Application/Bandwidth Requirements Enterprise IT managers must continually manage costs and maintain reliable WAN infrastructures to meet their business goals. But, success in today's business climate also depends on the ability to overcome a more complex set of challenges to their corporate WAN. Enterprise IT managers are faced with the following: Geographically dispersed sites and teams that must share information across the network and have secure access to networked corporate resources. Mission-critical, distributed applications that must be deployed and managed on a network-wide basis. Furthermore, IT managers are faced with a combination of centralized hosted applications and distributed applications, which complicates the management task. Security requirements for networked resources and information that must be reliably available but protected from unauthorized access. Business-to-business communication needs, for users within the company and extending to partners and customers. QoS features that ensure end-to-end application performance. Support for the convergence of previously disparate data, voice, and video networks resulting in cost savings for the enterprise. Security and privacy equivalent to Frame Relay and ATM. Easier deployment of productivity-enhancing applications, such as enterprise resource planning (ERP), e-learning, and streaming video. (These productivity-enhancing applications are IP-based, and Layer 2 VPNs do not provide the basis to support these applications.) Pay-as-you-go scalability as companies expand, merge, or consolidate. Flexibility to support thousands of sites. Which services and applications indeed drive bandwidth requirements? You can deconstruct service categories as follows: Examples of interactive services include the following: Real-time conversational voice services Point-to-point interactive multimedia services, including interactive real-time voice, video, and other media (video telephony, interactive gaming, whiteboarding, and so on) Point-to-multipoint interactive multimedia services (videoconferencing, video chat, and interactive gaming) Push to Talk Instant messaging (IM) and messaging services (Short Message Service [SMS], multimedia messaging service [MMS], and so on) Group messaging Existing public switched telephone network (PSTN)/ISDN services (PSTN/ISDN emulation) Data communication services (data file transfer, fax, electronic mailbox, chat, and so on) Data-retrieval applications (telesoftware) Online applications (online sales for consumers, e-commerce, online procurement for commercials, and so on) Speech-enabled services Web browsing Transaction services (high-priority, e-commerce, and so on) Content-delivery services, also referred to as noninteractive services, include the following: Audio and video streaming Music and video on demand Digital TV channel distribution Financial information distribution Professional and medical image distribution E-learning Electronic publishing Sensor network services Push services Remote control/teleaction services, such as home application control, telemetry, alarms, and so on Broadcast/multicast services Over-the-network device management Some of the interactive and noninteractive services are as follows: VPN services Hosted and transit services for enterprises (IP Centrex and so on) Information services (movie ticket information, highway traffic reports, advanced push services, and so on) Location-based services Presence and general notification services (display of peers that a user can contact, their current status, and any service-related notifications) Proceeding with bandwidth requirements, let's look at an example under interactive services for audio (voice messaging) that is primarily unidirectional. Note Voicespecifically, voice over IP (VoIP)is symmetrical when provisioning the service. Two-way VoIP will be discussed shortly. A typical data rate is between 4 and 13 kbps. Web browsing via HTML requires about 10 kbps; with e-mail (server access), it takes approximately < 10 kbps. Table 3-1 summarizes these data rates and performance targets for interactive services. Table 3-1. Performance Targets for Interactive ServicesMedium | Application | Degree of Symmetry | Typical Data Rate/Amount of Data | Key Performance Parameters and Target Values |
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| | | | One-Way Delay (Response Time) | Delay Variation | Information Loss |
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Audio | Voice messaging | Primarily one-way | 413 kbps | < 1 sec for playback < 2 sec for record | < 1 msec | < 3 percent packet loss ratio | Data | Web browsingHTML | Primarily one-way | ~ 10 kbps | < 4 sec/page | | 0 | Data | Transaction serviceshigh-priority (for example, e-commerce and ATM) | Two-way | < 10 kbps | < 4 sec | | 0 | Data | E-mail (server access) | Primarily one-way | < 10 kbps | < 4 sec | | 0 |
