CHAPTER 5: Signaling in ATM Networks Objective: Users must have the capability of signaling connection across the network. 1. Switched Virtual Circuits (SVC) => by Signaling 2. Permanent Virtual Circuits (PVC) => by Network Management
THREE CLASSES of SIGNALING PROTOCOLS 1. ITU Protocols (descendent from ISDN protocols) * Q. 2931 and related “Recommendations=Standards” e. g. , Q. 931 used for N-ISDN. 2. ATM FORUM PROTOCOLS * UNI 3. 0 (Sept’ 93) & UNI 3. 1 ( Q. 2931) (Sept. ’ 94) * UNI 4. 0 (April’ 95) 3. Vendor Specific Protocols (Proprietary) * SPANS (Simple Protocol for ATM Network Signaling from FORE) * Several protocols developed at Research Centers and Universities.
THREE CLASSES of SIGNALING PROTOCOLS Remarks: * Only Difference between 3. 0 and 3. 1 Data link protocol SSCOP used for reliable transport of ATM signaling packets. • Incompatible message formats between UNI 3. 0 & Q. 2931 but functionality is very similar. • UNI 3. 1 attempts to reconcile UNI 3. 0 & Q. 2931 but not completely successful. => Three incompatible standards. • UNI 4. 0 attempts supporting Qo. S. (Various aspects of an ATM network have been split into Signaling 4. 0, Traffic Management 4. 0, the PNNI, the ILMI, and the various physical interface documents. ) Need a universal standard to ensure interoperability.
UNI and NNI Signaling UNI = “Private” User/Network Interface NNI = “Public” Network/Network Interface UNI signaling NNI signaling UNI signaling Private ATM Switch “user” Public ATM Switch Private UNI Public ATM Switch Public UNI signaling Public UNI • UNI and NNI signaling protocols are very similar in • functionality. P-NNI is the routing protocol.
Basic Connection Setup Protocol RECEIVER SENDER Setup Start Call Proceeding NETWORK Setup Complete Connect ACK Call Received (Status Indication but not finished processing) Connect ACK Call Accepted Local ACK, optional • Connection setup completed in one round-trip. • Signaling performed through dedicated Virtual Channels. - UNI signaling VC: VPI=0, VCI =5
Basic Connection Setup Protocol (Cont. ) Remark: Signaling between the end-system and the ATM switch usually takes place over VPI=0 and VCI=5, although this is not always the case. If we implement a feature such as SVC tunneling, the signaling channel will often be over a VPI =/ 0. Also, some proprietary UNI and NNI protocols use VCI =/5 for signaling. Note that the use of more than one VP at an interface does not imply that we require multiple signaling connections, since a single signaling link may service multiple VPCs.
Signaling Channels 1. • • • Reserved VPI/VCI x/1 = Meta-signaling x/2 = Broadcast signaling (not used initially) 0/5 = ATM endpoint to local network signaling both point-to-point and point-to-multipoint signaling (NONASSOCIATED SIGNALING MODE: all VC connections are created, controlled, released via this channel) • x/5 = point-to-point signaling with other endpoints and other networks (ASSOCIATED SIGNALING MODE: only VC connections within the VP x are created, controlled and released via this channel).
Meta-Signaling • Used to set up signaling channels • All meta-signaling messages are one cell long and have • VPI/VCI = 0/1 Sets up 3 types of signaling channels: - Point-to-point - General broadcast - Selective broadcast • Procedures to: - Set up new signaling channels - Release channels - Verify channels
Signaling Messages i. ATM Signaling is a protocol used to set up, maintain, and clear SVCs between two ATM end users over private or public UNIs. i. The protocol is, in fact, an exchange of messages that takes place between the ATM end user (caller or receiver) and adjacent ATM switch. i. The messages contain information that is used to build, maintain, or clear the connection. i. The messages themselves are segmented into cells at the signaling AAL and then transported over a standard signaling channels, VPI=0, VCI=5.
Signaling Messages There are four types of messages: • CALL ESTABLISHMENT • CALL STATUS • CALL CLEARING • POINT-TO-MULTIPOINT OPERATIONS
1. CALL ESTABLISHMENT PROCESS NNI UNI ATM End User UNI ATM Switch SETUP CALL PROCEEDING CONNECT ACK ATM End User SETUP CALL PROCEEDING CONNECT ACK Accept DATA SETUP. Sent by calling, or source ATM end user, to network (defined here as nearest ATM switch connected to ATM end user over UNI) and from network (defined here as nearest ATM switch connected to destination ATM end user over UNI) to called, or destination ATM end user. Used to initiate connection setup. Contains information, such as destination ATM address, traffic descriptors, AAL Info, and Qo. S.
