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Dato : 15-09-03 09:27 |
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Og så kommer det næste spørgsmål nok 
Citat
kilde: http://www.ietf.org/html.charters/pint-charter.html
Based on the existing practice and agreed on improvements, develop a standards track RFC that specifies a Service Support Transfer Protocol (SSTP) between Internet applications or servers and PSTN Intelligent Network Service Nodes (or any other node that implement the Service Control Function). SSTP is an application-specific transport protocol operating over TCP. |
og fra http://www.globecom.net/ietf/draft/draft-sanchez-garcia-SSTP-v0r2-00.html
Citat
This document describes SSTP, a protocol architecture that provides the
support of SCCP and TCAP user applications over an IP network. The
purpose of SSTP is to provide a standard tunneling protocol to convey
SCCP messages over an IP based network. The core part of the SSTP
architecture is the specification of the SSTP (Simple SCCP Tunneling
Protocol) adaptation layer, that provides adaptation between the SCCP
layer already defined in [3] and [4], and the IP family protocols IP,
UDP, TCP and ICMP. TCP or UDP is used for SCCP class 0 messages. TCP is
used for SCCP class 1, 2 or 3. SSTP provides similar primitives and
parameters to SCCP than MTP, and provides seamless connection between
nodes implementing SSTP and classical SS7 nodes by means of a SSTP
gateway. The design of SSTP is oriented to fulfill the requirements of
TCAP user applications running on a WAN.
4. SSTP functionality
SSTP performs the functions in order to provide adaptation between
SCCP and the network functions provided by the IP network.
- Addressing: The network operator assigns an IP address and port to
the SS7 over IP node. The port assigned is the well known port for
"SCCP over IP", which is 14001.
There are two ways to define a Point Code in the SCCP over IP network:
a) The Destination Point Code is mapped to the IP address and port
number of the remote SCCP over IP node.
b) The Global Title is translated to the IP address and port number of
the remote SCCP over IP node.
As an IP address identifies an interface to the network just like a
Point Code does, the SCCP point of view introducing a new SS7 over IP
node is the same as introducing an existing SS7 over MTP node, but in
this case an IP address and port needs to be introduced in the GT
translation function or the DPC mapping table in the SCCP concerned
nodes in the network.
- Network control: SSTP uses ICMP to control the IP network. It uses
Echo/Echo Reply and Destination Unreachable messages from ICMP in
order to detect failures in remote SS7 over IP nodes. It also uses
Source Quench messages to detect congestion events in the IP transport
network.
The functionality is provided by the next primitives and parameters.
4.1. SSTP primitives and parameters
4.1.1. SSTP primitives
SSTP provides a very similar interface towards SCCP as MTP does. This is
in order to provide the information needed by SCCP in order to perform
the required functionality.
The primitives and the parameters associated to them are shown in
figure 2.
The Request primitives flow from SCCP to SSTP, whilst the Indication
primitives flow from SSTP to SCCP.
+-----------------------------+------------------------+
| Primitive | Parameter |
+=============================+========================+
| SSTP-TRANSFER-Request | Destination IP address |
| | Destination IP port |
| | Protocol Class |
| | SLS |
| | SIO |
| | Data |
+-----------------------------+------------------------+
| SSTP-TRANSFER-Indication | Source IP address |
| | Source IP port |
| | SLS |
| | SIO |
| | Data |
+-----------------------------+------------------------+
| SSTP-NOTICE-Indication | Source IP address |
| | Source IP port |
| | Error Code |
| | SLS |
| | SIO |
| | Data |
+-----------------------------+------------------------+
| SSTP-PAUSE-Indication | Affected IP address |
+-----------------------------+------------------------+
| SSTP-RESUME-Indication | Affected IP address |
+-----------------------------+------------------------+
| SSTP-STATUS-Indication | Affected IP address |
| | Cause |
+-----------------------------+------------------------+
| SSTP-CONNECT-Request | Destination IP address |
| | Destination IP port |
+-----------------------------+------------------------+
| SSTP-CONNECT-Indication | Destination IP address |
| | Destination IP port |
| | Result code |
+-----------------------------+------------------------+
| SSTP-DISCONNECT-Request | Destination IP address |
| | Destination IP port |
+-----------------------------+------------------------+
| SSTP-DISCONNECT-Indication | Destination IP address |
| | Destination IP port |
| | Result code |
+-----------------------------+------------------------+
Figure 2. SSTP primitives and parameters
4.1.1.1 SSTP-TRANSFER-Request
This primitive is used by SCCP to request from SSTP the transfer of
an SCCP message to a destination node.
4.1.1.2 SSTP-TRANSFER-Indication
This primitive is used by SSTP to indicate the reception of an SCCP
message from another SCCP node.
4.1.1.3 SSTP-NOTICE-Indication
This primitive is used by SSTP to indicate an error reported when
a message was sent through the IP network. Thus, this primitive is
issued as an error answer to a previous SSTP-TRANSFER-Request.
Errors are reported in ICMP messages, connection broken, or similar
situations. The Error Code parameter specifies the error reported by
the IP network.
