Sigtran Connectuon by Cisco

8/10/2019 Sigtran Connectuon by Cisco

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2008 Cisco Systems, Inc. All rights reserved. Cisco Public 1

Next GenerationSignalling and

Applications

BRKMWI-3007

Ching-Ying Tong

[email protected]
mailto:[email protected]:[email protected]


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2 2008 Cisco Systems, Inc. All rights reserved. Cisco Public

Agenda

SS7 background

Next Generation Signaling

SIGTRAN

SCTP

M2PA

M3UA

SUA

Sigtran in 3GPP

Applications

Sigtran design rules


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA

Sigtran in 3GPP

Applications



4/75


SS7 background

Describe SS7 background and evolution

List SS7 nodes, describe their functions

Describe switching network hierarchies

Describe some traffic engineering and dimensioning rules


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What is SS7 ? - Back to 60s

SS7 = Signalling System #7

- Derived from SS6 a Common Channel Signalling protocol

- SS6, signalling introduced in 60s in US between central offices

- SS6 initial deployment based on

2400 bps, upgraded to 4800 bps links Proprietary communication protocol

Used to request voice channel from other network entities

- SS6 first use of packet switching in PSTN network


6/756 2008 Cisco Systems, Inc. All rights reserved. Cisco Public

What is SS7 ? - Evolution to SS7ITU-T derived SS7 from SS6

- More capability / flexibility as for example:

Bandwidth of 56 Kbps ANSI / 64 Kbps ITU-T extended to High

Speed Links later ( 2 Mbits links )

Variable length signalling units

Reliability improvements

- First application WATS ( Wide Area Telephony Service ), 800number database access application

- First deployment starting from early 80s.

- Initial deployment between interoffice network

- Local office deployment years later

- SS6 phased out mid 80s

In parallel, network evolution to digital equipments



What is SS7 - SS7 nodes

SSP Switching Point ( C3/C4/C5/MSC )

TDM switches equipped with SS7 HW and SW

STP Signaling Transfer Point

Switches that receive & route SS7 messages only

SCP/SN Service Control Point and Service Node

IN services

HLR/VLR/AUC/SMSC

Specialized equipments for special call processing with embedded database

SSP

STP

SCP/SN



What is SS7 ? - PSTN networkcommon architecture / Quasi associated signalling

SSP

SSP SSP

SSP

Signaling layer

STP

IN Apps. and DataBase

SCP SCP

STPSTP

STP

TransportAccess layer

C5/C4/C3

Bearer trunks

Signaling links



What is SS7 ? Mobile SP networkCommon architecture Quasi associated signalling

MSC

MSC MSC

MSC

Signaling layer

STP

HLR/AUC/SMSC

SCP SCP

STPSTP

STP

MSC Layer

Bearer trunks

Signaling links



What is SS7 ? Mobile SP networkAlternative architecture Fully associated signaling

STP/ and switching

Layer

MSC layer

Bearer trunks

Signaling links

SCP

MSC

MSC

MSC

MSC

HLR/AUC/SMSC



ISDN User

Part (ISUP)TCAP

Non-Circuit Appl ications

SCCPSCCP

MTP

Enhanced Addressing,

Connectionless/Connection Oriented Services

Enhanced Addressing,

Connectionless/Connection Oriented Services

Level 1

Level 2

Level 3

NullNull Presentation,Session, TransportPresentation,Session, Transport

Application

CAMEL Operations, Maintenance and Administration Part

TCAPTransaction Capabilities Application Part

ISUPIntegrated Services Digital Network User Part

SCCPSignaling Connection Control Part

MTPMessage Transfer Part

TUPTelephone User Part (Before ISUP)

Circuit-Related

Services

OSI Reference Model

NetworkNetworkMessage Discrimination/Distribution/

Routing, Network Management

Message Discrimination/Distribution/

Routing, Network Management

NetworkNetwork

Data LinkData LinkData LinkData LinkSU Delimitation/Alignment, Error Detection/Correction,

Retransmission, SUERM, Alignment, Flow Control

SU Delimitation/Alignment, Error Detection/Correction,

Retransmission, SUERM, Alignment, Flow Control

aPhysicalPhysicalPhysicalPhysical Link Connection, Bit Rate, VoltagesLink Connection, Bit Rate, Voltages

T

U

P

IN-AINCAMEL

IN ServicesMAP

Call

Processing

What is SS7

SS7 Protocol Stack



What is SS7 ? - MTP2 and MTP3

Only MSUs carry payload of higher level messages (e.g. MTP3 and higher stack layers)

All signaling associated wi th call setup and tear down, database query and response, and SS7network management takes place using MSUs.

