Transcript ATM End User

5. Signaling in ATM Networks
Objective: Users must have the capability of signaling a
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 QoS.
(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”
Private UNI
Public
ATM
Switch
Public
ATM
Switch
Public
ATM
Switch
Public
ATM
Switch
Public UNI
UNI signaling
• UNI and NNI signaling protocols are very similar in
Public UNI
•
functionality.
P-NNI is the routing protocol.
Basic Connection Setup Protocol
RECEIVER
SENDER
Start
Call
Setup
Setup
Call Proceeding
Call Proceeding
NETWORK
Connect
Setup
Complete
Connect ACK
(Status Indication
but not finished
processing)
Connect
Connect ACK
Local ACK, optional
• Connection setup completed in one round-trip.
• Signaling performed through dedicated Virtual Channels.
- UNI signaling VC: VPI=0, VCI =5
Call Received
Call Accepted
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
ATM Signaling is a protocol used to set up, maintain, and
clear SVCs between two ATM end users over private or
public UNIs.
The protocol is, in fact, an exchange of messages that takes
place between the ATM end user (caller or receiver) and
adjacent ATM switch.
The messages contain information that is used to build,
maintain, or clear the connection.
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
ATM
Switch
SETUP
CALL PROCEEDING CALL PROCEEDING
CONNECT
CONNECT ACK
ATM
End User
SETUP
CALL PROCEEDING
CONNECT
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 QoS.
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
UNI
ATM
Switch
RELEASE COMPLETE
•
ATM
End User
ATM
Switch
RELEASE
RELEASE
COMPLETE
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 (Cont’d)
• 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-MULTIPOIINT
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
UNI
NNI
ATM
Switch
ATM
Switch
ATM_2
End User
ADD PARTY
ADD PARTY ACK
ADD PARTY ACK
ATM_1
End User
SETUP
CALL PROCEEDING
CONNECT
CONNECT ACK
POINT-TO-MULTIPOINT OPERATIONS (Cont’d)
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.
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
ATM
Switch
ADD PARTY
SETUP
CALL PROCEEDING
ADD PARTY NAK
RELEASE
(REJECT)
RELEASE COMPLETE
ADD PARTY NAK
(REJECT)
CASE 2 ROOT DROPS A PARTY.
UNI
ATM
End User
DROP PARTY
NNI
ATM
Switch
UNI
DROP PARTY
DROP PARTY ACK
DROP PARTY ACK
ATM
End User
ATM
Switch
RELEASE
RELEASE COMPLETE
CASE 3 ROOT DROPS LAST PARTY.
UNI
ATM
End User
RELEASE
NNI
UNI
RELEASE
RELEASE COMPLETE
ATM
End User
ATM
Switch
ATM
Switch
RELEASE
RELEASE COMPLETE
RELEASE
COMPLETE
CASE 4 A PARTY DROPS OUT.
UNI
ATM
End User
NNI
ATM
Switch
UNI
ATM
End User
ATM
Switch
DROP PARTY
RELEASE
DROP PARTY
DROP PARTY ACK
DROP PARTY ACK
RELEASE COMPLETE
CASE 5 NETWORK CLEARS THE CALL.
UNI
ATM
End User
NNI
ATM
Switch
UNI
CONNECTION
RELEASE
RELEASE COMPLETE
ATM
End User
ATM
Switch
DROP PARTY
TERMINATED
DROP PARTY ACK
RELEASE
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.
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: ROOT SETS UP A NETWORK LIJ CALL.
(The 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-to-multipoint 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
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
ATM
End User
LIJ SET UP REQUEST
SET UP
CALL PROCEEDING
CONNECT
CONNECT ACK
MODE 2: LEAF JOINS TO AN ACTIVE LIJ CALL.
