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Signalling System No. 7

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426:(NFAS) became possible. NFAS is signaling that is not directly associated with the path that a conversation will traverse and may concern other information located at a centralized database such as service subscription, feature activation, and service logic. This makes possible a set of network-based services that do not rely upon the call being routed to a particular subscription switch at which service logic would be executed, but permits service logic to be distributed throughout the telephone network and executed more expediently at originating switches far in advance of call routing. It also permits the subscriber increased mobility due to the decoupling of service logic from the subscription switch. Another ISUP characteristic SS7 with NFAS enables is the exchange of signaling information during the middle of a call. 759:
the Network Service Part (NSP). SCCP completes the functions of the OSI network layer: end-to-end addressing and routing, connectionless messages (UDTs), and management services for users of the Network Service Part (NSP). Telephone User Part (TUP) is a link-by-link signaling system used to connect calls. ISUP is the key user part, providing a circuit-based protocol to establish, maintain, and end the connections for calls. Transaction Capabilities Application Part (TCAP) is used to create database queries and invoke advanced network functionality, or links to Intelligent Network Application Part (INAP) for intelligent networks, or Mobile Application Part (MAP) for mobile services.
3024: 935: 356:), these earlier methods cannot communicate much signaling information. Usually only the dialed digits are signaled during call setup. For charged calls, dialed digits and charge number digits are outpulsed. SS7, being a high-speed and high-performance packet-based communications protocol, can communicate significant amounts of information when setting up a call, during the call, and at the end of the call. This permits rich call-related services to be developed. Some of the first such services were call management related, 548:(HSL) in contrast to the low speed (56 and 64 kbit/s) links. High-speed links are specified in ITU-T Recommendation Q.703 for the 1.5 Mbit/s and 2.0 Mbit/s rates, and ANSI Standard T1.111.3 for the 1.536 Mbit/s rate. There are differences between the specifications for the 1.5 Mbit/s rate. High-speed links utilize the entire bandwidth of a T1 (1.536 Mbit/s) or E1 (1.984 Mbit/s) transmission facility for the transport of SS7 signaling messages. 2864: 2874: 2853: 2884: 875:
on compromised computers, allowing them to collect online banking account credentials and telephone numbers. They set up redirects for the victims' telephone numbers to telephone lines controlled by them. Confirmation calls and SMS text messages of two-factor authentication procedures were routed to
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from virtually anywhere in the world with a success rate of approximately 70%. In addition, eavesdropping is possible by using the protocol to forward calls and also facilitate decryption by requesting that each caller's carrier release a temporary encryption key to unlock the communication after it
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Data reviewed by the Bureau shows that a series of signals designed to reveal phone location were sent to a US-registered mobile belonging to the yacht's skipper, Hervé Jaubert, the day before commandos stormed the yacht and seized the princess. The effort appears to have been part of a huge bid by
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The Message Transfer Part (MTP) covers a portion of the functions of the OSI network layer including: network interface, information transfer, message handling and routing to the higher levels. Signaling Connection Control Part (SCCP) is at functional Level 4. Together with MTP Level 3 it is called
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Another element of in-band signaling addressed by SS7 is network efficiency. With in-band signaling, the voice channel is used during call setup which makes it unavailable for actual traffic. For long-distance calls, the talk path may traverse several nodes which reduces usable node capacity. With
278:(SS6). In its 1980 Yellow Book Q.7XX-series recommendations ITU-T defined the Signalling System No. 7 as an international standard. SS7 replaced SS6 with its restricted 28-bit signal unit that was both limited in function and not amendable to digital systems. SS7 also replaced 258:, which can replicate the tones used by the network for call control and routing. As a remedy, SS6 and SS7 implements out-of-band signaling, carried in a separate signaling channel, thus keeping the call control and speech paths separate. SS6 and SS7 are referred to as 469:
through the Public Switched Telephone Network following the same path as the associated facilities that carry the telephone call. This mode is more economical for small networks. The associated mode of signaling is not the predominant choice of modes in North America.
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SS7 separates signaling from the voice circuits. An SS7 network must be made up of SS7-capable equipment from end to end in order to provide its full functionality. The network can be made up of several link types (A, B, C, D, E, and F) and three signaling nodes –
1606: 1576: 407:(PSTN) calls was adopted in North America. ISUP was later used in Europe when the European networks upgraded to the ISDN. As of 2020 North America has not accomplished full upgrade to the ISDN, and the predominant telephone service is still 273:
Since 1975, CCS protocols have been developed by major telephone companies and the International Telecommunication Union Telecommunication Standardization Sector (ITU-T); in 1977 the ITU-T defined the first international CCS protocol as
345:, in which the path and facility used by the signaling is separate and distinct from the signaling without first seizing a voice channel, leading to significant savings and performance increases in both signaling and channel usage. 1375: 812:
The Direct Transfer Application Part (DTAP) is used for transfer of those messages which need to travel directly to mobile equipment from MSC bypassing any interpretation by BSS. These messages are generally pertaining to
305:) and Signaling Connection Control Part (SCCP) (SUA). While running on a transport based upon IP, the SIGTRAN protocols are not an SS7 variant, but simply transport existing national and international variants of SS7. 429:
SS7 also enables Non-Call-Associated Signaling, which is signaling not directly related to establishing a telephone call. This includes the exchange of registration information used between a mobile telephone and a
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facility. One or more signaling links can be connected to the same two endpoints that together form a signaling link set. Signaling links are added to link sets to increase the signaling capacity of the link set.
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the Emiratis – mobilising boats, a surveillance plane and electronic means – to track down the fleeing princess. Signals were sent via mobile networks in Jersey, Guernsey, Cameroon, Israel, Laos and the USA.
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SS7, the connection is not established between the end points until all nodes on the path confirm availability. If the far end is busy, the caller gets a busy signal without consuming a voice channel.
