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This chapter describes the tiered network architecture that supports interface shelves (non-routing nodes) connected to an IPX/IGX/BPX routing network.
The chapter contains the following:
With Release 8.5, tiered networks now support voice and data connections as well as frame relay connections. With this addition, a tiered network can now provide a multi-service capability (frame relay, circuit data, voice, and ATM). By allowing CPE connections to connect to a non-routing node (interface shelf), a tiered network is able to grow in size beyond that which would be possible with only routing nodes comprising the network.
In a tiered network, interface shelves at the access layer (edge) of the network are connected to routing nodes via feeder trunks (Figure 11-1). Those routing nodes with attached interface shelves are referred to as routing hubs. The interface shelves, sometimes referred to as feeders, are non-routing nodes. The routing hubs route the interface shelf connections across the core layer of the network.
The interface shelves do not need to maintain network topology nor connection routing information. This task is left to their routing hubs. This architecture provides an expanded network consisting of a number of non-routing nodes (interface shelves) at the edge of the network that are connected to the network by their routing hubs.
Frame relay connections originating at IPX and IGX interface shelves and frame relay, ATM, CESM, and FUNI connections originating at AXIS interface shelves are routed across the routing network via their associated BPX routing hubs. Frame Relay connections originating at IGX interfaces shelves connected to IGX routing hubs may also be routed across BPX intermediate nodes.
Voice and data connections originating and terminating on IGX interface shelves (feeders) are routed across the routing network via their associated IGX routing hubs. Intermediate routing nodes must be IGX nodes. Refer to the Cisco StrataCom System Overview and IGX Reference manuals for additional information on IGX routing hubs and IGX interface shelves.
Tiered networks with BPX routing hubs have the capability of adding interface shelves/feeders (non-routing nodes) to an IPX/IGX/BPX routing network (Figure 11-2). The AXIS interface shelf, and IPX or IGX nodes configured as interface shelves are connected to BPX routing hubs. Interface shelves allow the network to support additional connections without adding additional routing nodes.
The AXIS supports frame T1/E1, X.21 and HSSI frame relay, ATM T1/E1, and CES, and is designed to support additional interfaces in the future. The IPX interface shelf supports frame relay ports, as does the IGX (option is available to configure as an interface shelf).
The following requirements apply to BPX routing hubs and their associated interface shelves:
Annex G, a bi-directional protocol, defined in Recommendation Q.2931, is used for monitoring the status of connections across a UNI interface. Tiered Networks use the Annex G protocol to pass connection status information between a Hub Node and attached interface shelf.
BPX Service Note Routing Hub | A BPX Service node in the routing network which has attached interface shelves. Also referred to as a hub node or BPX hub. |
AXIS Interface Shelf | A standards based service interface shelf that connects to a BPX routing hub, aggregrates and concentrates traffic, and performs ATM adapation for transport over broadband ATM networks. |
IPX Interface Shelf | A special configuration of the IPX narrow band node designated as a interface shelf that supports frame relay connections. |
IGX Interface Shelf | A special configuration of the IGX multi-band node designated as a interface shelf that supports frame relay connections. |
Feeder Trunk | Refers to a trunk which interconnects an interface shelf with the routing network via a BPX routing hub. A feeder trunk is sometimes referred to as an interface shelf trunk. |
IPX/AF | Another name for the IPX interface shelf |
IGX/AF | Another name for the IGX interface shelf |
Routing Network | The portion of the tiered network which performs automatic routing between connection endpoints. |
VPI | Virtual Path Identifier |
VCI | Virtual Connection Identifier |
Converting an IPX or IGX node to an interface shelf requires re-configuring connections on the node, as no upgrade path is provided in changing a routing node to an interface shelf.
A BPX node, acting as a Hub Node, is not restricted from providing any other feature which is normally available on BPX nodes. A BPX Hub supports up to 16 interface shelves.
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.
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.
Communication between CPE 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 AXIS 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.
Foresight for an IPX interface shelf terminated Frame Relay connections is provided end-to-end between Frame Relay ports, regardless as to whether these ports reside on an IPX interface shelf or within the routing network.
