네트워킹

오늘:
2,542
어제:
2,589
전체:
2,707,441

고객센타 : 070-7752-2000
팩스 : 070-7752-2001
휴대폰 : 010-9513-0019
email : voipkorea@yahoo.co.kr

국민은행
(주)제이에스솔루션
047101-04-155519

Flag Counter
■ 무료 : 유선 집전화 휴대폰 ( 한국 미국 중국 카나다) ↔ (국내 해외 여행자 상사 주재원 유학생) / 가입무 무제한무료■

 

http://www.telecomspace.com/ss7.html

 

Signalling System #7 (SS7)


There are two essential components to all telephone calls. The first, and most obvious, is the actual content—our voices, faxes, modem data, etc. The second is the information that instructs telephone exchanges to establish connections and route the “content” to an appropriate destination. Telephony signaling is concerned with the creation of standards for the latter to achieve the former. These standards are known as protocols. SS7 or Signaling System Number 7 is simply another set of protocols that describe a means of communication between telephone switches in public telephone networks. They have been created and controlled by various bodies around the world, which leads to some specific local variations, but the principal organization with responsibility for their administration is the International Telecommunications Union or ITU-T.

Signalling System Number 7 (SS#7 or C7) is the protocol used by the telephone companies for interoffice signalling. In the past, in-band signalling techniques were used on interoffice trunks. This method of signalling used the same physical path for both the call-control signalling and the actual connected call. This method of signalling is inefficient and is rapidly being replaced by out-of-band or common-channel signalling techniques.

To understand SS7 we must first understand something of the basic inefficiency of previous signaling methods utilized in the Public Switched Telephone Network (PSTN). Until relatively recently, all telephone connections were managed by a variety of techniques centered on “in band” signaling.

A network utilizing common-channel signalling is actually two networks in one:

   1. First there is the circuit-switched "user" network which actually carries the user voice and data traffic. It provides a physical path between the source and destination.
   2. The second is the signalling network which carries the call control traffic. It is a packet-switched network using a common channel switching protocol.

The original common channel interoffice signalling protocols were based on Signalling System Number 6 (SS#6). Today SS#7 is being used in new installations worldwide. SS#7 is the defined interoffice signalling protocol for ISDN. It is also in common use today outside of the ISDN environment.

The primary function of SS#7 is to provide call control, remote network management, and maintenance capabilities for the inter- office telephone network. SS#7 performs these functions by exchanging control messages between SS#7 telephone exchanges (signalling points or SPs) and SS#7 signalling transfer points (STPs).
SS7 architecture diagram

The switching offices (SPs) handle the SS#7 control network as well as the user circuit-switched network. Basically, the SS#7 control network tells the switching office which paths to establish over the circuit-switched network. The STPs route SS#7 control packets across the signalling network. A switching office may or may not be an STP.

SS7 Protocol layers:

The SS7 network is an interconnected set of network elements that is used to exchange messages in support of telecommunications functions. The SS7 protocol is designed to both facilitate these functions and to maintain the network over which they are provided. Like most modern protocols, the SS7 protocol is layered.

 

Physical Layer (MTP-1)

This defines the physical and electrical characteristics of the signaling links of the SS7 network. Signaling links utilize DS–0 channels and carry raw signaling data at a rate of 56 kbps or 64 kbps (56 kbps is the more common implementation).

Message Transfer Part—Level 2 (MTP-2)

The level 2 portion of the message transfer part (MTP Level 2) provides link-layer functionality. It ensures that the two end points of a signaling link can reliably exchange signaling messages. It incorporates such capabilities as error checking, flow control, and sequence checking.

Message Transfer Part—Level 3 (MTP-3)

The level 3 portion of the message transfer part (MTP Level 3) extends the functionality provided by MTP level 2 to provide network layer functionality. It ensures that messages can be delivered between signaling points across the SS7 network regardless of whether they are directly connected. It includes such capabilities as node addressing, routing, alternate routing, and congestion control.

SS7 layer architecture diagram

Signaling Connection Control Part (SCCP)

The signaling connection control part (SCCP) provides two major functions that are lacking in the MTP. The first of these is the capability to address applications within a signaling point. The MTP can only receive and deliver messages from a node as a whole; it does not deal with software applications within a node.

While MTP network-management messages and basic call-setup messages are addressed to a node as a whole, other messages are used by separate applications (referred to as subsystems) within a node. Examples of subsystems are 800 call processing, calling-card processing, advanced intelligent network (AIN), and custom local-area signaling services (CLASS) services (e.g., repeat dialing and call return). The SCCP allows these subsystems to be addressed explicitly.

ISDN User Part (ISUP)

ISUP user part defines the messages and protocol used in the establishment and tear down of voice and data calls over the public switched network (PSN), and to manage the trunk network on which they rely. Despite its name, ISUP is used for both ISDN and non–ISDN calls. In the North American version of SS7, ISUP messages rely exclusively on MTP to transport messages between concerned nodes.

