The Irm3 In The Multi Media Access Center - Cabletron Systems IRM-3 User Manual

• Budget and Propagation Delay - When determining the maximum
fiber optic cable length, the fiber optic budget delay and total network
propagation should be calculated and taken into consideration before
fiber runs are incorporated in any network design. Fiber optic budget
is the combination of the optical loss due to the fiber optic cable,
in-line splices, and fiber optic connectors. Propagation delay is the
amount of time it takes a packet to travel from the sending device to
the receiving device.
• Length - IEEE 802.3 specifications for fiber optic cable allow for a
maximum of 1 km. However, distances of at least 2 km can usually be
achieved.

2.2 THE IRM3 IN THE MULTI MEDIA ACCESS CENTER

The IRM3 is designed to be installed in a Cabletron Systems Multi Media
Access Center (MMAC) network hub with the Flexible Network Bus
(FNB) - See Figure 2-1. The MMAC is fully protocol independent and is
available in an eight slot (MMAC-M8FNB), five slot (MMAC-M5FNB)
and three slot (MMAC-M3FNB) model.
When installed in an MMAC, the IRM3 supports 10 Mbps Ethernet
(IEEE 802.3), as well as 4 and 16 Mbps Token Ring (IEEE 802.5) Media
Interface Modules (MIMs) using shielded twisted pair (STP) or
unshielded twisted pair (UTP), fiber optic, thin or thick coaxial and
standard AUI transceiver cabling. The IRM3 retimes and regenerates
packets for each port of each Ethernet MIM installed in the MMAC, and
allows users to access management information for all Token Ring and
Ethernet MIMs in the MMAC.
IRM3 User's Guide
The IRM3 in the Multi Media Access Center
Power & Management Bus
Ethernet A Bus
Flexible Network Bus
Ethernet B Bus
Ethernet C Bus
Figure 2-1 MMAC with FNB
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