MSUs are the basic envelope within which all addressed signaling information is placed; Hence,the MSUs are the message types upon which bandwidth requirements must be determined

The SS7 MTP2 (Message Transfer Part layer 2) is a point-to-point, reliable protocol. SS7 signalinglink alignment, error detection and corrections are performed at this level. MTP2 guarantees reliabledelivery of s ignal unit messages between SS7 nodes; Within the MTP2 layer, there are three Types ofSS7 Signal Units (SU), as show below:

Link Status Signal Units (LSSU)

Fill-In Signal Unit (FISU)

Message Signal Unit (MSU) e.g. MTP3

F BSN BIB FSN FIB LI SIO FCKSIF

8 7 1 7 1 6 8 8n, n>=2 816

Message Signal Unit (MSU) Format

F BSN BIB FSN FIB LI SF FCK

8 7 1 7 1 6 8 or 16 816

Link Status Signal Unit (LSSU) Format

F BSN BIB FSN FIB LI FCK

8 7 1 7 1 6 816

Fill-In Signal Unit (FISU) Format

BIB = backward Indicator Bit

BSN = Backward Sequence Number

CK = Check Bits

F = Flag

FIB = Forward Indicator Bit

FSN = Forward Sequence Number

LI = Length Indicator

SIF = Signaling information Field

SIO = Service Information octet

SF = Status Field



What is SS7 ? Protocol evolution- SS7 specifications red book - 1984

- SS7 specifications blue book 1988

- SS7 specifications white book 1991 ( the final one )- ISDN User Part specifications version 3 1997

- Bearer Independent Call Control specifications 2000

- SIP-I/SIP-T specifications 2004

SS7 as today is less than 30 years old


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Traffic Engineering Dimensioning rules

Traffic is normally measured in the busy hour

Busy Hour Call Attempts (BHCA) = number of calls arriving

in this hour

Erlang B used to design inter Central Office trunksbased on 3 parameters

Busy Hour Traffic in Erlang = CCPS * Mean Hold time

Blocking factor = X calls blocked per 100 calls due toinsufficient resource

Number of lines ( DS0 ) required in the trunk

BHCA=

Calls Attemps per Second(CAPS)

3600



Determining 70 Erlangs = 70x60 = 4200 call minutes per day

Busy hour 12% of 1000 calls = 120 BHCA

Busy hour 12% of 70 Erlangs = 8.4 Erlangs


Example

1000 calls completion per day and 70 Erlangs Busy Hours

12% in the busy hour

Blocking factor 0.02

Each SP has its own blocking factor for SLA




SS7 linkset and routeset

STP 1

A linkset is a collection of signaling links connecting 2 signaling points

A routeset is all of the routes from a signaling point to a particular

destination. A route is made of a collection of linksets

SCP Y

STP1 routeset to SCP Y

STP 3

STP 4STP 2SSP1

SCP X

SSP2

L1

L2

L3

Linkset Priority

L1 1

L2 1

L3 2




STP 1

Dimensioning SSP STP traffic

[(X)(Y)(Z)] + [(A)(B)(C)] / 3600 = n Bytes per second

STP 2

SSP64 kbit/s

A-link

A-link

ISUP load determination:

X - ISUP messages for each call 2 upstream/3 downstream => 5

Y - Average length in Bytes of ISUP messages => 20 Bytes

Z - Busy Hour Call Attempts BHCA

TCAP load determination:

A - TCAP/ database messages per sequence => 2

B - Average length in Bytes of TCAP messages => 80 Bytes

C - Busy Hour Database Call Attempt

SSP-, STP- and SCP-links are often engineered at 0,4 Erlang = 40%capacity, allowing the remaining node/links to carry 80% of the load in

case of any node or link failure

The remaining 20% is for traffic peaks



Traffic Engineering dimensioning rules

STP 1

Example dimensioning SSP STP traffic

[(X)(Y)(Z)] + [(A)(B)(C)] / 3600 sec = n Bytes per second

[(5)(20)(4.000.000)] + [(2)(80)(1.000.000)] / 3600 = 155,55 Kbytes/s

STP 2

A-link

A-link

A-links

64 Kbit/s x 2 links x 2 (duplex) = 256 Kbit/s => 32 KBytes/s

32 KBytes x 40 % = 12,8 KBytes/s

n Bytes per Second / 12,8 KBytes per Second = n A-link

155,55 / 12,8 = 12,15 => 7 x 2 A-links

SSP capacity :

BHCA = 4.000.000

Busy Hour Database Call Attempt=1.000.000

Erlang = 100.000

CPS (calls per second) = BHCA / 3600

CPS = 4.000.000 / 3600 => 1111

SSP



Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA

Sigtran in 3GPPApplications




Next Generationsignaling

Describe Sigtran motivation

Describe SCTP and some specific features

Describe M2PA architecture

Describe M3UA architecture

Describe SUA architecture



Cisco products with SS7 - Sigtran support

Cisco has several products with Sigtran capabilities

- Call control : PGW2200, BTS10200

- Voice gateways : MGX, AS5X00

- STP/SG : ITP - IP Transfer Point

This presentation will use the Cisco ITP as the reference forexamples

Rational for Cisco to develop the ITP :

1. Customer demand

2. IP convergence for SS7 transport over IP

3. SS7 nodes SCP/SMSC migration to IP

4. Unleash the CPU power of end nodes



ITP released to the market in June 2001. To date a total

of 1500+ ITPs deployed across 200+ service providers

ITPs deployed primarily as STPs and Signaling

Gateways with approx 50/50 split between SG and STP

deployments

Key drivers for ITP deployments include subscriber

adds, application growth (IP text messaging, etc),

services, VoIP, transition to IP-based signaling, etc

ITP comes in several sizes from 2 up to 2000 SS7 links

for the largest platforms.

ITP Market Activity



Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA




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Multi-vendor group that is designing SS7oIPstandards

Group includes all actors : Cisco, Lucent/ Alcatel,Ericsson, Nokia, Siemens, Tekelec, Huawei, NT,etc.

http://www.ietf.org/html.charters/sigtran-charter.html

Protocols include: SCTP, M2UA, M2PA,

M3UA, SUA

Cisco is co-author on all except SUA

IETF SIGTRAN Working Group
http://www.ietf.org/html.charters/sigtran-charter.htmlhttp://www.ietf.org/html.charters/sigtran-charter.html


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SIGTRAN Architecture Framework ( RFC2719 )

ISUP/SCCPISUP/SCCP

MTP3MTP3

M2UAM2UA

SCTP

IPIP

ISUP/SCCPISUP/SCCP

M3UAM3UA

SCTP

IPIP

TCAP/MAPTCAP/MAP

SUA(SCCP)

SUA(SCCP)

SCTP

IPIP

IETF

Sigtran

SS7SS7

ISUP/SCCPISUP/SCCP

MTP3MTP3

M2PA(Peer-to-peer)

M2PA(Peer-to-peer)

SCTP

IPIP

Q.931Q.931

IUA (Q.921)IUA (Q.921)

SCTP

IPIP

A standard network layer protocol: IP (v4 or v6)

A common signaling transport protocol: SCTP

SCTP supports a common set of reliable transport functions for signaling transport

An adaptation sub-layerSupports specific primitives, such as management indications, required by a particularsignaling application protocol


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Sigtran Protocols

SCTP Stream Control Transmission Protocol, RFC3309 transport layer that provides reliabledata transfer.

M2PA MTP2-User Peer-to-Peer Adaptation, RFC4165 provides MTP3 with equivalenttransport layer services as MTP2.

M3UA MTP3-User Adaptation, RFC4666 client/server protocol providing a gateway tolegacy SS7 network for IP-based applications that interface at the MTP3 layer.

SUA SCCP-User Adaptation, RFC3868 client/server protocol providing a gateway to legacySS7 network for IP-based applications that interface at the SCCP layer.