Preferred routing within the routing network can be used on all connections. Priority bumping is supported within the routing network, but not in the interface shelves. All other connection features such as conditioning, rrtcon, upcon, dncon, etc. are also supported.
Connection local and remote loopbacks are managed at the user interface of the FRP endpoint routing node or interface shelf. The existing IPX Frame Relay port loopback feature is supported on the IPX interface shelf. Remote loopbacks are not supported for DAX connections. A new command addlocrmtlp is added to support remote loopbacks at FRP DAX endpoints.
Tstcon is supported at the FRP endpoints in a non-integrated fashion and is limited to a pass/fail loopback test. Fault isolation is not performed. This is the same limitation currently imposed on inter-domain connections. Intermediate endpoints at the AIT and BNI cards do not support the tstcon feature. Tstdelay is also supported for the FRP and ASI in a non-integrated fashion similar to that of the tstcon command.
The IPX interface shelf supports the termination of Frame Relay connection segments to an AIT. DAX voice and low speed data connections are also supported, but they can't terminate on an AIT. The IPX interface shelf connects to the routing network via an AIT card on the IPX and a BNI card on the BPX routing hub.
Admission control and ForeSight rate control for IPX interface shelf terminated Frame Relay connections is performed at the FRP port on the IPX interface shelf. Only a single trunk line is supported between the IPX interface shelf and the routing network. Trunks on the IPX interface shelf linking other nodes are not supported.
Frame Relay type connections, remotely or locally terminated are supported on IPX interface shelves. Interface shelf connections for which both endpoints reside on the same interface shelf are not known to the routing network and will not route through the routing network.
IPX interface shelves support the following network management features:
The interface shelves attached to each hub must have unique names. Each interface shelf must also be assigned a unique IP address.
An interface shelf communicates with a routing hub over a new type of NNI. It is similar to the existing Frame Relay NNI in purpose and function, and is based on the ATM LMI message set described by Recommendation 2931, Annex G. A routing hub and interface shelf use this NNI to maintain a control session with each other. Any change to the status of the feeder trunk affects this control session.
Feeder trunks are the communication path between the routing hub and the Feeder. These feeder trunks are supported by the AIT trunk card on the IPX interface shelf and the BNI trunk card on the BPX routing hub. Feeder trunks are upped using the "uptrk" command. Feeder trunks must be upped on both the routing hub and the interface shelf before it can be joined to the routing network.
Once an IPX has been converted to an interface shelf, it can be joined to the BPX routing hub, by executing the addshelf command at the BPX routing hub. The addshelf command has the following syntax:
addshelf <trunk> <shelf_type>
trunk slot.port
shelf_type I (IPX/AF) or A (AXIS)
delshelf <trunk> | <shelf_name> deletes interface shelf
dspnode: | Displays feeder trunk status. BPX Hub nodes display the status of all attached Interface shelves. IPX interface shelves display a single status item, that of the attached BPX Hub node. |
dspalms | A new field, interface shelf alarms, shows a count of the number of interface shelves which are Unreachable, in Minor Alarm, or in Major Alarm. The nnn-A bit status failures for shelf connections are also shown. |
dspalms | A new field, routing network Alarms, shows a count of major and minor alarms in the routing network. Feeder A-bit connection status reported by Feeder NNI is shown in the "Connection A-Bit Alarms" field. |
dspnode: | Shows if the routing network is reachable and the attached BPX hub node. |
Uses existing commands
Parameters entered at SV+ when adding connection.
Parameters entered at SV+ when adding connection. Bandwidth performance monitored by viewing selected statistics at SV+ NMS.
Enabled an monitored via StrataView Plus.
Interface shelf and feeder trunk information is reported to StrataView Plus by the routing hub and interface shelf. StrataView Plus can virtually connect to any node in the network via a TCP/IP connection. The StrataView Plus Connection Manager is used to add, delete, and monitor voice and data connections for tiered networks with IGX hubs. It is also used to add, delete and monitor frame relay connections for tiered networks with BPX hubs. A sample of the Connection Manager GUI is shown in Figure 11-3.
Posted: Wed Jan 17 21:21:22 PST 2001
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