Bandwidth Optimization Solutions: Building Cost-Effective Protection Networks
Executive Summary Ensuring service and revenue generation in the event of technical failures or external events presents challenges for telecom carriers and service providers building critical failure protection network solutions. Critical failure protection backup minimizes the impact of these failures or events and can be implemented with various levels of redundancy, ranging from internal redundancy on a per-equipment basis up to fully redundant networks, including geographic redundancy network architectures. Typically, the costs involved in implementing redundant systems as effective backup solutions duplicates the costly investment demanded for just a single transmission network. This application note explains how the Dialogic Media Gateway and Dialogic 4000 EDGE Media Gateway can enable carriers and service providers to build cost-effective and highly reliable backup solutions for their transmission networks, allowing significant CAPEX and OPEX savings and short implementation cycles. Two example solutions are described for using these Dialogic 4000 Media Gateways in backup network solutions, both allowing telecom carriers and service providers to minimize expenses and/or better utilize the invested (deployed) transmission infrastructure by expanding the trafficcarrying capability and improving the overall Quality of Service performance. 2
Table of Contents Introduction............................................................................4 Network Protection Overview.......................................................4 Network Protection Models..........................................................5 Network Protection Reliability and Cost Challenges......................................7 Building Cost-Effective..............................................8 The Standalone Static Trunking Operating Mode Characteristics..............................8 Solution 1 Gateway Network Solution.............................11 Solution 2 Network Solution with Load-Sharing Mode..............................16 3
Introduction Telecom carriers and service providers worldwide have been challenged to build critical failure protection network solutions to ensure their services (and resulting revenue) continue in the event that one or more critical segments of their telecom infrastructure go out of service due to technical failure or an external agent (for example, accident, earthquake, terror attack, and so on). In order to minimize the impact should these risks actually occur, different levels of redundancy can be implemented, ranging from internal redundancy on a per-equipment basis up to fully redundant networks including geographically redundancy network architectures. Specifically, for the transmission networks that carry the interswitch traffic between 2G mobile (for example, Mobile ing Center [MSC]) and/or PSTN switches (for example, Class 4), despite the technical and operational benefits of highly resilient network architectures (for example, SDH/SONET dual-ring), maximum overall reliability calls for separating the two different transmission networks. However, building an effective backup network solution typically duplicates the investment demanded for a single transmission network alone, which can be high considering the multiple cost components of a network deployment project. Dialogic Media Gateway and Dialogic 4000 EDGE Media Gateway (collectively, Dialogic 4000 Media Gateways) provide an unparalleled opportunity for operators to build a fully featured backup transmission network and to achieve the high overall reliability target for their mobile and/or wireline interswitch traffic at greatly reduced CAPEX, while providing rapid infrastructure rollout, minimizing OPEX, and maintaining high-quality services. This application note describes characteristics and benefits to the operator of backup network solutions that use 4000 Media Gateways. It also introduces backup transmission networks concepts, including typical topologies and operating characteristics, and presents two examples of backup transmission network solutions that can be built using 4000 Media Gateways. Network Protection Overview Mobile 2G switches (for example, MSC) and wireline PSTN switches (for example, Class 4) are interconnected with other mobile and/or PSTN switches through long-distance international or domestic links (interswitch trunks) implemented over one or more transmission networks. Figure 1 shows a simplified example of a transmission network providing interconnection to MSC and/or PSTN switches. This figure shows the TDM trunks through which the switches are connected to the transmission network that carries the interswitch traffic (depicted by solid line arrows) between them. 3 5 Trunks Trunks Trunks Trunks Trunks Transmission Network Interswitch Traffic Figure 1. Interswitch From a network planning, deployment, and operations perspective, as well in view of CAPEX and OPEX considerations, it is important to keep in mind that although the transmission network is depicted as a single schematic entity (a cloud), the physical implementation of typical transmission links between any pair of switches can include one or several network segments, where each network segment can use a different transport technology (for example, fiber, microwave radio, satellite) and different transmission link hierarchical levels (for example, E1, T1, DS3, SDH/SONET). 4
