Module 1 Flashcards
Five Layer Network Model (OSI Model)
- Physical
- Data Link
- Network
4.Transport
5.Application
Physical layer
Represents the physical devices that interconnect computers
Data link layer
Responsible for defining a common way of interpreting these signals so network devices can communicate
Protocols: Ethernet
Ethernet Standard
Defines a protocol responsible for getting data to nodes on the same network or link.
Network Layer
Allows different networks to communicate with each other through devices known as routes
Protocol: IP
Transport Layer
Sorts out which client and server programs are supposed to get the data
Protocol: TCP/IP, UDP
Application Layer
Protocols: HTTP, SMTP
Two main kinds of cables
- Copper: Uses voltage changes to transmit binary data. For example: Cat5, Cat5e, Cat6
- Fiber: Contain individual optical fibers, which are tiny tubes made out of glass about the width of a human hair. Uses pulses of light to transmit binary data.
Crosstalk
When an electrical pulse on one wire is accidentally detected on another wire
Benefits of fiber cables over copper cables
Better for environment with a lot of electromagnetic interference, and can transmit data a lot faster and over longer distances than copper cables.
Copper cables are a lot more durable and cheaper than fiber
Collision domain
A network segment where only one device can communicate at a time. If multiple systems try sending data at the same time, the electrical pulses sent across the cable can interfere with each other. For example: Using a hub to connect computers
Why use a switch over a hub?
Reduces the size of collision domains, resulting in greater and faster data transmissions.
Which devices are used to connect devices in a local area network?
Hubs and switches.
BGP
Border gateway protocol. Routers share data with each other via this protocol, which lets them learn about the most optimal paths to forward traffic.
Node
A device connected to the internet
Client vs Server
A server is a node that provides data and a client is a node that requests data.
Bit
Smallest representation of data that a computer can understand. A bit is either a 1 or a 0
Modulation
A way of varying the voltage of a charge moving across the cable
In computer networking, modulation is called “line coding”
Twisted pair cable
Consists of pairs of copper wires that are twisted together. Its the most common type of cabling used for connecting computing devices
The twists helps to protect against electromagnetic interference and cross talk, and allow for duplex communication
The standard Cat6 cable has 4 twisted pairs
Duplex vs Simplex communication
With duplex communication information can flow in both directions across the cable, but simplex communication is unidirectional
Devices connected with duplex cables can communicate with each other at exactly the same time.
How do network cables enable duplex communication?
By reserving on or two pairs for communicating in one direction and another one or two pairs for communicating in the other direction
What are three types of twisted pair cables?
Unshielded twisted pair (UTP) - The most common and least expensive type of Ethernet cable found in business and home networks. UTP cables offer very basic protection against EMI, RFI, and crosstalk interference.
Shielded twisted pair (STP) - Used in environments where electromagnetic interference (EMI), radio frequency interference (RFI), and crosstalk with nearby cables have been identified as a problem for network communications. An STP cable uses a braided aluminum and/or copper shielding to encase the four twisted pairs underneath the outer jacket.
Foiled twisted pair (FTP) - Also used in environments where EMI, RFI, and crosstalk are a problem. An FTP cable uses a thin foil shield that wraps around the bundle of twisted pair wires underneath the outer jacket.
Patch Panel
A patch panel is a device used in networking to manage and organize multiple network cables in a central location. It acts as a static switchboard, where network cables from various devices (such as computers, servers, or switches) are terminated and connected to ports on the patch panel. These ports are usually connected to networking equipment like switches or routers via shorter patch cables.
Difference between straight-through and cross-over network cables
- Straight-through Cable:
Usage: This cable is used to connect different types of devices, such as a computer to a switch, router, or modem.
Wiring: The pinouts on both ends of the cable are identical. Specifically, the wire color pattern on pins 1-8 is the same on both connectors (T568A or T568B standard on both ends).
Common Example: Connecting a PC to a network switch or connecting a router to a modem. - Crossover Cable:
Usage: This cable is used to connect similar types of devices directly, such as PC-to-PC or switch-to-switch, without using an intermediate device like a hub or switch.
Wiring: In a crossover cable, some wires are “crossed” so that the transmit and receive signals are reversed. For example, in one standard (T568A on one end and T568B on the other), pin 1 connects to pin 3, and pin 2 connects to pin 6.
Common Example: Connecting two computers directly without a switch or hub.
Key Difference:
Straight-through cables maintain the same wire arrangement on both ends and are designed for connecting different types of devices.
Crossover cables reverse the transmit and receive signals and are meant for directly connecting similar devices.
In modern networks, most devices have auto-MDI/MDIX features, meaning they can automatically adjust for straight-through or crossover cables.
RJ45 Connector
An RJ45 connector is a standard type of physical connector commonly used to terminate Ethernet cables. It’s most widely known as the plug used to connect network devices such as computers, routers, and switches in a Local Area Network (LAN).
Ethernet
The protocol most widely used to send data across individual links.
CSMA/CD
Carrier Sense Multiple Access with Collision Detection is an ethernet protocol used to determine when the communications channels are clear, and when a device is free to transmit data (Solves the problem of collision domains)
If two devices send a signal and it collides, then both devices will stop and wait a random interval before attempting to send it again.
MAC address
A globally unique identifier attached to an individual network interface.
It is a 48-bit number normally represented by a six groupings of two hexadecimal numbers
The first three octets (two digits) of a MAC address is known as the organizationally Unique identifier. These are assigned to individual hardware manufacturers by the IEEE
The last three octets is vendor assigned, which means it can be assigned in any way that the manufacturer would like.
Octet
Any number that can be represented by 8 bits
MAC addresses and Ethernet
Ethernet uses MAC addresses to ensure that the data it sends has both an address for the machine that sent the transmission, as well as the one the transmission was intended for.
Unicast
A unicast transmission is always meant for just one receiving address
If the least significant bit in the first octet of a destination address is set to zero, it means that the ethernet frame is intended for only the destination address
Multicast
Transmission meant for a segment of devices on a LAN
f the least significant bit in the first octet of a destination address is set to one, it means that it is a multicast frame
Broadcast
Transmission meant for all devices on a LAN
This is accomplished through using a broadcast address FF:FF:FF:FF:FF:FF
Three ethernet transmission protocols
Unicast, Multicast, Broadcast
Data Packet
An all-encompassing term that represents any single set of binary data being sent across a network link
Ethernet Frame
A highly structured collection of information presented in a specific order
Parts of a Frame
- Preamble (7 bytes)
- SFD - Start Frame Delimiter(1 byte)
- Destination address (6 bytes)
- Source address (6 bytes)
- VLAN header (4 bytes)
- Payload (46 - 1500 bytes)
- FCS - Frame Check Sequence (4 bytes)
Check Sum Value
Calculated by performing what is known as a cyclical redundancy check against the frame. The check sum value is then used by the recipient to check whether it has received uncorrupted data.
