What Is a Packet?
a Packet — the unit of data at Layer 3 — a chunk of your message wrapped with an IP header carrying source and destination addresses so routers can deliver it.
How it works
Large data is split into many packets, each routed independently and reassembled at the destination. An IP header records addresses, TTL and protocol; the payload carries a Transport-layer segment inside. At Layer 2 each packet gets framed for its local hop.
Why it matters
Packet vs frame vs segment is a classic exam trap: segments (L4) ride inside packets (L3), which ride inside frames (L2). Tools like Wireshark show you real packets — reading them is a core analyst skill.
Frequently asked questions
What does a packet contain?
An IP header (source/destination address, TTL, protocol) plus the payload — typically a TCP or UDP segment carrying application data.
What is the difference between a packet and a frame?
A packet is the Layer 3 unit with IP addresses; a frame is the Layer 2 wrapper with MAC addresses that carries the packet across one hop.
Why is data split into packets?
Smaller units share links fairly, survive errors cheaply (only lost pieces resend) and can route around failures independently.
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