The ownership of the network segments is also an important factor to consider. The various network segments can be owned by the same operator (which may or may not be the operator that owns one or more of the switches) or by different operators or carriers (for example, leased lines). It should be noted that when the end-to-end transmission link between a pair of switches includes several transmission network segments, the overall reliability (that is, the service continuity characteristics) of the complete transmission link between the switches will be determined by the least reliable network segment that is between them. Under normal (that is, no failure) transmission network conditions, the depicted network carries the traffic between the switches. However, in case of a failure of the interswitch transmission network, part or all of the traffic-carrying capability of the network could be affected, resulting in traffic between two or more switches not being transported. Network Protection Models To overcome traffic interruptions when traffic-affecting failure conditions occur in the interswitch transmission network, the operator can follow different solution approaches: Use alternative routing on the mobile switches or PSTN switches, and route the traffic through other trunks and switches (not shown in Figure 1). Typically, due to limited transmission and switching resources, a Figure 1 solution can handle a small percentage of the total required traffic load demand. Use a two-network switch interconnection solution by building a redundant (that is, backup) transmission network in addition to the primary transmission network and connecting the switches simultaneously to both networks. Such a solution can be implemented by interconnecting the switches either through a dual-ring SDH/SONET network or through a pair of separate networks (for example, primary and backup transmission networks). Figure 2 provides an example of a simplified diagram of this type of solution architecture, where each switch is connected to the primary network through primary trunk links and to the backup network through separate backup trunk links. When using a two-network protection solution, the traffic between any pair of switches is normally carried over the primary network. In case of a failure on the primary network, this traffic is carried over the backup network. Operators can build a backup transmission network using their own transmission infrastructure, or they can lease one from one or more other operators. Trunk Links 3 5 Trunk Links Figure 2. and s 5
Figure 3, Figure 4, and Figure 5 are examples depicting the traffic handling flows for different primary network operating conditions. Figure 3 is an example of the interswitch traffic flow (depicted by solid line arrows) under a normal primary network operating condition. When the primary transmission network has no traffic-affecting failure, the traffic is fully transported through it. In the event of a failure that affects the traffic-carrying capability of the primary transmission network, the traffic between some or all of the switches is transported through the backup network, as shown in Figure 4 and Figure 5. Figure 4 is an example of the traffic flow for a case in which all the primary network links are affected, and accordingly all the traffic is transported through the backup network. Figure 5 is an example of the traffic flow where only some interswitch links on the primary network are affected (between switches 2 and 4) and their traffic is carried over the backup network. The interswitch traffic between other switches is not affected and is transported over the primary network (between switches 1, 3, and 5). For illustrative purposes, Figure 5 shows simplified examples only. Not shown is the traffic between switches 1, 3, and 5 and switches 2 and 4; that traffic can be carried either through the primary network or through the backup network, depending on the location of the failure(s) in the primary network. Trunk Links 3 5 Trunk Links Interswitch Traffic Figure 3. Traffic Handling for Fully Available Network 6
Trunk Links 3 5 Interswitch Traffic Trunk Links Figure 4. Traffic Handling for Fully Unavailable Network Trunk Links 3 5 Trunk Links Interswitch Traffic Figure 5. Traffic Handling for Partially Available Network Network Protection Reliability and Cost Challenges For maximum overall reliability, there can be layout separation between the primary transmission network and the backup network, whether the transmission network protection architecture is dual-ring SDH/SONET, or separate primary and backup networks. Building a backup network typically duplicates the costly investment for a primary network deployment project alone (for example, cable duct laying, cable construction, right of passage, radio links and associated repeaters, coordination with and authorization from government offices and service companies). 7
