1. Bits, Frames, Packets – Part 1

 

1. Bits, Frames, Packets – Part 1



14.12.2018
Topic Progress:

Bits, Frames and Packets Part 1 – Video: Register for Course


Bit, Frames, Packets Part 1 – Transcript:

What will you learn

  • Packets are transmitted from source to destination
  • Frames are strictly related of medium type and its protocols thus frames are imposed and stripped when changing network segments and medium types
  • Chains of Bits are grouped into packets while going across the network
  • In relation to medium type : e.g. wireless or wired packets are encapsulated with frames traversing network

Bits

You can ask what is 0 and 1 from the physical perspective? For example when the computers are connected with network cable, each bit is voltage level. Look at the picture, +5 Volts means 0, -5Volts means 1! Simple! In other words just imagine that series of Voltage levels makes YouTube stream!

Optical Bits

There is also wireless transmission of bits as everybody knows. Medium for wireless is Electromagnetic wave and Here, : Ones are represented with higher frequency of waves and Zeros with lower frequencies.

Packets

To make some logical order while transmitting those zeros and ones across the network : , series of bits is segmented into portions packets or IP Packets.

Hence most of traffic engineering rules were created for Internet network, the protocol describing those rules is called Internet Protocol or IP. That is why we call it IP.

Packets Flow

Packets flow from source to destination across the network based on IP addresses included in packet header. Every device connected to network has IP address that uniqely identifies and locates this device. And remember – if you see cloud on the map it is a metaphore of many devices connected together.

Quick Review

 

To sum up so far:

  • Devices produces information presented as bits – bit can be 0 or 1.
  • Bits can be presented as:
  • Electrical levels (voltage),
  • Laser Light
  • or electromagnetic frequency, dependednt on medium and link type

Bits Quick Review

-Chains of Bits are grouped into packets while going across the network

-Packets are transmitted from source to destination based on IP address information but where exactly this information is located ?

-Now It is time to explain what kind of information can be found within the packets

IP Packet Structure

-Lets Focus on packet structure.

-tIt is worth o remember that every IP packet has its HEADER where all crucial information regarding what is the type or what is the destination and source of the packet

-and PAYLOAD – where the actual Data travels

– Here it is worth to mention that we have two version of IP Packerts: IPv4 and IPv6. The two differs in terms of header structure but we will Focus on IPv4 for now:


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