Service Switching Point(SSP) 业务交换点是信令消息的产生或终结点，实质上就是本地交换系统（或交换中心CO），它发起呼叫或接收呼入。Signal Transfer Point(STP)完成路由器的功能，查看由SSP发来的消息，然后通过网络把每一个消息交换到合适的地方。STP把其它信令点和网络连接在一起组成更大的网络。Service Control Point(SCP) 是典型的访问数据库服务器，SCP是智能网业务的控制中心，负责业务逻辑的执行，提供呼叫处理功能，接收SSP送来的查询信息和查询数据库，验证后向SSP发出呼叫处理指令，接收SSP产生的话单并进行相应的处理。
在7号信令网中，ISUP信令（ISDN USER PART）消息是用来建立管理释放中心局话音交换机之间的话音中继电路的，提供话音和非话业务所需的信息交换，用以支持基本的承载业务和补充业务，例如：ISUP信令消息可以承载主叫ID, 主叫方的电话号码，用户名等。TCAP信令(Transaction Capabilities Application Part)消息 用以支持电话业务，如免费电话，本地号码可携带，卡业务，移动漫游以及认证业务。TCAP主要包括移动应用部分(MAP)和运营、维护和管理部分(OMAP)。MAP规定移动业务中漫游和频道越局转接等程序，OMAP仅提供MTP路由正式测试和SCCP路由正式测试程序。
偶的毕业设计就是那“未来”的SCTP。下面这封E-MAIL是11月3号由SCTP的设计者写给我们这些SCTP Player 的。该邮件回答的问题是
>I was wondering what kind of "Traditional Services" could be moved to SCTP
>to take fully advantage.
(不是打击你们噢。)
回答如下：
I believe that Peter Lei and I have at one time or another made:
1) ssh/openssh
2) mozilla
3) apache
4) ftp
But with a cavet.. we have not taken advantage of SCTP's
multi-streaming.. just switched the socket call to use SCTP's TCP model to test out to make sure we had no surprises :>
Now I know that University of Delewar PEL lab was showing some remarkable
results with FTP (modifying ftp to take advantage of mutli-streams).
They also were looking into enhancing mozilla/apache to use streams as well..
don't know how far they got ... I don't have there web site off the top of my head but google would find it for you.. they have quite a few papers and
studies.. and a lot of ongoing research..
I am sure there are other apps that could also benefit from SCTP.. the
problem I see consistently is the ole catch-22...
Developer of new app (or old app).. Gee I don't see ALL systems have
SCTP and I don't want to deploy something that is not everywhere without having to do fancy steps with the o/s to get it (translated buy additional software).
I will instead jury rig my application to fit TCP, which I fully admit would be better to run over SCTP.. but
I will make it fit over TCP anyway until that future day when SCTP is
everywhere (aka read windoz).
O/S developor (especially at the m-s company) .. Gee I don't see any
market pressure or demand from the outside world for SCTP, no applications are demanding it.. so why should I
invest in adding the transport stack to my OS?
Now whats the answer? Not really sure but I think the key
may be in that those O/S developors that don't implement may get
left behind.. go forward push out applicaitons that make sense over SCTP
and eventually the second group will wake up and find they are in a
bad position since they did not start early enough (look out m-s here comes
lk-sctp in 2.6 :->). And then of course the first group will eventually
switch..
but they will also be stuck with strange things in there protocol that
could have
been done more efficently.. but that seems to be the way of the world :-0
R
--
Randall R. Stewart
ITD
Cisco Systems Inc.
rrs@cisco.com 815-342-5222(cell) or 815-477-2127(office)