UNI
ATM
End User
NNI
ATM
Switch
UNI
ATM
End User
ATM
End User
ATM
Switch
LIJ SETUP REQ
SETUP
CALL PROCEEDING
NO ROOT
NOTIFICATION
CONNECT
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
Setup
Call Proceeding
ATM
Switch
Leaf Setup
Setup
UNI
ATM_1
End User
ATM
Switch
Leaf Setup
Setup
Call Proceeding
Call Proceeding
Connect
Connect Ack
Connect
Connect Ack
Connect
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
Add Party
Leaf Setup
Setup
Call Proceeding
Add Party Ack
Add Party Ack
Connect
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)
UNI 4.0
UNI 3.1
Q.2931
SSCS: Service Specific
Common Part
Sub-layer
SSCF: Service Specific
Coordination Function
SAP
SSCF
SSCS
SSCOP: Service Specific
Connection-Oriented
Protocol
SSCOP
SAAL
CPCS
SAR
CPCS: Common Part
Convergence Sub-layer
SAR: Segmentation &
Reassembly
UNI Signaling Protocol Stack
Like a management protocol
Signaling Protocol
Service-Specific Coordination
Function (SSCF)
Service-Specific ConnectionOriented Protocol (SSCOP)
CPCS
AAL 5
SAR
AAL servicespecific part
(SSCS)
Signaling
AAL (SAAL)
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.
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
Window size can be dynamically controlled by
receiver (buffer size)
Error control by selective retransmission of
frames (only lost frame is retransmitted; AAL5
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)
Contains 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.
Receiver 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

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

Enables fast retransmission in the presence of random loss

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
POLL
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)
•Public Networks:
Make
Compatible
With
Private
Network
address
- 8-byte (64 bits) E.164 format defined by ITU-T (has 16 digits each coded
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
Network Supplied
Authority& Data
High-order
Format
Country
Domain
Identifier(39) Code
Specific Part
“BD”
1 byte
2 bytes
IDP IDI
10 bytes
EndSystem Not used
In Routing
Supplied
End-System
Selector
Identifier
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
“C5”
1 byte
2 bytes
IDP
10 bytes
IDI
ICD codes identify particular international organizations.
End-System
Selector
Identifier
6 bytes
DSP
1 byte
ETHERNET & Token
Ring address field length
for IEEE assigned addresses
NSAP-Encoded E.164 Format
Public
Authority&
E.164
Format
Identifier(45) Address
“C3”
1 byte
8 bytes
IDP
High-order
Domain
Specific Part
End-System
Selector
Identifier
4 bytes
1 byte
6 bytes
DSP (Domain Specific Part)
IDI
High order domain specific part addresses can be assigned by “hand”.
•
•
•
•
•
Addressing
The IDP specifies an administration authority which has the
responsibility for allocating and assigning values for the DSP.
IDP has AFI (Authority and Format Identifier (AFI)) and IDI
(Initial Domain Identifier (IDI).
AFI specifies the format of the IDI, and the abstract syntax of the
DSP field.
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.
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
ICD (International Code Designator)
Identifies an authority which administers a coding scheme.
This authority is responsible for the allocation of identifiers within
this coding scheme to organizations.
The registration authority for the international code designator is
maintained by the British Standards Institute.
The digits of ICD are encoded using BCD.
•
•
ATM Forum extended E.164 address to NSAP format. E.164
number is filled with leading zeroes to make 15 digits.
A F16 is padded to make 8 bytes.
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.
•
•
•
End System Identifier (ESI): 48-bit IEEE MAC
address (to identify a specific host within an ATM
subnet) (Token Ring, Ethernet LAN MAC addresses)
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.
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 Number
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 subaddress (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)
39.840F.8001.BC88.2280.4110.4002.4000.OC80.0020.00
Address Registration
• Administration and configuration of 20-byte ATM addresses for end
users could turn into a very tedious and error-prone task.
• Therefore, the ATM Forum has defined a technique for automatically
registering an ATM address over the private or public UNI.
• This technique makes use of SNMP-based Interim Local Management
Interface (ILMI) protocols to exchange address information between the
ATM end user AND switch.
• This allows an ATM end user to inform ATM switch of its ESI address
and in exchange receive the network prefix from the ATM switch across
the UNI.
ATM
End User
ATM
Switch
ESI
Network Prefix
Address Registration
• Address registration over the UNI is a technique for
automatically configuring complete ATM addresses in enduser systems.
• At the same time, the ATM switch is provided with the ESIs
for all end users attached to the switch.
• This information will be used by the ATM switches (via a
switch-to-switch routing protocol) to properly route SVC
requests from a source to the destination.
•
•
Address Registration
ATM End system informs an ATM switch across the UNI, of its unique MAC address and
receive the remainder of the node’s full ATM address in return.
User and switch register addresses using
Interim Local Management Interface (ILMI)
= Simple Network Management Protocol (SNMP)
User
ColdStart Trap
Switch
Initialize
GetNext Request
What is your address?
