CompTIA Network+ N10-008 (updated)

Client

A device used by an end-user to access the network

Server

A device that provides resources to the rest of the network

Hub

Older technology that connects network devices together

Can lead to increased network errors

Wireless Access Point (WAP)

A device that allows wireless devices to connect to a wired network

Switch

A device that connects network devices together (like a next generation hub). Can learn which devices are connected to which ports.

Router

Connects two different networks together and forwards traffic to and from a network

Layer 3 device

Media

connects two devices or a device to a switch port

Wide Area Network (WAN) link

physically connects two geographically dispersed networks

Client/Server model

Uses a dedicated server to provide access to files, scanners, printers, and other resources

Administration and backup are easier

Client/Server benefits

1. centralized administration

2. easier management

3. better scalability

Client/Server Drawbacks

1. higher cost

2. requires specialized OS

3. Requires dedicated resources

Peer-to-peer model

Peers share resources (files/printers) directly with others

Peer-to-peer benefits

1. lower cost

2. no dedicated resources

3. no specialized OS

Peer-to-peer drawbacks

1. decentralized management

2. inefficient for large networks

3. poor scalability

Personal Area Network (PAN)

Smallest type of wired or wireless network and covers the least amount of area

Ex. Bluetooth, USB

Local Area Network (LAN)

Connects components within a limited distance

Up to a few hundred feet

Ex. Small office

IEEE 802.3

Ethernet

IEEE 802.11

Wi-Fi

Campus Area Network (CAN)

Connects LANs that are building-centric across a university, industrial park, or business park

Up to a few miles

Metropolitan Area Network (MAN)

Connects scattered locations across a city or metro area

up to about 25 miles

Wide Area Network (WAN)

Connects geographically disparate internal networks and consists of leased lines or VPNs

worldwide coverage

Physical

how devices are connected by media

Logical

how the actual network traffic flows

Bus Topology

Uses a single cable where each device taps into it by using either a vampire tap or a T-connector

Ring Topology

Uses a cable running in a circular loop where each device connects to the ring but data travels in a singular direction

Token Ring

Ring topology that uses an electronic token to prevent collisions when communicating on the network

"The talking stick"

FDDI

uses two counter-rotating rings for redundancy.

Ring = redundancy

Star topology

Most popular physical LAN topology where devices connect to a single point

if the central device fails, the entire network fails

Hub-and-Spoke Topology

Similar to Star but with WAN links instead of LAN connections and it is used for connecting multiple sites

Full-Mesh Topology

Optimal routing is always available as every node connects to every other node

Partial-Mesh Topology

Hybrid of the full-mesh and the hub-and-spoke topologies

provides optimal routes between some sites

Infrastructure Mode

Uses a wireless access point as a centralized point and supports wireless security controls

Ad Hoc Mode

Decentralized wireless network which creates P2P connections and does not require a router or access point

Wireless Mesh Topology

Interconnection of different types of nodes, devices, or radios

802.11

Wireless networks that can operate in infrastructure or ad hoc modes

Bluetooth

Low energy use variant of Bluetooth which allows for a mesh network

Radio Frequency Identification (RFID)

Uses electromagnetic fields to read data stored in embedded tags

Near Field Communication (NFC)

Enables two devices to communicate within a 4-cm range

Infrared (IR)

operates with line of sight

Z-Wave

provides short-range, low-latency data transfer with slower rates and less power consumption than Wi-Fi

used for home automation commonly

ANT+

collection and transfer of sensory data

ANT+ = sensors

Physical Layer

Where transmission of bits across the network occurs and includes physical and electrical network characteristics

Time Division Multiplexing (TDM)

Each session takes a turn, using time slots, to share the medium between all users

Statistical Time Division Multiplexing (STDM)

Dynamically allocates the time slots on an as-needed basis

Frequency Division Multiplexing (FDM)

Divides the medium into channels based on frequencies and each session is transmitted over a different channel

Multiplexing

simultaneous use of a baseband connection

Physical Layer Devices

1) Cables (media)

2) Bluetooth, Wi-Fi

3) Hubs, APs, Media Converters

Data Link Layer

Packages data into frames and transmits those frames on the network

Media Access Control (MAC)

Physical addressing system of a device which operates on a logical topology

Uses a 48-bit hexadecimal address assigned to a network interface card (NIC)

Logical Link Control (LLC)

Provides connection services and allows acknowledgement of receipt of messages. Limits the amount of data that a sender can send at once to prevent the receiver from overloaded

The most basic form of flow control.

