Global title: Difference between revisions
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A '''Global Title''' (GT) is an [[Network Layer|address]] used in the [[Signalling Connection Control Part|SCCP]] protocol for routing signaling messages on [[telecommunications]] networks. In theory, a global title is a unique address which refers to only one destination, though in practice destinations can change over time. |
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{{More citations needed|date=December 2016}} |
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A '''global title''' ('''GT''') is an [[Network Layer|address]] used in the [[Signalling Connection Control Part|SCCP]] protocol for routing signaling messages on [[telecommunications]] networks. In theory, a global title is a unique address which refers to only one destination, though in practice destinations can change over time. |
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__TOC__ |
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==Overview== |
==Overview== |
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The |
The global title is similar in purpose on the [[PSTN]] to the [[host name]] on the [[Internet]]. In design, however, global titles are quite different. The structure is usually hierarchical, the value can be of variable length, and is not necessarily a wholly numeric value—though it often is for issues of [[backward compatibility]] and association with regular [[telephone number]]s. |
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==Structure of the global |
==Structure of the global-title value== |
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The structure of a global title for [[ITU-T]] applications is officially defined in [http://www.itu.int/rec/T-REC-Q.713/en/ ITU-T Recommendation Q.713], and further extended in the supporting [[numbering plan]] standards. Other national variants of [[Signalling Connection Control Part]] ([[Signalling Connection Control Part|SCCP]]), such as the [[American National Standards Institute]] variant specified in ANSI T1.112/2000, define their own format for the Global Title. The value of a global title is a sequence of attributes which modify the address value. To summarize: |
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The structure of a global title for [[ITU-T]] applications is officially defined in [http://www.itu.int/rec/T-REC-Q.713/en/ ITU-T Recommendation Q.713], and further extended in the supporting [[numbering plan]] standards. Other national variants of [[Signalling Connection Control Part]] ([[Signalling Connection Control Part|SCCP]]), such as the [[American National Standards Institute]] variant specified in ANSI T1.112/2000, define their own format for the Global Title. The value of a global title is a sequence of attributes which modify the address value. To summarize: |
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===Global Title Format=== |
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===Global title format=== |
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A global title can be in a variety of formats, most of which are each defined in separate standards. The format parameter indicates which of the available formats are in use. Each format can include any of the subsequent parameters. |
A global title can be in a variety of formats, most of which are each defined in separate standards. The format parameter indicates which of the available formats are in use. Each format can include any of the subsequent parameters. |
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===Numbering |
===Numbering plan indicator=== |
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The [[Telephone numbering plan#Numbering plan indicator|numbering plan indicator]] (NPI) describes which numbering plan will be used for the global title. The chosen numbering plan will aid the routing system in determining the correct network system to direct the message. |
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===Type of number=== |
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The [[Numbering Plan Indicator]] (NPI) describes which [[numbering plan]] will be used for the global title. The numbering plan chosen will aid the routing system in determining the correct network system to direct the message. |
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The [[type of number]] (TON) or Nature of Address Indicator (NAI) parameter, which is of relevance to [[E.164]] (regular telephone) numbers for example, indicates the scope of the address value, such as whether it is an international number (i.e. including the [[List of E.164 country codes|country code]]), a "national" or domestic number (i.e. without country code), and other formats such as "local" format (e.g. in the U.S., without an [[area code]]). |
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=== |
===Translation type=== |
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The translation type (TT) parameter is used in a network to indicate the preferred method of ''global title analysis'' (see below). Normally in European networks, this parameter is set to 0 (the default) value. In [[North America]]n mobile networks, different translation types are used for analysis of the [[International mobile subscriber identity|IMSI]] and for messages between telephone systems. This parameter is valuable in complex routing problems, where the same number has to be routed differently depending on the circumstances, such as those introduced by [[Local number portability|number portability]] resolution. |
