Design Reference

The sum of margin, dispersion power penalty, and passive cable plant losses must be less than the
available power budget. Alternatively, if you calculate available power margin as the difference
between the available budget and the sum of losses and dispersion, the margin can be more or less
than required, which determines whether additional consideration is needed. If the power budget is
exceeded or margin is insufficient, you can either use a transceiver rated for longer distance
operation, or calculate budget and losses using actual values rather than specified limit values.
Either method can improve the link budget by 4 to 5 dB or more.
10/100BASE-X and 1000BASE-TX reach
The following table lists maximum transmission distances for 10/100BASE-X and 1000BASE-TX
Ethernet cables.
Table 10: Maximum cable distances
10BASE-T 100BASE-TX 1000BASE-TX
IEEE standard 802.3 Clause 14 802.3 Clause 21 802.3 Clause 40
Data rate 10 Mbps 100 Mbps 1000 Mbps
Cat 5 UTP distance 100 m 100 m 100 Ω, 4 pair: 100
m
10/100/1000BASE-TX Auto-Negotiation recommendations
Auto-Negotiation lets devices share a link and automatically configures both devices so that they
take maximum advantage of their abilities. Auto-Negotiation uses a modified 10BASE-T link integrity
test pulse sequence to determine device ability.
The Auto-Negotiation feature allows the devices to switch between the various operational modes in
an ordered fashion and allows management to select a specific operational mode. The Auto-
Negotiation feature also provides a parallel detection (also called autosensing) function to allow the
recognition of 10BASE-T, 100BASE-TX, 100BASE-T4, and 1000BASE-TX compatible devices,
even if they do not support Auto-Negotiation. In this case, only the link speed is sensed; not the
duplex mode. Avaya recommends the Auto-Negotiation configuration as shown in the following
table, where A and B are two Ethernet devices.
Table 11: Recommended Auto-Negotiation configuration on 10/100/1000BASE-TX ports
Port on A Port on B Remarks Recommendations
Auto-Negotiation
enabled
Auto-Negotiation
enabled
Ports negotiate on highest
supported mode on both
sides.
Avaya recommends that
you use this configuration if
Table continues…
Hardware fundamentals and guidelines
28 Network Design Reference for Avaya VSP 4000 Series June 2015
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