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associated with the setup and release of a telephone call on a telecommunications circuit. Examples of control information are the digits dialed by the caller and the caller's billing number.
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Kaskey, B.; Colson, J. S.; Mills, R. F.; Myers, F. H.; Raleigh, J. T.; Schweizer, A. F.; Tauson, R. A. (February 1978). "Common Channel Interoffice Signaling: Technology and Hardware".
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The links between nodes are full-duplex 56, 64, 1,536, or 1,984 kbit/s graded communications channels. In Europe they are usually one (64 kbit/s) or all (1,984 kbit/s)
506:(SCPs). Each node is identified on the network by a number, a signaling point code. Extended services are provided by a database interface at the SCP level using the SS7 network. 485:. This mode is more economical for large networks with lightly loaded signaling links. The quasi-associated mode of signaling is the predominant choice of modes in North America. 1509: 301:
protocols which translate the common channel signaling paradigm to the IP Message Transfer Part (MTP) level 2 (M2UA and M2PA), Message Transfer Part (MTP) level 3 (
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Apart from signaling with these various degrees of association with call set-up and the facilities used to carry calls, SS7 is designed to operate in two modes:
1660: 891:. The nature of SS7 normally being used between consenting network operators on dedicated links means that any bad actor's traffic can be traced to its source. 1447: 2128: 805:
The BSS Mobile Application Part (BSSMAP) supports procedures to facilitate communication between the MSC and the BSS pertaining to resource management and
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Cieslak, T. J.; Croxall, L. M.; Roberts, J. B.; Saad, M. W.; Scanlon, J. M. (September 1977). "No.4 ESS: Software Organization and Basic Call Handling".
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SS7 links at higher signaling capacity (1.536 and 1.984 Mbit/s, simply referred to as the 1.5 Mbit/s and 2.0 Mbit/s rates) are called
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The earliest deployed upper-layer protocols in the SS7 suite were dedicated to the setup, maintenance, and release of telephone calls. The
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SS7 has been shown to have several security vulnerabilities, allowing location tracking of callers, interception of voice data, intercept
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telephone numbers controlled by the attackers. This enabled them to log into victims' online bank accounts and effect money transfers.
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and No. 4A crossbar toll offices. The SS7 protocol is defined for international use by the Q.700-series recommendations of 1988 by the
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had been used "numerous attempts" to acquire location data, voice and text messages, deliver spyware, and influence voters in the US.
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The security vulnerabilities of SS7 have been highlighted in U.S. governmental bodies, for example when in April 2016 Congressman
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In Europe, SS7 links normally are directly connected between switching exchanges using F-links. This direct connection is called
723:(SCCP) of the SS7 protocol (together referred to as the Network Service Part (NSP)); for circuit related signaling, such as the 541:, which reduces the number of SS7 links necessary to interconnect all switching exchanges and SCPs in an SS7 signaling network. 2830: 571: 567: 167: 2825: 2815: 2795: 2597: 1773: 1270: 1175: 422:
Because SS7 signaling does not require seizure of a channel for a conversation prior to the exchange of control information,
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one signalling connection is used by BSSAP having at least one active transactions for the transfer of messages.
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In 2008, several SS7 vulnerabilities were published that permitted the tracking of mobile phone users.
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protocol suite that implements levels 2, 3, and 4 protocols compatible with SS7. Sometimes also called
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In March 2018, a method was published for the detection of the vulnerabilities, through the use of
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to the terminating switch, following a path through a separate SS7 signaling network composed of
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When signaling is performed on the same circuit as the conversation of the call, it is termed
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facility; in North America one (56 or 64 kbit/s) or all (1,536 kbit/s) timeslots (
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Because of the mechanisms in use by signaling methods prior to SS7 (battery reversal,
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to achieve unauthorized withdrawals from bank accounts. The perpetrators installed
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In 2014, the media reported a protocol vulnerability of SS7 by which anyone can
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The protocol was introduced in the Bell System in the United States by the name
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In February 2016, 30% of the network of the largest mobile operator in Norway,
795: 782:(BSS) to communicate with each other using signaling messages supported by the 732: 708: 665: 629: 400: 377: 212: 1787: 1346: 743:. TCAP provides transaction capabilities to its Users (TC-Users), such as the 715:
of a packetized digital protocol stack. OSI layers 1 to 3 are provided by the
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revealed that the SS7 protocol was exploited in an attempt to locate Sheikha
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Full Research on SS7/Sigtran Attack Vector, Exploits and Preventive Measures
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database, which tracks the location of the mobile. Other examples include
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tones transmitted on the telephone line audio channels, also known as
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Signaling System No. 7 (SS7/C7): Protocol, Architecture, and Services
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The Digital Network Introduction to Digital Communications Switching
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can warn when certain SS7 attacks occur against a phone, and detect
246:, in which the call-setup information is sent by generating special 2980: 2945: 2754: 2744: 2661: 2486: 2309: 857: 806: 510: 255: 201: 2749: 2734: 1952: 1799: 1285:"Understanding the Sigtran Protocol Suite: A Tutorial | EE Times" 850: 563: 551: 298: 185: 1636:"Definitive guide to SS7/Sigtran Attack and Preventive Measures" 2779: 2739: 2061: 1265:
Additions for a national option for high speed signaling links
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protocols developed in the 1970s that is used to set up and
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MetodologĂ­a de detecciĂłn de vulnerabilidades SS7/Sigtran
135:(PSTN). The protocol also performs number translation, 1009: 177:
keys, and possibly the delivery of spyware to phones.
