M2UA Peer-Peer Adaptation Layer SIGTRAN Working Group March 29, 2000

Page 1March 29, 2000 - W. Davis ALCATEL USA

M2UA Peer-Peer Adaptation Layer

SIGTRAN Working GroupMarch 29, 2000


M2UA Peer-Peer Adaptation

BackgroundFirst incorporated into M2UA draft-ietf-sigtran-m2ua-01

– Case 1: M2UA Backhaul– Case 2: M2UA Peer-Peer (“M2Peer”)

Ram Dantu presentation, IETF-46 November 1999

Drivers for M2UA Peer-Peer (Case 2)Support MTP3 transport over SCTP (RFC 2719)Seamless intermix of SS7 Links and IP LinksMaintain added MTP3 End-End Reliability Functions

– Changeover / Changeback / MSU Retrieval– Link Alignment / Proving– Congestion Detection / Notification– SLS Loadsharing


M2UA Case 1 (Backhaul) Architecture

SEP - SS7 Signaling Endpoint NIF - Nodal Interworking Function

SG - Signaling Gateway SCTP - Simple Control Transmission Protcol

SEP SG

SS7Appl

MTP3 MTP3

MTP2

MTP1

MTP2M2UA

SCTP

MTP1 IP

M2UA

SCTP

IP

MGCSS7 IP

NIF

IP Network

MTP2 Primitives Backhaul

SS7Appl


M2UA Case 2 (Peer-Peer) Architecture

SEP - SS7 Signaling Endpoint

SG - Signaling Gateway SCTP - Simple Control Transmission Protcol

SEP SG

SS7Appl

MTP3 MTP3

MTP2

MTP1

MTP2M2UA

SCTP

MTP1 IP

M2UA

SCTP

IP

MGCSS7 IP

IP Network

Peer-to-Peer

SS7Appl

MTP3

Link Protocol


Contrasting M2UA Case 1 and Case 2

Case 1: M2UA BackhaulProtocol Characteristics

Asymmetric– MGC Client – SG Server

Protocol DataUnitsDataEstablish RequestEstablish ConfirmRelease RequestRelease ConfirmRelease IndicationState RequestState ConfirmState IndicationData Retrieval RequestData Retrieval ConfirmData Retrieval IndicationData Retrieval Complete

Indication

Case 2: M2UA Peer-PeerProtocol

CharacteristicsSymmetric

– SP Peer – SP Peer

Protocol DataUnitsDataStatus - Out Of AlignmentStatus - Normal AlignmentStatus - Emergency AlignmentStatus - Out Of ServiceStatus – Processor OutageStatus – Busy


Contrasting M2UA Case 1 and Case 2

Case 1: M2UA BackhaulApplication Server

MessagesASP UpASP DownASP ActiveASP Inactive

State ControlASP-ActiveASP-Active-OldASP-Active-NewASP-UpASP-Down

Case 2: M2UA Peer-PeerApplication Server

MessagesNot applicable – covered by

alignment / changeover procedures)

State ControlLink Out-Of-ServiceLink AlignmentLink In-ServiceLink Congestion OnsetLink Congestion AbatementLink Remote Processor

Outage

Dissimilar functions makes it hard on the reader !


M2UA Peer-Peer Adaptation

Proposal: Split out Backhaul and Peer-Peer CasesM2UA Backhaul

draft-ietf-sigtran-m2ua-03M2UA Peer-Peer

draft-george-sigtran-m2peer-00

Requested ActionAdd M2UA Peer-Peer as SIGTRAN work itemUnique Port and SCTP Protocol Ids

Mail List Issues For ResolutionMultiple Streams per Link (SLS basis)Proving Period Functionality (Optional)SCTP Peer-Peer Association Setup (Collision

Resolution)


Backup Slides


Layered Communications - OSI Model

Layer N

Layer N Connections

Layer N

Layer N Protocol (Protocol DataUnits)

Layer N SAP (Service Access Point)

