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White Paper
Cisco IP Transfer Point Multilayer Short
Message Service Routing Solution
With the increased popularity of the Short Message Service (SMS), new SMS applications are being developed and deployed that demand a significant increase in the capacity of the traditional Signaling System 7 (SS7) network infrastructure. One such application is a televoting audience interaction service that allows a subscriber to send an SMS message containing a real-time vote pertinent to a broadcast event such as a television or radio game show.
The message load generated from such events is typically "bursty," generating a high volume of messages for a specified duration. Higher link, server, and switch capacities are required to meet subscriber demand, and these extreme traffic bursts can result in congestion, denial of service, and lost messages. As such, it is imperative that the signaling systems are enabled to provide traffic direction with more granularity than ever before. It is also important that such a solution can implement quality of service (QoS) that can differentiate between message types during periods of extreme congestion.
The Cisco® IP Transfer Point provides a cost-effective solution to intelligently route SMS messages based on the application or service to which they are destined.
To route a message in such a manner requires that the Cisco ITP use information stored within the network and application layers of the message to select the most appropriate destination for handling the transaction. This allows new SMS applications to be inserted in an operator's network without significant upgrade requirements placed on the existing Short Message Service centers (SMSCs). The Cisco ITP SMS offload solution can also be deployed to avoid the need for additional signaling transfer point (STP) capacity. Figure 1 depicts some of the ways in which the Cisco ITP can separate SMS traffic patterns for optimal delivery.
Figure 1
Generic SMS Layer Router
With the proliferation of SS7 over IP (SS7oIP) capable servers, new SMSCs can be inserted which communicate with the Cisco ITP signaling gateway using Internet Engineering Task Force (IETF) Signaling Transport (SIGTRAN) protocols or legacy link types. Using Sigtran (for example, SS7 Signaling Connection Control Part User Adaptation Layer [SUA], SS7 MTP3 User Adaptation Layer [M3UA], or SS7 MTP2 User Peer-to-Peer Adaptation Layer[ M2PA]) reduces the time-division multiplexing (TDM) hardware and software costs on the SMSC and provides virtually unlimited A-link bandwidth to the SMSC for maximum transaction rates.
The Cisco ITP signaling gateway is uniquely positioned to serve as the networking gateway to enable the widespread deployment of these new services.
Overview of the Cisco ITP Multilayer SMS Routing Solution
The Cisco ITP Multilayer SMS Routing solution allows a Global System for Mobile Communications (GSM) mobile-originated (MO) SMS message to be routed based on information found within the Signalling Connection Control Part (SCCP), Transactional Capabilities Application Part (TCAP), Mobile Application Part (MAP), and SMS layers of the message. The operator defines a set of rules specifying the application parameters that must match within a message, along with the results that identify the server or group of servers that should process the transaction. Figure 2 depicts the protocol stack architecture of the Cisco ITP solution.
Figure 2
- ITP MultiLayer SMS Router Architecture.
Within an operator's network, the Cisco ITP multilayer SMS router can be deployed at either the message service center (MSC) sites, or at a more centralized location. The Cisco ITP intercepts an SMS MO message sent by an MSC destined for one of the operator's home SMSC addresses. The ITP parses the message's application layers, and then determines if a rule has been matched. If no rule is matched, the message is routed normally to the original destination SMSC. If a rule is matched, an available destination server is selected from the appropriate server group. The origin and destination servers can be connected to the Cisco ITP multilayer SMS router by any supported connection type, including the SIGTRAN link types: M2PA, SUA and M3UA.
Figure 3 shows an example mobile operator deployment of two new SMS services using the Cisco ITP multilayer SMS routing solution. The first SMS service is the "Millionaire Game," and allows subscribers to answer trivia questions through SMS. To play the game, the subscriber answers questions by typing the correct answer within the text of the message, and provides a B-address short code of 1111 to address the appropriate game. The message is then routed toward the home SMSC address within the operator's network. In GSM networks, the home SMSC address is typically an E.164 global title address
Figure 3
Example of a New SMS Deployment.
The Cisco ITP multilayer SMS routers receive the messages destined for the operator's SMSC address, and inspect the SMS B-address. A rule is matched for the 1111 short code, and the SMS message is routed to an available server that is specifically handling the "Millionaire Game" event. SMS messages destined for the "Television Game" event are specified with a B-address short code of 2222, and are routed by the ITPs to the appropriate SMSC. All other SMS messages are routed to the existing SMSC(s).
The Cisco ITP multilayer SMS routing solution gives mobile operators the flexibility to designate a single server or group of servers to handle certain event traffic. This capability provides numerous advantages, including the ability to designate primary and back-up (or standby) SMSC(s), overflow SMSC(s) for regular text traffic, and to designate the paths in the network that carry specific traffic.