1508:(in Norwegian). digi.no / Teknisk Ukeblad Media AS. 930: 825: 1691:"It is dangerously easy to hack the world's phones" 1057:"It is dangerously easy to hack the world's phones" 846:that allow call interception and other activities. 207:In North America, SS7 is also often referred to as 2928: 415:and not for signaling between local exchanges and 860:called for an oversight committee investigation. 3039: 1747:Introduction to Digital Communications Switching 1745:Ronayne, John P. (1986). "The Digital Network". 913:Cybersecurity and Infrastructure Security Agency 477:, SS7 signaling progresses from the originating 1611:Vulnerability detection methodology SS7/Sigtran 1092: 290:variants are still used in numerous countries. 164:European Telecommunications Standards Institute 1725: 1494:(in Norwegian). Telenor ASA. 21 February 2016. 1232: 1219: 1120:Framework Architecture for Signaling Transport 2914: 1822: 1653: 908:on 3 March 2018, a day before her abduction. 688: 327:(CAS). This is the case for analogue trunks, 1604: 1574: 1445: 131:telephone calls on most parts of the global 2837:Global telecommunications regulation bodies 1246:"ITU-T Recommendation Q.700, section 2.2.3" 1192:"ITU-T Recommendation Q.700, section 3.2.1" 2921: 2907: 2873: 1829: 1815: 1782: 1492:"Feilen i mobilnettet er funnet og rettet" 1356:. 25th Chaos Communication Congress (25C3) 911:In 2024, Kevin Briggs, an official at the 695: 681: 1161: 1159: 1157: 1155: 1153: 1151: 1132: 1088: 1086: 1084: 835:track the movements of mobile phone users 737:Transaction Capabilities Application Part 1257: 1255: 227:(CCIS7). In Germany, it is often called 150:in the 1970s for signalling between No. 1768:(4th ed.). New York: McGraw-Hill. 1763: 1744: 1401: 1373: 1309:"ITU-T Recommendation Q.711, section 1" 1165: 801:BSSAP provides two kinds of functions: 14: 3048:Computer-related introductions in 1984 3040: 1836: 1549: 1263:"ITU-T Recommendation Q.703, Annex A, 1148: 1111: 1081: 1037: 1035: 1033: 225:Common Channel Interoffice Signaling 7 196:(SCTP) transport mechanism for use on 168:Telecommunication Technology Committee 2902: 1810: 1789:Exposing The Flaw In Our Phone System 1667:from the original on 19 December 2020 1583:(in European Spanish). Archived from 1344: 1271:International Telecommunication Union 1252: 1170:(4 ed.). New York: McGraw-Hill. 838:has been recorded. The software tool 585: 160:American National Standards Institute 2883: 1726:Dryburgh, Lee; Hewitt, Jeff (2004). 906:Latifa bint Mohammed Al Maktoum (II) 749:Intelligent Network Application Part 395:(TUP) was adopted in Europe and the 358:call forwarding (busy and no answer) 264:Common Channel Interoffice Signaling 194:Stream Control Transmission Protocol 148:Common Channel Interoffice Signaling 27:Set of telephony signaling protocols 1402:Timburg, Craig (18 December 2014). 1030: 774:) is a protocol in SS7 used by the 488: 397:Integrated Services Digital Network 229:Zentraler Zeichengabekanal Nummer 7 109:https://www.itu.int/rec/T-REC-Q.700 24: 1719: 1347:"Locating Mobile Phones using SS7" 1024:10.1002/j.1538-7305.1978.tb02093.x 997:10.1002/j.1538-7305.1977.tb00558.x 902:Bureau of Investigative Journalism 721:Signalling Connection Control Part 445: 25: 3084: 1374:Timburg, Craig (24 August 2014). 826:Protocol security vulnerabilities 424:non-facility associated signaling 405:public switched telephone network 209:Common Channel Signaling System 7 133:public switched telephone network 3022: 2882: 2872: 2863: 2862: 2851: 2472:Free-space optical communication 1460:from the original on 2014-12-31. 1453:. Chaos Communication Congress. 933: 465:, SS7 signaling progresses from 350:multi-frequency digit outpulsing 331:(MF) and R2 digital trunks, and 316:in telephony is the exchange of 308: 1683: 1628: 1598: 1568: 1543: 1523: 1512:from the original on 2022-09-26 1498: 1484: 1464: 1439: 1423: 1395: 1367: 1329: 1315: 1301: 1277: 1238: 1225: 1212: 711:may be partially mapped to the 382:malicious caller identification 374:calling name and number display 295:Internet Engineering Task Force 182:Internet Engineering Task Force 2930:Signaling (telecommunications) 1198: 1184: 1049: 1003: 976: 919:that hacks related to SS7 and 13: 1: 1730:. Indianapolis: Cisco Press. 