Avaya IP Telephony Průvodce konfigurací Strana 131

  • Stažení
  • Přidat do mých příruček
  • Tisk
  • Strana
    / 180
  • Tabulka s obsahem
  • ŘEŠENÍ PROBLÉMŮ
  • KNIHY
  • Hodnocené. / 5. Na základě hodnocení zákazníků
Zobrazit stránku 130
Efficient Networking 131
IP Telephony Configuration Guide
Other intranet resource considerations
Bottlenecks caused by non-WAN resources do not occur often. For a more complete evaluation,
consider the impact of incremental IP telephony traffic on routers and LAN resources in the
intranet where the IP telephony traffic moves across LAN segments that are saturated, or routers
whose central processing unit (CPU) utilization is high.
Implementing the network, LAN engineering
To minimize the number of router hops between the systems, connect the gateways to the intranet.
Ensure that there is enough bandwidth on the WAN links shorter routes. Place the gateway and the
LAN router near the WAN backbone. This prevents division of the constant bit-rate IP telephony
traffic from bursty LAN traffic, and makes easier the end-to-end Quality of Service engineering
for packet delay, jitter and packet loss.
Further network analysis
This section describes how to examine the sources of delay and error in the intranet. It also
discusses several methods for reducing one-way delay and packet loss.
The key methods are:
“Components of delay” on page 131
“Reduce link delay” on page 132
“Reducing hop count” on page 132
“Routing issues” on page 134
Components of delay
End-to-end delay is the result of many delay components. The major components of delay are:
Propagation delay: Propagation delay is the result of the distance and the medium of links
moved across. Within a country, the one-way propagation delay over terrestrial lines is under
18 ms. Within the U.S., the propagation delay from coast-to-coast is under 40 ms. To estimate
the propagation delay of long-haul and trans-oceanic circuits, use the rule of thumb of 1 ms per
100 terrestrial miles.
If a circuit goes through a satellite system, estimate each hop between earth stations adds 260
ms to the propagation delay.
Serialization delay: The serialization delay is the time it takes to transmit the voice packet one
bit at a time over a WAN link. The serialization delay depends on the voice packet size and the
link bandwidth, and is the result of the following formula:
serialization delay in ms = 8(IP packet size in bytes/link bandwidth in kbit/s)
Zobrazit stránku 130
1 2 ... 126 127 128 129 130 131 132 133 134 135 136 ... 179 180

Komentáře k této Příručce

Žádné komentáře