Suggest an editImprove this articleRefine the answer for “What tasks does the transport layer solve?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**The transport layer (L4)** solves tasks related to **transferring data between applications** on different devices and **controlling that transfer**. In simpler terms, the transport layer makes sure data reaches from one program to another correctly and on time. **Key point:** the transport layer handles delivering data between applications, segmenting and reassembling data, managing ports, ensuring reliability, and controlling order, flow, and congestion (depending on the protocol).Shown above the full answer for quick recall.Answer (EN)Image**The transport layer (L4)** solves tasks related to **transferring data between applications** on different devices and **controlling that transfer**. In simpler terms: **the transport layer makes sure data reaches from one program to another correctly and on time**. --- ## Main tasks of the transport layer ### 1. Delivering data from application to application The transport layer uses **ports**: - source port - destination port This allows: - one computer to simultaneously - serve many network programs Example: - browser → port 443 - email client → port 25 --- ### 2. Segmentation and reassembly of data The transport layer: - splits large application data into **segments** - sends them over the network - **reassembles** them into the original stream on the receiver's side --- ### 3. Ensuring reliability (TCP) If TCP is used, the transport layer: - acknowledges receipt of data - retransmits lost segments - ensures correct delivery order UDP does **not** do this. --- ### 4. Managing delivery order The transport layer: - numbers segments - assembles them in the correct sequence - protects against "mixed-up" data --- ### 5. Flow control The transport layer makes sure that: - the sender does not "overwhelm" the receiver with data - the transmission speed matches the receiving capacity --- ### 6. Network congestion control (mostly TCP) - reduces transmission speed when congested - increases it when the network is free This helps the network run more stably. --- ## What the transport layer does NOT do Important for the interview. The transport layer: - does not choose the route (that is L3) - does not work with IP or MAC addresses - is not responsible for delivering signals --- ## Brief comparison of TCP and UDP - **TCP** - reliability, order, control - **UDP** - speed, simplicity, minimal checks --- ## In short, for the interview > **The transport layer handles delivering data between applications, segmenting and reassembling data, managing ports, ensuring reliability, and controlling order, flow, and congestion (depending on the protocol).**For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.