Communication Network Basics Flashcards
Name all layers in order
- Physical
- Data Link
- Network
- Transport
- Session
- Presentation
- Application
Define layer 1 (OSI)
- defines the way information is sent in bits
- physical properties like timing, voltages, hardware etc. are systematized
Define layer 2 (OSI)
- transforms a raw transmission into a line that can be used as a data pipe
- specifies the system by which data is split into ‘frames’
- framing
- error checking
- flow control
- medium access control
- a little bit of traffic regulation
Define layer 3 (OSI)
- routing
- connects multiple sub networks into a bigger network
- is concerned with transferring ‘packets’ across the network
- regulates quality of service
- handles congestion on the network
- deals with protocol translation etc.
Define layer 4 (OSI)
- specifies the manner in which data is transported across the network
- splits data into units (if necessary)
- congestion control (sometimes network layer)
- transfers segments that only endpoints handle (communication of endpoints!)
- often: multiplexing of multiple transport layer connections into one network connection
- sometimes: split one transport layer connection into multiple network layer connections
Define layer 5 (OSI)
- establishes sessions between two different machines
- dialogue control
- token management for critical operations
- synchronization (setting checkpoints for long transmissions)
Define layer 6 (OSI)
- systematization of data
- specifies the syntax and semantics of transmitted data
- encoding of higher level data structures
Define layer 7 (OSI)
- usually offers the services needed by users (http, pop, imap)
Explain the function of a protocol
- agreement among communicating parties how communication shall proceed
- syntax: format, order
- semantics: actions taken when transmitting, receiving or when a timer expires
List the main components of a communication network
- network edge: applications, hosts
- network core: routers, internetworks
- access networks, physical media:
communication links
What is the end to end principle
- complex functions should be pushed to endpoints
- network only there to transfer information
What are entities and data units
For OSI layers:
- processes at layer N are called N-entities
- N-entities exchange N-Protocol-Data-Units
- PDU consists of Protocol control information and a Service Data Unit (SDU)
SDU contains upper layer data
- data structures and rules governing behavior of N-entity form an N-protocol
What types of services can a layer offer
- connection oriented:
connection required before SDU can be transmitted;
connection closed after transmission - connectionless:
SDUs directly exchanged via Service Access Points without setup - confirmed
- unconfirmed
Define broadcast communication networks
- class of comm. networks
- information that leaves one node reaches every other node
Define switched communication networks
- class of communication networks
- information is transmitted along a path of intermediary nodes (e.g. routers)
