Networks can be interconnected by different devices．In the physical layer，networks can be connected by (66) or Hubs，which just move the bits from one network to an identical network．One layer up we find bridgas and swiehes,which operate at data link layer．They can accept (67) ，examine the MAC address，and forward the frames to a different network while doing minor protocol translation in the process．In the network layer，we have routers that can connect two netwoks．If two networks have (68) network layer，the router may be able to translate between the packet formats．In the transport layer we find transport gateway，which can interface between the two transport connections．Finally，in the application layer，application gateways translate message (69) ．As an example，gateways between Internet e-mail and X．400 e-mail must (70) the e-mail message and change various header fields．(66)

A．reapers

B．relays

C．connects

D．modems(67)

A．frames

B．bytes

C．packages

D．cells(68)

A．special

B．dependent

C．similar

D．dissimilar(69)

A．syntax

B．semantics

C．languages

D．format(70)

A．analyze

B．pairs

C．delete

D．create

[单选题] Networks can be interconnected by different devices. In the physical layer，networks can be connected by（1）or hubs，which just move the bits from one network to an identical network. One layer up we find bridges and switches，which operate at data link

[单选题]Networks can be interconnected by different devices. In the physical layer, networks can be connected by(66)or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data l

[单选题]Networks can be interconnected by different devices in the physical layer networks can be connected by (71) or hubs．which just move the bits from one network to an identical network．One layer up we find bridges and switches which operate at data link

[单选题]The Internet is a （）system of interconnected computer networks that use the

[单选题]Communication networks can be classified in terms of their physical arrangement or (73) Three common (73) are the star,bus,and ring.(73) A．structuresB．topologiesC．protocolsD．frames

[单选题]C．ommunication networks can be classified in terms of their physical arrangement or(73)Three common(73)are the star, bus, and ring.A．structuresB．topologiesC．protocolsD．frames

[单选题]( )functions with two layers of protocols.It can connect networks of differ

[单选题]Communication networks can be classified in terms of their physical arrange

[单选题]When comparing different fuels for different engines, the ignition quality of diesel fuel oils becomes a less critical consideration as （）A . the amount of lube oil additives increaseB . piston speeds increaseC . injection pressure decreaseD . engine

[单选题]Wireless telecommunications networks are generally implemented and administered using（）communication.This implementation takes place at the （）level of OSI model network structure.A．microwave B．radio C．FM D．AMA．physical B．link C．network D．transport