RFC 2297
Ipsilon's General Switch Management Protocol Specification Version 2.0
8. Event Messages Event messages allow the switch to inform the controller of certain asynchronous events. Event messages are not acknowledged. The Result field and the Code field in the message header are not used and should be set to zero. Event messages are not sent during initialization. Event messages have the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Message Type | Result | Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transaction Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Port Session Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Event Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | zero | VPI | VCI | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Event Sequence Number
The current value of the Event Sequence Number for the
specified port. The Event Sequence Number is set to zero
when the port is initialized. It is incremented by one each
time the port detects an asynchronous event that the switch
would normally report via an Event message. The Event
Sequence Number must be incremented each time an event
occurs even if the switch is prevented from sending an
Event message due to the action of the flow control.
VPI/VCI
Field gives the VPI/VCI to which the event message refers.
If this field is not required by the event message it is
set to zero.
Each switch port must maintain an Event Sequence Number and a set of
Event Flags, one Event Flag for each type of Event message. When a
switch port sends an Event message it must set the Event Flag on that
port corresponding to the type of the event. The port is not
permitted to send another Event message of the same type until the
Event Flag has been reset. Event Flags are reset by the "Reset Event
Flags" function of the Port Management message. This is a simple flow
control preventing the switch from flooding the controller with event
messages. The Event Sequence Number of the port must be incremented
every time an event is detected on that port even if the port is
prevented from reporting the event due to the action of the flow
control. This allows the controller to detect that it has not been
informed of some events that have occurred on the port due to the
action of the flow control.
8.1 Port Up Message
The Port Up message informs the controller that the Line Status of a
port has changed from either the Down or Test state to the Up state.
When the Line Status of a switch port changes to the Up state from
either the Down or Test state a new Port Session Number must be
generated, preferably using some form of random number. The new Port
Session Number is given in the Port Session Number field. The VPI/VCI
field is not used and is set to zero. The Port Up message is:
Message Type = 80
8.2 Port Down Message
The Port Down message informs the controller that the Line Status of
a port has changed from the Up state to the Down state. This message
will be sent to report link failure if the switch is capable of
detecting link failure. The port session number that was valid before
the port went down is reported in the Port Session Number field. The
VPI/VCI field is not used and is set to zero. The Port Down message
is:
Message Type = 81
8.3 Invalid VPI/VCI Message
The Invalid VPI/VCI message is sent to inform the controller that one
or more cells have arrived at an input port with a VPI/VCI that is
currently not allocated to an assigned connection. The input port is
indicated in the Port field, and the VPI/VCI in the VPI/VCI field.
The Invalid VPI/VCI message is:
Message Type = 82
8.4 New Port Message
The New Port message informs the controller that a new port has been
added to the switch. The port number of the new port is given in the
Port field. A new Port Session Number must be assigned, preferably
using some form of random number. The new Port Session Number is
given in the Port Session Number field. The state of the new port is
undefined so the VPI/VCI field is not used and is set to zero. The
New Port message is:
Message Type = 83
8.5 Dead Port Message
The Dead Port message informs the controller that a port has been
removed from the switch. The port number of the port is given in the
Port field. The Port Session Number that was valid before the port
was removed is reported in the Port Session Number field. The
VPI/VCI fields are not used and are set to zero. The Dead Port
message is:
Message Type = 84
9. Quality of Service Messages
The GSMP Quality of Service (QoS) messages allow a controller to
group virtual path connections and virtual channel connections into
QoS classes, and to allocate QoS resources to both QoS classes and to
individual connections. At initialization, the switch describes its
QoS capabilities to the controller, in terms of the abstract switch
model, using the QoS Configuration message. The controller issues
Scheduler Establishment messages to configure the scheduler on each switch output port. It also issues QoS Class Establishment messages to configure QoS classes. Connections may be added to, or deleted from, a QoS class using the QoS Connection Management message. QoS resources may also be assigned to individual connections using the QoS Connection Management message. Connections that only require the scheduler may use the simple connection management messages defined in Section 3, "Connection Management Messages." 9.1 Abstract Switch Model The abstract switch model, fig. 1, is the means by which a switch can describe its fundamental QoS capabilities to a controller. It consists of four main functions: a policer, a classifier, a regulator, and a scheduler. The classifier groups multiple connections (VPCs or VCCs) together into a QoS class such that QoS resources may be shared by the QoS class as a whole. Within a QoS class there is no differentiation between members of the class in terms of QoS resources received. However, the ordering of cells within each constituent VPC or VCC must be preserved on exit from the switch. Connections are not required to be aggregated into a QoS class with other connections; they may be allocated individual QoS resources.