1605:Corletti Estrada, Alejandro. 1575:Corletti Estrada, Alejandro. 1012:Bell System Technical Journal 985:Bell System Technical Journal 969: 2858:Telecommunication portal 2639:Telecommunications equipment 1345:Engel, Tobias (2008-12-27). 1206:"ITU-T Recommendation Q.700" 1043:"ITU-T Recommendation Q.700" 883:monitoring software such as 788:connection-oriented services 325:channel-associated signaling 7: 2375:Alexander Stepanovich Popov 1446:Karsten Nohl (2014-12-27). 1433:Android mobile phones with 1248:. 1993-03-01. pp. 4–5. 926: 417:customer-premises equipment 409:Plain Old Telephone Service 143:(SMS), and other services. 10: 3089: 2079:Telecommunications history 1233:Dryburgh & Hewitt 2004 1220:Dryburgh & Hewitt 2004 598:SS7 protocols by OSI layer 539:quasi-associated signaling 234: 211:(CCSS7) (or CCS7). In the 170:(TTC) national variants. 3019: 2996:Multi-frequency signaling 2991:Dual-tone multi-frequency 2936: 2846: 2788: 2725: 2687:Public Switched Telephone 2647: 2611: 2568: 2509: 2499:telecommunication circuit 2460:Fiber-optic communication 2443: 2205:Francis Blake (telephone) 2152: 2000:Optical telecommunication 1844: 869:two-factor authentication 729:Telephone User Part (TUP) 676: 664: 652: 636: 602: 597: 554:provides signaling using 175:two-factor authentication 104: 94: 86: 78: 68: 58: 50: 42: 37: 2971:Special information tone 2598:Orbital angular-momentum 2035:Satellite communications 1874:Communications satellite 1764:Russell, Travis (2002). 1208:. 1993-03-01. p. 4. 1194:. 1993-03-01. p. 7. 1166:Russell, Travis (2002). 1093:Ronayne, John P (1986). 762: 496:Service Switching Points 440:local number portability 343:common channel signaling 260:common-channel signaling 242:and earlier systems use 137:local number portability 3011:Signalling System No. 7 3006:Signalling System No. 6 2477:Molecular communication 2300:Gardiner Greene Hubbard 2129:Undersea telegraph line 1864:Cable protection system 776:Mobile Switching Center 745:Mobile Application Part 192:, it is layered on the 184:(IETF) has defined the 117:Signalling System No. 7 38:Signalling System No. 7 3001:Signaling System No. 5 2619:Communication protocol 2405:Charles Sumner Tainter 2220:Walter Houser Brattain 2165:Edwin Howard Armstrong 1973:Information revolution 964:Signaling System No. 6 959:Signaling System No. 5 780:Base station subsystem 753:CAMEL Application Part 558:associations over the 504:Service Control Points 500:Signal Transfer Points 483:signal transfer points 473:When operating in the 461:When operating in the 432:home location register 354:A- and B-bit signaling 341:In contrast, SS7 uses 280:Signaling System No. 5 276:Signaling System No. 6 240:Signaling System No. 5 200:networks, such as the 3053:ITU-T recommendations 3029:Telephones portal 2593:Polarization-division 2325:Narinder Singh Kapany 2290:Erna Schneider Hoover 2210:Jagadish Chandra Bose 2190:Alexander Graham Bell 1921:online video platform 1448:"Mobile self-defence" 717:Message Transfer Part 475:quasi-associated mode 456:quasi-associated mode 141:Short Message Service 18:Signaling System No 7 2435:Vladimir K. Zworykin 2395:Almon Brown Strowger 2365:Charles Grafton Page 2020:Prepaid mobile phone 1948:Electrical telegraph 1663:. 16 December 2020. 894:An investigation by 768:BSS Application Part 562:. The protocols for 535:associated signaling 262:(CCS) protocols, or 82:Study Group XI, WTSC 2385:Johann Philipp Reis 2144:Wireless revolution 2106:The Telephone Cases 1963:Hydraulic telegraph 1766:Signaling System #7 1550:Khandelwal, Swati. 1429:SnoopSnitch is for 1409:The Washington Post 1381:The Washington Post 1168:Signaling System #7 815:mobility management 594: 436:Intelligent Network 393:Telephone User Part 318:control information 139:, prepaid billing, 125:telephony signaling 34: 3058:Signaling System 7 2583:Frequency-division 2560:Telephone exchange 2430:Charles Wheatstone 2360:Jun-ichi Nishizawa 2335:Innocenzo Manzetti 2270:Reginald Fessenden 2005:Optical telegraphy 1838:Telecommunications 1480:. August 15, 2016. 1222:, pp. 22–23). 