Tiered Networks 13-5
BPX Routing Hubs in a Tiered Network
Connections within tiered networks consist of distinct segments within each tier. A routing segment
traverses the routing network, and an interface shelf segment provides connectivity to the interface
shelf end-point. Each of these segments are added, configured and deleted independently of the other
segments. The SV+ Connection manager provides management of these individual segments as a
single end-to-end connection.
Interface shelves are attached to the routing network via a BPX routing hub using a BXM trunk
(T3/E3 or OC3) or BNI trunk (T3/E3). The connection segments within the routing network are
terminated on the BNI feeder trunks.
All frame relay connection types which can terminate on the BPX ASI card are supported on the BNI
feeder trunk (currently VBR, CBR, ABR, and ATF types). No check is made by the routing network
to validate whether the connection segment type being added to a BNI feeder trunk is actually
supported by the attached interface shelf.
Co-locating Routing Hubs and Interface Shelves
The trunk between an interface shelf and the routing network is a single point of failure, therefore,
the interface shelves should be co-located with their associated hub node. Card level redundancy is
supported by the Y-Cable redundancy for the BXM, BNI, AIT, and BTM.
Network Management
Communication between CPE devices and the routing network is provided in accordance with
Annex G of Recommendation Q.2931. This is a bidirectional protocol for monitoring the status of
connections across a UNI interface. (Note: the feeder trunk uses the STI cell format to provide the
ForeSight rate controlled congestion management feature.)
Communication includes the real time notification of the addition or deletion of a connection
segment and the ability to pass the availability (active state) or unavailability (inactive state) of the
connections crossing this interface.
A proprietary extension to the Annex G protocol is implemented which supports the exchange of
node information between an interface shelf and the routing network. This information is used to
support the IP Relay feature and the Robust Update feature used by network management.
Network Management access to the interface shelves is through the IP Relay mechanism supported
by the SNMP and TFTP projects or by direct attachment to the interface shelf. The IP Relay
mechanism relays traffic from the routing network to the attached interface shelves. No IP Relay
support is provided from the interface shelves into the routing network.
The BPX routing hub is the source of the network clock for its associated feeder nodes. Feeders
synchronize their time and date to match their routing hub.
Robust Object and Alarm Updates are sent to a network manager which has subscribed to the Robust
Updates feature. Object Updates are generated whenever an interface shelf is added or removed from
the hub node and when the interface shelf name or IP Address is modified on the interface shelf.
Alarm Updates are generated whenever the alarm state of the interface shelf changes between
Unreachable, Major, Minor and OK alarm states.
An interface shelf is displayed as a unique icon in the SV+ Network Management topology displays.
The colors of the icon and connecting trunks indicate the alarm state of each. Channel statistics are
supported by FRP, FRM, ASI, and MGX 8220 endpoints. BNIs, AITs, and BTMs do not support
channel statistics. Trunk Statistics are supported for the feeder trunk and are identical to the existing
BNI trunk statistics.
