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Cisco MGX 8220 Installation and Configuration
Release 5.0, Part Number 78-6430-03 Rev. D0, November 2003
Chapter
Core Module Overview
The major function of the B N M is t o pr ov id e a T 3 or E3 ATM interf ace to a B N I or B XM-T3/E3 card
in a Cisco BPX 8600 series node. The BNM also provides the following miscellaneous functions:
•Shelf mastership
Selects which core card to us e as th e m aster and which redundant bus to u se.
•Cell bus mastership
BNM polls the other cards on t he b u s a nd gr ant s pe rmi ssi on t o t rans mit cel l s acro s s th e b us. Po ll in g
is performed on a round-robin basis.
•Clock selection
BNM manages the clock selection and synchronization for the entire Cisco MGX 8220 shelf. The
BNM selects, regulates, and outputs t he selected clock for use by each service mo dule in the shelf.
The BNM back card contains a T1/E1 port for inputting an external T1/E1 clock source. Two
versions of the line module are av aila ble. V er sio n T3E3-B has a BNC exte rnal cl ock conne ctor us ed
with E1 clock timing input. Version T3E3-D has a DB-15 external cloc k conn ec tor us ed wi th T1 or
E1 clock timing input. The shelf can also obtain clock from the DS3 or E3 trunk itself or use an
internal clock source.
•External alarm interface
BNM provides the activation of four al ar m r el ay s , wh ich a re wired to a DB-15 connector on t he
back card faceplate allowing the cu st om e r to w ir e th eir own cab le from the connector to an
indicator panel. The four rela ys are Major Alarm Audible, M ajo r A lar m Visual, Minor Alarm
Audible, and Minor Alarm Visual. The pinouts for this connector are provided in AppendixB,
“Specifications.”
•Miscellaneous monitoring functions
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Fan performance in the cooling assembly
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Input voltage levels
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Shelf intake air temperature
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In-band management
BNM provides a separate path for ma nagement of the Ci sco MGX 82 20 using an ATM VCC from across
the ATM network.
ATM Trunk Interface
The BNM card accepts and trans mit s ATM cells over a T 3 or E3 l ine interfaces at 44.736 Mbps or
34.368 Mbps respectively, using Cisco StrataCom Trunk Interface (STI) protocol asynchronously.
Framing occurs on the card using C -bit p ar ity. An 8-kHz clock is extrac ted f rom the rece i ve d si gn al a nd
can be used to synchronize the entire Cisco MGX 8220 system.
The physical T3 or E3 ATM interface to the BNM is achieved using the BNM back card. This physical
connection is made with BNC conn ectors. There are also relays on the b ack card. These relays provide
the continuity or discontinuity between the internal circuitry and the external BNC connectors for the
transmit and receive lines.
These relays are also used as a mec hanical loopback for the T3 or E3 b it s t ream .
The Cisco MGX 8220 shelf impl ements the ATM STI cell format by using slot/cha nnel numbers in the
VPI/VCI fields in the cell format used between th e BNM and the Cisco BPX 8600 series BNI port. The
cell format is shown in Figure2-14 and Figure 2-15. The format on the left is the general STI format,
the format on the right is the Cisco MGX 8220 implementation.