Talk:Communication Networks/TCP and UDP Protocols

The section on Congestion is missing two linked images: Congestion1.jpg and Congestion3.jpg

https://en.wikibooks.org/w/index.php?title=Communication_Networks/TCP_and_UDP_Protocols&stable=1#Congestion

Brutzman (discuss • contribs) 21:00, 9 February 2019 (UTC)

This is the first page I've looked at in any WikiBook. One of the first things my eye catches within 2-3 seconds of glancing at this:

Most users think of TCP and IP as a tightly knit pair, but TCP can be, and frequently is, used with other transport protocols.

For example, TCP or parts of it are used in the File Transfer Protocol (FTP) and the Simple Mail Transfer Protocol (SMTP), both of which do not use IP.

This is glaringly wrong. In the real, modern world (there were past experiments that are not used today in practice):

• TCP is a Transport layer protocol always layered on top of IP (IPv4 or IPv6) as the Network layer. It is not mixed with other Transport layer protocols.
• FTP and SMTP are Application layer protocols which are always either directly on top of TCP or indirectly on TCP through a middle layer such as Transport Layer Security (TLS), formerly known as Secure Sockets Layer (SSL). This FTP or SMTP on TCP always uses IPv4 or IPv6 as its Network Layer.
• It could be argued that FTP and SMTP do not directly use IP (since TCP is always between them), but this would be very misleading as they always indirectly use IP.