A message sent from computer A to computer B in the internet is reached to computer B by sending the message as a series of data packets from the computer A. In between A & B, there comes details, how these packets are transmitted from the computer A and finally reached at the destination computer B.
There are 2 interesting areas to explore in this packet journey in the
internet.
1: How a sniffer is able to read these data packets and from which places in the journey of data packets sniffers sniff these packets.
2. How the data sent from A after reaching at B is read by the program in the destination computer.
I am interested to learn these 2 areas. The point 1 is most interesting bcoz it's where sniffing comes. And the point 2 will give you more in depth understanding about the underlying protocols used in the networking.
I will finish this series if I can successfully sniff the packets in an unsecured network.
Typically, when people think of network traffic, they think that it goes directly from their computers to the router or switch and up to the gateway and then out to the Internet, where it routes similarly until it gets to the specified destination. This is mostly true except for one fundamental detail. Your computer isn't directly sending the data anywhere. It broadcasts the data in packets that have the destination in the header. Every node on your network (or switch) receives the packet, determines whether it is the intended recipient and then either accepts the packet or ignores it.
For example, let's say you're loading the Web page http://example.com on your computer "PC". Your computer sends the request by basically shouting "Hey! Somebody get me http://example.com!", which most nodes simply will ignore. Your switch will pass it on to where it eventually will be received by example.com, which will pass back its index page to the router, which then shouts "Hey! I have http://example.com for PC!", which again will be ignored by everyone except you. If others were on your switch with a packet sniffer, they'd receive all that traffic and be able to look at it.
Picture it like having a conversation in a bar. You can have a conversation with someone about anything, but other people are around who potentially can eavesdrop on that conversation, and although you thought the conversation was private, eavesdroppers can make use of that information in any way they see fit.
We now just got the big picture about the journey of packets. For deep understanding it's good to know the basic details about each device mentioned above.
Switches:>
Switches connect multiple devices (computers, printers, servers) on the same network within a building or campus. A switch enables connected devices to share information and talk to each other. Building a small office network isn't possible without switches to tie devices together.
There are two basic types of switches to choose from as part of your networking basics: managed and unmanaged.
An unmanaged switch works out of the box and does not allow you to make changes. Home-networking equipment typically offers unmanaged switches.
A managed switch allows you access to program it. This provides greater flexibility to your networking basics because the switch can be monitored and adjusted locally or remotely to give you control over network traffic, and who has access to your network.
Routers:>
Routers tie multiple networks together. When building a small office network, you’ll need one or more routers. A router connects your networked computers to the Internet. This enables all connected computers to share one single Internet connection. A router acts as a dispatcher, choosing the best route for your information to travel. It connects your business to the world, protects information from security threats, and can even decide which computers get priority over others.
Routers analyze the data being sent over a network, change how it is packaged, and send it to another network, or over a different type of network. They connect your business to the outside world, protect your information from security threats,and can even decide which computers get priority over others.
Depending on your business and your networking plans, you can choose from routers that include different capabilities. These can include networking basics such as: Firewall: Specialized software that examines incoming data and protects your business network against attacks.
Routers can protect your network with a built-in firewall and Intrusion Prevention System (IPS) - specialized software that examines incoming data and protects against attacks.
There are 2 interesting areas to explore in this packet journey in the
internet.
1: How a sniffer is able to read these data packets and from which places in the journey of data packets sniffers sniff these packets.
2. How the data sent from A after reaching at B is read by the program in the destination computer.
I am interested to learn these 2 areas. The point 1 is most interesting bcoz it's where sniffing comes. And the point 2 will give you more in depth understanding about the underlying protocols used in the networking.
I will finish this series if I can successfully sniff the packets in an unsecured network.
Typically, when people think of network traffic, they think that it goes directly from their computers to the router or switch and up to the gateway and then out to the Internet, where it routes similarly until it gets to the specified destination. This is mostly true except for one fundamental detail. Your computer isn't directly sending the data anywhere. It broadcasts the data in packets that have the destination in the header. Every node on your network (or switch) receives the packet, determines whether it is the intended recipient and then either accepts the packet or ignores it.
For example, let's say you're loading the Web page http://example.com on your computer "PC". Your computer sends the request by basically shouting "Hey! Somebody get me http://example.com!", which most nodes simply will ignore. Your switch will pass it on to where it eventually will be received by example.com, which will pass back its index page to the router, which then shouts "Hey! I have http://example.com for PC!", which again will be ignored by everyone except you. If others were on your switch with a packet sniffer, they'd receive all that traffic and be able to look at it.
Picture it like having a conversation in a bar. You can have a conversation with someone about anything, but other people are around who potentially can eavesdrop on that conversation, and although you thought the conversation was private, eavesdroppers can make use of that information in any way they see fit.
We now just got the big picture about the journey of packets. For deep understanding it's good to know the basic details about each device mentioned above.
Switches:>
Switches connect multiple devices (computers, printers, servers) on the same network within a building or campus. A switch enables connected devices to share information and talk to each other. Building a small office network isn't possible without switches to tie devices together.
There are two basic types of switches to choose from as part of your networking basics: managed and unmanaged.
An unmanaged switch works out of the box and does not allow you to make changes. Home-networking equipment typically offers unmanaged switches.
A managed switch allows you access to program it. This provides greater flexibility to your networking basics because the switch can be monitored and adjusted locally or remotely to give you control over network traffic, and who has access to your network.
Routers:>
Routers tie multiple networks together. When building a small office network, you’ll need one or more routers. A router connects your networked computers to the Internet. This enables all connected computers to share one single Internet connection. A router acts as a dispatcher, choosing the best route for your information to travel. It connects your business to the world, protects information from security threats, and can even decide which computers get priority over others.
Routers analyze the data being sent over a network, change how it is packaged, and send it to another network, or over a different type of network. They connect your business to the outside world, protect your information from security threats,and can even decide which computers get priority over others.
Depending on your business and your networking plans, you can choose from routers that include different capabilities. These can include networking basics such as: Firewall: Specialized software that examines incoming data and protects your business network against attacks.
Routers can protect your network with a built-in firewall and Intrusion Prevention System (IPS) - specialized software that examines incoming data and protects against attacks.
Hubs:>
Hubs will broadcast all the packets to all the computers. Switches are a bit smarter and will try send each packet to the respective computer.
Default gateways:
A default gateway is the node(= a router) on the computer network that the network software uses when an IP address does not match any other routes in the routing table. The following illustration shows the role played by two default gateways (IP routers) for two networks: Network 1 and Network 2.
In order for Host A on Network 1 to communicate with Host B on Network 2, Host A first checks its routing table to see if a specific route to Host B exists. If there is no specific route to Host B, Host A forwards its TCP/IP traffic for Host B to its own default gateway, IP Router 1.
The same principle applies if Host B is sending to Host A. Without a specific route to Host A, Host B forwards any TCP/IP traffic destined for Host A to its own default gateway, IP Router 2.
will continue...
A default gateway is the node(= a router) on the computer network that the network software uses when an IP address does not match any other routes in the routing table. The following illustration shows the role played by two default gateways (IP routers) for two networks: Network 1 and Network 2.
In order for Host A on Network 1 to communicate with Host B on Network 2, Host A first checks its routing table to see if a specific route to Host B exists. If there is no specific route to Host B, Host A forwards its TCP/IP traffic for Host B to its own default gateway, IP Router 1.
The same principle applies if Host B is sending to Host A. Without a specific route to Host A, Host B forwards any TCP/IP traffic destined for Host A to its own default gateway, IP Router 2.
will continue...
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