Network engineering is a complex process.
It involves various addresses, checks, and destinations that happen almost simultaneously.
Part of network engineering is the concept of routing and forwarding.
Here’s what you need to know about the difference between routing and forwarding.
What Is The Difference Between Routing And Forwarding?
Routing is the process by which a network makes a forwarding table.
Besides handling all the addresses and destinations, it also maintains the forwarding table.
Using various algorithms, it converts the routing info that it receives into the forwarding table.
Forwarding, on the other hand, is the actual process of sending a data packet through the network.
It uses the forwarding table that the router creates to find its starting point and ending point.
The data packet also uses information that helps guide its transport through the network.
You can understand the difference better by thinking of routing and forwarding as moving from Los Angeles to San Francisco.
Routing is like planning the trip.
You pull out your map and look at all the various streets, highways, and other country roads that can take you to San Francisco from Los Angeles.
It includes other information like traffic stops, possible delays, and the amount of traffic on each route.
The router, as the driver, tries to determine the most efficient path between Los Angeles and San Francisco.
This is the route that has the fewest delays, traffic, and traffic stops.
Forwarding is the process of driving from Los Angeles to San Francisco.
It takes the information that the driver, or router, gave them and drives the vehicle, or data packet, to its destination.
The route that the driver takes is the most efficient one to their destination.
How Do Routing Tables Work?
Routing tables, or forwarding tables, are a series of addresses and information that’s stored in the router.
The information carries destination addresses for packets of data.
It knows where to send a data packet because of its IP address.
It first checks the prefix of the IP address on the data packet, then tries to find a matching IP address in its table.
Once it has the address, it sends the data packet through the network to its destination.
An example of how it looks for an IP prefix is by considering the IP 192.168.1.20/32.
This is the data packet with that IP address that needs moving.
There are two IP addresses that the routing table has for this particular IP address.
They include 192.168.1.0/24 and 192.168.1.20.
The IP that matches the data packet the most is 192.168.1.20.
The router chooses this destination, then forwards the data packet to that IP address.
There are also two different ways in which a router learns the destinations for each data packet in the first place.
The first way a router learns IP addresses is through static routing.
This is a lengthy process by which a network admin writes each destination by hand into the router.
This method is feasible if the router only has a few destinations that it needs to know.
In most cases, however, it needs to know hundreds, if not thousands, of different addresses.
A typical number of addresses that a router knows is 600,000.
A network admin could spend years writing all those addresses into a routing table.
It’s also easy for human error to occur.
A better process for routers to learn destinations and addresses is through dynamic routing.
During this type of learning, the router receives configuring in such a way that it’s able to learn from other routers.
Most routers will still receive some form of static routing, but they may only need a few hundred addresses entered.
Then they can speak to other routers to figure out the addresses that they don’t have.
Each router should have information about itself and the routers closest to it.
Once it has the address that it needs from another router, it forwards the data packet to the discovered IP address.
What’s The Difference Between Intradomain And Interdomain Routing?
There are two kinds of domains when it comes to routing.
Intradomain refers to all the routing and forwarding that takes place within the domain.
A domain is a section of the internet that covers various addresses.
Intradomain means that the router searches solely within its own domain.
Interdomain routing, on the other hand, refers to routing and forwarding that takes place within and between different domains.
Routers are able to seek information in a different domain than the one where it’s based.
There are a few other differences between intradomain routing and interdomain routing as well.
Intradomain routing only requires the routers to know about each other within the domain.
They don’t need to seek information from other routers outside of the domain.
The protocols that intradomain routing uses to establish and send information are interior gateway protocols.
The routing takes place within an autonomous network because the domain is autonomous.
It essentially ignores the internet outside of the autonomous domain.
Some popular protocols that you’ll find in intradomain routing are Resource Information Protocol and Open Shortest Path First.
Interdomain routing is different in that the router needs to know about routers that exist both within the domain and outside of the domain.
The protocols they use to receive and send information are exterior gateway protocols.
Instead of routing within the autonomous domain, interdomain routing performs routing between various autonomous networks.
This allows the protocol to assume that the internet has a collection of autonomous systems.
Popular protocols that interdomain routing uses are Border Gateway protocol and Autonomous System.
What’s The Difference Between A Routing Table And An ARP Table?
The main difference between a routing table and an ARP table is that they contain different information.
Both are part of the network through which information passes.
The routing table sends information to the ARP table.
The Address Resolution Protocol table then reads that information and determines the physical address of the gateway.
Once it has that address, it sends the packet to its destination.
It essentially helps the router find the right address.
What’s The Difference Between Forwarding And Switching?
Forwarding is the process by which data packets move to their destinations.
Switching is a specific form of moving information.
In particular, switching moves data packets from Layer 2 of the OSI to its destination address.
There are two different types of switching methods.
The first is connection-oriented switching.
This type of switching involves virtual switches.
It uses connection-oriented protocols that include x,25 and the Transmission Control protocol.
