1.7 Encapsulation Principle

The result of what happens when you combine layering and packet switching

• Each packet contains data from multiple layers

• The principle by which you organize information in packets so that you can maintain layers, yet let them share the contents of packets

• Each protocol layer has some headers, payload, footers

  • E.x. IP packet header: source addr, dest addr

  • To send TCP segment with IP, make the TCP format the payload of the IP packet (IP packet "encapsulates" the TCP segment)

Encapsulation

• Browsing a web using a computer connected through WiFi

• Generates an HTTP GET request

  • Payload of a TCP segment

  • Payload of IP packet

  • Payload of WiFi frame

• Both correct

Wireshark

Encapsulation Flexibility

• Able to layer recursively

• Transport layer security (TLS)

VPN

• Allows you to access private, protected network resources inside your office

• TLS session is inside a TCP stream that terminates at the virtual private network gateway

Example

• How we take protocol layers and assemble them into packets in a way that's flexible and maintains their separation of concerns