Suggest an editImprove this articleRefine the answer for “What data is transmitted 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)**, **packets** are transmitted - this is the basic data unit of this layer. **Key point:** the network layer works with packets, usually IP packets.Shown above the full answer for quick recall.Answer (EN)ImageAt the **network layer (L3)**, **packets** are transmitted - this is the basic data unit of this layer. Short and precise: **the network layer works with packets, usually IP packets**. --- ## What exactly is transmitted at the network layer ### 1. **Packets (IP packets)** The network layer: - receives data from the transport layer (TCP/UDP) - **packs it into a packet** - transmits the packet through one or more networks A packet is: - data + service information of the network layer --- ### 2. **IP header** Every packet contains an **IP header**, which includes: - the source IP address - the destination IP address - routing information - service fields (TTL, protocol type, etc.) It is this header that allows: - understanding **where to direct the packet** - making decisions at routers --- ### 3. **Payload** Inside an IP packet is: - a transport layer segment (TCP or UDP) The network layer: - **does not analyze the content** of the payload - simply delivers the packet further --- ## What is NOT transmitted at the network layer Important for an interview The network layer **does not work** with: - bits as signals (that is L1) - frames and MAC addresses (that is L2) - application ports (that is L4) - application data directly --- ## Relationship between data units across layers - **Physical layer** → bits - **Data link layer** → frames - **Network layer** → packets - **Transport layer** → segments --- ## Where packets exist - packets are transmitted **between networks** - routers work specifically with packets - at every hop between networks: - the IP packet is preserved - the L2 frame is rebuilt from scratchFor the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.