915:, reported to the 794:. For each active 592:SS7 protocol suite 590: 586:SS7 protocol suite 525:or DS0s) within a 413:telephone switches 399:(ISDN) User Part ( 370:conference calling 219:(CCITT number 7), 32: 3073:Telephony signals 3068:Network protocols 3035: 3034: 2896: 2895: 2634:Store and forward 2629:Data transmission 2543:Network switching 2494:Transmission line 2340:Guglielmo Marconi 2305:Internet pioneers 2170:Mohamed M. Atalla 2139:Whistled language 1775:978-0-07-138772-9 1539:. April 19, 2016. 1273:. pp. 81–86. 1177:978-0-07-138772-9 941:Telephones portal 705: 704: 560:Internet Protocol 244:in-band signaling 198:Internet Protocol 114: 113: 87:Related standards 16:(Redirected from 3080: 3027: 3026: 3025: 2923: 2916: 2909: 2900: 2899: 2886: 2885: 2876: 2875: 2866: 2865: 2856: 2855: 2854: 2727:Notable networks 2717:Wireless network 2657:Cellular network 2649:Types of network 2624:Computer network 2511:Network topology 2425:Thomas A. Watson 2280:Oliver Heaviside 2265:Philo Farnsworth 2240:Daniel Davis Jr. 2215:Charles Bourseul 2175:John Logie Baird 1884:Data compression 1879:Computer network 1831: 1824: 1817: 1808: 1807: 1803: 1797: 1796: 1779: 1760: 1741: 1713: 1712: 1710: 1709: 1687: 1681: 1680: 1674: 1672: 1657: 1651: 1650: 1648: 1647: 1632: 1626: 1625: 1623: 1622: 1613:. Archived from 1602: 1596: 1595: 1593: 1592: 1572: 1566: 1565: 1563: 1562: 1547: 1541: 1540: 1527: 1521: 1520: 1518: 1517: 1502: 1496: 1495: 1488: 1482: 1481: 1468: 1462: 1461: 1459: 1452: 1443: 1437: 1427: 1421: 1420: 1418: 1416: 1399: 1393: 1392: 1390: 1388: 1371: 1365: 1364: 1362: 1361: 1351: 1333: 1327: 1326: 1319: 1313: 1312: 1305: 1299: 1298: 1296: 1295: 1281: 1275: 1274: 1259: 1250: 1249: 1242: 1236: 1229: 1223: 1216: 1210: 1209: 1202: 1196: 1195: 1188: 1182: 1181: 1163: 1146: 1145: 1136: 1134:10.17487/RFC2719 1115: 1109: 1108: 1090: 1079: 1078: 1076: 1075: 1053: 1047: 1046: 1039: 1028: 1027: 1007: 1001: 1000: 991:(7): 1113–1138. 980: 954:Out-of-band data 943: 938: 937: 936: 796:mobile equipment 697: 690: 683: 595: 589: 546:high-speed links 489:Physical network 467:switch to switch 266:(CCIS) systems. 35: 31: 21: 3088: 3087: 3083: 3082: 3081: 3079: 3078: 3077: 3038: 3037: 3036: 3031: 3023: 3021: 3015: 2966:Disconnect tone 2932: 2927: 2897: 2892: 2852: 2850: 2842: 2784: 2721: 2643: 2607: 2564: 2513: 2505: 2446: 2439: 2345:Robert Metcalfe 2200:Tim Berners-Lee 2148: 1968:Information Age 1840: 1835: 1794: 1792: 1776: 1757: 1738: 1722: 1720:Further reading 1717: 1716: 1707: 1705: 1689: 1688: 1684: 1670: 1668: 1659: 1658: 1654: 1645: 1643: 1634: 1633: 1629: 1620: 1618: 1603: 1599: 1590: 1588: 1573: 1569: 1560: 1558: 1556:The Hacker News 1548: 1544: 1529: 1528: 1524: 1515: 1513: 1504: 1503: 1499: 1490: 1489: 1485: 1470: 1469: 1465: 1457: 1450: 1444: 1440: 1428: 1424: 1414: 1412: 1400: 1396: 1386: 1384: 1372: 1368: 1359: 1357: 1349: 1341:Wayback Machine 1334: 1330: 1321: 1320: 1316: 1307: 1306: 1302: 1293: 1291: 1283: 1282: 1278: 1261: 1260: 1253: 1244: 1243: 1239: 1230: 1226: 1217: 1213: 1204: 1203: 1199: 1190: 1189: 1185: 1178: 1164: 1149: 1117: 1116: 1112: 1105: 1091: 1082: 1073: 1071: 1055: 1054: 1050: 1041: 1040: 1031: 1008: 1004: 981: 977: 972: 939: 934: 932: 929: 828: 819:call management 765: 701: 620: 588: 491: 463:associated mode 452:associated mode 448: 446:Signaling modes 329:multi-frequency 311: 297:(IETF) defined 252:bearer channels 248:multi-frequency 237: 215:, it is called 162:(ANSI) and the 63: 28: 23: 22: 15: 12: 11: 5: 3086: 3076: 3075: 3070: 3065: 3060: 3055: 3050: 3033: 3032: 3020: 3017: 3016: 3014: 3013: 3008: 3003: 2998: 2993: 2988: 2983: 2978: 2973: 2968: 2963: 2958: 2953: 2948: 2943: 2937: 2934: 2933: 2926: 2925: 2918: 2911: 2903: 2894: 2893: 2891: 2890: 2880: 2870: 2860: 2847: 2844: 2843: 2841: 2840: 2833: 2828: 2823: 2818: 2813: 2812: 2811: 2806: 2798: 2792: 2790: 2786: 2785: 2783: 2782: 2777: 2772: 2767: 2762: 2757: 2752: 2747: 2742: 2737: 2731: 2729: 2723: 2722: 2720: 2719: 2714: 2709: 2704: 2699: 2694: 2689: 2684: 2679: 2674: 2669: 2664: 2659: 2653: 2651: 2645: 2644: 2642: 2641: 2636: 2631: 2626: 2621: 2615: 2613: 2609: 2608: 2606: 2605: 2600: 2595: 2590: 2585: 2580: 2578:Space-division 2574: 2572: 2566: 2565: 2563: 2562: 2557: 2556: 2555: 2550: 2540: 2539: 2538: 2528: 2523: 2517: 2515: 2507: 2506: 2504: 2503: 2502: 2501: 2491: 2490: 2489: 2479: 2474: 2469: 2468: 2467: 2457: 2451: 2449: 2441: 2440: 2438: 2437: 2432: 2427: 2422: 2417: 2415:Camille Tissot 2412: 2407: 2402: 