################################ ####################################========= ######## ## ## ######## \\ ############ ################## ############ \\ ############ ## DMS TELECOM ## ############ || ### ### || ############ ############ || ## ## // ## ## // ## Misc Telephony Part II by mechanic ## // ### ###====/ ########################################## _________ Contents: ^^^^^^^^^ 1.) Forward 2.) SS7: what it is and how it works 3.) European operators 4.) more acronyms : telco acro 5.) closing section: 1 ________ Forward: ^^^^^^^^ Hello yet again my phellow kiddies, today I will sk00l you yet again. In the first part of the misc. telephony series, I introduced you to the French Videotex/Minitel system and networks, and then gave you a taste of some acronyms. In This issue I will continue with the acronyms, sk00l ya'll a bit on signalling system 7, how it works, what it is, etc., andf I will also list the operator numbers for several different european countries, as well as a few extra goodies foe Europe. And, I will say this, since this is about telephony. NEWBIES! COSMOS is not the key or a huge joint in the telco arm. It is just a database manager that manages account information, etc. You all think that because Mitnick went through all that trouble to get the manuals, etc. for COSMOS that it is some huge thing, well, it is not. Sure, every telco has it, but it is not a very very very important part of the system. Ok, now that that is over and done with, time to continue on. Enjoy! section: 2 _________________________________ SS7: What it is and how it works: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Siganlling System 7 or SS7, is the magic that is behind even the simple calls that we place everyday. For the past five to ten years, telco's across the country have been upgrading to this seemingly "standard" communications protocol. This provides them with faster call setup times and the ability to expand the telco's service offerings. SS7 is an Advanced Intellegent Network, or AIN. =in-band versus out-of-band signalling= When a phone call is made, call-control information is sent to the local telco CO. The numbers or digits dialed are the main routing components that dtermine the destination of the call placed. If the call is local, the call may be connected through the same office from which the origionating line terminates. Many times when calls are placed, the switch at the CO that serv- ices a customers line, may have to route a call to another CO connected by a trunk line. If you remember from the last file, i explained the meaning of the trunk line, so just to refresh your memory it is defined as: a single circuit between two points, both of which are switching centers or individual distribution points. Call-control siganls like the digits dialed (number) and the answering indication from the other end are information used for managing a call connection. Using traditional signalling methods, the trunk line carries the call information between the CO's on the same set of wires that the signal for voice travels on. This is called in-band signalling. Because the call-control information is sent on the same wires as the voice call thus making it "in" the same wires as the information signals, making it IN-band signalling. SS7 hadles these tasks on a seperate facility called a signalling link. The signalling link can handle the call-control information for lots of calls going on at the same time. The voice signalling is still on the trunk lines. While the call-control information is sent on a seperate line. This is called out-of-band signalling. Thus the information is sent OUT of the voice signalling like to the signalling link, so the two are on seperate wires, but still are maintained. This is why it is called OUT-of-band signalling. Here is a simple diagram to depict the differences between signalling methods. in-band signalling _________ _________ | | | | | | | | | C.O. | | C.O. | | |--------------(voice trunk)------------| | |_________| |_________| out-of-band signalling _________ _________ | | | | | |------------(signalling link)----------| | | C.O. | | C.O. | | |--------------(voice trunk)------------| | |_________| |_________| SS7 is basically a packet switching network (PSN). Signalling info- rmation is carried in data packets between the CO's in much the same manner as X.25 or other packet switching protocols. SS7 is laid out over the existing telephony network. The primary benefit of SS7 is increased bandwidth for call signalling. The voice trunk is limited since it's existance was meant for just carrying voice or data. SS7 provides additional bandwidth, as a standardized protocol for sending information between different vendor equipment and increased data sending speed. Like a t-1 compared to ISDN. SS7 also provides the ability for CO's to provide more services to other CO's and their subscribers. Before SS7, many telecommunications vendors had proprietary means for sending feature related signals between CO's. This prevented true networking of services. When ISDN came about, or Integrated Digital Services Network, people complained about the minimum areas for usage of ISDN, thus creating "ISND islands", or isolated places where ISDN could be used. But with the advent of SS7, This is no longer a problem for complaint because SS7 encapsulates the ISDN call information in packets and transporting then across the network, bridging the islands. Signalling System 7 enhances alot of services including: -Enhanced 800 service -Custom Local Area Signalling Services (CLASS) -Advanced Intelligent network Services (AIN) -ISDN Connectivity -Cellular Service CLASS use SS7 capabilities to deliver services such as Caller ID (CID) automatic redial, and call screening. Call screening allows the customer to selectivyl accept or reject calls from selected numbers. The information for these services is transported between CO's by using the SS7 packets. This is a diagram depicting CLASS and enhanced 800 service using Transactions Capabilities Part (TCAP) queries. This shows the use of SS7 using special CLASS features. ___ /-------notify me when the called number is free-----> ___ | | | | |SSP| |SSP| |___| |___| <---------the called number is free---------------/ ___ /----------Who is the 800 service provider?