Through those protocols, the data packet passes through the network and to its destination.
The other type of switching is connection-less switching.
This uses a special kind of form for the data known as datagrams.
There are a few datagrams that are well-known like ethernet, internet protocol or IP, and the user datagram protocol.
This is different from forwarding.
Packet forwarding uses information from one network segment to another to pass its packet along through the system.
There are a few different forwarding types.
Unicasting is one of them.
During unicasting, the network uses a chain made up of various links.
The packet then relays from each link along the chain until it reaches its destination.
Broadcasting is the second type of forwarding process.
This occurs when the information needs duplicating.
The data packet duplicates itself, and then a copy of it passes to various devices within the network.
It still uses links to reach its destination, but several links are used because there are several copies sent through the network.
The final type of forwarding is multicasting forwarding.
Instead of duplicating all the data packets, multicasting only selects a few data packets for duplicating.
The copies pass through the network and only arrive at the networks that are actively looking for the information.
What’s The Difference Between Dropping And Rejecting Forwarding Packets?
Nothing is more frustrating than when a website doesn’t work.
It may ask you to refresh your page.
This occurs because the data packet wasn’t able to reach your router.
The reason is that the information was either dropped or rejected by your router.
There are a few reasons the forwarding packet was dropped.
The first is that the forwarding packets moved from a higher bandwidth to a lower bandwidth.
There’s a circuit that exists in front of each bandwidth.
Information has to pass through the bandwidth circuit.
If the information starts out in a high bandwidth area, then it may be large.
When it reaches the low circuit bandwidth, then it may not be able to fit through the circuit.
The circuit is unable to process all the information from the packet.
As a result, it drops the packet, and the website crashes.
Another reason the packet may drop is that the router can’t keep up with the traffic.
When either the router or the switch processor is unable to keep up with the traffic, then the information drops.
This is a popular way in which DDoS attacks occur.
Hackers will send so much information to the router that it becomes overwhelmed.
As a result, the hackers are able to stop any security checks from occurring and access the router’s information.
That allows them to steal valuable information like identity data and credit card data.
Outside of a DDoS attack, when a router or switch processor receives too much information, then the data has a chance of becoming lost.
The router can’t receive and read the information fast enough.
Anything that isn’t read becomes deleted.
A third way that data packets drop is when midspan devices are out of sync.
One of the major reasons a midspan device may be out of sync is a timing failure.
Since the timing is incorrect, the data may not be able to pass through the device.
The packet drops since it has nowhere to go.
One final reason a data packet may drop is that it’s part of a larger data packet.
Sometimes information travels through the network in different packets.
At some point through the network, the packets may lose their order.
Since a router needs to read a data packet in a certain way, if the data packets are out of order, then it’s impossible for the router to read them.
A router isn’t smart enough to switch the data packets around and find the correct order.
As a result, the data packet gets dropped.
Knowing the various ways a data packet drops is helpful in understanding how it differs from when a router rejects a data packet.
When a router rejects a data packet, it does so intentionally.
Something may be wrong with the data packet, or the router may recognize it as malware.
It purposely deletes the data packet.
A data packet that drops, however, is only sometimes intentionally.
It’s usually done by accident.
Rejection is intentional whereas dropping is accidental.
What Happens To A Dropped Packet In A Network?
You may wonder what happens to the data packet when it doesn’t get to your router.
If a data packet drops, then it’s deleted from the system.
If the router didn’t do this, then it would have hundreds if not thousands of data packets in its system.
This would clog the system and keep it from running at optimal performance.
New information may never be able to make it through the clog to reach the router.
After the data packet becomes deleted, the router tells the address to send the information again.
The router that sent the data packet originally will then re-transmit a new data package and send it to its destination again.
What Is The Difference Between A Packet Switch And A Circuit Switch?
The main difference between a packet switch and a circuit switch within the world of routing and forwarding is that a circuit switch uses physical switches.
The circuit switch uses a physical connection between the target and its destination.
The physical connection is what enables the data to reach its destination.
Along the connection are a few switches that feed more information to the packet.
These switches help guide the packet to its destination.
They can also stop the packet if it’s in the wrong area.
A packet switch doesn’t require a physical connection between its starting point and its destination.
Instead, the data packet uses a header and footer system to tell the switch where it needs to go.
Each header and footer contains a unique identification number and address.
The various protocols that the switch uses then guide the data packet to its destination.
There is a significant advantage to using packet switching over circuit switching in routing and forwarding.
Packet switching will only lose the data packet if something goes wrong.
Circuit switches will lose all the information if something goes wrong because of that physical connection.
Routing and forwarding are both parts of the complex process in network engineering.
Routing gains all the information that data needs to reach its endpoint whereas forwarding is the active movement of the data to its endpoint.
There are also various types of switches and forwarding that direct the data packet to its destination.
The routing table, or forwarding table, is responsible for finding the best path for the data packet to take.
These intricate pathways and checkpoints make up your ability to search for and receive information from the internet.