Data Link Layer Software Description Transmit blocks of data from the data link layer 76543 in one computer to another Detect errors in data blocks and either correct the -errers or ensure retransmissions ofthe effected data blocks Data link layer
Data Link Layer 1 2 3 4 5 6 7 Data Link Layer Software Description: Transmit blocks of data from the data link layer in one computer to another. Detect errors in data blocks and either correct the errors or ensure retransmissions of the effected data blocks
Protocols Token Passing(IBM) All blocks of data carried around the network with a source and destination address Traffic is guided physically from unit to unit around the ring lEEE8025;lsO|s8802-5 Token bus Traffic is guided on a common data bus, which directly connects all units in the network All units are part of an organized logical sequence All units at any point in time know the address of the unit before and after in logical sequence CSMA/CD(ethernet) All units connected to the common bus can come in at any point in time after the unit has tested and found out no one else is using the network When collisions happen, both units resend the data after a short break
Protocols Token Passing (IBM) – All blocks of data carried around the network with a source and destination address – Traffic is guided physically from unit to unit around the ring – IEEE 802.5; ISO IS 8802-5 Token Bus – Traffic is guided on a common data bus, which directly connects all units in the network – All units are part of an organized logical sequence – All units at any point in time know the address of the unit before and after in logical sequence. CSMA/CD (ethernet) – All units connected to the common bus can come in at any point in time after the unit has tested and found out no one else is using the network. – When collisions happen, both units resend the data after a short break
Protocols Medium Access control Interfaces to the actual transport media to enable applications to communicate lEEE802.5;lsO|s8802-5 Logical Link Control Insures that all software implemented on the top five layers of the OS Model remains independent of which physical network is implemented in the bottom of the model NETBIOS Constructs, maintains and uses a table of relations between the token ring addresses and the defined names of units and services in the network this enables real names to be used Advanced Program to Program Comm Supports program to program communications between different systems through the Token Ring Specific implementation of the IBM Systems Network Architecture(SNA) Logical Unit (LU)6.2 architecture
Protocols Medium Access Control – Interfaces to the actual transport media to enable applications to communicate – IEEE 802.5; ISO IS 8802-5 Logical Link Control – Insures that all software implemented on the top five layers of the OSI Model remains independent of which physical network is implemented in the bottom of the model. NETBIOS – Constructs, maintains, and uses a table of relations between the Token Ring addresses and the defined names of units and services in the network; this enables real names to be used. Advanced Program to Program Comm. – Supports program to program communications between different systems through the Token Ring. – Specific implementation of the IBM Systems Network Architecture (SNA) Logical Unit (LU) 6.2 architecture
Topologies Star Topology Bus Ring Physical Star, Logical Ring
Topologies Star Topology Bus Ring Physical Star, Logical Ring
Topologies Star Topology Connections are made from all connected machines to one central place Control unit controls traffic in the network Computer in the middle has absolute control over traffic in the machine
Topologies Star Topology – Connections are made from all connected machines to one central place. – Control unit controls traffic in the network. – Computer in the middle has absolute control over traffic in the machine