----------> ___ | | | | |SSP| |SSP| |___| |___| <-------Sprint is the 800 service provider--------/ The ability to provide the information between CO's without depending on which equipment is used to send and recieve the packets of data. This requires global standards for SS7, thus making it more compatible. Global SS7 standards are made and created by International Telecommunications Union Telecommunications Sector (ITU-TS), or formally known as CCITT. Different countries create their own ITU standards when nessesary to do so. Virtually anyone in the commumications field today will know and recognize the Open Systems Interconnection (OSI) model. The OSI stack was de- veloped by the International Standards Organization (ISO) and contains seven layers identifiing communications functions between two nodes such as the physical mediumused for connection, the error correction method, addressing scheme and so on. SS7 is also a protocol and is based on the OSI protocol stack. The SS7 protocol is composed of: -Message transfer part -Signalling connection control part -ISDN user part -Transaction capability application part The MTP (message transfer part) provides the basic transport system for all SS7 messages. It is responsible for getting informastion from one network node to another in a reliable fashion. It makes up the first three levels of the protocol stack; the physical, link, and network layers. Layer 1, the physical level, specifies the actual medium used for transmission. It uses a four wire connection and typically a bit rate transfer of 64 kilobits per second (kb/s) or 56 kb/s. Layer 2, the link level, provides a number of functions to ensure that there is a good connection between two nodes for communicating. Error detection, error correction, signalling unit alignment and signalling link allignment are all part of the link layer's responsibility. On this layer, the actual signalling unit is formed. Signalling units are actually SS7's version of packets. Packets are sent back and fourth across the signalling link wether or not there is any data to be sent or not. Messages when sent are sent in MSU's (message sugnalling units), and when there is no messages to be sent, FISU's (fill-in signalling units) are sent. Layer 3, the network layer, has two basic responsibilities: address routing and network management. The first of these involves looking at each address on a packet, to determine where it's destination should be. This also requires that alternate routing and recovery procedures are implemented when a network failure occurs. The SCCP (signalling-connection control part), which is part of layer 4, provides additional routing and network management functions to the MTP. It allows applications to talk to each other at different nodes. For example, an application may want to re-route a message in the even of an application failure. You'll note from the SS7 protocol model diagram below, that there is a connection between the ISUP and SCCP layers. SCCP contains connection-oriented procedures that may be used by ISUP; however, ISUP doesn't use them today. It can communicate directly with MTP which suffices for current ISUP needs. New services may however make use of the SCCP connection-oriented capabilities. The ISUP (ISDN user part) of layer four provides connection oriented signalling between nodes. This type of signalling relates to setting up, taking down, and monitoring the connection of the actual voice path between CO's. ISUP is what provides the capablility for phone calls to be completed. It also provides such services as Caller ID. TCAP (transaction capabilities application part), also part of layer 4, allows connectionlerss communication between two applications usina a generic language. It provides query and response capabilities allowing nodes to request and respond to network and service information regaurdless of wheather there is an actual voice call established between two CO's. OPEN SYSTEMS INTERCONNECTION (OSI) and Signalling System 7 (SS7) protocol models diagram OSI LEVELS SS7 LEVELS -------------- ------------------ ----------------- ----------------- LAYER 7 | | | | -------------- | | | | LAYER 6 | | | | -------------- | TCAP | | ISUP | LAYER 5 | | | | -------------- | | | | LAYER 4 | | | | -------------- |__________________| |_________________| | | | | | | LEVEL 4 -------------------------------------- | | SCCP | | -------------------------------------- | | | LAYER3 | | _________________ ----------------------------------------------- ______ | NETWORK | LEVEL 3 ----------------------------------------------- --------------- LAYER 2 | LINK | LEVEL 2 ------- ----------------------------------------------- --------------- LAYER 1 | PHISICAL | LEVEL 1 ------- ----------------------------------------------- --------------- And this concludes the exent of the SS7 system and how it works. This is just a basic backround of SS7. I may write more and get into more grubby details in a later file, but this is it for now. section: 3 ___________________ European operators: ^^^^^^^^^^^^^^^^^^^ Here is a list of countries and operator numbers within that country. Austria OPT: +43 1 515 51 50 40 Belgium Belgacom: +32 2 202 81 11 Finland Telecom Finland: +358 2040 2346 France France Telecom +33 1 44 76 27 28 Germany Deutsche Bundespost Telekom: +49 261 123 11 Ireland Telecom Eircann: +353 1 714444 Italy SIP: +39 02 6211 Luxembourg P&T: +352 49 91 55 55 Netherlands PTT: +31 70 3434343 Portugal TLP: +351 1 14 32 81 Spain Telefonica: +34 1 584 08 44 Sweden Telia: +46 8 713 10 00 Comvik: +46 8 709 12 00 NordicTel: +46 8 626 73 50 Switzerland Swiss Telecom: +41 313 387 767 section: 4 ___________________________ more acronyms : telco acro: ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Here are some acronyms that are not defined, but what they stand for that you would be most likely to hear around telco operations. LMOS: Loop Maintenance Operations Center NAC: Network Administration Center SWAD: SWitching ADministrator SCC: Switching Control Center DBMC: DataBase Maintenance Center RCMAC: Recent Change Memory Administration Center FMAC: Facility Maintenance Administration Center IMC: Installation and Maintenance Center CPC: Circuit Provisioning Center EI: Equipment Installation PICS: Plug-in Inventory Control System LIP: Loop Technology Planner section: 5 ________ Closing: ^^^^^^^^ Welp, that's it for the second part of this Misc. Telephony series. I have no idea what will be in the next one, it will be at least a month before the next one comes out, I hope this was educational and informational.