2397: 2392: 2390:Claude Shannon 2387: 2382: 2380:Tivadar Puskás 2377: 2372: 2367: 2362: 2357: 2352: 2350:Antonio Meucci 2347: 2342: 2337: 2332: 2327: 2322: 2320:Charles K. Kao 2317: 2312: 2307: 2302: 2297: 2295:Harold Hopkins 2292: 2287: 2282: 2277: 2272: 2267: 2262: 2257: 2252: 2247: 2242: 2237: 2232: 2227: 2222: 2217: 2212: 2207: 2202: 2197: 2195:Emile Berliner 2192: 2187: 2182: 2177: 2172: 2167: 2162: 2156: 2154: 2150: 2149: 2147: 2146: 2141: 2136: 2134:Videotelephony 2131: 2126: 2125: 2124: 2119: 2109: 2102: 2097: 2091: 2086: 2081: 2076: 2071: 2070: 2069: 2064: 2059: 2049: 2048: 2047: 2037: 2032: 2030:Radiotelephone 2027: 2022: 2017: 2012: 2007: 2002: 1997: 1996: 1995: 1985: 1980: 1975: 1970: 1965: 1960: 1955: 1950: 1945: 1940: 1935: 1934: 1933: 1928: 1923: 1918: 1916:Internet video 1908: 1907: 1906: 1901: 1896: 1891: 1881: 1876: 1871: 1866: 1861: 1856: 1850: 1848: 1842: 1841: 1834: 1833: 1826: 1819: 1811: 1805: 1804: 1786:(2024-09-21). 1780: 1774: 1761: 1755: 1742: 1736: 1721: 1718: 1715: 1714: 1682: 1652: 1627: 1597: 1567: 1542: 1522: 1497: 1483: 1463: 1438: 1422: 1394: 1366: 1328: 1314: 1311:. p. 1-2. 1300: 1276: 1251: 1237: 1235:, p. 23). 1224: 1211: 1197: 1183: 1176: 1147: 1110: 1103: 1080: 1048: 1029: 1018:(2): 379–428. 1002: 974: 973: 971: 968: 967: 966: 961: 956: 951: 945: 944: 928: 925: 827: 824: 823: 822: 810: 778:(MSC) and the 764: 761: 733:ISDN User Part 719:(MTP) and the 709:protocol stack 703: 702: 700: 699: 692: 685: 677: 674: 673: 668: 662: 661: 656: 654:Data link 650: 649: 640: 634: 633: 606: 600: 599: 587: 584: 490: 487: 447: 444: 403:) adapted for 378:call screening 310: 307: 236: 233: 213:United Kingdom 123:) is a set of 112: 111: 106: 102: 101: 96: 92: 91: 88: 84: 83: 80: 76: 75: 70: 66: 65: 60: 59:Latest version 56: 55: 52: 48: 47: 44: 40: 39: 26: 9: 6: 4: 3: 2: 3085: 3074: 3071: 3069: 3066: 3064: 3061: 3059: 3056: 3054: 3051: 3049: 3046: 3045: 3043: 3030: 3018: 3012: 3009: 3007: 3004: 3002: 2999: 2997: 2994: 2992: 2989: 2987: 2984: 2982: 2979: 2977: 2976:Off-hook tone 2974: 2972: 2969: 2967: 2964: 2962: 2959: 2957: 2954: 2952: 2949: 2947: 2944: 2942: 2939: 2938: 2935: 2931: 2924: 2919: 2917: 2912: 2910: 2905: 2904: 2901: 2889: 2881: 2879: 2871: 2869: 2861: 2859: 2849: 2848: 2845: 2838: 2834: 2832: 2829: 2827: 2824: 2822: 2819: 2817: 2814: 2810: 2807: 2805: 2802: 2801: 2799: 2797: 2794: 2793: 2791: 2787: 2781: 2778: 2776: 2773: 2771: 2768: 2766: 2763: 2761: 2758: 2756: 2753: 2751: 2748: 2746: 2743: 2741: 2738: 2736: 2733: 2732: 2730: 2728: 2724: 2718: 2715: 2713: 2710: 2708: 2705: 2703: 2700: 2698: 2695: 2693: 2690: 2688: 2685: 2683: 2680: 2678: 2675: 2673: 2670: 2668: 2665: 2663: 2660: 2658: 2655: 2654: 2652: 2650: 2646: 2640: 2637: 2635: 2632: 2630: 2627: 2625: 2622: 2620: 2617: 2616: 2614: 2610: 2604: 2603:Code-division 2601: 2599: 2596: 2594: 2591: 2589: 2588:Time-division 2586: 2584: 2581: 2579: 2576: 2575: 2573: 2571: 2567: 2561: 2558: 2554: 2551: 2549: 2546: 2545: 2544: 2541: 2537: 2534: 2533: 2532: 2529: 2527: 2524: 2522: 2519: 2518: 2516: 2514:and switching 2512: 2508: 2500: 2497: 2496: 2495: 2492: 2488: 2485: 2484: 2483: 2480: 2478: 2475: 2473: 2470: 2466: 2465:optical fiber 2463: 2462: 2461: 2458: 2456: 2455:Coaxial cable 2453: 2452: 2450: 2448: 2442: 2436: 2433: 2431: 2428: 2426: 2423: 2421: 2418: 2416: 2413: 2411: 2408: 2406: 2403: 2401: 2398: 2396: 2393: 2391: 2388: 2386: 2383: 2381: 2378: 2376: 2373: 2371: 2370:Radia Perlman 2368: 2366: 2363: 2361: 2358: 2356: 2353: 2351: 2348: 2346: 2343: 2341: 2338: 2336: 2333: 2331: 2328: 2326: 2323: 2321: 2318: 2316: 2313: 2311: 2308: 2306: 2303: 2301: 2298: 2296: 2293: 2291: 2288: 2286: 2283: 2281: 2278: 2276: 2273: 2271: 2268: 2266: 2263: 2261: 2260:Lee de Forest 2258: 2256: 2255:Thomas Edison 2253: 2251: 2248: 2246: 2245:Donald Davies 2243: 2241: 2238: 2236: 2233: 2231: 2230:Claude Chappe 2228: 2226: 2223: 2221: 2218: 2216: 2213: 2211: 2208: 2206: 2203: 2201: 2198: 2196: 2193: 2191: 2188: 2186: 2183: 2181: 2178: 2176: 2173: 2171: 2168: 2166: 2163: 2161: 2158: 2157: 2155: 2151: 2145: 2142: 2140: 2137: 2135: 2132: 2130: 2127: 2123: 2120: 2118: 2115: 2114: 2113: 2110: 2108: 2107: 2103: 2101: 2098: 2095: 2092: 2090: 2087: 2085: 2082: 2080: 2077: 2075: 2074:Smoke signals 2072: 2068: 2065: 2063: 