VPC/VCCs Policer Classifier Regulator Scheduler
+--+ +----+ +--------+
-------->| |---->| | | |
+--+ | | | |
| | | |
+--+ | | +----+ | |
-------->| |---->| | | |--------->| |
+--+ | | | |conforming| |
| |------>| | | |
+--+ | | QoS | | | |
-------->| |---->| | Class | |--------->| |
+--+ | | +----+ excess | |
| | | |
+--+ | | | |
-------->| |---->| | | |
+--+ +----+ | |
| |
| | Output
| | Port
| |---------->
| |
| |
+--+ +----+ | |
-------->| |---->| | | |
+--+ | | | |
| | | |
+--+ | | +----+ | |
-------->| |---->| | | |--------->| |
+--+ | | | |conforming| |
| |------>| | | |
+--+ | | QoS | | | |
-------->| |---->| | Class | |--------->| |
+--+ | | +----+ excess | |
| | | |
+--+ | | | |
-------->| |---->| | | |
+--+ +----+ | |
+--------+
Fig. 1: Abstract Switch Model
The policer is a single input, single output device that can discard
or tag cells. A policer may be applied to police each individual
connection. A policer may also be applied to police the aggregate
traffic of a QoS class. The policer is used to enforce an upper
bound on the traffic on a connection or on a QoS class.
The regulator follows the policer and classifier. It offers either a policing function or a shaping function. The policing function evaluates cells as conforming to the rate specified by the regulator parameters or as being in excess of that rate. One of three actions can be specified to be taken for each cell as a result of this evaluation: tagging, discard or differentiated scheduling. Tagging sets the CLP bit of cells deemed to be in excess of the rate defined by the regulator parameters. The discard function discards excess cells. The differentiated scheduling function allows conforming cells and excess cells to be scheduled for service at different points in the scheduler. This would allow conforming cells, for example, to receive service with a QoS guarantee, whereas excess cells receive best-effort service. The implementation of differentiated scheduling, however, is complicated by the requirement not to reorder cells within each connection. The shaping function of the regulator paces cells out, on each QoS class or individual connection, at the rate specified by the regulator parameters. No jitter requirement may be specified, nor is any specific guarantee of jitter given. If traffic arrives on any QoS class or individual connection at a greater rate than the output rate specified, that traffic will be delayed. If the delayed traffic for any QoS class or individual connection exceeds a bound, discard will occur. Differentiated scheduling is supported by the shaper but its application to shaping is somewhat different than its application to policing. Conforming traffic is that traffic which leaves the shaper as a result of the shaping process. The conforming pointer specifies the point in the scheduler structure where such traffic is scheduled for output. (This is typically the highest priority of the scheduler but the GSMP specification permits other priorities to be specified.) If an excess pointer is also enabled for a particular QoS class or individual connection, traffic in excess of the rate specified by the shaper may also be transmitted. The position of the excess pointer in the scheduler structure determines the undefined amount of additional traffic that will be supported. The excess traffic may be tagged if required, if tagging is supported. The excess pointer will receive the same share of bandwidth that a best-effort class or connection would receive at the same location in the scheduler structure. The location of the classifier and regulator functions in the switch is important. If the classifier is located on an input port, only virtual connections that arrive at that input port may be aggregated into a QoS class. If the classifier is centralized, or located on an output port, virtual connections that arrive at any input port may be aggregated into the same QoS class. If the regulator is located on an output port all virtual connections within a QoS class passing through that regulator must exit the switch at that output port.
However, if the regulator is centralized, or located on an input port, virtual connections that are part of the same QoS class may be switched to different output ports. Each switch port must specify the location of its classifier and regulator functions. The scheduler is located on the output port, fig. 2. It distributes the bandwidth of the output link between the QoS classes and individual connections. It is a two-level scheduler: a priority scheduler at one level and a FIFO or a weighted scheduler at the other. Up to 255 strict priority levels may be supported. Traffic in any specific priority level may only be transmitted if no traffic is queued for transmission in any higher priority level. Within each priority level a weighted scheduler may be defined. Each leaf of the scheduler tree is connected to a waiting room. The waiting room has two functions. When it receives service from the scheduler, it must select a QoS class or individual connection for transmission. When it is notified of traffic arrival on a QoS class or connection, it must decide whether there is enough room left in the waiting room to accept the traffic, else that traffic must be discarded. The waiting room has a size parameter indicating how much traffic may be accepted. Other queueing parameters may be attached to the waiting room. Multiple conforming and excess pointers from the regulators may point to each waiting room. Within a waiting room, the scheduling of multiple connections sharing that waiting room may support weighted sharing between the connections.