GetNext Response
Set Request
My address is AA-…
Use prefix +1 614-…
GetNext Response
Sure. Will do.
• Similar activities can occur in the reverse direction.
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
Call reference value (continued)
Call reference value (continued)
Message type
Message type (continued)
Message length
Message length (continued)
Information Elements
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
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
111
Type
Information
10101
Status Inquiry
11101
Status
Reserved for Extension
Protocol discriminator: Distinguishes messages for ATM end userto-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)
34
Description
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)
30
Minimum acceptable
traffic descriptors
Description
Describes alternate ATM traffic-descriptor values and is
used during negotiation of these values and is used during
negotiation of these values in UNI Signaling 4.0.
Describes minimum acceptable ATM traffic-descriptor
values and is used during negotiation of these values in UNI
signaling 4.0.
Connection identifier
9
VPI and VCI values.
QoS parameters
6
QoS class (0-4).
Extended QoS
parameters
25
Indicates individual QoS values acceptable on a per-call
basis. These include acceptable and cumulative forward and
backward cell loss ratio.
Broadband high-layer
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., DS1 emulation), ATM only, or
VP service (for switched VPs). Also specifies CBR or VBR.
Table. UNI Signaling Information Elements (Cont’d)
Information element
Broadband low-layer
information
Max. length ( bytes)
17
Description
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 low-layer
compatibility
20
Q.2931-based IE used to validate low-layer compatibility
for N-ISDN interworking device.
Narrowband high-layer
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 circuit-mode
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-to-end
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 V4.0 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 videoon-demand virtual connections.
Connection scope
selection
6
OAM traffic descriptor
56
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.
Provides information relating to the presence and handling
of the end-to-end F5 OAM information flow for
performance management and user-originated fault
management associated with the user connection involved
in the call.
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
User specifies 12 leaky bucket parameters
CLP=0
CLP=0+1
Forward
Backward
Peak Cell Rate
Sustainable Cell Rate
Maximum Burst Size
Peak Cell Rate
Sustainable Cell Rate
Maximum Burst Size
Peak Cell Rate
Sustainable Cell Rate
Maximum Burst Size
Peak Cell Rate
Sustainable Cell Rate
Maximum Burst Size
AAL Parameters
•
AAL 1 Parameters
1.
2.
3.
4.
5.
CBR Rate
Clock Recovery type
Error correction type
Structured Data Transfer
Partially filled cells
•
1.
AAL ¾ Parameters
MID Size
AAL Parameters
•
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
01101100
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 QoS (can define service classes; differentiate types of services
but no support for parameterized service classes)
• Flexibility in ATM address formats
UNI 3.0 Overview (Cont’d)
•
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 QoS)
(Not universal, only work within your private network)
UNI 3.0 Overview (continued)
•
•
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”!!!)
QoS Support
– Allows five distinct QoS classes (0-4) to be specified in SETUP
message
– Parameterized QoS 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:
•
•
Leaf-initiated join. Allows users to dynamically join existing
point-to-multipoint connections.
Group addressing: Well-known functional addresses can be
utilized to reduce signaling and configuration overhead.
UNI Signaling 4.0 Enhancements (C’td)
• 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.
Proxy Signaling. Used to support devices that do not
support ATM signaling, such as residential broadband.
Switched Virtual Paths. ATM virtual paths can be
dynamically provisioned. This will reduce administrative
overhead in public and private networks.
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 (Ctd)
• 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.
Available Bit Rate (ABR) Signaling for Point-toPoint Connections. Parameters for ATM end users
requesting ABR service can be designed into the
network.
UNI Signaling 4.0 Enhancements (C’td)
•
•
•
Signaling of Individual QoS 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 QoS class.
Traffic Parameters Negotiation. ATM traffic parameters can
be negotiated between ATM end users.
N-ISDN Inter-working. Enables inter-working between
narrowband and 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
CONNECT (to User A)
Network has established ATM connection
between users A and B
 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.
•
Proxy agent can be remotely located on another switch
Used to support devices that do not support ATM signaling, such as residential broadband.
Enables multiple ATM interfaces on end-system to share same ATM address, e.g., high
performance server with 3 adapters.
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 QoS 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
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
M
M
M
M
M
*
O
O
O
†
O
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.