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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 14-1). 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.
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.
Frame relay connections originating at IPX interface shelves and Frame Relay, ATM, CESM, and FUNI connections originating at MGX 8220 interface shelves are routed across the routing network via their associated BPX routing hubs.
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 14-2). The MGX 8220 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 MGX 8220 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 switch (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 Routing Hub | A BPX node in the routing network which has attached interface shelves. Also referred to as a hub node or BPX hub. |
MGX 8220 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 multiband 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 Cisco WAN Manager 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 OC-3) 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 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 Cisco WAN Manager 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.
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.
With tiered networks, IGX nodes on the edge of the network are configured as interface shelves and are connected to IGX nodes configured as router hubs. The interface shelves allow the network to support additional voice, data and Frame Relay connections without adding additional routing nodes. An example of 3-segment voice and data connections via an IGX interface shelf and IGX routing hubs is shown in (Figure 14-3). An example of a Frame Relay connection via an IGX interface shelf and routing hubs is shown in (Figure 14-4).
The following applies to IGX routing hubs and interface shelves:
The following applies to voice and data connections over IGX interface shelves:
The following applies to Frame Relay connections over IGX interface shelves via an IGX hub.
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 Shelf.
IGX Routing Hub | An IGX node in the routing network which has attached IGX interface shelves. Also referred to as a hub node or IGX hub. |
IGX Interface Shelf | A special configuration of an IGX switch that is connected as a shelf to an IGX routing hub. An IGX interface shelf is sometimes referred to as IGX A/F or feeder. The IGX interface shelf does not perform routing functions nor keep track of network topology. |
Feeder Trunk | Refers to a trunk which interconnects an IGX interface shelf with the routing network via an IGX routing hub. A feeder trunk is sometimes referred to as an interface shelf trunk. |
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 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.
Only IGX nodes are able to act hub nodes for IGX interface shelves for voice and data transport over the IGX tiered network. An IGX node, acting as a hub node, is not restricted from providing any other feature which is normally available on IGX nodes. An IGX hub supports up to 4 IGX interface shelves.
Connections within tiered networks consist of three distinct segments within each tier. A routing segment traverses the routing network, with an interface shelf segment at each end providing connectivity to the interface shelf end-point. Each of these segments are added, configured and deleted independently of the other segments. The Cisco WAN Manager Connection Manager provides management of these individual segments as a single end-to-end connection.
Interface shelves are attached to the routing network via an IGX node using a BTM E1 trunk. The connection segments within the routing network are terminated on IGX feeder trunks.
The feeder 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 CVM, LDM, and HDM.
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.
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 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.
IGX routing hubs are 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 Cisco WAN Manager Network Management topology displays. The colors of the icon and connecting trunks indicate the alarm state of each. Channel statistics are supported by CVM, HDM, and LDM endpoints. Trunk Statistics are supported for the feeder trunk and are identical to the existing IGX trunk statistics.
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 voice or data endpoint Routing Node or interface shelf. The existing IGX voice and data port loopback features are supported on the IGX interface shelf.
Tstcon is supported at the voice and data endpoints in a non-integrated fashion and is limited to a pass/fail loopback test. Fault isolation is not performed. Intermediate endpoints at the BTM cards do not support the tstcon feature. Tstdelay is also supported for the in a non-integrated fashion similar to that of the tstcon command.
The IGX interface shelf supports the termination of voice and data connection segments to a BTM. The IGX interface shelf connects to the routing network via a BTM and associated BMT-E1 back card on both the interface shelf and the IGX routing hub.
IGX 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 BTM trunk card on both the IGX interface shelf and the IGX 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.
An IGX node must be converted to an interface shelf by entering the appropriate command at the node. Once an IGX switch has been converted to an interface shelf, it can be joined to the IGX routing hub, by executing the addshelf command at the IGX routing hub. The addshelf command has the following syntax:
addshelf <trunk> <shelf_type>
trunk slot.port
shelf_type I (IGX/AF)
delshelf <trunk> | <shelf_name> deletes interface shelf
dspnode:
Displays feeder trunk status. IGX routing hubs display the status of all attached IGX interface shelves. IGX interface shelves display a single status item, that of the attached IGX hub node.
dspalms | The 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 interface shelf connections are also shown. |
dspalms | The field, routing network Alarms, shows a count of major and minor alarms in the routing network. Feeder Abit connection status reported by feeder NNI is shown in the "Connection Abit Alarms" field. |
dspnode: | Shows if the routing network is reachable and the attached IGX hub node. |
Uses existing commands.
Parameters entered at Cisco WAN Manager when adding connections.
Parameters entered at Cisco WAN Manager when adding connection. Bandwidth performance monitored by viewing selected statistics at Cisco WAN Manager NMS.
Since voice traffic is time sensitive, and low-speed voice connections can result in SGW cells being sent with only a single packet placed in the cell in order to avoid excessive delay between cells. It may be necessary to use the cnfcmb command on the interface shelves in order to configure the packet combining timeout rate for a particular application.
Enabled and monitored via Cisco WAN Manager.
Refer to the Command Reference manual for additional information on commands associated with tiered networks. The following is a list of most often used commands with IGX routing hubs and IGX interface shelves supporting voice and data connections.
addshelf
delshelf
dspnode
dspalms
dsptrks
addcon
dspcon
dspcons
cnfchdfm
cnfcheia
cnfcldir
cnfdchtp
cnfdclk
cnfict
addcon
cnfchadv
cnfchutil
cnfchkdl
cnfcos
cnfechec
cnfchgn
cnfcond
cnfrcvsig
cnfvchtp
cnfxmtisig
cnfcmb
Interface shelf and feeder trunk information is reported to Cisco WAN Manager by the routing hub and interface shelf. Cisco WAN Manager can virtually connect to any node in the network via a TCP/IP connection. The Cisco WAN Manager 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 14-5.
Posted: Sun Jan 14 18:45:09 PST 2001
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