Layer N-1

Layer N-1 SAP

Layer N+1 Layer N+1

Layer N-1

Bearer Functions

Management Functions

Bearer Functions

Management Functions

Layer N Primitives

Layer N Connection Endpoints

.request.confirm .response.indication


Standard SS7 MTP3 Layer

MTP3 (Network) Layer

(No Connections Defined)

MTP3 User Layers

MTP2 SAALM2UA /

SCTP / IP

MTP Link Layers

Unitdata (DPC, SLS, Priority) .request, .indication

Changeover / Changeback

Message (MSU) Transfer

Transfer Controlled / RouteSet Congestion Test

Transfer Prohibited / Restricted / Allowed

User Part Unavailable

MTP3 Protocol DataUnits

MTP Pause / Resume (DPC) .indication

MTP Status (DPC, Congestion Level) .indication

MTP Restart Begin / End ( ) .indication

Peer MTP3 Layer

Peer User Layers

Peer Link Layers

MTP3 Primitives


Standard SS7 MTP2 Layer

MTP2 Datalink Layer

MTP2 User Layer (MTP3)

DS0A V.35 T1E1 Chan

MTP1 Link Layers

Data (Length) .request, .indication

MessageSignal Unit (MSU)

Fill In Signal Unit (FISU)

Link Status Signal Unit (LSSU)


Link Start / Stop .request, .indication

Link Status (State) .indication

Data Retrieval (SN) .request, .indication

Peer MTP2 Layer

Peer User Layer

Peer MTP1 Link Layers

MTP2 Primitives

MTP2 Connection (Datalink)


MTP2 Adaptation Layer Variants

MTP2 Datalink Layer

MTP3 Layer (MTP2 User)

DS0A V.35 T1E1 Chan

MTP1 Link Layers

MessageSignal Unit (MSU)

Link Status Signal Unit (LSSU)


Peer MTP2 Layer

Peer MTP3 Layer

Peer MTP1 Link Layers

MTP2 Connection (Datalink)

SG

AS

STP/SCP

( Peer-Peer )

IP Network

Data (Length) .request, .indication

Link Start / Stop .request, .indication

Link Status (State) .indication

Data Retrieval (SN) .request, .indication

MTP2 Primitives

( Backhaul )


Standard SS7 Layer Summary

Signalling System

SCCP

PHY

MTP3

MTP2

TCAP Application Remote Operation Invocation, Parameter Encoding Application Transaction Control Example Application: LNP Ported Number

Translation

SCCP Layer Network Application Subsystem Addressing Global Title Translation (TN Digits -> Subsystem

Address) Remote Subsystem Status Management

MTP3 Layer Network PointCode Addressing PointCode Relay Routing, Re-routing, Multi-Link

Loadsharing Link, LinkSet, RouteSet Status Management

MTP2 Layer Link alignment, proving, error-rate monitoring MSU Seq# / CRC generation / checking MSU queuing / dequeuing, retrieval, congestion

monitoring MSU delineation, zero insertion, transmit / receive,

re-transmit

Physical Layer Physical connectivity (e.g. V.35) Point-to-point bitstream transmit / receive

TCAP Application


MTP2 User Adaptation Layer: Case 2

Ram DantuSIGTRAN Working Group

November 9, 1999


MTP2 User Adaptation Layer: Case2

Ram.Dantu - 1999-11-09


Overview

Background: SS7-IP Interface Adaptation OptionsProblem Definition (Case1 and Case2)Case 1: One application of M2UASSCOPMCE based solution for Case 2Case2: SCTP based solution for STP-IPSCP Interface

Overview of SolutionLink ChangeoverLink ProvingCongestion DetectionEmergency Alignment

