barcode scanner c# code project Figure 5-16 Examples of VoMPLS implementations in C#.NET

Recognizing PDF-417 2d barcode in C#.NET Figure 5-16 Examples of VoMPLS implementations

POTS & VOP VOP POTS Trunk Nextgen DLC Trunk Call Agent Packet Router or Switch Call Agent Packet Router or Switch Trunk

E911

E911

POTS & VOP VOP POTS TR-008/ GR-303 Nextgen DLC DS-1, DS-3, OC-3

POTS & VOP VOP POTS TR-008/ GR-303

said they had committed plans to deploy softswitches, and 666 percent of interoffice channels (IOCs) with 20,000 to 100,000 lines said they had committed deployment plans Among those who have deployed softswitches, the most popular applications cited were creating Internet offload (29 percent), replacing Class 4 switches (26 percent), and expanding revenue (19 percent) Among those not deploying softswitches, two of the more common reasons cited were that there was no compelling business reason to change and there were concerns about poor voice quality Some also said they still have a number of years to depreciate their current switches

This section highlights work efforts and issues that have been identified by standards-making bodies, particularly the IETF, for VoMPLS/VoIPoMPLS1 A VoIPoMPLS (vompls) Working Group has been proposed to define a framework for the operation of VoMPLS and identify requirements for possible extensions to existing protocols to support this application The Working Group would serve as a forum for discussing VoIPoMPLS technology integration issues Deliverables should include

VoIPoMPLS framework and informational Request for Comments (RFC) Mapping voice service definitions and packet transport performance requirements to MPLS and informational RFCs VoIPoMPLS call and device control protocol requirements, and informational RFCs VoIPoMPLS QoS/GoS parameter usage/requirements, best current practice (BCP), and RFCs

The consensus of the developers is that you should not attempt to modify application protocols (such as SIP, H323, and so on) to talk to the MPLS layer The idea is to keep a level of abstraction in the application layer (it should not know what technology it is running over) Any signaling should be asking for QoS, not specific implementations of QoS The latter would be too constraining for growth Some developers have considered adding circuit emulation in VoIPoMPLS/VoMPLS However, with the publication of PW documentation9 (see Section 57), circuit emulation can be relegated to these other technologies

VoIPoMPLS involves the use of MPLS as the efficient transport of VoIP services with predictable QoS/GoS in an IP/MPLS network

The desirable approach is to attempt to build VoMPLS on the work already done for VoIP For example, you could use existing call/device control

protocols (such as MEGACO, MGCP, H323, and SIP these are discussed in 7, Signaling Issues for Voice over MPLS ), existing voice encapsulation (such as RTP), and the existing IP over MPLS mechanisms along with existing signaling protocols (CR-LDP and RSVP-TE) The IETF has shown preference for having standard mappings of VoIP and IP over MPLS However, further work is necessary to combine call control and MPLS transport, including the exact details of mapping voice service requirements to MPLS The Internet Draft draft-kankkunen-vompls-fw01txt (covered in the next section) provides a VoMPLS framework that can be utilized as a starting point In general, VoMPLS needs to be signalingprotocol agnostic (both in terms of the MPLS signaling and the H323/ MGCP/SIP signaling The framework defines voice service requirements, but you want to avoid defining new protocols, if possible The VoIPoMPLS reference model10 (called VoMPLS by the authors of the draft, but it is really a VoIPoMPLS model) encompasses the following elements:

Intelligent endpoints (SIP phones and so on) Decomposed gateways Call agent Media gateways (MGs) MGCP/MEGACO Various gateways such as

Trunk gateway (TG) MPLS trunk-side PSTN (IMT with SS7) Access gateway (AG) Line-side gateway (LSG) Integrated Access Device (IAD) Signaling gateway (SG)

Single customer voice and data with Plain Old Telephone Service (POTS)/T1, channel associated signaling (CAS), and Integrated Services Digital Network (ISDN) signaling Multiple customer voice and data POTS/T1/E1/T3/E3 time-division multiplexing (TDM) with POTS, CAS, or ISDN

The signaling PDUs are expected to go over MPLS, but they would use normal IP over MPLS encapsulation The framework in question only focuses on the transport Data-plane requirements are as follows:

Provide a transparent path for VoIP bearers (RTP) Provide efficient transport (header compression)