CALL ESTABLISHMENT PROCESS • CALL PROCEEDING. Sent by destination ATM end user to network and by network to source ATM end user to indicate that call establishment has been initiated. • CONNECT. Sent by destination ATM end user to network and by network to source ATM end user to indicate that destination ATM end user accepts connection request. • CONNECT ACKNOWLEDGE. Sent by network to destination ATM end user to indicate call is accepted. May also flow from source ATM end user to network maintain symmetrical call-control procedures. • ALERTING. Sent by the destination ATM end user to the network and by the network to the source ATM end user to indicate that the destination ATM end user alerting has been initiated. For human interface (e. g. , voice). • PROGRESS. Sent by the ATM end user or the network to indicate the progress of a call in the event of inter-working.
2. CALL STATUS • • • STATUS. Sent by the ATM end user or network in response to a STATUS ENQUIRY message. STATUS ENQUIRY. Sent by the ATM end user or network to solicit STATUS message. NOTIFY. Sent by the ATM end user or network to indicate information pertaining to a call/connection.
3. CALL CLEARING NNI UNI ATM End User RELEASE ATM Switch RELEASE COMPLETE • UNI ATM End User ATM Switch RELEASE COMPLETE RELEASE. Sent by an ATM end user to request the network to clear the end-to-end connection or is sent by the network to indicate that the VCC is cleared and that the receiving ATM end user should release the VC and prepare to release the call reference after sending a RELEASE COMPLETE.
3. CALL CLEARING • RELEASE COMPLETE. Sent by an ATM end user or network to indicate that virtual channel and call reference have been released and that the entity receiving the message should release the call reference. • RESTART. Sent by the ATM end user or network to request the recipient to restart the indicated virtual channel or all virtual channels controlled by the signaling channel. • RESTART ACKNOWLEDGE. Acknowledges restart message and indicates restart is complete.
4. POINT-TO-MULTIPOINT OPERATIONS Point-to-multipoint SVCs enable a single ATM end user to communicate with one or more ATM end users. Information flowing from the source ATM end user is replicated by the network, not at the source and received by all destination ATM end users attached to the point-to-multipoint connection. The calling or source ATM end user is called the ROOT, and the called or destination ATM end users are called LEAVES. Conceptually viewed, leaves are connected to the root in a tree structure. UNI ATM End User ADD PARTY ACK UNI NNI ATM Switch ADD PARTY ACK ATM_1 End User ATM_2 End User SETUP CALL PROCEEDING CONNECT ACK
POINT-TO-MULTIPOINT OPERATIONS The root establishes a connection to the first leaf using standard callestablishment messages as shown in Figure. After that, additional leaves can be added or removed to the point-to-multipoint tree by the root. The leaves have the option of accepting the invitation and unilaterally removing themselves. Point-to-multipoint messages consist of the following: • • • ADD PARTY. Adds party (leaf) to an existing connection. ADD PARTY ACKNOWLEDGE. Acknowledges a successful ADD PARTY REJECT. Indicates that ADD PARTY request was unsuccessful. DROP PARTY. Drops or removes party (leaf) from an existing point-to-multipoint connection. DROP PARTY ACKNOWLEDGE. Acknowledges a successful DROP PARTY Figure shows the messages required to be sent by the root to add a leaf (ATM_2) to an existing point-to-multipoint connection.