Fortunately, telecom operators and service providers requiring backup protection transmission networks can position themselves to benefit from bandwidth optimization systems that use Gateway and/or 4000 EDGE Gateway products. By using these 4000 Media Gateways to build fully featured and cost-effective backup transmission network solutions, they can stand to achieve the high overall reliability target for their interswitch traffic networks at a greatly reduced CAPEX budget, while providing rapid infrastructure rollout, minimizing OPEX, and maintaining high-quality services. The following sections describe examples of solutions that incorporate 4000 Media Gateways. Building Cost-Effective The main components of the proposed backup protection network solution examples are a Dialogic Gateway and an 4000 EDGE Gateway operated in static trunking mode. In a static trunking application, 4000 Media Gateways are deployed at both ends of the long-distance links that interconnect 2G mobile (for example, MSC) and/or PSTN (for example, Class 4) switches, performing bandwidth optimization algorithms on the telephony and signaling interswitch traffic. The 4000 Media Gateways bandwidth optimization algorithms allow a significant reduction in the required bandwidth (typically 88% to 94% bandwidth savings after the solution is deployed) while also providing high voice quality and highly reliable switch signaling (for example, SS7, PRI, CAS) performance. The following sections briefly describe 4000 Media Gateways standalone static trunking operation mode; and how 4000 Media Gateways operating in static trunking mode can be used when it is desired to build cost-effective and highly reliable backup network protection solutions. The Standalone Static Trunking Operating Mode Characteristics The following two 4000 Media Gateways products are discussed in this application note: Media Gateway ( Gateway) For medium and heavy traffic applications (several thousands of simultaneous calls) and support for E1, T1, DS3, STM1, and OC-3 TDM network interfaces 4000 EDGE Media Gateway ( 4000 EDGE Gateway) For lower-volume traffic applications of up to 496 simultaneous calls and support for E1 and T1 TDM network interfaces These 4000 Media Gateways use the same core technologies and provide the same traffic handling, bandwidth savings, and service quality performance, including: Significant bandwidth savings (typically 88% to 94%) for short Return on Investment (ROI) period High-quality voice services and successful fax and modem calls handling for end-user satisfaction Reliable detection and transport of H.324 video calls Bandwidth-efficient and robust signaling transport (SS7, PRI, CAS) for maximizing call completion rate Reliable echo cancellation for all supported calls Smart end-to-end compression algorithm for providing high voice quality in call paths including two or more bandwidth optimization hop segments 8
Figure 6 is an example of a simple static trunking of a two site application, including a pair of Gateways carrying the longdistance traffic between two MSC or PSTN switches. This example configuration has the following characteristics: The Gateways are connected to the MSC or PSTN switches through standard TDM trunk links (for example, E1, T1, DS3, STM1, or OC-3). The TDM trunks carry the standard (that is, PCM format) telephony signals (for example, voice, fax, and modem) and signaling (for example, SS7, PRI, CAS). The solid line arrows depict this standard interswitch traffic. The interconnection between the Gateways (called the bearer link) is typically implemented over standard TDM transmission links. Bearer links can be optionally implemented over IP networks. At the Gateway, the standard interswitch traffic received from the switches over the TDM trunk links (solid line arrows) is processed using high quality and highly reliable bandwidth optimization mechanisms, and the optimized interswitch traffic payloads (dashed line arrows) are carried over the bearer link (using a long-distance transmission network) to the Gateways at the distant site, where the received payloads are processed back to the original PCM format and transmitted to the associated MSC or PSTN switch. The 4000 Media Gateways bandwidth optimization algorithms allow for a significant reduction in the required bandwidth (typically 88% to 94% bandwidth savings) while also providing high voice quality and highly reliable signaling (for example, SS7, PRI, CAS) performance. It should be stressed that in a static trunking application, the 4000 Media Gateways execute the traffic handling tasks automatically as standalone terminals, without requiring additional external call control or signaling systems. Dialogic 4000 PRO Media Gateway 88% - 94% Bandwidth Savings Optimized Traffic (Bearer Link) TDM Trunks TDM Trunks Original Interswitch Traffic Optimized Interswitch Traffic Figure 6. Two-Site Static Trunking Application In addition to what is shown in the simple two-site application example of Figure 6, an 4000 Gateway can simultaneously support static trunking operation with multiple 4000 Gateways installed at different remote sites. Figure 7 is an example where each Gateway supports static trunk operation with multiple distant Gateway terminals. The Figure 7 solution example has the following characteristics: Each Gateway independently processes and optimizes the traffic carried between its unit and each one of the remote Gateways, providing a significant bandwidth savings (typically between 88% and 94%) while also providing high quality and reliable traffic transport performance. Each Gateway independently supports the bearer link(s) between its unit and one or more of the remote Gateways. 9