Conclusions

Ram.Dantu - 1999-11-09


Background: SS7-IP Adaptation Layer Options

ISUP/SCCP

MTP3

MTP2UA

SCTP

UDP

IP

E-Net/DS1/DS3/OC3

ISUP/SCCP

MTP3UA

SCTP

UDP

IP

E-Net/DS1/DS3/OC3

Q.923

Q.921UA

SCTP

UDP

IP

E-Net/DS1/DS3/OC3

IETF

Sigtran

SS7MTP3

Q.2140

SSCOPMCE

UDP

IP

E-Net/DS1/DS3/OC3

ITU

ATM/IP

SAAL

ATM

Ram.Dantu - 1999-11-09


Problem Definition

A protocol M2UA (MTP2 User Adaptation Layer) is being defined by IETF Sigtran Group. The users of this layer are MTP3 and a MTP2-backhauling layer (Case1). One application is the inter working of MTP3 layer and IP networks seamlessly similar to MTP3 layer and MTP2 layer in SS7 network (Case2). In particular, this interface is useful between STP and IP enabled SCPs (IPSCP). To this end, several primitives and procedures are defined for MTP2 User Adaptation Layer.

Ram.Dantu - 1999-11-09


Case1

SignalingTransfer

ORMedia

Gateway

SignalingGateway IP Network

MediaGateway

Controller

MTP3MTP2

MTP2

MTP3MTP2UA

SCTPUDPIP

MTP2UASCTPUDPIP

Ram.Dantu - 1999-11-09


Case1

Backhauling signaling traffic at layer 2 to the Media Gateway Controller.

Using MTP2 user adaptations layer as an extension of MT2 link layer

SGW has no point code and not visible in SS7 network

Ram.Dantu - 1999-11-09


SSCOPMCE Solution for High Speed Link

MTP3Q.2140

SSCOPMCEATM

MTP3Q.2140

SSCOPMCEATMATM Link

STP SCP

Ram.Dantu - 1999-11-09


SSCOPMCE Solution

A Solution for high speed interface between two STPs or between STP and SCP.

SSCOPMCE is a similar transport protocol like SCTP

SSCOPMCE solution is primarily meant for ATM but Interface between SSCOPMCE and IP requires considerable work (under progress)

SCTP has several additional features.

Ram.Dantu - 1999-11-09


Case2: STP-IPSCP Interface

SSP

TCAPSCCPMTP3MTP2

MTP3MTP2

IPSSP

STP

MTP3MTP2UASCTP

TCAPSCCPMTP3MTP2UASCTP

MTP3MTP2

MTP3MTP2

MTP3MTP2UASCTP

MTP3MTP2UASCTP STP

SCCPMTP3MTP2 SCCP

MTP3MTP2

SCP

TCAPSCCPMTP3MTP2UASCTP

SCCPMTP3MTP2UASCTP

IPSCP

Ram.Dantu - 1999-11-09


MTP2 and MTP3 Functions

MTP2 Functions Signal unit deliminations Signal unit alignment Signal unit detections Signal unit error corrections Signaling link initial

alignment Signaling link error

monitoring Flow control Sequence numbering Cyclic Redundancy Check Preventive Cyclic

Retransmission Data Retrieval Congestion Management

MTP3 Functions Link activation Link restoration Link deactivation Change over Change back Emergency change over MTP restart Transfer prohibited Transfer allowed Transfer restricted Transfer controlled Signaling-route-set-test Signaling-route-set-

congestion-test Transfer cluster prohibited Transfer cluster allowed Transfer cluster restricted Cluster-route-set-test

Ram.Dantu - 1999-11-09


M2UA: Case2

High speed IP link between SEP/STP and STP/SCPNew functions are added to M2UA. In particular, M2UA

supporting SS7 link management features. Enhancements

Mapping of sequence numbers between SS7 Network and IP Network

Additional primitives Data Retrieval during link change over

Additional primitives for Link provingAdditional primitives for Congestion DetectionAdditional primitives for Emergency alignmentProcedures for Data Retrieval during link change over Procedures for Link provingProcedures for Congestion DetectionProcedures for Emergence Alignment

