Nortel Meridian 1 Description, Installation And Operation page 72

Page 72 of 262 IP Telecommuter Engineering Guidelines
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553-3001-119 Standard 2.00 April 2000
router4 (10.3.0.1) 92 ms
SubnetA (10.3.2.7) 94 ms
The average rtt time on that link is about 40 ms; the one-way link delay is
about 20 ms, of which the circuit transmission and serialization delay are just
a few milliseconds. Most of this link's delay is due to queueing.
The IP Line card nodes must be connected to the intranet so as to minimize
the number of router hops between the Meridian 1 systems, assuming
adequate bandwidth on the WAN links for the shorter route. This will reduce
the fixed and variable IP packet delay, and improve the Voice over IP Quality
of Service. It is recommended that no more than 8 cards share the same
10BaseT LAN collision domain, provided that the preferred codec
throughout the IP telephony network is set to G.729 AB with 30 ms default
payload size. (In a passive Ethernet hub, all ports on the hub share one
10Mbps collision domain; in a switched Ethernet hub, each port has its own
collision domain.)
The technician may want to consider implementing LAN resiliency. This is
achieved by provisioning Leader and Follower cards on separate Ethernet
hubs (but served by the same router). In this design the IP Line card node can
still provide voice services even if one of the hubs fails.
The IP Line card node and the T-LAN router should be placed as close to the
WAN backbone as possible, again to minimize the number of router hops,
segregate constant bit-rate Voice over IP traffic from bursty LAN traffic, and
simplify the end-to-end Quality of Service engineering for packet delay,
jitter, and packet loss. If an access router separates the IP Line card node from
the WAN router, there should be a high-speed link (e.g., Fast Ethernet, FDDI,
SONET, OC-3c, ATM STS-3c) between the access router and the WAN
backbone router.
90 ms 101 ms
97 ms 95 ms