M3UA Operation

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M3UA Operation

• M3UA over SCTP
• Application Server
• A logical entity handling signaling for a scope
• A CA handles ISUP signaling for a SS7
  DPC/OPC/CIC-range
• An AS contains a set of Application Server
  Processes (ASPs)
• ASP
• A process instance of an AS
• Can be spread across multiple IP addresses
• Active ASPs and standby ASPs

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• Routing Key
• A set of SS7 parameters that identifies the
  signaling for a given AS
• OPC/DPC/CIC-range
• Network Appearance
• A mechanism for separating signaling traffic
  between an SG and an ASP
• E.g., international signaling gateway

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Signaling Network Architecture

• No single point of failure
• SGs should be set up at least in pairs
• ASPs
• A redundant or load-sharing configuration
• Spread over different hosts
• Point code
• All ASPs and the connected SG share the same PC
• A single SS7 signaling endpoint
• All ASPs share a PC ! that of the SG
• ASPs a signaling endpoint SG an STP
• A group of ASPs share a PC

4

• Robust Signaling Architecture

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Services Provided by M3UA

• Offer the same primitives as offered by MTP3
• MTP-Transfer request
• MTP-Transfer indication
• MTP-Pause indication
• Signaling to a particular destination should be
  suspended
• MTP-Resume indication
• Signaling to a particular destination can resume
• MTP-Status indication
• Some change in the SS7 network
• E.g., network congestion or a destination user
  part becoming unavailable

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• Transferring application message
• A CA sends an ISUP message
• MTP-Transfer request
• A SCTP DATA chunk
• Transmitted to a SG
• M3UA MTP3
• To the SS7 network

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• M3UA Messages
• Messages between peer M3UA entities
• A header the M3UA message content
• The entities can communicate information
  regarding the SS7 network
• If a remote destination becomes unavailable
• The SG becomes aware of this through SS7
  signaling-network management messages
• The SG pass M3UA messages to the CA
• The ISUP application at the CA is made aware
• MTP-Pause indication

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Signaling Network Management MSGs

• S7ISO SS7 Network Isolation
• When all links to the SS7 network have been lost
• DUNA Destination Unavailable
• Sent from the SG to all connected ASPs
• Destination(s) within the SS7 network is not
  available
• Allocate 24 bits for each DPC
• DUNA is generated at the SG
• It determines from MTP3 network management
  message
• The M3UA of the ASP
• Create MTP-Pause indication

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• DAVA - Destination Available
• Sent from SG to all concerned ASPs
• Mapped to the MTP-Resume indication
• DAUD Destination State Audit
• Sent from an ASP to an SG
• To query the status of one or more destination
• The SG responds with DAVA, DUNA, or SCON
• SCON SS7 Network Congestion
• Sent from the SG to ASPs
• The route to an SS7 destination is congested
• Mapped to the MTP-Status indication

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• DUPU Destination User Part Unavailable
• Sent from the SG to ASPs
• A given user part at a destination is not
  available
• The DPC and the user part in question
• Mapped to MTP-Status indication
• Cause codes
• DRST Destination Restricted
• Sent from the SG to ASPs
• One or more SS7 destinations are restricted from
• The M3UA may use a different SG

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ASP management

• ASPUP ASP Up
• Used between M3UA peers
• The adaptation layer is ready to receive traffic
  or maintenance messages
• ASPDN ASP Down
• An ASP is not ready
• UP ACK ASP Up Ack
• DOWN ACK ASP Down Ack

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• ASPAC ASP Active
• Sent by an ASP
• Indicate that it is ready to be used
• To receive all messages or in a load-sharing mode
• Routing context
• Indicate the scope is applicable to the ASP
• DPC/OPC/CIC-range
• ASPIA ASP Inactive
• ACTIVE ACK ASP Active Ack
• INACTIVE ACK ASP Inactive Ack

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• BEAT Heartbeat
• Between M3UA peers
• Still available to each other
• When M3UA use the services of SCTP
• The BEAT message is not required at the M3UA
  level
• SCTP includes functions for reachability
  information
• ERR Error message
• A received message with invalid contents
• NFTY Notify
• Between M3UA peers
• To communicate the occurrence of certain events

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Routing Key Management Messages

• Registration Request (REG REQ)
• An ASP a DPC/OPC/CIC range
• Registration Response
• Deregistration Request
• Deregistration Response

15
M2UA Operation

• MTP3/M2UA/SCTP
• The CA has more visibility of the SS7 network
• More tightly coupled to the SG
• MTP3
• Routing and distribution capabilities
• M2UA uses similar concepts to those used by M3UA
• ASPUP, ASPDN, ASPAC, ASPIA and ERR
• Exactly the same functions
• In M2UA, the ASP is an instance of MTP3

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• M2UA-specific messages
• DATA
• Carry an MTP2-user Protocol Data Unit
• ESTABLISH REQUEST
• To establish a link to the SG
• ESTABLISH CONFIRMATION
• RELEASE REQUEST
• Request the SG to take a particular signaling
  link out of service
• RELEASE CONFIRM
• RELEASE INDICATION
• The SG autonomously take a link out of service

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• STATE REQUEST
• Sent from a CA to the SG to cause the SG to
  perform some action on a signaling link
• Link alignment, or flushing transmit buffers
• STATE CONFIRM
• STATE INDICATION
• The SG can autonomously send
• During link changeover
• The CA must retrieve certain information from the
  SG
• DATA RETRIEVAL REQUEST
• DATA RETRIEVAL CONFIRM
• DATA RETRIEVAL INDICATION

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M2PA Operation

• IP-based SS7 links
• No FISUs sent only LSSUs and MSUs
• Establish SCTP associations between M2PA peers
• Two streams
• One for MSU
• The other for LSSU

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Interworking SS7 with VoIP Arch

• Interworking softswitch and SS7
• At least two SGs
• Use SCTP as MEGACO Transport
• An Internet draft
• Reliable and quick transport
• Use SCTP to transport SIP message?
• Might not be easy
• No semi-permanent relationship

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• ISUP encapsulation in SIP
• When the softswitch network provides a transit
  function
• Interworking often leads to a lowest common
  denominator result
• Retry-after header
• ISUP -gt SIP -gt ISUP
• Are the ISUP messages the same?
• The reliable delivery of provisional response

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Interworking H.323 and SS7

• The H.323 gateway
• Terminate SS7 links and voice trunks
• A close relationship exits between ISUP and Q.931
• IAM and Setup
• ANM and Connect

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