Hubs broadcast data to all connected devices. Operate on layer 1 of OSI model. Available as active (amplifying) or passive (unamplifying) types. Limited to half-duplex operation. Useful for small LAN environments with limited router ports
Packet encapsulation marks beginning and end of data units. Header carries packet information, trailer indicates end of packet. Decapsulation removes header and trailer information from packets
Application layer specifies shared communication protocols for hosts in networks. TCP/IP application layer depends on transport layer for data transfer. Original RFC 1123 specification recommends robustness principle. TCP/IP combines session and presentation layers into single layer
Protocols define rules for information transmission between communicating entities. Protocols can be implemented by hardware, software, or combination. Protocols must be agreed upon by parties and may become technical standards
Network packet is a formatted data unit carried by packet-switched networks. Packet consists of control information and user data (payload). Control information found in headers and trailers. Packet concept resembles postal letter: header, payload, footer
TCP was first published in 1973 by Kahn and Cerf. Current version (RFC 7323) released in 2014. TCP enables two-way data transmission between network endpoints. Protocol operates at transport layer of OSI model