Ram.Dantu - 1999-11-09


MTP3-M2UA Primitives

MTP3Received Message

Link Congested

Link Congestion Ceased

Emergency

Emergency Ceased

STOP Communicating To Peer

START Communicating To Peer

Link Available

Link Out Of Service

Flush Buffers

Continue

Retrieve_BSNT

BSNT Confirm

Retrieval_Reqest_And FSNC

Retrieved Messages

Retrieved Complete

BSNT Delivery of BSTN Value

BSNT_Not_Retrievable

Primitives

M2UA

Ram.Dantu - 1999-11-09


M2UA-SCTP Primitives

UDP

SCTP

UDP Port

INITIALISE

ASSOCIATE

Terminate

SEND (associates ID, buffer address

Byte count (mode flags)(context) (stream ‘D)

RECEIVE (buffer address, byte count)

(association ID) (max size of data to be released)

STATUS (association ID)

Status date (receive windows size, send window size, connecting state, numberof buffers awaiting acknowledgment, number of buffers pending transmit, Round trip time on all active interfaces

Ram.Dantu - 1999-11-09


SCTP

SEND FAILURE

NETWORK STATUS CHANGE

Communication up

Data Arrive

Communication Lost

Ram.Dantu - 1999-11-09

M2UA – SCTP Primitives


SEP/SCP STP/SCP

SS7network

Internal IPTransport

LeasedIP Network

1. If there is a link fail, link can change over 2. If link is congested then also there can be change over3. Change over for links of unequal bandwidth for further study

Ram.Dantu - 1999-11-09

Link Changeover


MTP3 MTP2UA SCTP SCTP MTP2UA MTP3

Communication lost

Link out of service

Retrieve BSNTXFind gaps in the received msgs(numbered beforefirst gap)

Indicate BSNCOO (BSN)

Relieve BSN

Indicate BSN

COA (BSN)

Retrieve FSN

FSN Not

Retrievable

Retrieval Msg

Retrieval Complete

Go through thetransmit queueand find unackand unsent msg.

0000000

15 7 0

Last 7 bits are used for FSN/BSN

- Extending to 24 bits for further study

Link Changeover

Ram.Dantu - 1999-11-09


Link Proving


Communication

Status(or heartbeat

Link In Service

Link in service

1. During proving, only unorderedservice is considered. This meansmessage is delivered immediately.2. Proving time is configurable.3. Estimated - parameters arecompared with performancerequirements of the application thatopened the stream.4. Link Proving is done on both sides.

Emergency

Ceased

Emergency

Up

Status

“n” SecEstimate- average delay- packet loss- etc.,

Communicationslink up

Link is same

No. of messages for “n” sec RTT

RTT

RTT

Ram.Dantu - 1999-11-09



Send failure

Congestion

Send failure

Detected

Send failure

3 consecutivefailures(implemen-tation dependent)

Polled for certain time till the congestionis ceased (implementation specific)

Status

Status

Status

Congestion

ceased

Terminate

Terminate Successful

Communication Lost

Link Out of Service(Link Change Over

Procedures areStarted)

Link brought back to service after proving

Ram.Dantu - 1999-11-09

Congestion Detection


MTP3 MTP2UA SCTP

Emergency

EmergencyCeased

Enable proving

Disable proving

Ram.Dantu - 1999-11-09

Emergency Alignment


Conclusions

With wireless and other new configurations, SCPs require high bandwidth links. A high speed link based on SCTP/IP is defined between STPs as well as STP and SEP/SCPs. M2UA seems to be a good fit for interface between SS7 and IP networks.

SCP applications require reliable, available, and proved links. To this end, new primitives/procedures are defined in M2UA.

Minor enhancements are made to SCTP for supporting this feature. M2UA document will be modified to clearly distinguish the Case1 and Case2 solutions.

Ram.Dantu - 1999-11-09

Documents

M2UA Peer-Peer Adaptation Layer SIGTRAN Working Group March 29, 2000