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The [[Type of Number]] (TON) or Nature of Address Indicator (NAI) parameter, which is of relevance to [[E.164]] (regular telephone) numbers for example, indicates the [[scope]] of the address value, such as whether it is an international number (i.e. including the [[List of E.164 country codes|country code]]), a "national" or domestic number (i.e. without country code), and other formats such as "local" format (e.g. in the U.S., without an [[area code]]). |
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===Translation Type=== |
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The translation type (TT) parameter is used in a network to indicate the preferred method of ''global title analysis'' (see below). Normally in European networks, this parameter is set to 0 (the default) value. In [[North America]]n mobile networks, different translation types are used for analysis of the [[IMSI]] and for messages between telephone systems. This parameter is valuable in complex routing problems, where the same number has to be routed differently depending on the circumstances, such as those introduced by [[Telephone number portability|number portability]] resolution. |
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==Global title translation== |
==Global title translation== |
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'''Global title translation''' ('''GTT''') is the [[Signaling System 7|SS7]] equivalent to [[Internet Protocol|IP]] routing. Translation examines the destination address (e.g. the number being called) and decides how to identify it over the telephone network. This process can include ''global title analysis'', which is the act of looking up the number and finding a result address, and ''global title modification''. |
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It is possible for the result of global title translation to be '''route on [[Subsystem number|SSN]]'''. This means that, instead of the Global Title routing, lower level [[Message Transfer Part|MTP]] routing will be used for this message from this point on. Equivalently, in a system using [[SS7 over IP]] (for example, [[SIGTRAN]]), the result from Global Title Translation may be to route to an IP server, though the exact details depend greatly on which variant of SS7 over IP is being used.<ref>{{IETF RFC|3868}}</ref> |
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'''Global title translation''' is the [[Signaling System 7|SS7]] equivalent to [[Internet Protocol|IP]] routing. Translation examines the destination address (e.g. the number being called) and decides how to identify it over the telephone network. This process can include ''global title analysis'', which is the act of looking up the number and finding a result address, and ''global title modification''. |
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===Global title analysis=== |
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It is possible for the result of '''Global Title Translation''' to be '''Route on [[Subsystem number|SSN]]'''. This means that, instead of the Global Title routing, lower level [[Message Transfer Part|MTP]] routing will be used for this message from this point on. Equivalently, in a system using [[SS7 over IP]] (for example, [[SIGTRAN]]), the result from Global Title Translation may be to a route to an IP server, though the exact details depend greatly on which variant of [[SS7 over IP]] is being used.<ref>RFC 3868</ref> |
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The situation in this case is somewhat complicated by the additional parameters possible in the global title. Each set of parameter values (TT=0 NP=E.164, TON=INT) can be treated separately from each other one (TT=0 NP=E.214, TON=INT). This means that, instead of one single table, we potentially need a separate table for each possible set of values. |
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The variable length of the global title makes certain optimisations that can be used in IP routing not so easy to use here. The number analysis of a Global Title is most often done in a tree structure. This allows reasonably efficient analysis to any depth which is chosen. |
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===Global Title Analysis=== |
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Global Title Analysis together with Global Title Translation. The situation in this case is somewhat complicated by the additional parameters possible in the global title. Each set of parameter values (TT=0 NP=E.164, TON=INT) can be treated separately from each other one (TT=0 NP=E.214, TON=INT). This means that, instead of one single table, we potentially need a separate table for each possible set of values. |
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The variable length of the global title makes certain optimisations that can be used in IP routing are not so easy to use here. The number analysis of a Global Title is most often done in a tree structure. This allows reasonably efficient analysis to any depth which is chosen. |
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In the end, global title analysis gives some result. The exact possibilities vary from system to system, is sometimes called an "action" or is integrated into the analysis table. |
In the end, global title analysis gives some result. The exact possibilities vary from system to system, is sometimes called an "action" or is integrated into the analysis table. |
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The ''destination'' would typically be given as a signalling [[point code]] in an [[Message Transfer Part|MTP]] network, but could also be an IP system if we are using |
The ''destination'' would typically be given as a signalling [[point code]] in an [[Message Transfer Part|MTP]] network, but could also be an IP system if we are using SS7 over IP.<ref>{{IETF RFC|3868}}</ref> |
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===Routing |