From Waiting FIFO/Weighted Priority
Regulator Room Scheduler Scheduler
Net +---+
+------+ Weight | |
---------->| |-%-------->| 0 |------\
+------+ | | \
+---+ \
---------->+------+ |
| |-%--\ +---+ |
---------->+------+ \---->| | |
| 1 |---\ |
+------+ /---->| | \ \
---------->| |-%--/ +---+ \ \ +---+
+------+ \ \-->| |
\----->| |--------->
---------->+------+ /-->| | Output
---------->| |-%-\ / +---+ Port
---------->+------+ \ /
\ +---+ /
+------+ \--->| | /
---------->| |-%-------->| 2 |-----/
+------+ /--->| |
/ +---+
+------+ /
---------->| |-%-/
+------+
Fig. 2: The Scheduler
9.2 QoS Configuration Message
The QoS Configuration message permits the controller to discover the
QoS capabilities of each switch port in terms of the abstract switch
model. The QoS Configuration message is:
Message Type = 96
The QoS Configuration request message has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The QoS Configuration success response message has the following
format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Session Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scheduler Flags | Regulator Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Excess Capabilities | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hi Sharing | Lo Sharing | Max Classes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Default Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Default Discard Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Buffer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Shaper Buffer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scaling Factor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Port
The switch port to which the QoS configuration information
refers. QoS configuration information relating to both the
input and the output sides of the switch port is given.
Scheduler Flags
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|W|Q|S|G|D|F|M|B|I|x x x x x x x|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
W: Weighted Connections
Bit 0 of the Scheduler Flags field, if set, indicates that
a weighted service algorithm (such as weighted round-robin)
is available for allocation of service to individual
connections within at least some waiting rooms. It means
that a Connection Weight parameter can be attached to a QoS
Connection Management message. Not all waiting rooms at all
priority levels may be able to support this function.
Whether a particular waiting room can support this function
will be discovered when a QoS Connection Management message
is issued.
Q: Weighted QoS Classes
Bit 1 of the Scheduler Flags field, if set, indicates that
a weighted service algorithm (such as weighted round-robin)
is available for allocation of service to QoS classes
within at least some waiting rooms. It means that a QoS
Class Weight parameter can be attached to a QoS Class
Establishment message. Not all waiting rooms at all
priority levels may be able to support this function.
Whether a particular waiting room can support this function
will be discovered when a QoS Class Establishment message
is issued.
S: Shared Waiting Room
Bit 2 of the Scheduler Flags field, if set, indicates that
multiple QoS classes and multiple connections may be
scheduled within a single waiting room. This is expected to
be the normal case. If Bit 2 of the Scheduler Flags field
is zero, it indicates that only a single QoS class or a
single connection may be directed to any single waiting
room.
G: Global Max Classes
Bit 3 of the Scheduler Flags field, if set, indicates that
the Max Classes field gives the maximum number of QoS
classes that may be supported by the entire switch. If
zero, it indicates that the Max Classes field gives the
maximum number of QoS classes that may be supported by this
switch port.
D: Packet Discard
Bit 4 of the Scheduler Flags field, if set, indicates that
the scheduler on this output port is capable of packet
discard. Packet discard indicates a discard algorithm that
is aware of AAL-5 packet boundaries and attempts to discard
whole packets. No specific algorithm is indicated though
Early Packet Discard (EPD) is likely to be the most common.
Other algorithms such as "push from front" schemes, dynamic
threshold, or Random Early Detection (RED) are also
examples of possible packet discard algorithms. The only
parameters available to the packet discard algorithm, via
GSMP, are the Size and Discard Threshold of the waiting
room.
F: Frame-Based Scheduling
Bit 5 of the Scheduler Flags field, if set, indicates that
the scheduler on this output port is capable of frame-based
scheduling. In frame-based scheduling, a connection is only
scheduled for transmission when a complete AAL-5 packet is
available. When a connection is scheduled for
transmission, all cells belonging to one or more complete
packets from that connection will be transmitted without
being interleaved with any other cells on that output port
(regardless of their priority). Frame-based scheduling is
a property of the waiting room and is requested in the
Scheduler Establishment message. A QoS class may be routed
through a waiting room configured with frame-based
scheduling. In this case each component connection of the
QoS class will receive frame based scheduling. For correct
distribution of bandwidth, each QoS class that requires
frame-based scheduling should have its own waiting room.
