Home > Articles > Cisco Network Technology > IP Communications/VoIP > VoIP Deployment Models in Service Provider Networks

VoIP Deployment Models in Service Provider Networks

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Oct 5, 2010.

Chapter Description

This chapter gives you an understanding of how Voice over IP (VoIP) is deployed in service provider (SP) networks by describing a use case in which the VoIP infrastructure and the transport and the access are managed by an SP.

Common Issues and Problems When Deploying IP-Based Telephony Services

This section discusses some of the common issues encountered by providers when deploying IP-based telephony services over their IP infrastructure. The issues are ongoing and need to be maintained for the life of the VoIP service.

Convergence-Related Issues

As discussed earlier in the chapter, VoIP is primarily deployed on converged IP networks. Recall that a converged network is defined as a network capable of transmitting all types of traffic including data, voice, video, and images. Most existing SP IP networks have been designed to carry primarily data traffic and are geared toward data applications such as email, web traffic, and so on. The VoIP traffic is sensitive to time, the packets need to be delivered within a specific time period, and the network needs to facilitate this through various mechanisms. Deploying VoIP in such networks introduces new challenges for the SP's operations staff that needs to carefully monitor the health of their network and work closely with other groups in the company to provide VoIP continuity across the network. For example, in a DOCSIS/IP network, different groups are responsible for managing and maintaining the HFC/RF network, and another group is responsible for the IP network. Although these groups have totally different job responsibilities and technical background, they both need to work closely to provide quality service to the cable providers' customers.

Issues in Media Affecting Quality

Unlike circuit-switched voice networks that have dedicated paths and fixed bandwidth for every call, VoIP networks can share the same resources for data and voice traffic. In some cases, link overutilization or poor media characteristics (noise on RF links) can result in dropped or delayed packets.

VoIP traffic or packetized voice traffic needs to be sent at fixed intervals at the transmitting end so that the receiving end can predictably receive these packets and decode them. Because of serialization delay at the transmitting end, network delay, and jitter, these packets can arrive at the receiving end at varying intervals.

VoIP endpoints use dejitter buffers to compensate for variance in delay during media packet transmission through Real-time Transmission Protocol (RTP). If the dejitter buffers overflow because of excessive delay, this can impact voice quality so that it might sound like a robotized voice. Excessive packet loss can cause issues such as choppy voice quality.

Other voice quality issues can be caused by things such as codec mismatch, where each endpoint uses a different codec (for example, G.711 versus G.729).

Issues in Signaling Affecting the Services and Features

Voice signaling protocols such as MGCP, NCS, and SIP carry important information about how voice calls need to be set up, how resources need to be allocated, and how QoS needs to be provided to the voice traffic.

Network congestion and resource oversubscription can adversely affect voice-signaling protocols that can affect the services and features these protocols support. Voice signaling–related issues can also be caused because of improper network design and misconfigurations.

If voice signaling gets impaired, it can have a range of effects from delayed call setup to failed call setup, from loss of dial tone to one-way voice, and so on.

These issues are often caused by interoperability issues between equipment from different VoIP vendors. Even though they claim to be compliant with protocol standards, they can still have varying implementations of protocol stacks in their products.

IP Routing–Related Issues

SPs might deploy various routing protocols such as Open Shortest Path First (OSPF), Intermediate System–to–Intermediate System (ISIS), Border Gateway Protocol (BGP), and so on for providing IP connectivity across their infrastructure. These routing protocols carry network information that is used for calculating the most efficient path for carrying customer traffic through the SP network.

The failure of these routing protocols can result in a loss of IP connectivity or degraded service for the SP's customers. Such failures can severely impact VoIP traffic. If a link or node in the SP network fails, causing the routing protocol to reconverge or recalculate its routes, the voice traffic might be sent over a low-bandwidth link that can cause voice degradation. For this reason, the SP needs to carefully tweak routing protocol timers to make sure that the network can converge in a timely manner, minimizing the impact to VoIP traffic.

High Availability and Convergence for Business Continuity

A lot of non-Tier1 and non-Tier2 SPs might not implement redundancy in their network when deploying data-only applications. This becomes a critical issue when VoIP is deployed in such networks. A failed router or switch in the SP core network can cause loss of service to data and voice customers.

Therefore, it is critical for the SP to implement redundancy in the network so that a loss of a link or node does not result in loss of service to its users. Implementing redundancy in the network might involve deploying hardware and software with high-availability features. Redundancy is implemented at a device level where the hardware has active and standby components. If the active component fails, the standby can take over without causing a network outage. Redundancy is also implemented at a link level where multiple links provide connectivity to other network resources, so if a link fails, the other links can carry all the traffic. In some cases, the SP might also choose to deploy redundancy in the form of additional hardware that can take over if certain devices in the network fail. Redundancy can also be implemented in software, such as in routing protocol implementations, which can provide alternate routes through the SP network if the primary/best path fails.

The focus here is not the type of redundancy, or the various specific challenges, but the impact of the failures. Thus, effectively tracking key metrics can help in sustaining the VoIP service. These metrics can range from protocol to Layer 2/3 and h/w uptime metrics.

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020