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Model #: 3C8951B
NETBuilder II WAN Extender 2T1, Refurbished
90 Day Warranty!
3Com 3C8951B NETBuilder II WAN Extender 2T1, Refurbished, 3C8951B
Provides transparent access to ISDN PRI and channelized T1 WAN services for easy software upgrades and configuration changes.
A WAN Extender provides virtual paths to be used for interconnecting remote NETBuilder devices to a central site NETBuilder II bridge/router running PPP. The interconnection is established using channelized T1 and E1 leased-circuit services, and switched 56 and ISDN PRI switched-circuit services.
WAN Extender Models
There are two WAN Extender models:
The WAN Extender 2T is intended for WAN networks that support the T1 interface. It provides two network interfaces, each of which can be independently connected to channelized T1, switched 56, or ISDN PRI services. The WAN Extender 2T supports 24 channels on each network interface for channelized T1 and switched 56 environments. It supports 23 B channels and one D channel on each network interface for ISDN PRI environments.
The WAN Extender 2E is intended for WAN networks that support the E1 interface. It provides two network interfaces, each of which can be independently connected to channelized E1 or ISDN PRI services. The WAN Extender 2E supports 31 channels on each network interface for channelized E1 environments. It supports 30 B channels and one D channel on each network interface for ISDN PRI environments.
How Virtual Paths are Created
The WAN Extender provides an RS-530 connector (called the local port), which connects to a NETBuilder II bridge/router high-speed serial (HSS) RS-449 module, to provide a synchronous link between the two devices. A 3Com proprietary interface protocol, called the WAN Extender/NETBuilder II Interface (WNI) Protocol, runs on this link.
The WAN Extender virtual paths are created automatically by the NETBuilder II bridge/router after it synchronizes with the WAN Extender over this link. Each virtual path can initiate a call to the WAN Extender and accept a call from the WAN Extender. There are three types of virtual paths: leased, DS0 dial, and H0 dial virtual paths.
Leased Virtual Paths
During the synchronization between the NETBuilder II bridge/router and the WAN Extender, the NETBuilder II bridge/router reads the profiles residing in the WAN Extender and sets aside a virtual path for each channelized T1 or E1 leased-line profile configured.
Although each virtual path is allotted one channel with a baud rate of 64 kbps when created, the channel expands to the size of the sum of all the channels specified in the profile when a connection is established.
The leased virtual paths occupy the bottom of the virtual path ID range.
DS0 Dial Virtual Paths
The virtual paths that are not used for leased lines are automatically available as dynamic paths in a dial-up path pool for interconnecting remote devices over switched ISDN or switch 56 lines.
The number of DS0 Dial virtual paths that are actually created is determined by the DialPathLimit setting, which considers the following information:
If the DialPathLimit setting is greater than the number of virtual paths that can be supported by the WAN Extender port, the number of virtual paths created will be the number of virtual paths supported, which is the smaller amount. For details on setting the DialPathLimit for DS0 virtual paths, refer toChapter 68.
The DS0 Dial virtual paths occupy the top of the virtual path ID range.
H0 Virtual Paths
The number of H0 Dial virtual paths created is determined entirely by the value set for the H0 path count with the -WE DialPathLimit parameter. The range of H0 virtual paths is 0 to 3. Each H0 virtual path is 384 kbps, or equal to six DS0 dial virtual paths (6 x 64 kbps = 384 kbps). H0 and DS0 virtual paths can run on the same port at the same time.
For details on setting the DialPathLimit for H0, refer toChapter 68.
For a complete description on ports and paths including how to number them, and for a description on how to set up ports and paths for a bridge/router using wide area interfaces, refer toChapter 1 and Chapter 2.
For information on setting up physical and virtual paths in dial-up pools for ISDN and switch 56 lines, refer toChapter 36.
How the WAN Extender Operates
The WAN Extender is managed by an external software application called the WAN Extender Manager, which runs under Microsoft Windows 3.1 or later on a PC. The PC connects to the console port on the WAN Extender.
The WAN Extender maps each WAN connection to a data channel and makes that data channel available to the NETBuilder II bridge/router through a virtual path. The NETBuilder II bridge/router operates as follows:
When a connection to a remote site is first made using the WAN Extender, the end-to-end data link is established using PPP. After the end-to-end link is established, various higher-layer PPP NCP negotiations occur, depending upon your configuration at either end of the link, and then network layer protocol connection is established.Figure 35-4 shows the WAN Extender connection.
NETBuilder II bridge/router PPP-based virtual ports can be used to establish bridging, routing, and Boundary Routing connectivity. The NETBuilder software operates the same way for WAN Extender virtual path-based ports as for any other point-to-point virtual port or port running PPP.
Figure 35-4 WAN Extender Connections From NETBuilder II to Remote NETBuilder Systems.
When a frame is received by the WAN Extender from the NETBuilder II bridge/router, frame forwarding proceeds as follows:
1 . The WNI protocol header is stripped.
2 . The data channel identifier is extracted from the WNI protocol header.
3 . The data channel identifier is mapped to the corresponding network channel.
4 . The frame is transmitted on the network channel.
When a frame is received by the WAN Extender on a network channel, frame forwarding proceeds as follows:
1 . The network channel is mapped to the corresponding data channel.
2 . The frame is prepended with a WNI protocol header containing a data channel identifier.
3 . The frame is transmitted on the WAN Extender-to-NETBuilder II bridge/router connection.
When either the NETBuilder II bridge/router or the WAN Extender are initialized, or any time the link between the two systems is connected or enabled, the two systems engage in a local link synchronization process. On the NETBuilder II bridge/router side, the path associated with the WAN Extender connection goes to an UP state. After synchronization, the data channels may also get established, and the virtual port associated with each data channel may also go to an UP state. The data channel that gets established, and its associated virtual port that goes to an UP state, depends on the type of network the WAN Extender is connected to and the NETBuilder II bridge/router ports configurations.