Network recovery
354 Avaya Application Solutions IP Telephony Deployment Guide
Multipath routing
Modern routers and Layer 3 switches allow multiple routes for a particular destination to be
installed in the routing table. Depending on the implementation, this can be as high as six
routes. Some implementations require that all routes that are inserted in the routing table have
the same metric, while others allow unequal metric routing. In cases where the metric for all
installed routes are the same, the router will load balance traffic evenly across each path. When
the metric for multiple routes vary, the traffic is load balanced in proportion to the metric (in other
words, if one path is “twice as good” as another, two-thirds of the traffic travels down the good
path, and one-third of the traffic selects the other one). Asymmetric routing is suboptimal for
voice, so route-caching (described earlier) should be considered in this environment.
In addition to using all (up to 6) active paths and optimally using available bandwidth, multipath
routing greatly improves convergence time. As soon as a router detects a path failure, it remove
it from the routing table, and sends all traffic over the remaining links. If this is a physical link
failure, the detection time is nearly instantaneous. Therefore, Avaya recommends the use of
multipath routing, where available, across multiple links to a particular location.
Dial backup
One cost-effective technique for installing backup WAN links is to use dial backup. This can be
done using either ISDN-BRI or analog lines. ISDN lines typically take 2 seconds to connect,
while 56-k analog modems take approximately 1 minute. While this strategy is effective for data
traffic, it is less effective for voice. First, the bandwidth may have been greatly reduced. If this is
the case, the number of voice channels that can be supported might have been reduced
proportionally. Also, if QoS is not properly applied to the backup interface, high packet loss and
jitter can adversely affect voice quality. Finally, the time that is required to establish the new link
can be up to 1 minute, which disrupts active calls. However, providing that these considerations
are taken into account, proper QoS is applied, and a compressed codec is chosen, dial backup
can be an effective solution for two to four users.
Содержание Application Solutions
Страница 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Страница 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Страница 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 74: ...Avaya Application Solutions platforms 74 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Страница 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 214: ...Voice quality network requirements 214 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 239: ...Reliability Issue 3 4 1 June 2005 239 Figure 69 S8700 Media Server in a high reliability configuration ...
Страница 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Страница 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 350: ...Implementing Communication Manager on a data network 350 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Страница 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...