Deploying Cisco® Voice over IP Solutions

284 Chapter 7: Managed Multiservice Networks and Packet Voice VPNs

• Customers who would prefer to outsource the management of their WAN.

• Customers who need to improve the efficiency and reduce the overall cost of their

networks. Specifically, retail and financial enterprises have benefitted from MMS

networks.

Peer-to-Peer Managed Multiservice Networks

A peer-to-peer MMS network is a network that has the same architecture as the older, data-

only networks, as shown in Figure 7-1. Each customer has data and voice traffic coming in

from edge CPE devices resident at their various customer sites.

Figure 7-1 Peer-to-peer MMS network architecture.

This architecture is designed primarily for customers that are outsourcing their enterprise

WANs. Note that the traffic on the network is from one Company X location to another

Company X location. A peer-to-peer MMS network is not well suited for SP value-added

services offered on common or shared equipment accessed by multiple end customers such

as voice VPNs or Unified Messaging services. In contrast, there is additional secure traffic

on a voice VPN between different customers and traffic from customers to shared servers

that provide services such as Unified Messaging or web applications.

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Peer-to-Peer Managed Multiservice Networks 285

Peer-to-Peer MMS Network Elements

A peer-to-peer MMS network has a relatively simple architecture consisting of the

following:

• CPE router(s)—This is typically a Cisco 2600 series, 3600 series, or MC3810

concentrator. Customer data traffic enters the SP network through this router, which

is typically connected by an Ethernet or Token Ring LAN on the customer side, and

a Frame Relay, ATM, or IP connection on the SP side.

The customer PBX, phone sets, and/or key system are also connected to this router

and are responsible for originating and terminating the voice traffic. Earlier

incarnations of MMS networks frequently used Voice over Frame Relay (VoFR) and

Voice over ATM (VoATM) technologies. Many of the carriers that currently offer

VoFR or VoATM solutions are planning or considering VoIP-based services, to either

replace or augment their existing services.

A variation on CPE voice traffic that is also under consideration is IP telephony. In

this architecture, the CPE router doesn’t originate or terminate the voice. IP phones,

softphones, and/or other H.323, SIP, or VoIP endpoints originate and terminate voice

traffic, and the CPE router aggregates and routes the traffic destined for the SP

backbone. More challenges (billing, security, call admission control, and so on) exist

with this design than with traditional telephony equipment connecting via the CPE

router (which also acts as the voice gateway).

• SP Points of Presence (POP)—These are geographically dispersed aggregation

points of CPE traffic that typically use Frame Relay or ATM connectivity.

• SP backbone—The backbone carries traffic between the POP, usually using an ATM-

based, high-speed network (Frame Relay is more often used as a CPE access

technology).

• Network management—The premise of an MMS network is that it can be managed.

SPs run elaborate Network Operations Centers (NOCs) where the status of the

network is monitored and alarms are raised when outages occur. SPs can use Cisco

management platforms such as CiscoWorks, or they can write their own applications

and use various products as elements in their network management scheme.

There is also a network management overlay network, typically using a separate PVC

to the CPE equipment and separate IP addressing, to carry SNMP and remote-access

traffic to allow the SP to gather the information necessary to manage the network.

• Billing—This function is key to the SP’s ability to charge accurately for services

rendered. Peer-to-peer MMS networks tend to use a relatively simple, flat-rate basis

for billing, such as CPE access bandwidth or committed information rate (CIR).