Alcatel-Lucent 9500 MXC, Руководство пользователя

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9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. II-2-19
Maximum Frame Size
Maximum Frame Size sets the largest size frame for the interface, which
determines the largest datagram than can be transmitted without it being broken
down into smaller units (fragmented). The IDU ES supports two maximum frame
sizes, 1518/1522 bytes (1518 for non-tagged frames, 1522 for tagged frames) or
1536 bytes.
Latency
Network latency refers to the time taken for a data packet to get from source to
destination. For an IP network it is particularly relevant to voice (VoIP) or video
conferencing; the lower the latency, the better the quality.
For phone conversations a one-way latency of 200 ms is considered acceptable.
Other applications are more tolerant; Intranet access should be less than 5
seconds, whereas for non real-time applications such as email and file transfers,
latency issues do not normally apply.
Other contributors to overall latency are the devices connected to the 9500 MXC
network, which for a VoIP circuit will include the external gateway processes of
voice encoding and decoding, IP framing, packetization and jitter buffers.
Contributing to external network latency are devices such as routers and
firewalls.
Table 2-9 lists typical one-way performance over a 100 Mbps IDU ES link.
Table 2-9.
Typical Performance for a 100 Mbps Hop
Frame Size Latency Throughput
64 240 uSec 72 Mbps
128 250 uSec 83 Mbps
256 270 uSec 88 Mbps
512 300 uSec 93 Mbps
1024 390 uSec 95 Mbps
1518 460 uSec 95.5 Mbps