CASE 1 ADD THE NEXT PARTY. THE PARTY REJECTS. UNI ATM End User ADD PARTY NNI UNI ATM End User ATM Switch ADD PARTY SETUP CALL PROCEEDING ADD PARTY NAK RELEASE ADD PARTY NAK (REJECT) RELEASE COMPLETE CASE 2 ROOT DROPS A PARTY. UNI ATM End User DROP PARTY ACK NNI ATM Switch UNI ATM End User ATM Switch DROP PARTY ACK RELEASE COMPLETE
CASE 3: ROOT DROPS LAST PARTY. UNI ATM End User RELEASE NNI UNI RELEASE COMPLETE RELEASE COMPLETE ATM End User ATM Switch COMPLETE CASE 4: A PARTY DROPS OUT. UNI ATM End User NNI ATM Switch DROP PARTY ACK UNI ATM End User ATM Switch DROP PARTY ACK RELEASE COMPLETE
CASE 5 NETWORK CLEARS THE CALL. UNI ATM End User NNI ATM Switch UNI CONNECTION RELEASE COMPLETE ATM End User ATM Switch TERMINATED DROP PARTY ACK RELEASE COMPLETE
Leaf Initiated Join (LIJ) UNI 3. 1 only allowed the root the option of adding leaves to an existing point-to-multipoint connection. This was deemed restrictive and would not provide the flexibility for applications to take full advantage of this capability. Therefore, UNI Signaling 4. 0 added a capability for leaves to join a point-to-multipoint connection without intervention from the root. This is called leaf initiated join (LIJ). LIJ is supported in one of the FOLLOWING MODES.
Leaf Initiated Join (LIJ) MODE 1. ROOT SETS UP A NETWORK LIJ CALL (ROOT PROMPTED JOIN) (ROOT LIJ CONNECTION) MODE 2. LEAF PROMPTED JOIN WITHOUT ROOT NOTIFICATION MODE 3: LEAF JOIN TO AN INACTIVE LIJ CALL (I. e. , No Multicast Group Exists and a leaf wants to initiate a multicast group) MODE 4: LEAF JOIN TO A NON-LIJ CALL (A multicast group exists but not created by a LIJ procedure. A Leaf wants to join that existing multicast group. )
LIJ EXTENSION IN UNI 4. 0 Two new messages were added to support LIJ in Signaling 4. 0: LEAF SETUP REQUEST. Sent by leaf to initiate leaf-joining procedures. LEAF SETUP FAILURE. Sent to leaf by root or network to indicate failure to join the point-to-multipoint connection.
MODE 1: (The ROOT SETS UP A NETWORK LIJ CALL. set up message contains LIJ parameters. ) Also known as Root-prompted Join. In this model the leaf generates and sends a request over the UNI to join a point-tomultipoint connection. This request, in turn, is forwarded up to the root which then invokes established procedures for adding a leaf to an existing connection. This is also called a root LIJ connection. UNI ATM End User NNI ATM Switch LIJ SET UP REQUEST ADD PARTY CALL PROCEEDING ADD PARTY ACK CONNECT ACK UNI LIJ SET UP REQUEST ADD PARTY CALL PROCEEDING ADD PARTY ACK CONNECT ACK ATM End User LIJ SET UP REQUEST SET UP CALL PROCEEDING CONNECT ACK
MODE 2: LEAF JOINS TO AN ACTIVE LIJ CALL. UNI ATM End User NNI ATM Switch UNI ATM End User ATM Switch LIJ SETUP REQ SETUP CALL PROCEEDING NO ROOT NOTIFICATION CONNECT ACK Also known as Leaf-prompted Join without root notification. In this model a leaf generates and sends a request over the UNI to join a point-to-multipoint connection. The network handles the request and the leaf joins the connection without notifying the root. This is called a NETWORK LIJ CONNECTION.
MODE 3: LEAF JOIN TO AN INACTIVE LIJ CALL NNI UNI ATM End User Leaf Setup Call Proceeding Connect Ack ATM Switch Leaf Setup Call Proceeding Connect Ack UNI ATM_1 End User ATM Switch Leaf Setup Call Proceeding Connect Ack No Multicast Group Exists and a LEAF wants to initiate a MULTICAST GROUP.
MODE 4. LEAF JOIN TO A NON-LIJ CALL NNI UNI ATM End User ATM Switch UNI ATM_1 End User ATM Switch ATM_2 End User Leaf Setup Add Party Leaf Setup Call Proceeding Add Party Ack Connect Ack Suppose a MULTICAST GROUP exists but created by a NON-LIJ set-up. Now a LEAF wants to join that existing MULTICAST GROUP by LIJ Set Up Request.