Transaction Capabilities Application Part (TCAP)

TCAP defines the messages and protocol used to communicate between applications (deployed as subsystems) in nodes. It is used for database services such as calling card, 800, and AIN as well as switch-to-switch services including repeat dialing and call return. Because TCAP messages must be delivered to individual applications within the nodes they address, they use the SCCP for transport.

Operations, Maintenance, and Administration Part (OMAP)

OMAP defines messages and protocol designed to assist administrators of the SS7 network. To date, the most fully developed and deployed of these capabilities are procedures for validating network routing tables and for diagnosing link troubles. OMAP includes messages that use both the MTP and SCCP for routing.

 Read more on the individual SS7 protocol layers:  MTP  --  SCCP  --  ISUP  --   TCAP  --  MAP  --  INAP         

 

SS7 Resources:

SS7 Discussion Forum

IEC: SS7 Tutorial

SS7 History (pdf)

www.pt.com SS7 Tutorial (html) (pdf)

Cisco SS7 Fundamentals(html) (pdf)

SS7 Suite

조회 수 :
13662
등록일 :
2012.01.22
17:00:58 (*.160.42.233)
엮인글 :
http://webs.co.kr/index.php?document_srl=716&act=trackback&key=d48
게시글 주소 :
http://webs.co.kr/index.php?document_srl=716
List of Articles
번호 제목 글쓴이 날짜 조회 수
38 IPAD MINI2 아이패드 미니2 LTE 4G 지원국가 리스트 admin 2015-09-26 1022
37 Remote Party ID SIP Privacy Headers P-Preferred-Identity Header admin 2015-05-15 1695
36 Voice over LTE - approaches, implementation, and test solutions admin 2014-11-02 3607
35 가상화 성능을 떨어뜨리는 다섯 가지 함정 클라우드 데이타센터 admin 2014-05-28 4427
34 데이터센터 가상화 admin 2014-05-28 4064
33 IP Multimedia Subsystem IMS file admin 2014-03-16 5365
32 통신회사/MVNO 통신사 목록/미국 admin 2013-12-21 10206
31 GSM 개요 개념 역사 기술규격 이동통신 표준 admin 2013-12-21 8395
30 프로그램별 포트 사용현황 file admin 2013-09-15 6328
29 SIP Status Codes admin 2013-08-14 8175
28 SS7_Tutorial 간단한 NO7 신호망 교환망 설명 file admin 2013-06-08 7397
27 Audios Video Image Codecs compression decompression admin 2013-05-25 11915
26 Telephone World 교환 통신시스템 정리 및 신호음 각종 톤 admin 2013-04-19 10655
25 H.323 연동의 문제점 2003년 admin 2013-03-22 6263
24 NHN 개발자 블로그 Hellow World admin 2013-03-09 6557
23 Detailed ISDN Cause Codes admin 2013-01-11 11683
22 DialingCode and CountryCode admin 2012-10-16 13151
21 Prepaid Roaming Using CAMEL (Roaming Implementation for Prepaid) Part 3 admin 2012-09-18 18436
20 SIP VOIP STUN TURN ICE SBC NAT 와 방화벽 admin 2012-08-22 12069
19 클라우드 컴퓨팅 시대가 다가오면서.. admin 2012-05-17 7962
18 IPTV의 핵심 기술. (전송 관련 기술 및 제품) admin 2012-05-11 11069
17 IPTV의 기본 개념 (VOD 와 IP multicating 그리고 인터넷 방송) admin 2012-05-11 10948
16 GSM GSMA RCS-e v1.1 admin 2012-05-07 17940
15 LTE 기술 개요 admin 2012-05-07 37947
14 이동통신 규격 LTE file admin 2012-05-07 13984
13 기간망 전자교환실 교환기와 내부랙 및 PCB admin 2012-04-04 8938
12 SIP h248 MECAGO MEDIA GATEWAY Control , SS7 admin 2012-03-03 8421
11 정부공공기관을 위한 인터넷전화 SIP 상호연동 서비스 시나리오 file admin 2012-02-07 11572
10 SS7 Protocol PPT file admin 2012-01-23 10612
9 SIP h248 MECAGO MEDIA GATEWAY Control , SS7 file admin 2012-01-22 8161
8 NGN file admin 2012-01-22 7553
» Signalling System #7 (SS7) admin 2012-01-22 13662
6 SS7 Protocol Book admin 2012-01-22 28682
5 Symmetrical RTP Support for MGCP-Based Calls admin 2011-12-16 30000
4 SIP 프로토콜 admin 2011-12-16 34398
3 KT 위성서비스 자료 file admin 2011-12-14 11643
2 PCM (Pulse Code Modulation) admin 2011-12-14 9774
1 PCM, G.711 admin 2011-12-14 10082