OSI (3-7) Flashcards
Logical Addressing
IP, IPX, AppleTalk
Layer 3
Switching
Forwarding decisions Packet Switching Circuit Switching Message Switching Layer 3
Packet Switching
AKA routing
Data stream divided into packets with Layer 3 header with source and destination address
Circuit Switching
Dynamically brings up a dedicated communication link between two parties.
e.g. phone call
Layer 3
Message Switching
Not well suited for real-time applications
Data stream divided into messages tagged with destination address
Affiliated with store-and-forward network
Connection Services
Improve communication reliability
Flow (congestion) control
Packet reordering
Layer 3
Flow Control
aka Congestion Control
Prevents sender from sending data more rapidly than receiver can handle
Packet Reordering
Packets placed in proper sequence
Layer 3 devices
Router, multilayer switch
TCP
Transmission Control Protocol
Connection-oriented transport protocol
Reliable
UDP
User Datagram Protocol
Connectionless transport protocol
Unreliable
Layer 4 flow control
Windowing
Buffering
Windowing
Used by TCP
Multiple segments can be set at a time, receiver sends single acknowledgement for all in window
RTT
Round-Trip Time
aka Real Transfer Time
Time receiver has to acknowledge receipt of window
Buffering
Device uses chunks of memory to store segments if bandwidth not available to send
ICMP
Internet Control Message Protocol
Layer 4
Procedures involved in setting up a session
Checking user credentials
Assigning numbers to communication flows
Negotiating services
Negotiating sending device
Procedures involved in maintaining a session
Transferring data
Reestablishing disconnected session
Acknowledging receipt of data
