HCIA-Ethernet Frame Structure-OSI Model

OSI (Open System Interconnection) seven-layer model of open system interconnection:
user-oriented: application layer http ssh telnet
presentation layer data decoding and encoding data encryption and decryption data compression and decompression
session layer establishment and maintenance management of sessions between applications
Data transmission-oriented: The transmission layer establishes an end-to-end link to ensure that the message is transmitted between end-to-end. The
network layer transmits data from the source to the peer.Function: Provides logical addresses for network devices,
broadcast control,
multicast control, and
determine the optimal path
Traffic management
provides logical addresses to
connect the wide area network (WAN)
data link layer to move frames from one hop to another on an unreliable physical link. It is
divided into two layers: LogicLinkControl provides a field to indicate Whether the upper layer uses IPV4 or V6 (Type field)
Media Access Control (MediaAccessControl) physical address addressing The
physical layer is responsible for moving bits one by one from one hop to another.
MAC address 48 bits: the first 24 bits are the last 24 of the vendor identifier The bit is allocated by the manufacturer.
Features: Each layer of the OSI model has its own set of functions. The
layers are independent and
dependent on each other. The upper layer depends on the lower layer. The lower layer provides
three modes of service signal transmission for the upper layer :
simplex: only one Direction transmission
half duplex: both ends cannot send data
at the same time Full duplex: both ends can send data at the same time
Port numbers below 1024 have been assigned to each application. When the source sends data to the destination, the source host will randomly open a port number above 1024 to connect to the destination host
. There are three ways of data transmission: Unicast ) 1-to-1
multicast (Mutticast) 1-to-many join to form an address to receive multicast information
broadcast (broadcast) 1-to-all