Suggest an editImprove this articleRefine the answer for “What protocols work at the network layer?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)At the **network layer (L3)**, protocols work that are responsible for logical addressing, delivering packets between networks, and routing. **Key point:** network layer protocols determine how IP packets are addressed and transmitted between networks.Shown above the full answer for quick recall.Answer (EN)ImageAt 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**. --- ## 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 --- ### 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. --- ### 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. --- ## 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 **RIP** - a simple routing protocol - rarely used (outdated) ### 6.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 --- ## 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 --- ## Short table | Protocol | Purpose | |---|---| | IP | delivering packets | | ICMP | errors and diagnostics | | IPsec | protecting IP | | OSPF / RIP / BGP | routing | --- ## 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.**For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.