Cisco Router 860, 880 Series User Manual

 
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APPENDIXB
Concepts
This appendix contains conceptual information that may be useful to Internet service providers or 
network administrators when they configure Cisco routers. To review some typical network scenarios, 
see 
Chapter 18, “Deployment Scenarios.”
The following topics are included in this appendix:
 ADSL, page B-1
 SHDSL, page B-2
 Network Protocols, page B-2
 Routing Protocol Options, page B-2
 PPP Authentication Protocols, page B-3
 TACACS+, page B-5
 Network...

 
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Appendix B      Concepts
  SHDSL
SHDSL
SHDSL is a technology based on the G.SHDSL (G.991.2) standard that allows both data and voice to be 
transmitted over the same line. SHDSL is a packet-based network technology that allows high-speed 
transmission over twisted-pair copper wire between a network service provider (NSP) central office and 
a customer site, or on local loops created within either a building or a campus. 
G.SHDSL devices can extend the reach from central...

 
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Appendix B      Concepts
  PPP Authentication Protocols
RIP and Enhanced IGRP differ in several ways, as shows Ta b l e B-1.
RIP
RIP is an associated protocol for IP, and is widely used for routing protocol traffic over the Internet. RIP 
is a distance-vector routing protocol, which means that it uses distance (hop count) as its metric for route 
selection. Hop count is the number of routers that a packet must traverse to reach its destination. For 
example, if a particular...

 
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Appendix B      Concepts
  PPP Authentication Protocols
PPP originated as an encapsulation protocol for transporting IP traffic over point-to-point links. PPP also 
established a standard for the assignment and management of IP addresses, asynchronous (start/stop) 
and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link 
quality testing, error detection, and option negotiation for such capabilities as network-layer address...

 
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Appendix B      Concepts
  TACACS+
TACACS+
Cisco 860 and Cisco 880 series routers support the Terminal Access Controller Access Control 
System
 Plus (TACACS+) protocol through Telnet. TACACS+ is a Cisco-proprietary authentication 
protocol that provides remote access authentication and related network security services, such as event 
logging. User passwords are administered in a central database rather than in individual routers. 
TACACS+ also provides support for separate...

 
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Appendix B      Concepts
  Dial Backup
PVC
A PVC is a connection between remote hosts and routers. A PVC is established for each ATM end node 
with which the router communicates. The characteristics of the PVC that are established when it is 
created are set by the ATM adaptation layer (AAL) and the encapsulation type. An AAL defines the 
conversion of user information into cells. An AAL segments upper-layer information into cells at the 
transmitter and reassembles the cells...

 
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Appendix B      Concepts
  NAT
line is up, the backup interface is placed in standby mode. In standby mode, the backup interface is 
effectively shut down until it is enabled. Any route associated with the backup interface does not appear 
in the routing table.
Because the backup interface command is dependent on the router’s identifying that an interface is 
physically down, it is commonly used to back up ISDN BRI connections, asynchronous lines, and leased 
lines. The...

 
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Appendix B      Concepts
  Easy IP (Phase 1)
Translations can be static or dynamic. A static address translation establishes a one-to-one mapping 
between the inside network and the outside domain. Dynamic address translations are defined by 
describing the local addresses to be translated and the pool of addresses from which to allocate outside 
addresses. Allocation occurs in numeric order, and multiple pools of contiguous address blocks can be 
defined.
NAT eliminates the...

 
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Appendix B      Concepts
  QoS
QoS
This section describes quality of service (QoS) parameters, including the following:
 IP Precedence
 PPP Fragmentation and Interleaving
 CBWFQ
 RSVP
 Low Latency Queuing
QoS refers to the capability of a network to provide better service to selected network traffic over various 
technologies, including ATM, Ethernet and IEEE 802.1 networks, and IP-routed networks that may use 
any or all of these underlying technologies. Primary goals of QoS...

 
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Appendix B      Concepts
  QoS
In general, multilink PPP with interleaving is used in conjunction with CBWFQ and RSVP or IP 
Precedence to ensure voice packet delivery. Use multilink PPP with interleaving and CBWFQ to define 
how data is managed; use Resource Reservation Protocol (RSVP) or IP Precedence to give priority to 
voice packets.
CBWFQ
In general, class-based weighted fair queuing (CBWFQ) is used in conjunction with multilink PPP and 
interleaving and RSVP or IP...