Advantages of the Cisco ITP Multilayer SMS Routing Solution
- New SMS services can be deployed without expensive upgrades to the legacy SMSC and STPs
- Additional server capacity can be added to scale the service to required performance levels
- Flexible deployment model allows traditional TDM links, high-speed links, or SS7oIP links to be used to connect all network elements
Multilayer SMS Routing Options
Upon receiving a GSM SMS MO-ForwardSM request message, the SMS router examines the SCCP, TCAP, MAP (versions 1, 2 and 3, are supported), and SMS MAP payload to make a customizable routing decision based on any of the following message criteria:
When a packet arrives over the network, the Cisco ITP first determines if the SCCP parameters match a specified signature, such as the home SMSC global title address. The Cisco ITP next parses the application layers of the message. A set of operator defined rules is associated with the matched SCCP address parameters, and the Cisco ITP then searches the for a match. The first successful match terminates the search, and the corresponding result table identifies the destination server that will handle the message. The destination point code (DPC), CdPA Global title, or M3UA/SUA application server name is specified for the selected result, and the message is forwarded to the new destination server. The Cisco ITP routes messages that do not match a defined rule to the existing SMSC according to MTP3 and SCCP routing procedures.
The Cisco ITP multilayer SMS routing table will map the messages to one of the following result types:
If a result table is specified, traffic is routed based on a weighted round-robin (WRR) distribution algorithm. This offers an SMS workload-balancing scheme among servers of varying capacity. Each server within a result table is assigned a server weight from 0 to 10. At the time a message is processed, the next-available server is chosen based on the WRR algorithm. Servers defined with a weighting factor of 0 are backup servers, and are only used in the event that all other servers with non-zero weighting factors are unavailable.
In addition to Cisco ITP multilayer SMS result tables, messages can be distributed according to MTP3 routing table features, Global title translation (GTT) application groups, or M3UA/SUA application server traffic handling.
Figure 4 shows an example of SMSC server distribution in which SMSC A1 (PC 3.3.1) will handle twice as many SMS MO messages as SMSC A2 (PC 3.3.2). SMSC A3 is a backup server, and will only process SMS MO messages if both SMSC A1 and SMSC A2 fail
Figure 4
Weighted SMSC Distribution.
Parsing application-layer information and intelligently routing messages are the functions of the Cisco multilayer SMS routing solution that positively affect network performance. With a small set of defined rules (1-10), the Cisco ITP incurs a 10-percent throughput cost in terms of message signal units (MSUs)/second can be expected using the platform's GTT routing-based performance numbers. Please refer to the Cisco ITP data sheet for the most current platform-based GTT performance numbers.
During times of network congestion, it is very important to be able to manage traffic so that messages are not dropped, and so that time-sensitive and high-priority traffic get right of way over less-critical traffic. Delays of only milliseconds can be critical in an SS7 network. The Cisco ITP has a unique capability of "tagging" message packets so that all traffic can be intelligently managed when the network is congested. The benefits to network operators are cost savings and higher reliability of their SS7 networks. Cost savings are possible because operators do not need to design their networks with expensive bandwidth that may only be used for occasions when network traffic is unusually high, such as on holidays or during sporting events. Enhanced reliability of delivery of SS7 messages is made possible because messages are not dropped during times of network congestion.
IP packets (including SS7oIP packets) have a segment (or a byte) that is used for "tagging" or marking a packet with a priority number. When network congestion is present in the network, the Cisco ITP and other routers in the network look at the "tagged" number and prioritize delivery of traffic. Traffic with lower priorities is held in a buffer, while higher-priority traffic is delivered first.
The Cisco ITP can "tag" messages based on:
The prioritization feature, or QoS, does not add latency to the network. On the contrary, it reduces latency, and the need to retransmit lost messages, in the event of network congestion. QoS smoothes out traffic peaks. In this way, Cisco ITP with QoS further enhances traffic handling for enhanced SMSC routing.
Cisco Multilayer SMS Routing is available on all supported Cisco ITP platforms.
Cisco Customer Advocacy monitors mean time between failure (MTBF) and mean time to repair (MTTR) for Cisco 7500 series hardware and software in large service provider networks. From customer results, single Cisco IP Transfer Point availability can achieve "six nines" or 99.9999 percent availability which equates to downtime of less than one second per year. Mated pair Cisco IP Transfer Point availability far exceeds "six nines" or 99.9999 percent availability.
Standards and Interoperability
Table 1 describes the standard protocols used in the Cisco ITP Multilayer SMS Routing solution.
Table 1 Cisco IP Transfer Point Features
1 International Telecommunication Union Telecommunication Standardization Sector
2 American National Standards Institute