===Routing structure=== |
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The most commonly used numbering plans for global title routing are [[E.164]] and [[E.214]] (although E.212 is also common in America). These simply look like telephone numbers. That is to say, in the most common, international, variant there is a [[country code]] at the start of the number and a [[Network Code]] immediately following the ''country code''. Beyond that is the ''subscriber number'' or ''mobile subscriber identity'' number, though even that may be divided into sections. This structure allows for the use of hierarchical routing: |
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* International SCCP gateways know which systems handle each of the other countries |
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* The international SCCP gateway belonging to each country knows which SCCP gateways handle each network |
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* The SCCP gateway of each network knows the network's own internal structure |
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In America, the limitations of the [[North American Numbering Plan]] mean that the destination country is not immediately obvious from the '''called party address'''. However, the fact that there is unified administration means that this can be overcome by having complete analysis at every point where it is needed. |
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The most commonly used numbering plans for global title routing are [[E.164]] and [[E.214]] (although E.212 is also common in America). These simply look like telephone numbers. That is to say, in the most common, international, variant there is a [[country code]] at the start of the number and a [[Network Code]] immediately following the ''country code''. Beyond that is the ''subscriber number'' or ''mobile subscriber identity'' number, though even that may be divided into sections. This structure allows for the use of hierarchical routing. |
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==Global title routing in mobile networks== |
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* international SCCP gateways know which systems handle each of the other countries |
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{{See also|Mobile Application Part}} |
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* the international SCCP gateway belonging to each country knows which SCCP gateways handle each network |
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* the SCCP gateway of each network knows the networks own internal structure |
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In mobile networks, there are database queries such as "how can I tell if this subscriber is really who he says he is" (MAP_Send_Authentication_Info) which have to be routed back to the database which holds the subscriber's information (the [[Network switching subsystem#Home location register (HLR)|home location register]] [HLR], or in this case, the [[Network switching subsystem#Authentication center (AuC)|authentication center]] [AuC]). |
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In America, the limitations of the [[North American Number Plan]] mean that the destination country is not immediately obvious from the '''called party address'''. However, the fact that there is unified administration means that this can be overcome by having complete analysis at every point where it is needed. |
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Unfortunately, at the time the subscriber first arrives, we don't know which HLR is the subscriber's HLR. For this reason, the queries have to be routed on the subscriber's identity (IMSI) is used to generate the '''called party address''' in the message. How this is done depends whether we are in world area 1 (North America) or somewhere else. |
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===Global Title Modification=== |
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There are three types of GT in use in mobile networks known as E.164 (MSISDN), E.212(IMSI) and E.214(MGT):<ref>[http://www.3gpp.org/ftp/Specs/html-info/29002.htm 3GPP TS 29.002] Mobile Application Part (MAP) specification, section SCCP addressing</ref> |
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In Global Title Translation it is quite normal that at some point the Global Title will have to be changed. This happens, for example, as GSM mobility management messages enter and leave networks in America. In America, typically most routing of mobility management messages for all [[mobile network]]s is done using the [[E.212]] (IMSI) number. In international networks, [[E.214]] is always used. |
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* E.164(MSISDN) = CC+NDC+SN - ( Country Code+National Destination Code+Subscriber Number) e.g. 91-98-71405178 |
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At the boundary incoming toward America (this can mean the [[Signaling Transfer Point]] at the edge of the American operator's network), numbers routed from European networks are converted from E.214 numbers into E.212 numbers. In the outgoing direction, from America toward the rest of the world, are converted from E.212 numbers into E.214 numbers. |
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* E.212(IMSI) = MCC+MNC+MSIN - (Mobile Country Code+Mobile Network Code+Mobile Subscription Identification Number) e.g. 404-68-6600620186 (MTNL delhi) - |
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* E.214(MGT) = combination of E.212 and E.164(CC+NDC+MSIN) (Exact combination is defined in the operators IR21 document) |
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===Mobile global title routing (except North America)=== |