SIGNALING PROTOCOL STACK (S-AAL) SSCS: Service Specific Common Part Sub-layer UNI 4. 0 UNI 3. 1 Q. 2931 SAP SSCS SAAL SSCF: Service Specific Coordination Function SSCF SSCOP CPCS SAR SSCOP: Service Specific Connection-Oriented Protocol CPCS: Common Part Convergence Sub-layer SAR: Segmentation & Reassembly
UNI Signaling Protocol Stack Signaling Protocol Service-Specific Coordination Function (SSCF) Service-Specific Connection. Oriented Protocol (SSCOP) AAL 5 AAL servicespecific part (SSCS) Signaling AAL (SAAL) CPCS SAR ATM Layer Physical Layer • Signaling messages transported over ATM network using Signaling AAL (SAAL) • Based on AAL 5 • SSCOP provides reliable transport
Signaling AAL (SAAL) Provides a structured & reliable means to transport signaling traffic between two ATM end users. As part of the C_PLANE (Control Plane), it serves as the interface between higher layer control & signaling functions such as UNI 3. 1/Q. 2931 and the ATM layer. SSCF: responsible for mapping the higher layer application to SSCOP: a powerful connection-oriented data link protocol that provides a reliable transport for signaling messages. It supports end-to-end error detection, correction, frame sequencing & selective frame recovery.
SSCOP Operation SSCOP can be used as general Transport Layer over ATM • • Flow control based on sliding window üWindow size can be dynamically controlled by receiver (buffer size) Error control by selective retransmission of frames (only lost frame is retransmitted; AAL 5 packets which consist of multiple ATM cells). Separate frames for control and data Data frames up to 64 Kbytes
SSCOP Control Frames {POLL, STAT, USTAT} used for reliable delivery TCP uses a timer, whereas SSCOP uses explicit delivery • POLL(Next): Periodically used by SOURCE to request status of receiver (DESTINATION) üContains sequence number (SN) of next frame (NEXT) to be transmitted and timestamp --- if frames #1, #2, and #3 sent, POLL will send number for frame #4. üReceiver responds with sequence number of next sequential frame expected and list of any outstanding frames.
SSCOP Control Frames • STAT(Next; Missing): Status ACKing next and list of missing data. Response to POLL frame generated by receiver ü SOURCE uses STAT frame to: 1. Retransmit lost frames 2. Release ACKed frames from the retransmission buffer 3. Advance transmission window to last sequential frame received by receiver • USTAT (Unsolicited Status): Sent by receiver upon detecting a “hole” in the received sequence of frames ü Enables fast retransmission in the presence of random loss ü Used to improve performance. Can have in-frequent POLLs, yet not send too many frames following a lost frame.
SSCOP Operation: Example Transmitter 0 1 2 POLL 3 4 5 6 7 8 9 7 10 11 12 X Receiver time STAT(5) Acknowledges Frames 0 -4 USTAT Receiver detects Loss of frame 7 Transmitter does not Retransmit frame 7 Because POLL transmitted Before first retransmission STAT(10; 7) Again requests Retransmission Of frame 7 Transmitter buffer size determined by frame rate and round trip delay between POLL and Receiver STAT
ATM Addressing PEER MODEL: Use existing IP or MAC Addresses. IP routing protocols (OSPF) could be used. Advantages: Simplifies end system address administration. Disadvantages: Increases the complexity of ATM switches since they must act like multiprotocol routers and support address tables for all current protocols. OVERLAY MODEL: Decouple ATM from existing Infrastructure and have unique addressing mechanism. Accordingly new routing protocols were needed + Address resolution protocols from IP to ATM or from LANs to ATM address conversions. Advantages: Decoupling of ATM from higher layers allows independent development, applications and ATM technology. OVERLAY MODEL CHOSEN!!!
ATM Host Addressing Each ATM end user must have a UNIQUE ADDRESS. There is a STANDARDIZED ADDRESSING STRUCTURE for both PUBLIC and PRIVATE ATM NETWORKS!!! Private Networks: (based on HIERARCHICAL ADDRESSING DOMAINS) - 20 -byte format based on syntax of OSI Network Service Access Point (NSAP) address -Two different formats: 1. DCC (Data Country Code) 2. ICD (International Code Designator)
ATM Host Addressing Public Networks: Make Compatible With Private Network address - 8 -byte (64 bits) E. 164 format defined by ITU-T (has 16 digits each code with Binary Coded Decimal (BCD) using 4 bits. ) - Can be extended to a 20 -byte private address format by appending end-system address (e. g. , MAC address)
ATM Network Address Formats ATM Forum specifies 3 NSAP (Network Service Access Points) – like Address Formats DCC ATM Format Private End. System Not used Network Supplied In Routing Authority&Data High-order End-System Format Country Domain Selector Identifier(39)Code Specific Part “BD” 1 byte 2 bytes IDP IDI 10 bytes 6 bytes DSP 1 byte Multiple addresses assigned to the same ATM adapter.
