The transport layer divides a data stream into segments and may add reliability and flow control information.
The data link layer adds physical source and destination addresses and an FCS to the segment.
Packets are created when the network layer encapsulates a frame with source and destination host addresses and protocol-related control information.
Packets are created when the network layer adds Layer 3 addresses and control information to a segment.
The presentation layer translates bits into voltages for transmission across the physical link.
第1题：
Which OSI layer does a Router operate at?
A．the Physical Layer
B．the Data Link Layer
C．the Transfer Layer
D．the Network Layer
第2题：
A. Application Layer
B. Presentation Layer
C. Data Link Layer
D. Physical Layer
第3题：
●LANs can be connected by using bridges，which operate in the (67) .
(67) A．data-link layer
B．Physical layer
C．network layer
D．transport layer
第4题：
A. The application layer
B. The session layer
C. The data link layer
D. The transport layer
E. The network interface layer
F. The physical layer
第5题：
A. Transport layer divides a data stream into segments & adds reliability & flow control information
B. Data link layer adds physical source & destination address & an FCS to the segment
C. Packets are created when the network layer encapsulate a frame with source & destination host address& protocol related control information
D. Packets are created when the network layers adds layers 3 address & control information to a segment
E. The presentation layer translated bits into bits into voltages for transmission across the physical link
第6题：
In the open systems interconnection (OSI) reference model, "layer" means one of seven conceptually complete,(71) arranged groups of services, functions, and protocols, that extend across all open systems.Application layer provides means for the application(72) to access the OSI environment. Presentation layer provides for the selection of a common syntax for representing data.(73) layer provides the means necessary for cooperating presentation entities to organize and synchronize their dialog and to manage their data exchange. Transport layer provides a reliable end-to-end data transfer service. Network layer provides for the entities in the transport layer the means for transferring blocks of data, by(74) and switching through the network between the open systems in which those entities reside. Data link layer provides services to transfer data between network layer entities. Physical layer provides the mechanical, electrical, functional, and procedural means to establish, maintain and(75) physical connections for transfer of bits over a transmission medium.
A．rankly
B．levelly
C．layered
D．hierarchically
第7题：
Together with the network layer,the transport layer is the heart of the protocol（ ）The network layer provides end-to-end（ ） delivery using datagrams or virtual circuits.The transport layer builds on the network layer to provide data transport from a process on a（ ）machine to a process on a destination machine with a desired level of reliability that is independent of the physical （ ） currently in use.It provides the abstractions that applications nedd to use the network..Without the（ ） layer,the whole concept of layered protocols would make little sense.
A.transport B.network C.hierarchy D.service A.packet B.data C.command D.record A.connection B.terminal C.source D.destination A.traffic B.connection C.lines D.networks A.network B.transport C.link D.physical
第8题：
LANs can be connected by using bridges, which operate in the
A．physical layer
B．data link layer
C．network layer
D．transport layer
第9题：
A.Application
B.Internet
C.Transport
D.Network
E.Data Link
第10题：
A. data link
B. network
C. transport
D. presentation
E. physical