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==Global Title Routing in Mobile Networks== |
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Everywhere in the world, except North America, the subscriber's IMSI is converted to a Mobile Global Title (MGT) [[E.214]] number. See the entry about the [[International mobile subscriber identity|IMSI]] for more details. The E.214 number has a structure which is similar to the E.164 number, and, except in a mobile network it can be routed identically. This means that the same routing tables can be used for both and means considerably reduced administrative overhead in maintaining the tables. |
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{{seealso|Mobile Application Part}} |
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In mobile networks, there are database queries such as "how can I tell if this subscriber is really who he says he is" (MAP_Send_Authentication_Info) which have to be routed back to the database which holds the subscriber's information (the [[Network Switching Subsystem|HLR]], or in this case, the [[Authentication Center|AUC]]). |
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Unfortunately, at the time the subscriber first arrives, we don't know which HLR is the subscriber's HLR. For this reason, the queries have to be routed on the subscriber's identity ([[IMSI]]) is used to generate the '''called party address''' in the message. How this is done depends whether we are in world area 1 (North America) or somewhere else. |
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Mainly there are three type of GT in use in mobile networks known as E.164 (MSISDN), E.212(IMSI) and E.214(MGT).{{Citation needed|date=June 2008}} |
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* E.164(MSISDN) = CC+NDC+SN, e.g. 91-98-71405178 |
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* E.212(IMSI) = MCC+MNC+MSIN, e.g. 404-68-6600620186 (MTNL delhi) |
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* E.214(MGT) = combination of E.212 and E.164 (Exact combination is defined in the operators IR21 document) |
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===Mobile Global Title Routing (Except North America)=== |
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Everywhere in the world, except North America, the subscriber's IMSI is converted to a Mobile Global Title (MGT) [[E.214]] number. See the entry about the [[IMSI]] for more details. The E.214 number has a structure which is similar to the E.164 number, and, except in a mobile network it can be routed identically. This means that the same routing tables can be used for both and means considerably reduced administrative overhead in maintaining the tables. |
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Once a signalling message with an E.214 number enters a mobile network in its own country, the routing is dependent on the operator of that mobile network. In networks without [[Mobile number portability|number portability]], it is normal that the [[MSIN]] has a structure and that, by analysing the first few digits we can further route the message to the right element. |
Once a signalling message with an E.214 number enters a mobile network in its own country, the routing is dependent on the operator of that mobile network. In networks without [[Mobile number portability|number portability]], it is normal that the [[MSIN]] has a structure and that, by analysing the first few digits we can further route the message to the right element. |
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===IMSI |
===IMSI routing (North America)=== |
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In World Area 1 (corresponding to North America) [[American National Standards Institute|ANSI]] [[Signalling Connection Control Part|SCCP]] is in use. In this case, due to North American standards, the routing of mobility related messages must be done with the E.212 number directly. This has the advantage that it is easier to identify to which country messages should be routed based on the mobile country code. The design of the [[North American Number Plan]] means that there is not a separate country code for each country in [[North America]]. Working with E.214 numbers would not be an insurmountable challenge, as can be seen from the fact that routing of phone calls using E.164 numbers is normal, but it would mean adding full E.164 routing tables to [[Signal transfer point|signalling transfer points]] where it has never been needed before. |
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==References== |
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In World Area 1 (corresponding to North America) [[American National Standards Institute|ANSI]] [[Signalling Connection Control Part|SCCP]] is in use. In this case, due to North American standards, the routing of mobility related messages must be done with the E.212 number directly. This has the advantage that in it is easier to identify to which country messages should be routed based on the mobile country code. The design of the [[North American Number Plan]] means that there is not a separate country code for each country in [[North America]]. Working with E.214 numbers would not be an insurmountable challenge, as can be seen from the fact that routing of phone calls using E.164 numbers is normal, but it would mean adding full E.164 routing tables to [[Signal transfer point|signalling transfer points]] where it has never been needed before. |
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That is the simplest way to search the destination. |
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===Routing of mobility messages on the ANSI / ITU Boundary=== |