M2UAMTP2-User Adaptation, RFC3331 client/server protocol providing a gateway to

legacy SS7 network for IP-based applications that interface at the MTP2 layer.

Security Considerations for SIGTRAN Protocols RFC 3788 - specifies anInternet security standards track protocol (TLS/IPSec)


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SIGTRAN Architecture

SCTP, has been defined for all SS7 signaling transportover IP

Various protocol user adaptation layers provideinterworking functions between IP and various SS7 orother PSTN signaling

Two basic Signaling Gateway architectures:

Backhaul model

SG (server) backhauls user adaptation application data to MGC(client) through SCTP/IP

Peer-to-Peer model

SG/ASP to SG/ASP connection through SCTP/IP


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SIGTRAN Architecture:An Example Backhaul Model

M3UAM3UA

SCTP

IPIP

ISUPISUP

MTP3MTP3

MTP2MTP2

MTP1MTP1

MTP3MTP3

MTP2MTP2

MTP1MTP1

M3UAM3UA

SCTP

IPIP

ISUPISUPInterworking FunctionInterworking Function

IP Network

SEPSEP MGCMGCSGSG

SS7 Link IP Link

BackhaulBackhaul

SS7 IP


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SIGTRAN Architecture:An Example Peer-to-Peer Model

M2PAM2PA

SCTP

IPIP

MTP3MTP3

MTP2MTP2

MTP1MTP1

M2PAM2PA

SCTP

IPIP

Full MTP3 or LinkManagement Only


IP Network

SGSG

SS7 Link IP Link

Peer-to-PeerPeer-to-Peer

IP

MTP2MTP2

MTP1MTP1

Link

Protocol



Link

Protocol

SS7 SS7

SGSG

M2PAMTP2 User Adaptation

for Peer-to-Peer Connection


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA




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SCTP Stream Control Transmission Protocol (RFC 2960 last update RFC4960)

ISUP/SCCPISUP/SCCP

MTP3MTP3

M2UAM2UA

SCTP

IPIP

ISUP/SCCPISUP/SCCP

M3UAM3UA

SCTP

IPIP

TCAP/MAPTCAP/MAP

SUA(SCCP)

SUA(SCCP)

SCTP

IPIP

SS7SS7

ISUP/SCCPISUP/SCCP

MTP3MTP3

M2PA(Peer-to-peer)

M2PA(Peer-to-peer)

SCTP

IPIP

Q.931Q.931

IUA (Q.921)IUA (Q.921)

SCTP

IPIP

IETF

Sigtran


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SCTP - Motivations

TCP imposes limitations for some emerging applications:

Reliability mechanisms

Some applications need reliable transfer without sequencemaintenance; others need only partial ordering of data

No support for multi-homing

Real-time issues

Head-of-line blocking caused by TCP adds unnecessary delayand makes it inappropriate for real time traffic

Inability to tune parameters (e.g. retransmission timer)

Security issues

TCP is more vulnerable to denial-of-service attacks


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SCTP - What Is It ?

Can be used anywhere TCP or UDPwould be used

Broader scope than just SIGTRAN, e.g.Netflow, HTTP, other signaling H.248

Transport protocol for messageoriented data transfer

SCTP stream is a sequence ofmessages

Each SCTP connection can havemultiple streams named association

Multi-homing support

Session monitoring and detection ofloss

Path/session through heartbeat

IPIP

PhysicalPhysical

Adaptation ProtocolAdaptation Protocol

UDP TCP SCTP


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SCTP Main services

Acknowledged error-free, non-duplicated transfer of datastreams

Data fragmentation to conform to Message Transfer Unit (MTU)size (Path MTU discovery built in)

Sequenced delivery of user messages within multiple streamswith an option for order of arrival and delivery of individual usermessages

Bundling of multiple user messages into a single SCTP packet

Multi-homing Network level fault tolerance at either or both endsof an association

Heartbeat/Keep-alive mechanisms are integral part of the design


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SCTP - What is a stream ?

A stream is a uni-directional flow of messages.

It is NOT a stream of bytes as in TCP.

Each SCTP association can have multiple streams allowing partialordering of messages.