Provides basic error control functions using a checksum

Isochronous mode

Network devices use a common reference clock source and create time slots for transmission

Synchronous mode

Network devices agree

Asynchronous mode

Network devices reference their own internal clocks and use start/stop bits

Data Link Layer Devices

NIC, Bridge, Switch

Network Layer

Forwards traffic (routing) with logical address

Packet switching

data is divided into packets and then forwarded

Circuit Switching

Dedicated communication link is established between two devices

Message Switching

Data is divided into messages which may be stored and then forwarded

Route Discovery and Selection

Manually configured as a static route or dynamically through a routing protocol

Connection Services

Augment Layer 2 connection services to improve reliability

Internet Control Message Protocol (ICMP)

Sends error messages and operational information to an IP destination. Used to communicate information about network connectivity issues back to the sender

Layer 3 Devices

Routers, Layer 3 switches (multilayer switch)

Transport Layer

responsible for providing communication with the application by acknowledging and sequencing the packets to and from the application

Transmission Control Protocol (TCP)

Connection-oriented protocol that is a reliable way to transport segments across the network

User Datagram Protocol (UDP)

Connectionless protocol that is an unreliable way to transport segments across the network

TCP attributes

- Reliable

- Connection-oriented

- Segment retransmission and flow control through windowing

- Segment sequencing

- Acknowledges segments

UDP attributes

- Unreliable

- Connectionless

- No windowing or retransmission

- No sequencing

- No acknowledgement

Windowing

allows the clients to adjust the amount of data in each segment

Buffering

Occurs when devices allocate memory to store segments if bandwidth isn't readily available

Layer 4 Protocol and Devices

TCP, UDP

WAN accelerators

Firewalls

Session Layer

Keeps conversations separate to prevent intermingling of data

Set Up Session

Checking of user credentials and assigning numbers to sessions to help identify them

Tear Down Session

Ending of a session after the transfer is done or when the other party disconnects

Session Layer Protocols

H.323, NetBIOS, RTP

H.323

Used to setup, maintain, and tear down a voice/video connection

NetBIOS

Used to share files over a network

Presentation Layer

Formats the data to be exchanged and secures that data with proper encryption

Data Formatting

Data is formatted by the computer to have compatibility between different devices

Encryption

Used to scramble the data in transit to keep it secure from prying eyes and provide data confidentiality

Presentation Layer Examples

Scripting languages, standard text, pictures, movie files, encryption algorithms

Application Layer

Provides application-level services where users communicate with the computer

Application Services

Unites communicating components from more than one network application

Service Advertisement

Sending out announcements to other devices on the network to state the services they offer

Application Layer Protocols

POP3, IMAP, SMTP, HTTP, HTTPS, DNS, FTP, FTPS, SFTP, Telnet, SSH,

Encapsulation

The process of putting headers (and sometimes trailers) around some data

Protocol Data Unit (PDU)

A single unit of information transmitted in a computer network

TCP Header

20 bytes

SYN (synchronization)

Used to synchronize connection during the three-way handshake

ACK (acknowledgment)

Used during the three-way handshake, but also used to acknowledge the successful receipt of packets

FIN (Finished)

Used to tear down the virtual connections created using the three-way handshake and the SYN flag.

RST (Reset)

Used when a client or server receives a packet that it was not expecting during the current connection

PSH (Push)

Used to ensure data is given priority and is processed at the sending or receiving ends

URG (Urgent)

Similar to PSH and identifies incoming data as urgent

UDP Header

8 bytes

IP Header

Ethernet Header

Segment

Source and destination ports

Packet

Source and destination IP addresses

Frame

Source and destination MAC addresses

Bits

transmitting layer 2 frames as a series of 1's and 0's