M: VC Merging
Bit 6 of the Scheduler Flags field, if set, indicates that
the scheduler on this output port is capable of VC merging
by a mechanism other than frame-based scheduling. VC
merging indicates that the switch is capable of the
multipoint-to-point merging of two or more incoming virtual
connections onto a single outgoing virtual connection
without interleaving cells from different AAL-5 packets
that bear the same VPI/VCI. VC merging differs from frame-
based scheduling in that cells with a different VPI/VCI may
be interleaved with those of a multipoint-to-point VC
merging connection. Thus, higher priority cells may be
interleaved during the transmission of a packet on a lower
priority VC merging connection. Most switches achieve VC
merging by using frame-based scheduling. VC merging is a
property of the waiting room and is requested in the
Scheduler Establishment message. A QoS class may be routed
through a waiting room configured with VC merging. In this
case each component connection of the QoS class will
receive VC merging.
B: Shared Buffer
Bit 7 of the Scheduler Flags field, if set, indicates that
at least some of the buffer space specified by the Max
Buffer field is shared with other ports. If zero, it
indicates that the buffer space specified by the Max Buffer
field is not shared with other ports.
I: Identical Ports
Bit 8 of the Scheduler Flags field, if set, indicates that
all ports of the switch have identical QoS capabilities. If
this bit is set the controller does not have to request the
QoS configuration of each port individually as all ports
have the same capability.
x: Bits 9--15 of the Scheduler Flags field are not used.
Regulator Flags
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C|Q|I O|P|S|H|M|x x x x x x x x|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
C: Connection Policing
Bit 0 of the Regulator Flags field indicates that this
input port supports the policing of individual incoming
connections. The parameters for the policer are specified
in the QoS Connection Management message when the
connection is established.
Q: QoS Class Policing
If bit 1 of the Regulator Flags field is set, a policer
function is available to police each QoS class on output
from the classifier. The parameters for this policer are
specified in the QoS Class Establishment message. If this
bit is zero, no policer function is available to police a
QoS class.
IO: QoS Class Location
Bits 2 and 3 of the Regulator Flags field specify the
location of the classifier and regulator functions. If both
bits 2 and 3 of the Regulator Flags field are zero, no
classifier or regulator function is available to this port.
If bit 2 of the Regulator Flags field is set and bit 3 is
zero, the classifier and regulator functions are available
on the input port. This implies that only virtual
connections arriving at this input port may be grouped into
QoS classes by this classifier. However, connections in a
QoS class output from this regulator may be switched to any
output port.
If bit 2 of the Regulator Flags field is zero and bit 3 is
set, the classifier and regulator functions are available
on the output port. This implies that virtual connections
arriving at any input port may be grouped into QoS classes
by this classifier. However, all connections in any QoS
class output from this regulator may only be switched to
this output port.
If both bits 2 and 3 of the Regulator Flags field are set,
this switch port has access to centralized classifier and
regulator functions. This implies that virtual connections
arriving at any input port may be grouped into a QoS class
by this classifier. Also, connections in a QoS class output
from this regulator may be switched to any output port.
Regulator Function
P: If bit 4 of the Regulator Flags field is set, the regulator
is able to support the policing function.
S: If bit 5 of the Regulator Flags field is set, the regulator
is able to support the shaping function on all priority
levels of the scheduler.
H: If bit 5 of the Regulator Flags field is zero and bit 6 is
set, the regulator is able to support the shaping function
but only on the highest priority level of the scheduler.
All connections and QoS classes using this regulator must
be routed to a waiting room at the highest priority level
of the scheduler.
M: QoS Multicast
If bit 7 of the Regulator Flags field is set, any point-
to-multipoint connection arriving on this input port, with
QoS parameters established by the GSMP Quality of Service
messages, must use the same QoS parameters for all output
branches.
x: Bits 8--15 of the Regulator Flags field are not used.
Excess Capabilities
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D|T|S|A|B|x x x x x x x x x x x|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Policer:
D: If bit 0 of the Excess Capabilities field is set, the policer
function of the regulator is able to support discard.
T: If bit 1 of the Excess Capabilities field is set, the policer
function of the regulator is able to support tagging.
S: If bit 2 of the Excess Capabilities field is set, the policer
function of the regulator is able to support differentiated
scheduling.