ICD ATM Format Private Authority&Int’l High-order Format Code Domain Identifier(47)Designator Specific Part “C 5” 1 byte 2 bytes IDP IDI 10 bytes End-System Selector Identifier 6 bytes DSP 1 byte ETHERNET & Token ICD codes identify particular international organizations. Ring address field length for IEEE assigned addresses
NSAP-Encoded E. 164 Format Public Authority& E. 164 Format Identifier(45)Address “C 3” 1 byte 8 bytes IDP High-order Domain Specific Part 4 bytes End-System Selector Identifier 6 bytes 1 byte DSP (Domain Specific Part) IDI High order domain specific part addresses can be assigned by “hand”
Addressing n The IDP specifies an administration authority which has the responsibility for allocating and assigning values for the DSP. n IDP has AFI (Authority and Format Identifier (AFI)) and IDI (Initial Domain Identifier (IDI). n AFI specifies the format of the IDI, and the abstract syntax of the DSP field. n IDI specifies the network addressing domain, from which DSPs are allocated and the network addressing authority responsible for allocating values of the DSP from that domain. n DCC (Data Country Code) Specifies the country in which the address is registered. These addresses are administered by the ISO’s national member body in each country. The digits of data country code are encoded using BCD.
Addressing n. ICD (International Code Designator) n Identifies an authority which administers a coding scheme. n This authority is responsible for the allocation of identifiers within this coding scheme to organizations. n The registration authority for the international code designator is maintained by the British Standards Institute. n The digits of ICD are encoded using BCD.
n ATM Forum extended E. 164 address to NSAP format. E. 164 number is filled with leading zeroes to make 15 digits. A F 16 is padded to make 8 bytes. n High Order DSP (HO-DSP) field will be used to construct multi-level address hierarchies for routing. Remark: In real NSAPs, DSP is subdivided into a hierarchy of Routing Domain (RD) and an Area Identifier (AREA) and an End System Identifier (ESI). ATM Forum combined the RD and AREA fields into HO-DSP. A range of addressing hierarchies will be supported -> increases the scalability.
n. End System Identifier (ESI): 48 -bit IEEE MAC address (to identify a specific host within an ATM subnet) (Token Ring, Ethernet LAN MAC addresses) n. SELECTOR is for use inside the host and is not used for routing (used for local multiplexing within end stations and has no network significance). This is used to distinguish between different destinations reachable at the end device. n. All ATM addresses are 20 bytes long.
Addressing • Private networks must support all three formats Type of Number field = Unknown Numbering Plan Indication field = ISO NSAP • Public networks must support native E. 164 and may optionally support three NSAP-encoded formats. For E. 164: Type of Number field = International Numbering Plan Indication field = Recommendation E. 164 • If only native E. 164 addresses, subaddress field in signaling messages used to convey private ATM address across. • One Transit network selection possible using carrier identification code field
E. 164 Addresses (ITU-T) • North American Numbering Plan (NANP): 1(614)-555 -1212 • E. 163 numbering plan for telephony: 12 digits • E. 164 numbering plan for ISDN: 15 digits • Defined in ITU-T recommendation E. 164 for ISDN • ISDN numbers uniquely identify interfaces to public networks • Several ISDN numbers can identify the same interface • ISDN signaling allows ISDN number followed by a sub-address (extension) of up to 40 digits • Administrated by public networks (Therefore, are not easily available for private network use)
EXAMPLE ATM Address for SVC connecting BWN Lab Testbed (GCATT) to OIT-OC-3 (Rich Building) 39. 840 F. 8001. BC 88. 2280. 4110. 4002. 4000. OC 8 0. 0020. 00
ATM Signaling Message Format (Q. 2931, UNI 3. 0, UNI 3. 1) • Each message includes the following components: Bits 8 0 Flag 7 0 6 5 4 3 2 1 Protocol Discriminator Length of call reference value 0 0 (in octets) Call reference value (continued) Message type (continued) Message length (continued) Information Elements. . . Octets 1 2 3 4 5 6 7 8 9 10 11
Message Format • Protocol Discriminator (1 byte): Distinguishes Q. 2931 messages from other messages. • 08 = Q. 931 • 09 = Q. 2931 • Call Reference (4 bytes): Identifies call to which this message is related to. One user may have many calls simultaneously. • Flag = 1 : Message is from call reference originator • Flag = 0 : Message is to call reference originator • Message Type (2 bytes): Many types, e. g. , connect, call proceeding, setup, release, etc. • Message Length (2 bytes): Length of contents of this message
