CoreBuilder 5000 Token Ring Module Features
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Jitter is the tendency of signalling on Token Ring networks to grow
increasingly out-of-phase as the network size increases. CoreBuilder
5000 Token Ring Media Modules remedy jitter problems by:
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Reducing Internal (CoreBuilder 5000) Jitter
■
Reducing External (Non-CoreBuilder 5000) Jitter
Reducing Internal (CoreBuilder 5000) Jitter
To minimize jitter and increase the number of stations allowed on each
ring, each CoreBuilder 5000 Token Ring active port incorporates Dual
Phase-Locked Loop (DPLL) circuitry.
Dual PLL minimizes accumulated jitter and phase slope on the ring, and
increases the number of attached stations to 250 (190 at 4 Mbps) on
each ring. To reduce jitter, DPLL uses a two-pronged approach:
■
An optimized, wide-band PLL tracks the incoming signal even in the
presence of jitter, thus allowing more margin for jitter sources.
■
A narrow-band PLL removes all fluctuations in the recovered clock
and provides a stable source to retime and retransmit the signal.
Reducing External (Non-CoreBuilder 5000) Jitter
In addition to port-level DPLLs, CoreBuilder 5000 Token Ring Media
Modules support optional Jitter Attenuator daughter cards. Daughter
cards reduce jitter accumulated in external, non-CoreBuilder 5000 rings,
even if the rings are built from other vendor’s products.
A combination of port-level DPLLs and Jitter Attenuator daughter cards
allows you to use Level 3 UTP lobe cabling to configure the following
ring (using active ports):
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250 stations
■
16 Mbps ring speed
■
100 meter lobes
A major feature of reduced jitter is reliability. A network that can
support 250 stations, under worst case conditions, is assured to be
extremely robust and reliable when configured with 50, 75, or 125
stations.
