ISO Model Flashcards
Layer 1
Physical layer
Signaling, cabeling, connectors
Sending Bits
Hubs, wireless access points, media converters
Layer 2
Datalink layer
Datalink control DLC protocols.
MAC address
Bridges
NIC cards
Switching layer
Extended unique identifier
(EUI-48, EUI- 64)
Sends frames = several Bits
Layer 3
Network Layer
Routing layer = packet switching
Logical addressing
IP address
Packet
Switching not (switches)
Multilayer switched
Frames are fragmented
IPv4 and IPv6 protocols
ICMP Internet control message protocol
Layer 4
Transport layer
Post office layer
TCP Transmission Control Protocol= reliable
UDP User data protocol= speed
Connection oriented = the handshake
Layer 5
Session layer
Communication management between devices
Start and stop and restart between one end point an another.
Control protocols
Tunneling protocols
Checking user credentials
Layer 6
Presentation layer
Encryption
Data formatting
Character encoding
Application encryption
Often combined with the application
layer 7
SSL/TLS, HTML, texting, GIF, JPG, MPG
Layer 7
Application layer
Layer we get to see
Browser window we see
HTTP, FTP, DNS, Email-POP3/IMAP/SMTP, Telnet, SNMP
PDU
Protocol Data Unit
Data transmission
Transmission units
A different group of data at different OSI layers
Ethernet
Operates on a frame of data. Its doesn’t care what’s inside
IP
Operates on a package of data
Inside is TCP or UDP
But IP doesn’t really care
TCP or UDP
TCP segment
UDP datagram
TCP Header
Contain important control info
Called flags
Flags control the payload
MTU maximum transmission unit
If packet is too large it is fragmented. Slows things down.
MTU sizes are usually configured once when the network is set up.
Maximum IP packet size
1500 bytes
Minus 8 byte ICMP header
Minus 20 bytes IP address
= 1472 bytes
