

Firewall

a part of a computer system or network that is designed to block unauthorized access while permitting outward communication. It prevents attackers from attacking your network.

A device or software that provides a barrier between your machine or network and the rest of the world.

Advantages of Ipv4

is 32-bit IP addresses
More support - since most traffic uses this still

Disadvantages of IPv4

Running out of unique IP addresses
lack of security
lack of configuration

Advantages of IPv6

Larger address space, IPsec offering confidentiality and integrity, QoS, faster throughput

Disadvantages of IPv6

accessibility issues, large overhead, and have to upgrade devices

NAT (Network Address Translation)

Replaces the private IP address on an outgoing packet with the public IP address of the gateway router so that the packet can be routed through the internet.

nslookup

query DNS records

DNS (Domain Name System)

translates URLs to IP addresses, (web addresses)
(ex: www.amazon.com -> 192.9.2.44)

ARP (Address Resolution Protocol)

is used to map IP addresses to MAC addresses. The arp command shows existing IP-to-MAC address mappings you computer is currently aware of.

Identify the IPv4 address class and default subnet mask.

0-126

Class A
Used for extremely large networks, none left

Identify the IPv4 address class and default subnet mask.

128-191

Class B
Large corporate and government networks. All IP address have been used.

Identify the IPv4 address class and default subnet mask.

192-223

Class C
The most common group. Your ISP probably has a class C address.

Identify the IPv4 address class and default subnet mask.

224-247

Class D

These are reserved for multicasting (transmitting different data on the same channel)

Identify the IPv4 address class and default subnet mask.

248-255

Class E

reserved for experimental use

Subnet mask for Class A?

255.0.0.0

Subnet mask for Class B?

255.255.0.0

Subnet mask for Class C?

255.255.255.0

What is the binary number for Class A? (masking)

11111111.0.0.0 (8 1's)

What is the binary number for Class B? (masking)

11111111.11111111.0.0

What is the binary number for Class C? (masking)

11111111.11111111.11111111.0