Each side indicates how many outbound streams that it wants (OS)and the maximum inbound streams (MIS) it can accept.

If a side cannot tolerate the number of streams it is limited to by the

other side it should ABORT the association. Each side is limited to and agrees to min(OS,peers-MIS) if it accepts

the association.


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SCTP How/when streams are used

Streams are used to provide a non-head-of-line blocking discipline

Common uses would be to route a given SLS from an SS7 link setfor ISUP over independent streams.

Another possible use might be to download and display in parallelmultiple pictures on a html page.

Another common use is H.248 signaling transport in a 3GPP or

TISPAN architecture

SGSGMGCMGC

Network A

Network B

SGSGMGCMGC

Network A

Network B

Held in the

Kernel Awaiting

Retransmission


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SCTP Associations multi-homingMachine "A" Machine "Z"

Network Y

Network X

Process2Process2

Port 1120Port 1120

IP:X2 IP:Y2

Process1Process1

Port 2344Port 2344

IP:Y1 IP:X1

Transport AddressA combination of an SCTP port and an IP address

EndpointA sender/receiver of SCTP packets, can be represented as a list oftransport addresses sharing the same SCTP port

AssociationA relationship or conversation between two endpoints(in TCP we would call this a connection)


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SCTP - Multi-Homing feature

SGSGMGCMGC

Network A

Network B

Retransmission on B while checking status for A

Decreasing delay for failover recovery, more suitable for real-timetraffic


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SACK = Selective

Acknowledgement

SACK = Selective

Acknowledgement

SGSG

5 3 1MGCMGC

Network A

Network B

24

SCTP - SACK Built-In

SGSG

4 2MGCMGC

Network A

Network B

Retransmission of dropped packets only instead of the entire group

as in TCP


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SCTP - Heartbeat Built-In

SGSGMGCMGC

Network A

Network B

HBHB-ACK

While traffic is sent on stream A, HB is sent on stream B HB timer 30s

configurable

Allows proactive failure detection then recovery, similar to FISU in SS7


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SCTP - Optional Unordered Delivery

SGSGMGCMGC

Network B

Network A

66 UU 22 55 1

For example, control message dont need to be ordered

Allows unreliable delivery ( U-SCTP )


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SCTP bundling of Messages

Many of the message chunks can be bundled together. Each message chunk is self descriptive, I.E. It describes its own

length.

Bundling is simply a matter of combining the chunks into one SCTPdatagram before transmission.

All chunks can be bundled with some exceptions, E.G., The followingtypes CAN NOT be bundled:

An INIT chunkAn INIT-ACK chunk


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MTP2 TDM M2PA/SCTP

MSU4

SCTP Chunk Bundl ing Timeout(0 ~ 10 msec configurable)

FISUs wil l be terminated at ITP

FISU FISU MSU2MSU1 MSU2MSU1

0.4 Elrang

FISU FISUFISUFISU IP

Example: Up to 1480 bytes for Ethernet

MSU3

MSU2

MSU1

MSU4 MSU3 MSU2 MSU1 IP

Available Bandwidthfor Other MSU Transport

SCTP Bundling-Bandwidth Savings


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SCTP Bundling-Bandwidth Savings (cont.)

8 Byte 200 Byte

ETH IP SCTP M2PA MSU

20 Byte 28 Byte 17 Byte 200 Byte

MTP1/2 MSU

64K Link IP SCTP Link

MSC ITP ITP

Average Size of MSU : 200 Byte

Condition of Link Erlang : 0.4 No. of MSU per second : 16 ea

Average Size of MSU : 200 Byte

Condition of Link Erlang : 0.4

No. of MSU per second : 16 ea

Required IP BW for single Link :

279Byte * 16 * 8 = 35,712 bps (No bundle)

Required IP BW for single Link :

279Byte * 16 * 8 = 35,712 bps (No bundle)

14 Byte

208 Byte 279 Byte

ETH IP SCTP M2PA MSU SCTP M2PA MSU

20 Byte 28 Byte 17 Byte 200 Byte

Required IP BW for Bundled single Link :

(14+20+28+17+16+17) / 2 = 56 Byte (Header)

