tn sp011 e1 1 sigtran protocol-33

8/9/2019 TN SP011 E1 1 Sigtran Protocol-33

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SigTran Protocol

ZTE University

CN Team

TN_SP011_E1_1



Course Objectives

Principal Concept of Sigtran

Transport Layer Protocol

Signal Adaptation Protocol



Definition

SIGTRANSignaling TransportSIGTRAN is used to

transfer SS7 signaling in IP network. The standard

primitive interface supported by the SIGTRAN does not

require any modification to the application part of the SS7.

It transfers SS7 signaling over standard IP transport

protocol and adds functions to meet the transport

requirements of the SS7 signaling.




Transport

Adaptation

IP layer

Application

SIGTRAN Protocol Structure

,3

6&73

IUA M2UA/M2PA M3UA SUA

Q931/QSIG MTP3 TUP ISUP SCCP TCAP

TCAP




Course Objectives






SCTP Protocol

The Stream Control Transmission Protocol (SCTP) is

designed to transfer SCN narrowband signaling

messages over the IP network. Actually the SCTP is a

connection-oriented protocol, but the concept of the

SCTP association is broader than that of the TCP

connection.

SCTP is a reliable datagram transfer protocol based on

an unreliable transfer protocol such as UDP.




SCTP Terminology

Host: it is a physical entity, e.g. one computer configured

with one or more IP addresses.

SCTP End Point: it is a logical entity, e.g. datagram

sender and receiver. Each end point is just identified by

IP address and port number, similar to TCP.

SCTP Association: it is a logical association or channel

established between two SCTP End Points. C/S mode is

adopted.

Stream: there¶re multiple streams per SCTP association.

It¶s a single-way logical channel from one End Point to

another one in one SCTP association.




SCTP Terminology

TSN & SSN

Transmission Sequence Number (TSN) : A 32-bit

sequence number used internally by SCTP. One TSN is

attached to each chunk containing user data to permit the

receiving SCTP endpoint to acknowledge its receipt and

detect duplicate deliveries.

Stream Sequence Number (SSN): A 16-bit sequence

number used internally by SCTP to assure sequenced

delivery of the user messages within a given stream.

One stream sequence number is attached to each user

message.




SCTP user

SCTP layer

IP layer One or more IP addresses

Network transfer SCTP endpoint A SCTP endpoint B

SCTP user

SCTP layer

IP layer

SCTP Layer model




SCTP Features

Features of SCTP:

fMessage-oriented

f Supporting sequenced or unsequenced transfer of user

datagram within the stream;

f Establishing multiple streams within an association, and the

transfer of the data between the streams is independent;

f Supporting multi-homing at either or both ends of the

association to improve the reliability of the association;

f Using COOKIE authentication to ensure the security of the

association setup;

f Real-time path fault test function.




SCTP and TCP Comparision

Similarities between SCTP and TCP:

f Startup: to establish an association between two nodes, both

protocols will exchange a series of messages.

f Reliability and Ordering: both SCTP and TCP implement

mechanisms to endure the successful delivery of user

datagrams.

f Congestion Control: this is a critical element in any transport

protocol. It regulates the flow of data entering the network,

limiting it to accommodate for occurrences of congestion.

f Closing Down: both protocols have two different close

procedures, a graceful close and an abortive one.





Deference between SCTP and TCP:

f There are two key differences between TCP and SCTP:

fMultihoming: an essential property of SCTP is its support of

multi-homed nodes, i.e. nodes which can be reached under

several IP addresses.

f

Multistreaming: is an effective way to limitH

ead-of-LineBlocking.





f TCP is byte oriented, but SCTP is based on message.

f In contrast to the three-way handshake that occurs in TCP,

SCTP uses a four-way handshake to initiate an association.

f A cookie mechanism is employed during the SCTP

initialization to provide protection against security attacks..