2060: 2058: 2055: 2054: 2053: 2052:Semiconductor 2050: 2046: 2043: 2042: 2041: 2038: 2036: 2033: 2031: 2028: 2026: 2023: 2021: 2018: 2016: 2013: 2011: 2008: 2006: 2003: 2001: 1998: 1994: 1991: 1990: 1989: 1986: 1984: 1981: 1979: 1976: 1974: 1971: 1969: 1966: 1964: 1961: 1959: 1956: 1954: 1951: 1949: 1946: 1944: 1941: 1939: 1936: 1932: 1929: 1927: 1924: 1922: 1919: 1917: 1914: 1913: 1912: 1911:Digital media 1909: 1905: 1902: 1900: 1897: 1895: 1892: 1890: 1887: 1886: 1885: 1882: 1880: 1877: 1875: 1872: 1870: 1867: 1865: 1862: 1860: 1857: 1855: 1852: 1851: 1849: 1847: 1843: 1839: 1832: 1827: 1825: 1820: 1818: 1813: 1812: 1809: 1801: 1791: 1790: 1785: 1781: 1777: 1771: 1767: 1762: 1758: 1756:0-672-22498-4 1752: 1748: 1743: 1739: 1737:1-58705-040-4 1733: 1729: 1724: 1723: 1704: 1700: 1696: 1695:The Economist 1692: 1686: 1679: 1666: 1662: 1656: 1641: 1637: 1631: 1617:on 2018-04-03 1616: 1612: 1608: 1601: 1587:on 2018-04-03 1586: 1582: 1578: 1571: 1557: 1553: 1546: 1538: 1537: 1532: 1526: 1511: 1507: 1501: 1493: 1487: 1479: 1478: 1473: 1472:"SnoopSnitch" 1467: 1456: 1449: 1442: 1436: 1435:Qualcomm chip 1432: 1426: 1411: 1410: 1405: 1398: 1383: 1382: 1377: 1370: 1355: 1348: 1342: 1338: 1332: 1324: 1318: 1310: 1304: 1290: 1286: 1280: 1272: 1268: 1266: 1258: 1256: 1247: 1241: 1234: 1228: 1221: 1215: 1207: 1201: 1193: 1187: 1179: 1173: 1169: 1162: 1160: 1158: 1156: 1154: 1152: 1143: 1140: 1135: 1130: 1126: 1122: 1121: 1114: 1106: 1104:0-672-22498-4 1100: 1096: 1089: 1087: 1085: 1070: 1066: 1062: 1061:The Economist 1058: 1052: 1045:. 1993-03-01. 1044: 1038: 1036: 1034: 1025: 1021: 1017: 1013: 1006: 998: 994: 990: 986: 979: 975: 965: 962: 960: 957: 955: 952: 950: 947: 946: 942: 931: 924: 922: 918: 914: 909: 907: 903: 899: 898: 892: 890: 886: 882: 877: 874: 870: 866: 865:O2 TelefĂłnica 863:In May 2017, 861: 859: 854: 852: 847: 845: 844:IMSI-catchers 841: 836: 831: 820: 816: 811: 808: 804: 803: 802: 799: 797: 793: 789: 785: 781: 777: 773: 769: 760: 756: 754: 750: 746: 742: 738: 734: 730: 726: 722: 718: 714: 710: 698: 693: 691: 686: 684: 679: 678: 675: 672: 669: 667: 663: 660: 657: 655: 651: 648: 644: 641: 639: 635: 631: 627: 623: 618: 614: 610: 607: 605: 601: 596: 593: 583: 581: 577: 573: 569: 565: 561: 557: 553: 549: 547: 542: 540: 536: 531: 528: 524: 520: 516: 512: 507: 505: 501: 497: 486: 484: 480: 476: 471: 468: 464: 459: 457: 453: 443: 441: 437: 433: 427: 425: 420: 418: 414: 410: 406: 402: 398: 394: 389: 387: 386:busy callback 383: 379: 375: 371: 367: 363: 359: 355: 351: 346: 344: 339: 337: 334: 330: 326: 321: 319: 315: 309:Functionality 306: 304: 300: 296: 291: 289: 285: 282:(SS5), while 281: 277: 271: 267: 265: 261: 257: 253: 249: 245: 241: 232: 230: 226: 222: 218: 214: 210: 205: 203: 199: 195: 191: 187: 183: 178: 176: 171: 169: 165: 161: 157: 153: 149: 144: 142: 138: 134: 130: 126: 122: 118: 110: 107: 103: 100: 97: 93: 89: 85: 81: 77: 74: 71: 67: 61: 57: 53: 49: 45: 41: 36: 30: 19: 3010: 2961:Reorder tone 2951:Ringing tone 2570:Multiplexing 2445:Transmission 2410:Nikola Tesla 2400:Henry Sutton 2355:Samuel Morse 2285:Robert Hooke 2250:Amos Dolbear 2185:John Bardeen 2104: 2084:Telautograph 1988:Mobile phone 1943:Edholm's law 1926:social media 1859:Broadcasting 1798:– via 1793:. Retrieved 1788: 1765: 1746: 1727: 1706:. Retrieved 1694: 1685: 1676: 1669:. Retrieved 1655: 1644:. Retrieved 1642:. 2019-01-28 1639: 1630: 1619:. Retrieved 1615:the original 1610: 1600: 1589:. Retrieved 1585:the original 1580: 1570: 1559:. Retrieved 1555: 1545: 1536:The Guardian 1534: 1525: 1514:. Retrieved 1500: 1486: 1475: 1466: 1441: 1425: 1413:. Retrieved 1407: 1397: 1385:. Retrieved 1379: 1369: 1358:. Retrieved 1353: 1337:Ghostarchive 1335:Archived at 1331: 1317: 1303: 1292:. Retrieved 1288: 1279: 1264: 1240: 1227: 1214: 1200: 1186: 1167: 1119: 1113: 1094: 1072:. Retrieved 1060: 1051: 1015: 1011: 1005: 988: 984: 978: 910: 897:The Guardian 895: 893: 878: 862: 855: 848: 839: 832: 829: 800: 771: 767: 766: 757: 706: 591: 550: 543: 538: 534: 532: 517:) within an 508: 502:(STPs), and 492: 474: 472: 462: 460: 455: 451: 449: 428: 421: 390: 366:call waiting 347: 340: 322: 312: 292: 272: 268: 263: 251: 238: 228: 224: 220: 216: 208: 206: 189: 179: 172: 147: 145: 120: 116: 115: 90:Q.701, Q.711 69:Organization 51:Year started 33:Q.700 series 29: 2956:Busy signal 2770:NPL network 2482:Radio waves 2420:Alfred Vail 2330:Hedy Lamarr 2315:Dawon Kahng 2275:Elisha Gray 2235:Yogen Dalal 2160:Nasir Ahmed 2094:Teleprinter 1958:Heliographs 1671:19 December 1477:Google Play 1415:19 December 1387:27 December 881:open-source 840:SnoopSnitch 671:MTP Level 1 659:MTP Level 2 643:MTP Level 3 604:Application 442:databases. 