256Byte * 16 * 8 = 32,768 bps (2 Chunks bundled)(14+20+28+17+16+17+16+17+16+17+16+17+16+17) / 6 = 41 Byte (Header)

241Byte * 16 * 8 = 30,848 bps (6 Chunks bundled Maximum 1480 )

Required IP BW for Bundled single Link :

(14+20+28+17+16+17) / 2 = 56 Byte (Header)

256Byte * 16 * 8 = 32,768 bps (2 Chunks bundled)

(14+20+28+17+16+17+16+17+16+17+16+17+16+17) / 6 = 41 Byte (Header)

241Byte * 16 * 8 = 30,848 bps (6 Chunks bundled Maximum 1480 )

14 Byte

512 Byte

16 Byte 17 Byte 200 Byte

SCTP common header 12 bytesChunk type 12 bytes

Chunk description 4 bytes


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA




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Adaptation Layer Protocols

ISUP/SCCPISUP/SCCP

MTP3MTP3

SCTPSCTP

IPIP

ISUP/SCCPISUP/SCCP

SCTPSCTP

IPIP

TCAP/MAPTCAP/MAP

SCTPSCTP

IPIP

IETF

Sigtran

SS7SS7

ISUP/SCCPISUP/SCCP

MTP3MTP3

SCTPSCTP

IPIP

Q.931Q.931

SCTPSCTP

IPIP

M2UAM2UA M3UAM3UASUA

(SCCP)SUA

(SCCP)M2PA

(Peer-to-peer)M2PA

(Peer-to-peer) IUA (Q.921)IUA (Q.921)


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M2PA MTP2 Peer-to-Peer Adaptation Layer

M2PA defines a protocol supporting the transport ofSS7 MTP3 signaling messages over IP, using the services of SCTP

M2PA allows for full MTP3 message-handling and network-management capabilities between any two SS7 nodescommunicating over an IP network

M2PA supports:

1. Operation of MTP3 protocol peers over an IP network connection

2. The MTP2/MTP3 interface boundary, management of SCTP transport

associations, and traffic instead of MTP2 links3. Asynchronous reporting of status changes to management


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MTP2MTP2

MTP3MTP3

MTP1MTP1

M2PAM2PA

SCTPSCTP

IPIP

MTP2MTP2

MTP1MTP1

MTP3MTP3

IPIP

SCTPSCTP

M2PAM2PA

MTP3MTP3

MTP2MTP2

MTP1MTP1

SCCP

TCAP

MAP IS-41 I

S

U

P

MTP3MTP3

MTP2MTP2

MTP1MTP1

SCCP

TCAP

MAP IS-41 I

S

U

P

SCTPAssociations

SEPSEPSEPSEP SS7 SGSS7 SGSS7 SGSS7 SG SS7SS7SCTP/IP

MTP3 AdjacentNodes

TDM TDM

PURE MTP3 Routing

M2PA - Architecture

IPNetwork


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M2PA - Architecture

Remote Remote

Exist ing TDM based SS7 Network

Before

STP1_1

STP1_2

STP2_1

STP2_2

MSCMSC

IP Core NetworkAfterSG2_1

SG2_2Local Local

MSCMSC SG1_1

SG1_2

M2PA


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M2PA Reliabili ty and dimensioning aspects

SG should have on TDM side

At least 2 linksets to the TDM node

Each linkset has the appropriate number of links Usually each link is used at 0.4 Erlang

Each linkset has links distributed on different SS7 adpator

SG should have on IP side

Multi-homing defined on 2 separate NIC

Bandwidth required depends on bundling and traffic load

M2PA overhead

ETH IP SCTP M2PA MSU

20 Byte 28 Byte 17 Byte N Byte14 Byte


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA




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MTP3 User Adaptation Layer (M3UA)

M3UA supports the transport of any SS7 MTP3 user signaling (e.g.ISUP/SCCP), transparent to the MTP3-user, over IP; using theservices provided by SCTP

Allows flexible message distribution (e.g., SS7OPC/DPC/SLS/CIC) to ASPs

Open/closes SCTP transport associations n+k redundancy support (server pooling)

