Page 1 March 29, 2000 - W. Davis ALCATEL USA 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
Page 2March 29, 2000 - W. Davis ALCATEL USA
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
Page 3March 29, 2000 - W. Davis ALCATEL USA
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
Page 4March 29, 2000 - W. Davis ALCATEL USA
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
Page 5March 29, 2000 - W. Davis ALCATEL USA
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
Page 6March 29, 2000 - W. Davis ALCATEL USA
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 !
Page 7March 29, 2000 - W. Davis ALCATEL USA
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)
Page 8March 29, 2000 - W. Davis ALCATEL USA
Backup Slides
Page 9March 29, 2000 - W. Davis ALCATEL USA
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
Page 10March 29, 2000 - W. Davis ALCATEL USA
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
Page 11March 29, 2000 - W. Davis ALCATEL USA
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)
MTP2 Protocol DataUnits
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)
Page 12March 29, 2000 - W. Davis ALCATEL USA
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)
MTP2 Protocol DataUnits
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 )
Page 13March 29, 2000 - W. Davis ALCATEL USA
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
Page 14March 29, 2000 - W. Davis ALCATEL USA
MTP2 User Adaptation Layer: Case 2
Ram DantuSIGTRAN Working Group
November 9, 1999
Page 15March 29, 2000 - W. Davis ALCATEL USA
MTP2 User Adaptation Layer: Case2
Ram.Dantu - 1999-11-09
Page 16March 29, 2000 - W. Davis ALCATEL USA
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
Page 17March 29, 2000 - W. Davis ALCATEL USA
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
Page 18March 29, 2000 - W. Davis ALCATEL USA
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
Page 19March 29, 2000 - W. Davis ALCATEL USA
Case1
SignalingTransfer
ORMedia
Gateway
SignalingGateway IP Network
MediaGateway
Controller
MTP3MTP2
MTP2
MTP3MTP2UA
SCTPUDPIP
MTP2UASCTPUDPIP
Ram.Dantu - 1999-11-09
Page 20March 29, 2000 - W. Davis ALCATEL USA
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
Page 21March 29, 2000 - W. Davis ALCATEL USA
SSCOPMCE Solution for High Speed Link
MTP3Q.2140
SSCOPMCEATM
MTP3Q.2140
SSCOPMCEATMATM Link
STP SCP
Ram.Dantu - 1999-11-09
Page 22March 29, 2000 - W. Davis ALCATEL USA
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
Page 23March 29, 2000 - W. Davis ALCATEL USA
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
Page 24March 29, 2000 - W. Davis ALCATEL USA
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
Page 25March 29, 2000 - W. Davis ALCATEL USA
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
Page 26March 29, 2000 - W. Davis ALCATEL USA
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
Page 27March 29, 2000 - W. Davis ALCATEL USA
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
Page 28March 29, 2000 - W. Davis ALCATEL USA
SCTP
SEND FAILURE
NETWORK STATUS CHANGE
Communication up
Data Arrive
Communication Lost
Ram.Dantu - 1999-11-09
M2UA – SCTP Primitives
Page 29March 29, 2000 - W. Davis ALCATEL USA
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
Page 30March 29, 2000 - W. Davis ALCATEL USA
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
Page 31March 29, 2000 - W. Davis ALCATEL USA
Link Proving
MTP3 MTP2UA SCTP SCTP MTP2UA MTP3
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
Page 32March 29, 2000 - W. Davis ALCATEL USA
MTP3 MTP2UA SCTP SCTP MTP2UA MTP3
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
Page 33March 29, 2000 - W. Davis ALCATEL USA
MTP3 MTP2UA SCTP
Emergency
EmergencyCeased
Enable proving
Disable proving
Ram.Dantu - 1999-11-09
Emergency Alignment
Page 34March 29, 2000 - W. Davis ALCATEL USA
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