- VISM Overview
- MPLS Overview
- RPM Overview
- VISM Voice Features
- Voice Connections
- Voice Over AAL2 Network
- VoIP Network
- Voice Over ATM Services on the VISM
- Digital Signal Processors
- VISM Clocking
- Commands for Adding, Configuring, and Displaying Voice Connections
- Commands for Verifying Voice Connections
- Introduction to Multiprotocol Label Switching
- The Problem of Persistent Loops Due to Protocol Conflicts
- Cisco WAN Switches with MPLS Support
- Setting Up MPLS on the MGX Switch
- MPLS and Virtual Private Networks Using the Route Processor Module
- RPM Memory Locations
- RPM Port Numbering
- Cisco IOS Command-Line Interface
- Commands for Configuring the RPM
- Commands for Setting Up the RPM ATM Switch Interface
- How to Set Up the RPM
- Configuring Subinterfaces
- PVCs on the RPM
- Commands for Configuring Subinterfaces
- Commands for Creating and Displaying PVCs on the RPM
- Creating Connections on the RPM
- Summary
This chapter is from the book
This chapter is from the book
This chapter is from the book
Voice Over AAL2 Network
The Voice over AAL2 (VoAAL2) solution with VISM is used to replace trunk lines between voice switches. A separate PVC is needed for voice channels destined for a specific remote endpoint. Signaling information is sent using one of two methods: CAS signaling is sent with voice traffic, and CCS signaling is sent on a separate AAL5 connection. Except for signaling extraction and insertion, the VISM does not participate in the signaling process.
As described with the previous VISM features, the VISM supports standards-compliant AAL2 adaptation for the transport of voice over an ATM infrastructure with AAL2 trunking mode.
Here are the major features of AAL2 trunking mode:
The voice payload is transported across the packet network using an AAL2 PVC. Multiple voice channels are supported in a single PVC using CIDs (channel identifiers) and subcell multiplexing. A single VISM supports up to 64 AAL2 PVCs.
Call setup through a call agent is not supported. All bearer paths are provisioned using either the command-line interface (CLI) or Simple Network Management Protocol (SNMP).
If CAS signaling is used, the signaling is transported across the packet network along with the voice payload using AAL2 Type 3 packets.
CCS signaling channels are supported and are transported across the packet network using a separate AAL5 PVC.
In AAL2 trunking mode, VISM provides a set of AAL2 trunks carrying the voice payload over the packet network. Figure 22-6 shows a high-level view of VoAAL2 between two voice switches.
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Figure 22-6 VoAAL2 with VISM
Voice payloads and CAS signaling are transported across the AAL2 trunk. If a channel is configured for CCS signaling, the signaling is transmitted by extracting HDLC frames and forwarding them over preprovisioned AAL 5 virtual circuits (the voice payload is still transmitted using AAL 2).
In this role, the VISM merely passes signal traffic to and from the trunk.