ASP fail-over support within AS list

Load-balancing support Allows ASP signaling through redundant SGs to SS7 Network


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MTP3M3UA

SCTP

IP

MTP2

MTP1

N

I

F

ISUP/SCCP over MTPISUP and SCCP messages

SEPSEPASPASP SS7 SGSS7 SG

IP

Network

M3UA

SCTP

IP

SCCP

TCAP

MAP IS-41 I

S

U

P

MTP2

MTP1

SCCP

TCAP

MAP IS-41 I

S

U

P

MTP3

SS7SCTP/IP

SS7

Network

Signaling Gateway

M3UA - Architecture

M3UA A hit t


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M3UA - Architecture

Exist ing TDM basedSS7 Network

Before

STP2_1

STP2_2

MSCHLR / SMC STP1_1

STP1_2

After HLR/ SMSC

LAN SwitchSG1_1

SG1_2

SUA / M3UA / SCTP / IP

100Mbps/NIC

QoS Available

STP2_1

STP2_2

MSC

Exist ing TDM basedSS7 Network

SG2_1

SG2_2

MSC

M2PA / SCTP / IP

M3UA


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M3UA Reliabili ty and dimensioning aspects

SG should have on TDM side if any


Each linkset has the appropriate number of links

Usually each link is used at 0.4 Erlang Each linkset has links distributed on different SS7 adpator



Bandwidth required depends on bundling and traffic load

M3UA overhead for transfert message

ETH IP SCTP M3UA MSU

20 Byte 28 Byte 20 Byte 12 Byte14 Byte

MSU header

N Byte


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA




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SUA - SCCP User Adaptation Layer

SUA defines a protocol for the transport of any SS7 SCCP user signaling,mainly TCAP over IP using SCTP services

Designed to be modular and symmetric to allow it to work in diversearchitectures such as:

SG-to-IP signaling-endpoint

Peer-to-peer IP Signaling Endpoint

SUA supports the following:

Transfer of SCCP user part messages (TCAP, etc.)

SCCP connectionless service

SCCP connection oriented serviceManagement of SCTP transports associations between a SG and one or more

IP-based signaling nodes Distributed IP-based signaling nodes

Asynchronous reporting of status changes to management

SUA A hit t


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MTP3

SUA

SCTP

IP

MTP2

MTP1

I

W

FSCCP

SCCP messagesSCCP messages

Signaling Gateway

SEPSEPASPASP SS7 SGSS7 SG

IPNetwork

SS7Network

SS7SCTP/IP

GTTGTT

SUA

SCTP

IP

TCAP

MAP IS-41

MTP2

MTP1

MTP3

SCCP

TCAP

MAP IS-41

SUA - Architecture

SUA Architect re


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SUA - Architecture

Before

SMSCIP Core NetworkSG1_1

SG1_2

SG2_1

SG2_2

Router

LAN Switch

Router

LAN Switch

M2PA / SCTP / IP

MSC

After

IP Core Network

SMSC

LAN Switch

Router Router

SG1_1

SG1_2

M2PA / SCTP / IPSUA / SCTP / IP

Mated-SG

100Mbps/NIC

SG2_1

SG2_2

LAN Switch

MSC

TDMlinks

SUA


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SUA Reliabili ty and dimensioning aspects

SG should have on TDM side if any


Each linkset has the appropriate number of links

Usually each link is used at 0.4 Erlang Each linkset has links distributed on different SS7 adpator



Bandwidth required depends on protocol overhead and traffic load

Note each MAP message has up to 234 bytes ( 120 + SUA header )

SUA overhead is the following for connectionless data transfert CLDT message

ETH IP SCTP SUA CLDT data

20 Byte 28 Byte 12 Byte 40 Byte14 Byte

CLDT header

N Byte


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA



Sigtran in 3GPP


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Gi

Sigtran in 3GPP UMTS R5 architecture

GGSN

External VoIP

and IP MM Network

Legacy Mobile

Signaling NetworkApplication

and Services (SCP)

