B-TO-C mode

section b-b b-b

section c-c c-c

C to C

c to c transport

FUNI Frame User C to C Network Interface

GGP Gateway C to C Gateway Protocol

OAB One C to C All Broadcast

OAS One C to C All Scatter

THC Terminal C to C Host Connection

TPC Time C to C Pulse height Converter

UNI User C to C Network Interface

UUI User C to C User Indicators

WTO Write C To C Operator

Highway C to C Group Demultiplexer

A B C method

A、B、C、D domain

AB，B，C

A-B-C intuition