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Where a signalling message travels from North America to the rest of the world or from the rest of the world to North America, there must be a conversion done from [[E.212]] based global title to [[E.214]] based global title. This conversion is reasonably simple, well defined and fully reversible. The conversion is not totally simple since each individual network must be listed. |
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Recommendation E.214 has been interpreted as suggesting that the analysis of the Mobile Country Code (MCC) and Mobile Network Code (MNC) should be done separately. The relationship between the MNC and the Network Code (NC), however, varies from country to country as does the length of the MNC (two or three digits). This means that the analysis of the MNC is dependent on the analysis of the MCC, or alternatively that the analysis must be done for all five or six digits at once (which is how it is done in practise across at least five separate switch vendors). |
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Examples |
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Outbound from America: |
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*NPI=E.212: 28405 xxxxxxxxxx (284 = [[Bulgaria]] [[List of mobile country codes|MCC]] + 05 = [[Globul]] MNC) -> |
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*NPI=E.214: 359888 xxxxxxxxx (359 = [[Bulgaria]] [[country code]]) |
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Please note the truncation of the number by one digit since E.214 numbers, as with E.164 numbers, have a maximum length of 15 digits. |
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Inbound toward America: |
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*NPI=E.214: 14054 xxxxxxxxx (1 = [[United States|U.S.]] [[country code]]) -> |
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*NPI=E.212: 310150 xxxxxxxxx (310 = [[United States|U.S.]] [[List of mobile country codes|MCC]] + 150 = [[Cingular]] MNC) |
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==Notes== |
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{{Reflist}} |
{{Reflist}} |
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[[Category: |
[[Category:ITU-T recommendations]] |
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[[Category:Signaling System 7]] |
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[[fr:Global Title]] |
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Latest revision as of 19:21, 24 March 2023
| SS7 protocols by OSI layer | |
| Application | INAP, MAP, IS-41... TCAP, CAP, ISUP, ... |
|---|---|
| Network | MTP Level 3 + SCCP |
| Data link | MTP Level 2 |
| Physical | MTP Level 1 |
 | This article needs additional citations for verification. (December 2016) |
A global title (GT) is an address used in the SCCP protocol for routing signaling messages on telecommunications networks. In theory, a global title is a unique address which refers to only one destination, though in practice destinations can change over time.
Overview[edit]
The global title is similar in purpose on the PSTN to the host name on the Internet. In design, however, global titles are quite different. The structure is usually hierarchical, the value can be of variable length, and is not necessarily a wholly numeric value—though it often is for issues of backward compatibility and association with regular telephone numbers.
Structure of the global-title value[edit]
The structure of a global title for ITU-T applications is officially defined in ITU-T Recommendation Q.713, and further extended in the supporting numbering plan standards. Other national variants of Signalling Connection Control Part (SCCP), such as the American National Standards Institute variant specified in ANSI T1.112/2000, define their own format for the Global Title. The value of a global title is a sequence of attributes which modify the address value. To summarize:
Global title format[edit]
A global title can be in a variety of formats, most of which are each defined in separate standards. The format parameter indicates which of the available formats are in use. Each format can include any of the subsequent parameters.
Numbering plan indicator[edit]
The numbering plan indicator (NPI) describes which numbering plan will be used for the global title. The chosen numbering plan will aid the routing system in determining the correct network system to direct the message.
Type of number[edit]
The type of number (TON) or Nature of Address Indicator (NAI) parameter, which is of relevance to E.164 (regular telephone) numbers for example, indicates the scope of the address value, such as whether it is an international number (i.e. including the country code), a "national" or domestic number (i.e. without country code), and other formats such as "local" format (e.g. in the U.S., without an area code).
Translation type[edit]
The translation type (TT) parameter is used in a network to indicate the preferred method of global title analysis (see below). Normally in European networks, this parameter is set to 0 (the default) value. In North American mobile networks, different translation types are used for analysis of the IMSI and for messages between telephone systems. This parameter is valuable in complex routing problems, where the same number has to be routed differently depending on the circumstances, such as those introduced by number portability resolution.
Global title translation[edit]
Global title translation (GTT) is the SS7 equivalent to IP routing. Translation examines the destination address (e.g. the number being called) and decides how to identify it over the telephone network. This process can include global title analysis, which is the act of looking up the number and finding a result address, and global title modification.