TDM Trunks TDM Trunks Dialogic 4000 PRO Media Gateway TDM Trunks TDM Trunks 88% - 94% Bandwidth Savings Original Interswitch Traffic Optimized Interswitch Traffic TDM Trunks TDM Trunks Figure 7. Multiple Site Static Trunking Application It should be noted that although Figure 6 and Figure 7 show Gateway terminals only, an actual application could include a combination of Gateway and 4000 EDGE Gateway terminals, or 4000 EDGE terminals only. For example, an Gateway can be deployed at sites requiring the support of a large number of trunks, and an 4000 EDGE Gateway can be deployed at sites requiring support for a small number of trunks. An example of a solution using only 4000 EDGE Gateway terminals would be one in which multiple low-traffic rural or island switch sites are interconnected through thin-route satellite links. 4000 Media Gateways can be connected to transmission networks using supported TDM interfaces and network topologies. Figure 8 is an example of multiple Gateway terminals and mobile and/or PSTN switches interconnected through SDH transmission links. In the Figure 8 example, the trunk links carrying the traffic between the MSC and/or PSTN switches and the Gateway terminals, as well as the bearer links carrying the optimized traffic between the Gateway terminals, are implemented on the SDH transmission network. Dialogic 4000 PRO Media Gateway ADM 4000 PRO 4000 PRO ADM 4000 PRO ADM SDH ADM ADM 4000 PRO 4000 PRO ADM Figure 8. SDH-based Network Topology 10
In the Figure 8 configuration, the Gateway provides operators with the flexibility to define the allocation of trunk and bearer links to best match their planning and budget targets. For example, one operator can allocate different STM1 interfaces and links for trunk and bearer traffic, whereas another can allocate some E1 spans within an STM1 interface and link to carry trunk traffic, and allocate other E1 spans within the same STM1 interface and link to carry bearer traffic. Solution 1 Gateway Network Solution Figure 9 is an example of a backup network solution in which Gateways are connected between the MSC or PSTN switches and the backup transmission network that provides operational protection to the primary transmission network. The Gateways are configured to operate in Static Trunking mode, as described in The Standalone Static Trunking Operating Mode Characteristics section of this application note. In this network protection solution, the traffic between a pair of switches is normally carried over the primary network. In case of a failure in the primary network, the traffic to be carried through the failed links is routed by the switches to the associated Gateway terminals, and this traffic is optimized by these terminals and transported over the backup network. The following sections describe three different examples of primary transmission network operating conditions for traffic handling flows for a Solution 1 example. Dialogic Media Gateway 3 5 Figure 9. Solution 1 Architecture 11
Solution 1 Traffic Flow for Fully Available Network When the primary transmission network has no traffic-affecting failure, the traffic between the switches is fully transported through the transmission network. Figure 10 is an example of the interswitch traffic flow (solid line arrows) under a normal primary network operating condition. Dialogic Media Gateway 3 5 Original Interswitch Traffic Figure 10. Solution 1 Traffic Flow when Network is Fully Available 12
Solution 1 Traffic Flow for Fully Unavailable Network In the case of a critical failure in the primary transmission network that makes it totally unavailable, in the Figure 10 example the traffic is automatically routed by the switches through the Gateway terminals, which optimize and transmit the optimized traffic over the backup network. Figure 11 is an example of the interswitch traffic flow transmitted from the switches to the Gateways (solid line arrows) and the optimized traffic flow transmitted between the Gateways over the backup network (dashed line arrows). Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 11. Solution 1 Traffic Flow when Network is Fully Unavailable The highly reliable compression mechanisms of the Gateway terminals provide that the telephony signals (for example, voice, fax, modem) and signaling (for example, SS7, PRI, CAS) are carried over the backup network with minimal bandwidth requirements (88% to 94% bandwidth savings), thus allowing substantial savings on equipment and operations, together with the high-quality service necessary to avoid negatively impacting a company s competitiveness and revenue generation. In this example, it is assumed that all the primary network links are unavailable and accordingly that all the traffic is transported through the backup network. 13