Sample Message Types Bits 876 Bits 54321 000 Type Call Establishment Messages 00010 Call proceeding 00111 Connect 01111 Connect ACK 00101 Setup 01101 Setup ACK 010 Call Clearing Messages 01101 Release 11010 Release Complete 011 Information 10101 111 Status Inquiry Status Reserved for Extension
Protocol discriminator: Distinguishes messages for ATM end user-to-user network call control from other messages. Call reference value: Associates message with connection at UNI. Local significance only. Message type: Identifies type of message as described in previous section. Message length. TLV information elements: Parameters associated with a particular message. The presence of the first four components is mandatory in every message. A message will contain different information elements (IE) depending on the type of message. The IEs are Type/Length/Value (TLV) fields that contain information that is used by the ATM end user or network to process the connection
Information Elements Table describes most of the relevant IEs that have been defined in UNI 3. 1 and UNI Signaling 4. 0, and may be present (mandatory or optional) in ATM signaling messages: Table. UNI Signaling Information Elements Information element Cause Max. length (bytes) Description 34 Why certain messages are generated and may provide diagnostic information. Call state 5 Current status of call. Endpoint reference 7 Identifies individual endpoint in point-to-multipoint connection. Endpoint state 5 Indicates state of an endpoint (i. e. , add parity, drop parity, etc) in point-to-multipoint connection. AAL parameters 20 AAL specific parameters such as CPCS-SDU size, AAL type ATM traffic descriptors 30 Forward and backward PCR, SCR, and burst sizes
Table. UNI Signaling Information Elements (Cont’d) Information element Alternative ATM traffic descriptors Max. length (bytes) Description 30 Minimum acceptable traffic descriptors Describes alternate ATM traffic-descriptor values and is used during negotiation of these values in UNI Signaling 4. 0. Describes minimum acceptable ATM trafficdescriptor values and is used during negotiation of these values in UNI signaling 4. 0. Connection identifier 9 VPI and VCI values. Qo. S parameters 6 Qo. S class (0 -4). Extended Qo. S parameters 25 Indicates individual Qo. S values acceptable on a percall basis. These include acceptable and cumulative forward and backward cell loss ratio. Broadband highlayer information 13 Validate compatibility of high-layer information such as ISO or vendor-specific protocols Broadband bearer capability 7 Indicates request for connection-oriented service that will provide interworking (I. e. , DS 1 emulation), ATM only, or VP service (for switched VPs). Also specifies CBR or VBR.
Table. UNI Signaling Information Elements (Cont’d) Information element Broadband lowlayer information Max. length (bytes) Description 17 Validates compatibility of layer-2 and layer-3 protocols. Broadband locking shift 5 Indicates new active code set. Broadband nonlocking shift 5 Indicates temporary shift to specified code set. Broadband sending complete 5 Indicates completion of the called party number. Broadband repeat indicator 5 Indicates if IE is repeated in message and how they should be interpreted. Calling party number 26 ATM address of source ATM end user. Calling party subaddress 25 Used to convey a private ATM address across a public E. 164 network. Called party number 26 ATM address of destination ATM end user. Called party subaddress 25 Used to convey a private ATM address across a public E. 164 network.
Table. UNI Signaling Information Elements (Cont’d) Information element Max. length ( bytes) Description Transit network selection 8 Identifies requested transit network Restart indicator 5 Identifies class of facility to be restarted, such as indicated VC or all VCs. Narrowband lowlayer compatibility 20 Q. 2931 -based IE used to validate low-layer compatibility for N-ISDN interworking device. Narrowband highlayer compatibility 7 Q. 2931 -based IE used to validate high-layer compatibility for N-ISDN interworking device. Notification indicator 5 Q. 2931 -based IE used to indicate information pertaining to a call. Progress indicator 6 Q. 2931 -based IE used to describe an event which has occurred during the life of a call. Narrowband bearer indicator LIJ call indentifier LIJ parameters Q. 2931 -based IE used to indicate a requested circuitmode N-ISDN bearer service to be provided by the network. 9 Identifies point-to-multipoint LIJ call at root’s interface. LIJ parameters used by root to associate options with call at call setup.
