Course Module 5 - Network

physical layer

represents the physical devices/hardware that connects to a computer

hardware includes:

• fiber optic cables

• twisted pair cables

• network interface cards

purpose to transmit raw bits (1s and 0s) across a physical medium i.e cables. To determine if a bit is 1 or 0 you can look at the voltage level. And through a process call modulation which can access if a bit is a 1 or zero by the voltage of the electric charge

data link layer

deliver locally

responsible for traversing data on the same network. (ethernet, WIFI)

Network layer

the layer where all the networks communicate with each other

transport layer

target app

makes sure that data is getting to the right server (app)

two main category of cables

copper cables

• made out of metal

• slower but affordable

• transmits electrical signals (1s and 0s)

fiber optic cables

• made out of thin strains of plastic or glass

• faster but more expensive

• transmits light signals

crosstalk

a single transmitted from one wire interfers with a single from an adjacent wire

switch

a physical hardware that connects multiple devices in a network. (Data Link Layer) and it forwards data packets to its intended destination. Reduces collision domain

inspects ethernet data to determine where to send things

when a device is connected, the switch will store its physical address (MAC addresses) in the switch table. In this table that is how the switch knows the destination to route the data.

Collision Domain

When more that one device sends data packets simutanelously across a wire (For example computer A and computer C at the same time is transmitting a frame) so their signals can collide causing data corruption and collision of the electirc current sedning our ones and zeros

Hub

a hardware device that connects multiple device to an internal network. It ha multiple ports that accepts ethernet cables

Different from a switch because data packet is sent to all devices connected to the network not just the intended destination.

Physical layer

High risk for collision because if two devices are sending data on the same network it can cause collision and data corrupti

routers

A hardware that connects multiple devices to multiple networks by forwarding data packets to its intended destination by analysising the IP protocol

routers use routing tables

ISP have more sophsticated routers

duplex communication

data can travel in both directions simutaneously

socket programming

The process of connecting two nodes over a network to communicate with each other

CSMA/CD

Carrier Sense Multiple Access

A protocol that determines when communication channels are free and when devices are free to transport data. Listens for open lines of communication on a network segment.

Collision Detection
if a collision domain occurs (2 or more devices transmitting data on the same network segment) then in this protocol it will stop all communications of devices and make the devices wait a random interval of time (different times) to then resume transport

Ethernet broadcast

data that is sent to every device on a LAN

data packet

a container that contains a set of binary data that is being sent across a network segment

mac address

A unique 12 digit hexadecimal number used for communicating on LAN (local area networks)

more suitable on local networks when trying to send data packets because there is no system to know where a MAC address is geographically

MAC addresses will always be the same no matter where you are

dotted decimal notation

IP addresses are 32 bit long numbers. Made up of 4 octets

12.34.56.78

IP address

IP addresses belong to the network not devices so it will not always remain the same

a valid ip address is a number between 0 and 255

DHCP

Dynamic host configuration protocol

when a new devices is connected to the internet your router gives you an IP address using DHCP

these are dynamic IP addresses

dynamic ip address vs static IP address

dynamic IP addresses is when the DHCP give a devices an IP address

and static IP addresses is when you manually provide IP address to the node. usually reserved for networks and servers

what are data packets called on the ethernet layer

ethernet frames

what are data packets called in the network layer

IP datagrams

What is in a datagram

datagram consits of two things header and payload:

header has
- the source and destination IP
- the size of the datagram
- specifies the protcol that will be used in the next layer (TCP or UDP)
- TTL (Time To Live) prevents routing loop

payload:
- the actual contents/data of the datagram
- its job is the carry the contents to the next layer by using the contents from the header this process is called encapsulation

because once a datagram is fully formed it needs to be encapsulated into a ethernet frame

fragmentation

the process of breaking datagrams into smaller sizes if the payload exceed the max size specification that the network allows and apon arrival it is put back together

List the address classes

Class A: the first octet is the network ID the rest is the host ID: 9.100.100.100 (9 Net Id rest Host Id)

Class B: the first two octet is the network ID the rest is the host ID

Class C: the first three octet is the network ID the rest is the host ID

Think of the first octet (the first number) in an IP address like a label on a box:

Class A Box: Label range is 0-127.

ex: 10.100.50.1

Class B Box: Label range is 128-191.
ex: 176.16.0.10

Class C Box: Label range is 192-223
ex: 198.168.1.1

What is the ARP

Address Resolution Protocol

the ability to find the MAC address by using an IP address. It will most likely use the ARP table. Howver if the IP address does not exsit on the ARP table then the node will broadcast an ARP message to all devices on the LAN.

the device with the IP address will send back a response with the MAC address and add it to the ARP table for future use

ARP tables do have an expiration date

subnetting

sub-pizza: dividing a large pizza (network) into small slices (subnets) to make it more manageable

submasking

It is used to determine the network id and host id in an IP address

First you need to convert the IP address and the sub mask IP address into binary

whatever is a ‘1’ it is reserved for the network id and the rest for the host

submasking example

example shown in image

the number of networks and host submasking example (image)

CIDR Notation

something like this 9.100.100.100/24 just means there at 24 1s in front leaving the last 8 digits to be hsot

the steps in a router when sending a data packet

1. recieve the data packet

   1. take apart the encaspulation of the ethernet frame and turn to datagram

2. examine the IP address

3. look up the destination IP through the routing table

4. send the IP address to its intended destination

steps in a router

1. recieves data packet

2. examine ip address destination

3. look up ip destination in routing table

4. forward traffic to appropriate router

whats in a routing table

1. ip address destination title

2. next hop (the immediate next router that the data packet will go towards)

3. total hops (the total number of routers to get to the ip address destination

4. interface ip address

What are the protocols for routers

interior gateway protocol and exterior gateway protocol

Define interior gateway protocol and its protocol

This functions as a way for routers to share their information (tables,etc) with routers within their single autonomous network. A large company can have multiple networks so the routers are communicated withthin this network

distance vector protocol: routers can share the routing infromation with neighboring routers

link-state protocol: routers can share their information with all routers within their network

define exterior gateway protocol

This allows for rotuers to communicated with other routers in different organization’s networks

What is MDF?

Main Distribution Frame
It is is the the heart of an internal network. It houses equipment like routers, switches, and patch panels and helps route data to and from the internal to external network