Solution 1 Traffic Flow for Partially Unavailable Network In case of a failure in the primary transmission network that makes it partially unavailable, the traffic to be carried through the failed links is routed by the corresponding switches to the associated Gateway terminals, which optimize and transmit the optimized traffic over the backup network. Figure 12 and Figure 13 are examples of two cases of partially unavailable network operating conditions, and examples of traffic flows. In both cases, some primary network links are affected, and accordingly the corresponding traffic is transported through the backup network. The traffic of the non-affected primary network links is transported over the primary network. These two figures show the interswitch traffic flow transmitted from the switches to the Gateways or directly to the primary network (solid line arrows) and the optimized traffic flow transmitted between the Gateways over the backup network (dashed line arrows). Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 12. Solution 1, Case 1 Traffic Flow when Network is Partially Unavailable 14
In the example depicted in Figure 12 (Case 1), for a given switch, all its traffic is transmitted through the backup network (switches 1, 3, and 5) or through the primary network (switches 2 and 4). In the example in Figure 13 (Case 2), for a given switch, the links that carry traffic to certain switches are affected, and the links that carry traffic to the other switches are not affected. Accordingly, part of the switch s traffic (to certain routes) is carried through the primary network, and part of its traffic (to other routes) is carried through the backup network. In the example in Figure 13, the traffic between switches 2 and 5 is carried over the primary network, whereas the traffic between switches 1, 3, and 4, as well as the traffic between switches 1, 3, and 4 and switches 2 and 5, is carried over the backup network. Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 13. Solution 1, Case 2 Traffic Flow when Network is Partially Unavailable 15
Solution 2 Network Solution with Load-Sharing Mode In Solution 1, the backup network architectural solution is based on a network protection approach comprising a primary transmission network and a backup transmission network, where the backup network is used only when a failure takes place in the primary network. In Solution 1, interswitch traffic is either directly transmitted over the primary transmission network (normal primary network condition), or optimized and transmitted over the backup transmission network if the primary transmission network has a failure condition. For Solution 2, an alternative network architecture and traffic handling solution can be implemented, as shown in the example in Figure 14, where the interswitch traffic is always optimized. When the primary network has no traffic-affecting failure, the optimized traffic is split among both networks, primary and backup, and carried in load-sharing mode. This solution allows an enhanced utilization of the bandwidth resources, in turn allowing the operator to expand the traffic-carrying capability of the primary network with minimal CAPEX and OPEX. Dialogic Media Gateway 3 5 Figure 14. Solution 2 Architecture The following sections describe three different examples of primary transmission network operating conditions for Solution 2 s traffic handling flows. 16
Solution 2 Traffic Flow for Fully Available Network Figure 15 is an example of the interswitch traffic flow when the primary network has no traffic-affecting failure. The original traffic is transmitted between the MSC or PSTN switches and the Gateways (solid line arrows), and the optimized traffic (dashed line arrows) is split among the primary and the backup network and carried in load-sharing mode. This solution allows significant bandwidth savings on the primary network. Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 15. Solution 2 Traffic Flow when Network is Fully Available 17
Solution 2 Traffic Flow for Fully Unavailable Network In case of a critical failure in the primary transmission network that makes it unavailable, all of the optimized traffic from the Gateway terminals is transmitted over the backup network. Figure 16 is an example of the interswitch traffic flow transmitted from the switches to the Gateways (solid line arrows) and the optimized traffic flow transmitted between the Gateways over the backup network (dashed line arrows). Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 16. Solution 2 Traffic Flow when Network is Fully Unavailable In the Figure 16 example, all the primary network links are affected; accordingly, all the traffic is transported through the backup network. 18
Solution 2 Traffic Flow for Partially Unavailable Network In case of a failure in the primary transmission network that makes the primary network partially unavailable, the corresponding optimized interswitch traffic is transmitted between Gateways over the backup network. Figure 17 is an example of the interswitch traffic flow transmitted from the switches to the Gateways (solid line arrows) and the optimized traffic flow transmitted between the Gateways over the backup network (dashed line arrows). In this example, some primary network links are affected; accordingly, the corresponding traffic is transported in its entirety through the backup network (long dashed line arrows). The traffic of the non-affected primary network links is split among the primary and backup networks and carried in loadsharing mode (short dashed line arrows). Dialogic Media Gateway 3 5 Original Traffic Optimized Traffic Figure 17. Solution 2 Traffic Flow when Network is Partially Unavailable 19
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