Table. UNI Signaling Information Elements (Cont’d) Information element LIJ sequence number Max. length (bytes) Description 8 Used by joining leaf to associate SETUP, ADD PARTY, or LEAF SETUP FAILURE response message with corresponding LEAF SETUP REQUEST. End-to-end transit delay 12 Q. 2931 -based IE used to indicate the maximum end-toend transit delay acceptance on a per-call basis, and to indicate the cumulative transit delay actually experienced by a virtual channel connection. Equal to forward maximum cell transfer delay per traffic management V 4. 0 specification. Extended end-to-end transit delay 12 Indicates backward maximum cell transfer delay. Generic identifier transport 30 Used to indicate session and resource identifier for video-on-demand virtual connections. Connection scope selection 6 Enables calling user to indicate to the network that the connection should proceed within the selected routing range. Used to limit search for anycast services. 56 Provides information relating to the presence and handling of the end-to-end F 5 OAM information flow for performance management and user-originated fault management associated with the user connection involved in the call. OAM traffic descriptor
Table. UNI Signaling Information Elements (Cont’d) Information element Max. length (bytes) Description ABR setup parameters 36 Specifies set of ABR parameters used during connection setup. ABR additional parameters 14 Specifies additional ABR parameters.
Bandwidth Contract n User specifies 12 leaky bucket parameters Forward Backward Peak Cell Rate Sustainable Cell Rate Maximum Burst Size CLP=0+1 Peak Cell Rate Sustainable Cell Rate Maximum Burst Size CLP=0
AAL Parameters n AAL 1 Parameters 5. CBR Rate Clock Recovery type Error correction type Structured Data Transfer Partially filled cells 1. MID Size 1. 2. 3. 4. n AAL ¾ Parameters
AAL Parameters n 1. 2. 3. 4. AAL 3/4/5 Parameters Forward maximum SDU size Backward maximum SDU size Mode: message or streaming Service Specific Convergence Sublayer (SSCS) Type § Null, Assured SSCOP, non-assured SSCOP, or Frame relay
Sample Information Elements Bits 87654321 Information Element 01110000 01110001 01111000 01101101 01011000 01011001 01011010 01011100 01000010 01011110 Called party number Called party sub-address Transit network selection Calling party number Calling party sub-address AAL parameter ATM Traffic Descriptor Connection Identifier Quality of Service Parameter End-to-end transit delay Broadband bearer capability
UNI 3. 0 Overview • Two types of VC’s • Unidirectional channel to single destination or multicast tree (e. g. , distribute video or audio streams) * Joins to multicast VC must be initiated by root (Set up VC then use “Add Party” according to instructions from source) • Two channels in opposite directions with symmetric or asymmetric bandwidths (asymmetric: files/ACK) • Defines interaction between end-points and the network • Support for specifying traffic burstiness (CBR, VBR) • No support for Qo. S (can define service classes; differentiate types of services but no support for parameterized service classes) • Flexibility in ATM address formats
UNI 3. 0 Overview Three classes of services 1. Class A: CBR with stringent cell-loss, delay, and jitter requirements. 2. Class C: VBR with no end-to-end timing requirements no delay guarantees 3. Class X: – User-defined traffic type and timing requirements (setup message specifies only desired bandwidth and Qo. S) (Not universal, only work within your private network)
UNI 3. 0 Overview n. Traffic parameters supported – Peak Cell Rate (PCR) – Sustained Cell Rate (SCR) – Maximum Burst Size – Can be specified separately for CLP = 0 and 1 – No support for traffic parameter negotiation (If over-request on network resources (bandwidth), request will be rejected at signaling, e. g. , ask for 100 Mbps but network can only support 50 Mbps, then the request will receive a “Reject”!!!) n. Qo. S Support – Allows five distinct Qo. S classes (0 -4) to be specified in SETUP message – Parameterized Qo. S not supported
UNI 3. 1 Overview very similar to 3. 0 Goal: Revision of UNI 3. 0 to make it compatible with Q. 2931 Several incompatibilities with UNI 3. 0 Many message formats different Refinement of Domain-Specific Part (DSP) to E. 164 address UNI 3. 1 still incompatible with Q. 2931 Three incompatible protocols {UNI 3. 0, UNI 3. 1, Q. 2931}
UNI Signaling 4. 0 Enhancements UNI 4. 0 Signaling includes a number of significant functional enhancements over AND above what is provided in UNI 3. 0/3. 1. Some have already been discussed, but it is helpful to review here the primary functional enhancements: n. Leaf-initiated join. Allows users to dynamically join existing point-to-multipoint connections. n. Group addressing: Well-known functional addresses can be utilized to reduce signaling and configuration overhead.
