$6\mathrm{.}7-1.$ To which protocol do these fields belong? We learned way back in Chapter $1$ that "a protocol defines the format and the order of messages exchanged between two or more communicating entities $..."$ and throughout the course, we saw many, many different messages being used throughout the protocol stack, each with different fields.

In this question, for a given field name in a protocol message $($i$.$e$.,$ in an application$-$layer message, transport$-$layer segment, networklayer datagram, or link$-$laye $[$Choose $]$ match the field name with TCP and UDP this field name is used. Eac IPv$6$ names$)$ in the pull$-$down men DNS description. $,$ TCP to

SMTP

IPv$4$ and IPv$6$

WiFi $(802\mathrm{.}11)$

$802\mathrm{.}11($WiFi$)$ and $802\mathrm{.}3($Ethernet$)$

HTTP

where

l

e field

IF$-$Modified$-$Since

$802\mathrm{.}11(WiFi)$ and $8C$

$128-$bit Source IP address field

Source MAC address