What tasks does the network layer solve?

The network layer (L3) solves tasks related to delivering data between different networks, not just between neighboring devices.

Put simply: if data needs to be delivered "outside a single local network", the network layer is responsible for that.

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#Main tasks of the network layer

#1. Logical addressing

The network layer uses IP addresses.

It is responsible for:

• assigning addresses to devices
• understanding which network the destination is in
• distinguishing "this is my network or a foreign one"

Without logical addressing:

• the Internet simply could not exist

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#2. Routing

One of the key tasks.

The network layer:

• determines which routers to send data through
• chooses the path from source to destination
• can change the route if part of the network is unavailable

This is handled by:

• routers
• routing tables
• routing protocols

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#3. Transmitting packets between networks

At the network layer, data exists as packets.

It:

• receives data from the transport layer
• packs it into IP packets
• passes packets further, from network to network

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#4. Determining the next hop

For each packet, the network layer decides:

• where to send it next, right now
• which next router to use

Important:

• the decision is made at each router
• separately for each packet

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#5. Fragmentation and reassembly of packets

If a packet is too large:

• it can be split into parts (fragmented)
• transmitted across the network
• reassembled at the destination

This is needed to work with networks that have different packet size limits.

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#What the network layer does NOT do

Important for an interview The network layer:

• does not use MAC addresses
• does not guarantee packet delivery
• does not correct errors
• does not control delivery order

This is handled by:

• the data link layer (MAC, frames)
• the transport layer (TCP/UDP)

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#Short comparison for understanding

• L2 (data link) - delivery within a single network
• L3 (network) - delivery between networks
• L4 (transport) - reliability and transmission control

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#In short, for an interview

The network layer solves tasks of logical addressing, routing, and transmitting packets between different networks, determining the path data takes from source to destination.