UNI Signaling 4. 0 Enhancements n. Anycast Addressing. Enables server (and or servers) to be assigned a well-known group address. The ability to control access to anycast servers is included using a connection/membership scope. n. Proxy Signaling. Used to support devices that do not support ATM signaling, such as residential broadband. n. Switched Virtual Paths. ATM virtual paths can be dynamically provisioned. This will reduce administrative overhead in public and private networks. n. Multiple Signaling Channels. This enables multiple ATM end users to share a single UNI interface or port on the switch.
UNI Signaling 4. 0 Enhancements n. Frame Discard Capability. Cells belonging to an entire frame can be discarded to prevent or relieve congestion, e. g. , “early packet discard” and “partial packet discard” enabled/disabled on a per VC basis. n. Available Bit Rate (ABR) Signaling for Pointto-Point Connections. Parameters for ATM end users requesting ABR service can be designed into the network.
UNI Signaling 4. 0 Enhancements n. Signaling of Individual Qo. S Parameters. Cell loss ratio, mean cell transfer delay, maximum cell transfer delay, and cell delay variation can be signaled into the network rather than just one Qo. S class. n. Traffic Parameters Negotiation. ATM traffic parameters can be negotiated between ATM end users. n. N-ISDN Inter-working. Enables interworking between narrowband broadband ISDN networks.
Proxy Signaling PSA (Proxy Signaling Agent) PSA Network SETUP (to User B, from A, VPCI at UNI A) SETUP (to User B, from A, VPCI at UNI B) CONNECT (to User A) Network has established ATM connection between users A and B Ü Suppose you have a low cost adapter, a “proxy” can do the signaling for that piece of equipment. • • Allows a user (proxy agent) to perform signaling on behalf of other users. • Enables multiple ATM interfaces on end-system to share same ATM address, e. g. , high performance server with 3 adapters. • Used to support devices that do not support ATM signaling, such as residential broadband. Proxy agent can be remotely located on another switch
Anycasting A well-known group address associated with a PARTICULAR SERVICE. ( like dialing 555 -1212 in the telephone service) Examples: Name server, time-of-day server, etc. . ; Specify service only and protocol will find server that provides desired service. Do not have to know location of service; just specify the desired service. Allows a user to request a point-to-point connection to any host within a specified group • • • - Useful for connecting to a server providing a specific service (e. g. , LAN Emulation Server, ARP Servers, NHRP Servers) ATM group addresses obtained by setting most significant bit of first byte (AFI) in the address formats. Well-known groups for standardized service functions Also allows specification of “scope” of service provided by each member (within LAN, within organization, etc. ). (Route the request to the server valid for the service “context”).
Overview of UNI 4. 0 Functions This table shows the new functions provided in the UNI Signaling 4. 0, and whether the functions are mandatory (M) or optional (O) on both ATM end user (terminal equipment) and switch (switching system). Feature Point-to-point calls Point-to-multipoint Leaf-initiated join capability Notification of end-to-end connection completion ATM anycast capability Multiple signaling channels Switched virtual path (VP) service Proxy signaling Frame discard capability ABR signaling for point-to-point calls Generic identifier transport Traffic parameters negotiation Signaling of individual Qo. S parameters Supplementary services Direct dialing in (DDI) Multiple subscriber number (MSN) Calling line identification presentation (CLIP) Calling line identification restriction (CLIR) Connected line identification presentation (COLP) Connected line identification restriction (COLR) Subaddressing (SUB) User-user signaling (UUS) Terminal Equipment Switching System M O O O O O M M M * O O O † O O O O O ‡ O This feature is optional for public networks/switching systems and is mandatory for private networks/switching systems. † Transport of the frame discard indication is mandatory. ‡ This feature is mandatory for network/switching systems (public and private) that support only native E. 164 address formats. *
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