Suggest an editImprove this articleRefine the answer for “What is multiplexing at the transport layer?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**Multiplexing at the transport layer** is a mechanism that lets **several applications simultaneously use a single network connection (a single IP address)**. **Key point:** multiplexing is when the transport layer gathers data from different applications and sends it over the network, distinguishing them by port.Shown above the full answer for quick recall.Answer (EN)Image**Multiplexing at the transport layer** is a mechanism that lets **several applications simultaneously use a single network connection (a single IP address)**. More simply: **multiplexing is when the transport layer gathers data from different applications and sends it over the network, distinguishing them by port**. --- ## Why multiplexing is needed On one computer, the following run at the same time: - a browser - mail - messengers - system updates All of them: - use **a single IP address** - go out onto the network **in parallel** Multiplexing makes this possible. --- ## How multiplexing works ### On the sender's side The transport layer: 1. accepts data from **different applications** 2. for each data stream: - assigns a **source port** 3. packs the data into segments 4. sends them onto the network --- ### On the receiver's side (demultiplexing) The transport layer: 1. receives segments from the network 2. looks at: - the IP address - the destination port - the protocol (TCP/UDP) 3. delivers the data to the **right application** --- ## Multiplexing and demultiplexing Important for the interview. - **Multiplexing** - combining streams from different applications when sending - **Demultiplexing** - parsing incoming data and delivering it to the right application These two processes are usually mentioned together. --- ## The role of ports Ports are the key element of multiplexing: - they let applications be distinguished - they enable parallel connections - they make end-to-end communication possible Without ports, multiplexing would be impossible. --- ## Example - browser → port 54321 → HTTPS - mail → port 54322 → SMTP - messenger → port 54323 → its own server All the data: - goes through **a single network interface** - but is **not mixed up** --- ## What is important to remember - multiplexing is a function of the **transport layer** - it works on top of IP - it is not tied to physical channels - TCP and UDP have **separate multiplexing**For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.