Acronym for Type Of Service.
These are the bits in the beginning of the IP header which try and say how you want this packet treated, you can specify things like this is a packet that prefers lower delay over speed, or prefers reliability over anything else, or is carrying some low priority mail like mail.
In practise they were never used, and so they got replaced with DiffServ a while ago, which also isn't used, but hey, at least it's new hip and trendy.
No page links to TOS.
