1.1 OSI Model Flashcards
Layer 1 called
(Physical)
Layer 2 called
(Data link) “Switching layer.”
Layer 3 called
(Network) “routing layer.”
Layer 4 called
(Transport) “post office layer.”
Layer 5 called
(Session)
Layer 6 called
(Presentation)
Layer 7 called
(Application)
Layer 1(Physical) do
signaling, cables, connectors
Layer 2(Data link) do
foundation of communication. Data Link Control (DLC) protocols. MAC address
Layer 3(Network) do
IP addresses. Fragments frames to traverse different networks.
Layer 4(Transport) do
how data is being delivered or from where it’s being delivered. Use TCP & UDP.
Layer 5(Session) do
start, stop, restart communication between devices. Uses control & tunneling protocols. VPN can be used
Layer 6(Presentation) do
character encoding, app encryption(SSL/TLS) combined with layer 7(Application).
Layer 7(Application) do
layer we can see. HTTPS, FTP, DNS, POP3.
Layer 1 devices
hubs, repeaters, modem(layer 1 & 2), Media converter
Layer 2 devices
switch, access point, bridge, network interface card(NIC), modem(layer 1 & 2), Load Balancer(layer 2 & 3), firewall(Layer 2/3)
Layer 3 devices
routing capable switch, router, Load Balancer(layer 2 & 3), firewall(Layer 2/3)
Ethernet(Layer 2) header encapsulation or decapsulation
IP header, TCP/UDP header & Data Payload.
Ethernet(Layer 2) header contains
Mac Address info
Internet Protocol (IP) (Layer 3)header encapsulation or decapsulation
TCP/UDP header & Data Payload.
Internet Protocol (IP) (Layer 3)header contains
IP addresses info
TCP/ UDP (Layer 4) headers encapsulation or decapsulation
Data Payload.
TCP/ UDP (Layer 4) headers contains
TCP/UDP & port info
TCP flags
tells a device what to do with each header in the OSI Model
SYN flag
Synchronize sequence numbers
PSH flag
Push the data to app without buffering
RST flag
Reset connection
FIN flag
Last packet from sender
Payload encapsulation or decapsulation
contains layer 5-7. App data that is needed
Maximum transmission unit (MTU)
set amount of data allowed through a network without fragmenting.