C

ourse Objectives






Adaptation Protocols

According to the different upper users, different

adaptation protocols are adopted.

fM3UA

fM2UA

fM2PA

fSUA

fIUA




Adaptation Layer-M3UA

M3UA (MTP3-User Adaptation Layer) protocol conducts

conversion between SPCs and IP addresses. It is used

for the SS7 signaling transfer between the Softswitch andthe SG. It supports transferring the MTP3 user messages

over the IP network, including ISUP, TUP, and SCCP

messages.




M3UA Terminology Introduction

AS (Application Server): AS is a logical concept and

relevant to a physical equipment.

ASP (Application Server Process): ASP is a progress

instance. The AS contains a set of one or more unique

ASPs, of which one or more is normally actively

processing traffic.

In our system, we can have more than 1 ASP to server an

AS.





Signaling Gateway(SG): located at the edge of the SS7

network to an IP-resident Media Gateway Controller

(MGC) and vice versa. Transfers all the MTP3 user part(ISUP, SCCP, and TUP) messages received from MTP3

(via IWF) to the ASs, consisting of redundant or load-

sharing ASPs.

Signaling Gateway Process(SGP): it is one of the process

instances in SG, its working mode is active/standby or

load-sharing.





Host 1

Host 2

Host 3

Host 4

SCTP Association





IP Server Process (IPSP): it is the process instance based

on IP application. Essentially, IPSP is the same as ASP

but SCTP just uses the end-to-end service not SG.




MTP3-user

Structure of M3UA




L1

MTP2

ISUP

MTP3

L1

MTP2

NIF

MTP3 M3UA

IP

SCTP

ISUP

M3UA

SCTP

IP

SP SG ASP

SS7 IP

M3UA occurred in SG




IP

SCTP

ISUP

M3UA

IPSP

IPIP

SCTP

ISUP

M3UA

IPSP

M3UA occurred in IPSP




Adaptation Layer-M2UA

M2UA: The MTP2 user adaptation layer (M2UA)

terminates the MTP2 at the edge SG of the packet-based

network, and transparently transfers MTP2 user messages (MTP3 messages) to the MTP3 in the packet-

based network.




L1

MTP2

MTP3

L1

MTP2

(NIF)

M2UA

IP

SCTP

MTP3

M2UA

SCTP

IP

SP SG ASP

SS7 IP

M2UA in SG




Adaptation Layer-M2PA

M2PAM2PA is used to support the operations between

the peer layers of the MTP3 in the IP network, support the

boundary interface between the MTP2 and MTP3,support the message transfer through the SCTP

association, implement the MTP2 link function, and report

the change to the management status.




L1

MTP2

MTP3

L1

MTP2

MTP3M2PA

IP

SCTP

MTP3M2PA

SCTP

IP

SP SG ASP

SS7 IP

M2PA in SG




IP

SCTP

MTP3

M2PA

IPSP

IPIP

SCTP

MTP3

M2PA

IPSP

M2PA in IPSP




M2UA and M2PA Comparision

f Similarities

Both transport MTP3 data messages;

Both present an MTP2 upper interface to MTP3.

f Difference

M2PA processes MTP3-to-MTP2 primitives, but M2UA just

transports MTP3-to-MTP2 primitives ;

Using M2PA, SG is an SS7 node with a point code; Using M2UA,

SG is not an SS7 node and has no SPC;

SG adopting M2PA can have upper SS7 layers, e.g., SCCP; but

SG does not have upper SS7 layers because it has no MTP3.




Adaptation Layer-SUA

SUA: The SUA defines how to transfer SCCP user

messages between two SPs through IP. It can be used by

the SG for the interworking between the SS7 and IP; itcan also be used for the interworking between two IPSPs

in the IP network.




L1

MTP2

TCAP

L1

NIF

SUA

IP

SCTP

TCAP

SUA

SCTP

IP

SP SG ASP

SS7 IP

MTP3

SCCP

MTP2

MTP3

SCCP

SUA in SG


tn sp011 e1 1 sigtran protocol-33

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