PSTN

Legacy/External

Applicationand Services (SCP) CS Domain

HLRHLR

EIREIR

HSSHSS

BSCBSC

RNCRNC

BSS/

GERAN

UTRAN

Mw

Mm

MgMrGi

Mc

Gi

Gi

Cx

C,D,Gc

Gc

Gn / Gp

Gf

Gr

Mc McNc

C

D

MhCAP

CAP

CAP

NbGp

RANAPIu-ps

Iu-ps

Iu-cs

RANAP

RANAP

RANAP

VoIP Signal

VoIP Bearer

Legacy Signal

Legacy Bearer

Mi

Mj

Go

PS Domain/ IM Domain

SGSN

CS-

MGW

SGW

SGW

GGSN

CS-

MGW

VLRMSCServer

GMSCServer

SGW

SGW

MGC

BGCFCSCF

CSCF

MRFC/PMRFC/P

Candidate to SIGTRAN


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Agenda

SS7 background


SIGTRAN

SCTP

M2PA

M3UA

SUA



E l C t M2PA t k


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Example - Customer M2PA network

Gateway-STP pairPair B

InternalPair A

OLOs

InternalPair C

SMSCPair D

M3UA

TDM

SLCs

M3UA

TDM

SLCs

SUA

M2PA core


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Example - Customer deployment

TDM

SEP

TDM

SEP IPSEPIP

SEP

STPOLO

TDM

SEP

TDM

SEP

IP

MSC

IP

MSC

BTISMSC

IP

SCCPRSCCPR

TDM

SEP

TDM

SEPTDM

SEP

TDM

SEP

M3UA Associations

M2PA Associations (full mesh)

TDM signalling links

IP

HLR

IP

HLR

A mesh of M3UAassociations amongst

SigTran enabled MSCs,

HLRs and SCCP Relays

SigTran enabled

MSC

IPMSCIP

MSC

A full mesh of M2PA

associations onlybetween SGws (for

example an addition

of a SEP will not

change this mesh)

Note: the number of nodes in the diagram

does not represent the actual figures

An SCTP

association will

also be provisioned

between each co-

located SGs

E l


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Exemple IP-enabled SMSC & Messaging Offload

SUA

SUA

SMSC

SMSC

Op

e n Me s s

a g i n

g Ga

te wa y

Signaling & SMS Platform

STP

STP

MSCMSC

MSC

MSC

-Increased bandwidth and capacity to SMSC-Decreased signaling transport/infrastructure costs

M2PA

M2PA

MLR

MLR

SS7 LSL or HSL

Exemple


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ARD Application Routing Director

PSTN

HLR2

1) MAP SRI 2) MAP SRI

3) MAP SRI

w/ newDPC/SSN

M3UA enabled AS

Exemple Flexible numbering HLR Management

HLR1 HLRn

SRI = Where is mobile station?


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Sigtran design rule of thumbs

Full physical and logical network redundancy is required in IPnetworks carrying SIGTRAN (path diversity)

All L2 and L3 switches, routers and Gateways have to be fullyredundant (mated pairs) and carrier class

If QoS is used for SIGTRAN, QoS policies need to be configured andenforced throughout the IP cloud

Routing protocols need to be appropriately configured to minimizerouting convergence times in case of network congestion and/or IPnode failure

MPLS VPNs may be used to segregate SIGTRAN traffic from othertypes of traffic (GPRS, management, corporate etc..)

Refer to BRKMWI-3006 sessions


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Sigtran design rule of thumbs

Basic SS7 design rules ALL apply

Use M2PA in the core (inter-STP) and TDM/ATM/xUA to the edge

(SMSC, SCP etc.)

Ensure bandwidth available for Max throughput rate in failoverscenario (remember erlang)

QoS and Traffic Engineering becomes essential if Network isShared

SCTP relies on IP and IP-based routing protocols. As such Ensureappropriate IP design and appropriate routing protocol used

Average IP network delay should not exceed 50 ms, Maximumdelay should not exceed 100 ms


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Why Sigtran and the ITP ?

Sigtran = SS7, everything old is new again

No more bandwidth limits with Sigtran!

The ITP supports all relevant SS7 (TDM and ATM) andSigtran (SUA, M3UA and M2PA) protocols in a any-to-

any fashion The ITP is widely deployed and has a proven track

record for investment protection and interoperability

The ITP is available on multiple hardware platforms

The ITP is based on Cisco IOS and as such supportsmany IP features for a true merge of the SS7 and IP

world


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Documents

Sigtran Connectuon by Cisco