What are three factors that limit the maximum distance of an amplified optical signal without regeneration? （）(Choose three.)

A .  codec B .  link speed C .  Layer 2 encapsulation D .  packet overhead （IP/UDP/RTP） E .  link delay F .  total number of simultaneous calls that are allowed

A .  programming interface to external applications B .  FXS and FXO port negotiation C .  AutoQos VoIP trust boundaries D .  signaling and device control E .  LLQ for voice and video traffic F .  directory and XML service

A . A more efficient use of bandwidth can be achieved allowing many physical groups to use the same network infrastructure B . Broadcast storms can be mitigated by decreasing the number of broadcast domains,thus increasing their size. C . A higher level of network security can be reached by separating sensitive data traffic from other network traffic. D . Port-based vlans increase switch-port use efficient,thanks to 802.1Q trunks E . A more efficient use of bandwidth can be achieved allowing many logical networks to use the same network infrastructure. F . Broadcast storms can be mitigated by increasing the number of broadcast domains,thus reducing their size. G . VLANs make it easier for IT staff to configure new logical groups,because the vlans all belong to the same broadcast domain.

A . 6to4 tunneling B . VPN tunneling C . GRE tunneling D . ISATAP tunneling E . PPP tunneling F . Teredo tunneling

A .  low optical powe B .  high optical power C .  few optical channels D .  many optical channels E .  low chromatic dispersion F .  high chromatic dispersion G .  too much power differential in the optical channel

A . GLBP supports up to eight virtual forwarders per GLBP group B . GLBP supports clear text and MD5 password authentication between GLBP group members C . GLBP is an open source standardized protocol that can be used with multiple vendors D . GLBP supports up to 1024 virtual routers E . GLBP can load share traffic across a maximum of four routers F . GLBP elects two AVGs and two standby AVGs for redundancy

A . CPU utilization B . where Netflow data will be sent C . number of devices exporting Netflow data D . port availability E . SNMP version F . WAN encapsulatio

A . VLANs establish broadcast domains in switched networks. B . VLANs utilize packet filtering to enhance network security. C . VLANs provide a method of conserving IP addresses in large networks. D . VLANs provide a low-latency internet working alternative to routed networks. E . VLANs allow access to network services based on department, not physical location. F . VLANs can greatly simplify adding, moving, or changing hosts on the network.

A . low optical power B . high optical power C . few optical channels D . many optical channels E . low chromatic dispersion F . high chromatic dispersion G . too much power differential in the optical channel

A . codec B . link speed C . Layer 2 encapsulation D . packet overhead （IP/UDP/RTP） E . link delay F . total number of simultaneous calls that are allowed

A . Effect of the moon's gravity B . Fetch C . Wind velocity D . Length of time a wind has been blowing

A . number of product features B . return on investment C . competitiveness D . regulation E . day one costs F . availability of budget

A . VLANs establish broadcast domains in switched networks. B . VLANs utilize packet filtering to enhance network security. C . VLANs provide a method of conserving IP addresses in large networks. D . VLANs provide a low-latency internetworking alternative to routed networks. E . VLANs allow access to network services based on department,not physical location. F . VLANs can greatly simplify adding,moving,or changing hosts on the network.

A .  fiber dispersion B .  signal attenuation C .  transmitter power D .  amplifier bandwidth E .  receiver dispersion tolerance

A．Magnitude. B．Weight. C．Direction. D．Power. 此题为多项选择题。

A．Environmental endocrine disruptors B．Organic pollutants C．Social environment D．Physical factors 此题为多项选择题。