SMS Over SS7

Автор не указан. NCS Techical Information Bulletin, Издание Office of the Manager National Communications System, 2003 — 73 p The Short Message Service (SMS) allow textual messages to be delivered between SMS enabled, digital cell phones. These messages travel on the SS7 network in tandem with voice call signaling traffic. The service is extremely popular in Europe and Asia, generating tens of billions of messages a month. A number of factors slowed initial SMS acceptance in the United States, but traffic has grown remarkably in the last two years, and this trend is expected to continue. SMS has also demonstrated utility as an alternative to voice communications. During the terrorist attacks on September 11, 2001, high traffic volumes made it extremely difficult to connect calls. However, SMS text messaging continued to operate and provided communications means for people who understood how to use it. The conflux of these events raises the question: given that SMS shares the SS7 network, that popularity and awareness of SMS are increasing rapidly, and that SMS might be a person’s means of communications during another crisis, how would the wireless network handle the surge in short messaging traffic? This Technical Information Bulletin (TIB) answered this question by researching multiple aspects of SMS technology, including wireless network reliability, capacity and congestion handling, security and vulnerability, priority services, and new SMS-related developments. The TIB concluded that networks are theoretically capable of continued operation and service (including NS/EP service) during a crisis. However, it may be possible for extremely high volumes of SMS traffic, when combined with high numbers of voice call attempts, to interfere with a wireless network’s performance. The absence of a definitive conclusion is due to the unavailability of key information: the network configuration details (known only by the network operator), the congestion handling algorithms (known only by the equipment manufacturers). The report makes several recommendations: Characterize the anticipated traffic load (voice and messaging) better Obtain details of congestion handling algorithms from equipment vendors Using this information, probable bottlenecks can be identified and a specific analysis can be performed for areas of concern. Introduction Background Basic Principles History SMS Network Elements Base Transceiver System/Base Station Controller (BTS/BSC) Mobile Switching Center (MSC) Signaling Transfer Point (STP) Signaling System 7 (SS7) SS7 Application Protocols SMS Protocols. Short Message Peer-to-Peer Protocol (SMPP) Universal Computer Protocol (UCP). Computer Interface to Message Distribution (CIMD2) Open Interface Specification (OIS) Telocator Alphanumeric Protocol (TAP) Technical Analysis Reliability. Definition of Reliability Signaling Network Reliability Capacity Wireless Network Capacity Fixed Portion of the Wireless Network Capacity Vulnerability Assessment Denial of Service (DOS) Attack Service Interruption Attack Service Hijacking Attack Spoofing Non-Internet Based Methods of Attack SMS-Related Developments Cell Broadcast. Enhanced and Multimedia Messaging. Current and Future SMS Services . Security Application Originated Messages Mobile Originated Messages Writer-to-Reader Security Conclusions. Recommendations Appendix A - SMS Operation. Appendix B - List of Acronyms. Appendix C - List of References