Gabarito B
Squid is operating at layers 4-7 on the OSI data model. So unlike most networking applications there is no relationship between packets (a layer 3 concept) and the traffic received by Squid. Instead of packets HTTP operates on a message basis (called segments in the OSI model definitions), where an HTTP request and response can each be loosely considered equivelent to one "packet" in a transport architecture. Just like IP packets HTTP messages are stateless and the delivery is entirely optional for process. See the RFC 7230 texts for a better description on HTTP specifics and how it operates.
At the broad level Squid consists of four generic processing areas;
a client-side which implements HTTP, HTTPS, FTP, ICP and HTCP protocols to communicate with clients, and
a server-side which implements HTTP, HTTPS, FTP, Gopher and WAIS to communicate with web servers, and
between them is the cache storage. Which in broad terms provides the buffering mechanisms for data transit, and provides switching logic to determine data source between disk, memory, and server-side.
there is also a set of components performing extra support tasks; security (authentication and access control), DNS client, IDENT client, and WHOIS client.
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