In determining bandwidth for streaming services, the amount of bulk data transfer/retrieval and synchronization information is approximately < 384 kbps. A movie clip, surveillance, or real-time video requires 20384 kbps, as shown in Table 3-2. Table 3-2. Performance Targets for Streaming ServicesMedium | Application | Degree of Symmetry | Data Rate/Amount of Data | Key Performance Parameters and Target Values |
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| | | | Start-Up Delay | Transport Delay Variation | Packet Loss at Session Layer |
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Audio | Speech, mixed speech and music, and medium and high-quality music | Primarily one-way | 5128 kbps | < 10 sec | < 1 msec | < 1 percent packet loss ratio | Video | Movie clips, surveillance, and real-time video | Primarily one-way | 20384 kbps | < 10 sec | < 1 msec | < 2 percent packet loss ratio | Data | Bulk data transfer/retrieval, layout and synchronization information | Primarily one-way | < 384 kbps | < 10 sec | | 0 | Data | Still image | Primarily one-way | | < 10 sec | | 0 |
Finally, bandwidth requirements for conversational/real-time services, such as audio and video applications, include videophone, which is 32384 kbps; Telnet, about < 1 KB; and telemetry, approximately < 28.8 kbps. (See Table 3-3.) Table 3-3. Performance Targets for Conversational/Real-Time Services (Audio and Video Applications)Medium | Application | Degree of Symmetry | Typical Data Rates/Amount of Data | Key Performance Parameters and Target Values |
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| | | | End-to-End One-Way Delay | Delay Variation Within a Call | Information Loss[1] |
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Audio | Conversational voice | Two-way | 425 kbps | < 150 ms preferred[2] < 400 ms limit[2] | < 1 ms | < 3 percent packet loss ratio | Video | Videophone | Two-way | 32384 kbps | < 150 ms preferred < 400 ms limit Lip-synch: < 100 ms | | < 1 percent packet loss ratio | Data | Telemetry two-way control | Two-way | < 28.8 kbps | < 250 ms | | 0 | Data | Interactive games | Two-way | < 1 KB | < 250 ms | | 0 | Data | Telnet | Two-way (asymmetric) | < 1 KB | < 250 ms | | 0 |
[1] Exact values depend on the specific codec, but this assumes the use of a packet loss concealment algorithm to minimize the effect of packet loss.
[2] Assumes adequate echo control. Note that the values for VoIP depend on the codec in use as well as the Layer 2 overhead. For example, G.729A over 802.1Q/P Ethernet requires 37 kbps, whereas G.722 requires 322 kbps plus Layer 2 overhead. You need to factor in Layer 2 overhead in assessing the VoIP values. Service providers tend to bundle (propose multiple services with a target) to prevent customer churn. An example is a triple play where voice, data, and video may be offered as a bundle, perhaps over a single transport link. Bandwidth requirements for cable modem may be approximately 1 Mbps upstream to the provider and 3 Mbps downstream to the subscriber. You can additionally have prioritized traffic for VoIPtwo VoIP phone lines, per-call charging, and broadcast video MPEG 2, one-half D1, with one channel per set-top. Table 3-4 further illustrates service bundles with bandwidth requirements. Table 3-4. Triple-Play Service BundlesService Bundle | Service Elements |
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Internet with video on demand (VoD) Turbo Button | Broadband digital subscriber line (DSL) access pipe128 kbps up and 640 kbps down Turbo Button bandwidth on demand3 Mbps down Access control list (ACL)-based firewall Uncached VoD MPEG 2, one-half D1 Wholesale Layer 3 VPN access | Triple Play | Maximum transmission unit (MTU)-based ETTx10 Mbps bidirectional Best-effort transport Two VoIP phone lines, prepaid calling Broadcast video MPEG 2, one-half D1, one channel per home Residential grade Internet access | Triple Play Plus | Cable modemapproximately 1 Mbps up and 3 Mbps down Prioritized transport: VoIP stream Two VoIP phone lines, per-call charging Broadcast video MPEG 2, one-half D1, one channel per set-top Residential grade Internet access | Quadruple Play Platinum Service | Fiber to the Home (FTTH)10 Mbps bidirectional (up to 32 Mbps downlink) Residential gateway router with wireless Prioritized transport: VoIP stream and gaming Four VoIP phone lines, one emergency POTS line, unlimited calling Mobile phone integration with 802.11 Deep packet inspection network-based firewall Uncached VoD, MPEG 2, one-half D1 and MPEG 4, High-Definition Television (HDTV) 12 Mbps Broadcast video, MPEG 2, one-half D1 and MPEG 4, HDTV 12 Mbps Per-subscriber session Layer 3 VPN access |
The next section identifies requirements for backup and resiliency that are pivotal to Layer 3 services. You cannot assume that all interactive applications (especially those bundled into a service package) are equal in terms of priorities as negotiated by the customer with the service provider. Specifically, the fact that an application may be interactive does not mean it will be a high priority for a business. Customers negotiate priorities as part of the service-level agreement (SLA) discussions with a service provider. |