1,连线题
point-to-point serial IP connections:
serial link internet protocol(SLIP)
ITU-T standard protocol with error-correction:
X.25
standard-based, host to network over aynch/sync connections:
point-to-point protocol(PPP)
proprietary router-to-router corrections:
high level data link(HDLC)
international standard cell switching protocol:
asynchronous transfer mode
high performance, packet switched protocol:
Frame relay
2,功能比较
leased lines:high control, full bandwidth, high-cost enterprise networks, and last-mile
access
frame relay:medium control,shared bandwidth, medium-cost enterprise backbones; branch
sites
ISDN:low control, shared bandwidth, more bandwidth than dialup
Asynchronous dialup:low control, shared bandwidth, variable cost, cost-effective for
limited-use connections like DDR
X.25:low control, shared bandwidth, variable cost, cost-effective for limited-use
connections, high reliability
3,猫的启动过程
According to the DOCSIS(data-over-cable service interface specifications) when you
first power up a cable modem it starts scanning(starting at a low frequency)for a cable
signal. when it 'hears' a cable modem stream it listens for a broadcast(from the
service provider) which contains information needed to talk back with the head end. It
then 'talks back' and if it communicates the right authentication information, it is
allowed to proceed
4,名词解释
Custom Queing:
establishes bandwidth allocations for each type of traffic
Weighted Fair Queing:
prioritizes interactive traffic over file transfers in order to ensure satisfactory
response time for common user applications
Priority Queuing:
transmits traffic of a specified protocol or type
Priority Queuing:
four queues; packet starvation possible
Low latency queuing:
designed to prioritize VoIP traffic; priority and weighted classes
class-based WFQ:
up to 64 classes; no priority queue
Custom Queuing:
round robin service; user defined bandwidth allocation
Flow-based WFQ:
interactive traffic gets priority; no classes
5,三A认证的三个方面
authentication:authentication determines the identify of users and whether they should
be allowed access to the network.
authorization:authorization allows network managers to limit the network services
available to each user.
accounting:system administrators might need to bill departments or customers for
connection time or resources used on the network. Accounting tracks this kind of
information. You can also use the accounting syslog to track suspicious connection
attempts into the network and trace malicious activity
6,多链路协议(MLP)及它的作用
MLP solves several problems related to load balancing across multiple WAN links,
including the following:
Multivendor interoperability,as specified by RFC 1990,which replaces RFC 1717
Packet fragmentation, improving latency of each packet
Packet sequence and load calcuation
This feature negotiates the Maximum received reconstructed unit(MRRU) option during the
PPP LCP negotiation to indicate to its peer that it can combine multiple physical links
into a bundle
7,有关PPP的连线题
Start of PPP authentication process: incoming PPP negotiation
Second step if authentication is configured:Determine authentication method
Checks using username and password:local database
Queries this with TACAS+ or RADIUS:security server database
Does this if authentication fails:disconnect
Does this if authentication passes:continure with PPP negotiation
8,G.Lite的优点
is prominent in residential applications
has 120 subchannels
doesn't need a splitter
has a 1.5 Mbps maximum downstream speed
9,对L2TP的介绍
L2TP extends the PPP model by allowing the L2 and PPP endpoints to reside on different
devices interconnected by a packet-switched network. With L2TP, a user has an L2
connection to an access concentrator, and the concentrator then tunnels individual PPP
frames to the NAS. This allows the actual processing of PPP packets to be divorced from
the termination of the L2 circuit
10,对PPP链路控制协议(LCP)的介绍
The PPP LCP (Link Control Protocol) provides a method of establishing,
configuring,maintaining, and terminating a point-to-point connection. The four PPP LCP
options are authentication, callback,compression, and multilink. With LCP, the link is
maintained via the use of error correcting mechanisms.