152:4ESS switch 3042:Categories 2816:Antarctica 2775:Toasternet 2697:Television 2180:Paul Baran 2112:Television 2096:(teletype) 2089:Telegraphy 2067:transistor 2045:Phryctoria 2015:Photophone 1993:Smartphone 1983:Mass media 1795:2024-09-24 1784:Veritasium 1708:2024-05-28 1646:2020-07-03 1621:2018-03-31 1591:2018-03-31 1561:2017-05-05 1516:2024-09-23 1360:2016-04-19 1294:2016-06-30 1074:2024-05-28 970:References 362:voice mail 190:Pseudo SS7 64:March 1993 3063:Telephony 2941:Dial tone 2800:Americas 2789:Locations 2760:Internet2 2521:Bandwidth 2225:Vint Cerf 2122:streaming 2100:Telephone 2040:Semaphore 1931:streaming 1703:0013-0613 1069:0013-0613 949:SS7 probe 885:Wireshark 731:, or the 713:OSI Model 511:timeslots 333:DSS1/DASS 314:Signaling 231:(ZZK-7). 129:tear down 99:telephony 79:Committee 2981:Zip tone 2946:Ringtone 2868:Category 2755:Internet 2745:CYCLADES 2662:Ethernet 2612:Concepts 2536:terminal 2487:wireless 2310:Bob Kahn 2153:Pioneers 1978:Internet 1869:Cable TV 1665:Archived 1510:Archived 1455:Archived 1339:and the 927:See also 921:Diameter 900:and the 858:Ted Lieu 817:(MM) or 809:control. 807:handover 751:and the 707:The SS7 666:Physical 498:(SSPs), 338:trunks. 256:blue box 221:number 7 202:Internet 46:In force 2986:2600 Hz 2888:Commons 2878:Outline 2831:Oceania 2750:FidoNet 2735:ARPANET 2548:circuit 2117:digital 1846:History 1800:YouTube 1354:Youtube 1350:(Video) 1289:EETimes 873:malware 851:Telenor 790:of the 638:Network 564:SIGTRAN 552:SIGTRAN 299:SIGTRAN 235:History 186:SIGTRAN 105:Website 62:(03/93) 2826:Europe 2796:Africa 2780:Usenet 2740:BITNET 2677:Mobile 2553:packet 2062:MOSFET 2057:device 1854:Beacon 1772:  1753:  1734:  1701:  1431:rooted 1174:  1101:  1067:  747:, the 725:BT IUP 479:switch 95:Domain 43:Status 2809:South 2804:North 2765:JANET 2702:Telex 2692:Radio 2531:Nodes 2526:Links 2447:media 2025:Radio 2010:Pager 1938:Drums 1904:video 1899:image 1889:audio 1458:(PDF) 1451:(PDF) 889:Snort 821:(CM). 772:BSSAP 763:BSSAP 741:RANAP 632:, ... 617:IS-41 523:DS0As 156:ITU-T 73:ITU-T 2821:Asia 2707:UUCP 2667:ISDN 1770:ISBN 1751:ISBN 1732:ISBN 1699:ISSN 1673:2020 1417:2014 1389:2014 1172:ISBN 1142:2719 1125:IETF 1099:ISBN 1065:ISSN 887:and 792:SCCP 786:and 647:SCCP 630:ISUP 622:TCAP 609:INAP 578:and 576:M3UA 572:M2UA 568:M2PA 566:are 556:SCTP 515:DS0s 454:and 438:and 401:ISUP 303:M3UA 293:The 286:and 223:and 180:The 54:1984 2712:WAN 2682:NGN 2672:LAN 1953:Fax 1894:DCT 1139:RFC 1129:doi 1020:doi 993:doi 917:FCC 784:MTP 626:CAP 619:... 613:MAP 580:SUA 336:PBX 121:SS7 3044:: 1697:. 1693:. 1675:. 1638:. 1609:. 1579:. 1554:. 1533:. 1474:. 1406:. 1378:. 1352:. 1343:: 1287:. 1269:. 1254:^ 1150:^ 1137:. 1127:. 1123:. 1083:^ 1063:. 1059:. 1032:^ 1016:57 1014:. 989:56 987:. 755:. 727:, 645:+ 628:, 624:, 615:, 611:, 582:. 574:, 570:, 527:T1 519:E1 458:. 419:. 388:. 384:, 380:, 376:, 372:, 368:, 364:, 360:, 352:, 288:R2 284:R1 217:C7 204:. 2922:e 2915:t 2908:v 2839:) 2835:( 1830:e 1823:t 1816:v 1802:. 1778:. 1759:. 1740:. 1711:. 1649:. 1624:. 1594:. 1564:. 1519:. 1419:. 1391:. 1363:. 1325:. 1297:. 1267:" 1231:( 1218:( 1180:. 1144:. 1131:: 1107:. 1077:. 1026:. 1022:: 999:. 995:: 770:( 696:e 689:t 682:v 513:( 119:( 20:)

Index

Signaling System No 7
ITU-T
telephony
https://www.itu.int/rec/T-REC-Q.700
telephony signaling
tear down
public switched telephone network
local number portability
Short Message Service
4ESS switch
ITU-T
American National Standards Institute
European Telecommunications Standards Institute
Telecommunication Technology Committee
two-factor authentication
Internet Engineering Task Force
SIGTRAN
Stream Control Transmission Protocol
Internet Protocol
Internet
United Kingdom
Signaling System No. 5
in-band signaling
multi-frequency
blue box
common-channel signaling
Signaling System No. 6
Signaling System No. 5
R1
R2

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