What protocols work at the network layer?

At the network layer (L3), protocols work that are responsible for logical addressing, delivering packets between networks, and routing.

Put simply: network layer protocols determine how IP packets are addressed and transmitted between networks.

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#Main network layer protocols

#1. IP (Internet Protocol): the main protocol

The key protocol of the network layer.

Functions of IP:

• logical addressing (IP addresses)
• delivering packets between networks
• routing (together with routers)

Exists in two versions:

• IPv4
• IPv6

Important:

• IP does not guarantee delivery
• IP works on a best effort basis

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#2. ICMP (Internet Control Message Protocol)

A service protocol of the network layer.

Used for:

• transmitting error messages
• network diagnostics
• checking host reachability

Examples:

• ping
• traceroute (partly)

ICMP does not carry user data, only service information.

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#3. IPsec

A protocol (suite of protocols) for protecting IP traffic.

Functions:

• encryption
• authentication
• ensuring the integrity of IP packets

Works on top of IP, but belongs specifically to the network layer.

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#Routing-related (control) protocols

These protocols do not carry user data, but help routers build routes.

#4. OSPF

• an interior routing protocol
• used within a single autonomous system

#5. RIP

• a simple routing protocol
• rarely used (outdated)

#6. BGP

• the main routing protocol of the Internet
• used between autonomous systems

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#A common interview question

Is ARP at the network layer or the data link layer?

Short answer:

• ARP works between L2 and L3
• it is used to map IP ↔ MAC
• it is often called a "boundary" protocol

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#Short table

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#In short, for an interview

At the network layer, the protocols IP, ICMP, and IPsec work, along with routing protocols (OSPF, RIP, BGP), which provide addressing, transmission, and routing of packets between networks.