The SLS and SIO are the same parameters sent in a previous
SSTP-TRANSFER-Request primitive. However, the Data parameter may
contain a partial copy (not a complete one) of the Data sent in the
SSTP-TRANSFER-Request primitive.
The SCCP is responsible to take the proper actions (generate a return
message or N-NOTICE-Indication primitive) upon the reception of this
primitive.
The Source IP address and Source IP port correspond to that where the
error message was generated.
4.1.1.4 SSTP-PAUSE-Indication
This primitive is used by SSTP to indicate to SCCP the inability of
sending any SCCP message to the indicated node. The SSTP layer may
generate this indication upon:
- Receiving a Destination Unreachable message from ICMP indicating
net unreachable or host unreachable.
- If the SSTP performs periodic polling to remote SS7 over IP nodes
by means of ICMP, SSTP can detect a failure on the remote node if
several Echo Reply messages are not answered by the remote host.
When SSTP detects a failure in a remote host, it starts a polling
routine towards that node in order to detect when the node becomes
available again.
4.1.1.5 SSTP-RESUME-Indication
This primitive is used by SSTP to indicate to SCCP the availability of
sending again SCCP messages to the indicated node. The SSTP layer
generates this indication when the remote SS7 over IP node starts to
answer again to the echo messages.
4.1.1.6 SSTP-STATUS-Indication
This primitive is used by SSTP to indicate to SCCP some special events:
- Remote SCCP layer unavailability
- Remote SCCP congestion
- Completion of IP local layer restart: If the IP transmission layer
has been temporarily unavailable due to a failure in the local
hardware or software, SSTP detects when it is available again and
indicates this to SCCP by means of this primitive. The value of the
Affected IP address and Cause parameters are left to the
implementation (these values are not specified in [3]), but in case
of using an existing SCCP layer, it would be desirable that the
values provided by SSTP are the same as the values used by the
implementation of the existing SCCP layer.
4.1.1.7 SSTP-CONNECT-Request
Whenever a new node is defined in the SCCP over IP network, the SCCP
indicates SSTP to establish a TCP connection to the destination IP
address and port identifying such a node.
4.1.1.8 SSTP-CONNECT-Indication
When the TCP connection described in 4.1.1.7 has been acknowledged
(either successfully or not), SSTP sends this primitive to SCCP.
This primitive is asynchronously sent when an incoming TCP connection
is received by SSTP.
4.1.1.9 SSTP-DISCONNECT-Request
Whenever an already defined node is deleted in the SCCP over IP
network, the SCCP indicates SSTP to close the previously established
TCP connection with the destination IP address and port identifying
such a node.
4.1.1.10 SSTP-DISCONNECT-Indication
When the TCP connection described in 4.1.1.9 has been closed
(either successfully or not), SSTP sends this primitive to SCCP.
This primitive is asynchronously sent when a previously established
TCP connection is closed.
4.1.2 SSTP primitive parameters
4.1.2.1 Source IP address
The Source IP address is used to indicate the node that originates the
message. This parameter is sent in the primitives:
- SSTP-TRANSFER-Indication
- SSTP-NOTICE-Indication
4.1.2.2 Source IP port
The Source IP port is used to indicate to SCCP the node that
originates the message. This parameter is sent in the primitives:
- SSTP-TRANSFER-Indication
- SSTP-NOTICE-Indication
4.1.2.3 Destination IP address
The Destination IP address is used to indicate the destination node for
a message or TCP connection. This parameter is sent in the primitives:
- SSTP-TRANSFER-Request
- SSTP-CONNECT-Request
- SSTP-CONNECT-Indication
- SSTP-DISCONNECT-Request
- SSTP-DISCONNECT-Indication
4.1.2.4 Affected IP address
The affected IP address is used to indicate the node affected by some
status indication. This parameter is sent in the following primitives:
- SSTP-PAUSE-Indication (SSTP to SCCP): The affected IP address
indicates the unavailability of the node SCCP over IP node, and that,
SCCP must not send any message to that node through the SSTP layer.
- SSTP-RESUME-Indication (SSTP to SCCP): The affected IP address
indicates the availability of a previously unavailable SCCP over IP
node. SCCP can resume to send messages to that node through the SSTP
layer.
- SSTP-STATUS-Indication (SSTP to SCCP): In this primitive the
affected IP address indicates the IP node where the reported error
applies.
4.1.2.5 Destination IP port
The Destination IP port is used to indicate the SSTP application in the
destination node. The port number reserved for SCCP over IP is 14001.
The Destination IP Port parameter is sent in the primitives:
- SSTP-TRANSFER-Request
- SSTP-CONNECT-Request
- SSTP-CONNECT-Indication
- SSTP-DISCONNECT-Request
- SSTP-DISCONNECT-Indication
4.1.2.6 Protocol Class
SSTP uses the value of Protocol Class received from SCCP to decide the
layer where the message is sent (UDP or TCP). If class 0 is used, then
SSTP may use either TCP or UDP as transport protocol (this is
implementation dependant). If class 1, 2 or 3 is used, then SSTP shall
use TCP as transport protocol. |
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