It is possible for the result of global title translation to be route on SSN. This means that, instead of the Global Title routing, lower level MTP routing will be used for this message from this point on. Equivalently, in a system using SS7 over IP (for example, SIGTRAN), the result from Global Title Translation may be to route to an IP server, though the exact details depend greatly on which variant of SS7 over IP is being used.[1]
Global title analysis[edit]
The situation in this case is somewhat complicated by the additional parameters possible in the global title. Each set of parameter values (TT=0 NP=E.164, TON=INT) can be treated separately from each other one (TT=0 NP=E.214, TON=INT). This means that, instead of one single table, we potentially need a separate table for each possible set of values.
The variable length of the global title makes certain optimisations that can be used in IP routing not so easy to use here. The number analysis of a Global Title is most often done in a tree structure. This allows reasonably efficient analysis to any depth which is chosen.
In the end, global title analysis gives some result. The exact possibilities vary from system to system, is sometimes called an "action" or is integrated into the analysis table.
The destination would typically be given as a signalling point code in an MTP network, but could also be an IP system if we are using SS7 over IP.[2]
Routing structure[edit]
The most commonly used numbering plans for global title routing are E.164 and E.214 (although E.212 is also common in America). These simply look like telephone numbers. That is to say, in the most common, international, variant there is a country code at the start of the number and a Network Code immediately following the country code. Beyond that is the subscriber number or mobile subscriber identity number, though even that may be divided into sections. This structure allows for the use of hierarchical routing:
- International SCCP gateways know which systems handle each of the other countries
- The international SCCP gateway belonging to each country knows which SCCP gateways handle each network
- The SCCP gateway of each network knows the network's own internal structure
In America, the limitations of the North American Numbering Plan mean that the destination country is not immediately obvious from the called party address. However, the fact that there is unified administration means that this can be overcome by having complete analysis at every point where it is needed.
Global title routing in mobile networks[edit]
In mobile networks, there are database queries such as "how can I tell if this subscriber is really who he says he is" (MAP_Send_Authentication_Info) which have to be routed back to the database which holds the subscriber's information (the home location register [HLR], or in this case, the authentication center [AuC]).
Unfortunately, at the time the subscriber first arrives, we don't know which HLR is the subscriber's HLR. For this reason, the queries have to be routed on the subscriber's identity (IMSI) is used to generate the called party address in the message. How this is done depends whether we are in world area 1 (North America) or somewhere else.
There are three types of GT in use in mobile networks known as E.164 (MSISDN), E.212(IMSI) and E.214(MGT):[3]
- E.164(MSISDN) = CC+NDC+SN - ( Country Code+National Destination Code+Subscriber Number) e.g. 91-98-71405178
- E.212(IMSI) = MCC+MNC+MSIN - (Mobile Country Code+Mobile Network Code+Mobile Subscription Identification Number) e.g. 404-68-6600620186 (MTNL delhi) -
- E.214(MGT) = combination of E.212 and E.164(CC+NDC+MSIN) (Exact combination is defined in the operators IR21 document)
Mobile global title routing (except North America)[edit]
Everywhere in the world, except North America, the subscriber's IMSI is converted to a Mobile Global Title (MGT) E.214 number. See the entry about the IMSI for more details. The E.214 number has a structure which is similar to the E.164 number, and, except in a mobile network it can be routed identically. This means that the same routing tables can be used for both and means considerably reduced administrative overhead in maintaining the tables.
Once a signalling message with an E.214 number enters a mobile network in its own country, the routing is dependent on the operator of that mobile network. In networks without number portability, it is normal that the MSIN has a structure and that, by analysing the first few digits we can further route the message to the right element.
IMSI routing (North America)[edit]
In World Area 1 (corresponding to North America) ANSI SCCP is in use. In this case, due to North American standards, the routing of mobility related messages must be done with the E.212 number directly. This has the advantage that it is easier to identify to which country messages should be routed based on the mobile country code. The design of the North American Number Plan means that there is not a separate country code for each country in North America. Working with E.214 numbers would not be an insurmountable challenge, as can be seen from the fact that routing of phone calls using E.164 numbers is normal, but it would mean adding full E.164 routing tables to signalling transfer points where it has never been needed before.