Shaper:
A: If bit 3 of the Excess Capabilities field is set, the shaper
function of the regulator is able to support tagging.
B: If bit 4 of the Excess Capabilities field is set, the shaper
function of the regulator is able to support differentiated
scheduling.
x: Bits 5--15 of the Excess Capabilities field are not used.
Hi Sharing
Lo Sharing
Defines a range of priority levels that support weighted
sharing. Each priority level in the range Lo Sharing to Hi
Sharing inclusive, supports weighted sharing. A priority
level that supports weighted sharing offers a weighted
sharing algorithm (for example, weighted round-robin)
between waiting rooms within that priority level. This
permits the output link bandwidth available at that
priority level, to be shared between the waiting rooms
allocated to that priority level, according to the Net
Weight parameter of each waiting room. The value 0xFF for
both parameters indicates that this output port does not
support weighted sharing in any priority level.
Max Classes
If bit 3 of the Scheduler Flags field is zero, Max Classes
gives the maximum number of QoS classes that may be
supported by this switch port. In this case the maximum
number of QoS classes that may be supported by this switch
port is not affected by the number of QoS classes in use by
other switch ports. If bit 3 of the Scheduler Flags field
is set, Max Classes gives the maximum number of QoS classes
that may be supported by the entire switch. In this case it
is assumed that use of these QoS classes may be distributed
among the various switch ports.
Default Size
The size of waiting room that this output port allocates by
default. The actual size of waiting room may be specified
in the Scheduler Establishment message. The size of a
waiting room specifies the maximum number of cells
permitted to wait for transmission via that waiting room.
Any further cells arriving at that waiting room beyond this
number will be discarded.
Default Discard Threshold
The value of discard threshold that this output port
allocates by default. The actual value of discard threshold
may be specified in the Scheduler Establishment message.
The discard threshold specifies the number of cells waiting
for transmission via a waiting room after which further
arriving cells will be subject to a discard mechanism.
Max Buffer
The maximum amount of buffer space, measured in cells,
available to this port. If bit 7 of the Scheduler Flags
field is zero this, buffer space is not shared with other
ports. If bit 7 of the Scheduler Flags field is set, at
least some of this buffer space is shared with other ports.
Max Shaper Buffer
The maximum amount of buffer space, measured in cells,
available to a QoS connection or a QoS class within the
shaper function of the regulator. This shaper buffer space
is likely to be shared among all QoS classes and QoS
connections using the shaper, so there is no guarantee that
the amount of buffer space defined by the Max Shaper Buffer
field will be available to any particular QoS class or QoS
connection.
Scaling Factor
The QoS Class Establishment and QoS Connection Management
messages require parameters that describe cell rates in
cells per second or their reciprocal, cell interarrival
periods, in seconds per cell. In order that these
parameters may be specified with a 32-bit unsigned integer,
the switch defines a Scaling Factor to be used in defining
such parameters. By appropriate choice of the Scaling
Factor the switch can select the range and granularity of
rate or time that can be specified with the 32-bit unsigned
integer. Further details are given in the discussion of
the UPC Parameters field of the QoS Connection Management
message.
9.3 Scheduler Establishment Message
The Scheduler Establishment message is used to configure the
scheduler on a specified output port. It is used to configure a
waiting room, attach it to a leaf of the scheduler tree, and return a
Scheduler Identifier to reference the waiting room. The Scheduler
Establishment message may also be used to modify the parameters of an
already established waiting room.
Scheduler Identifiers in the range 0--255 represent default values.
They are used for the priority levels that may be specified in the
Class of Service field of Connection Management messages without
requiring explicit establishment via a Scheduler Establishment
message. Each of these default values specifies a single waiting
room with default parameters, configured as a FIFO queue, on each of
the valid scheduler priority levels. (This permits Connection
Management messages to continue to specify QoS requirements as a
priority without requiring the use of any of the QoS messages.) The
number of priority levels available to the scheduler is specified in
the Priorities field of the Port Configuration and All Ports
Configuration messages.
The Scheduler Establishment Message is:
Message Type = 97
The Scheduler Establishment request and success response messages
have the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Session Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scheduler Identifier | Net Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|F|M|W|x x x x| Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Waiting Room Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discard Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Scheduler Identifier
The Scheduler Identifier is selected by the controller. It
is used to identify the waiting room being established or
modified in future messages. The Scheduler Identifier is
taken from a namespace that is local to the switch port. A
Scheduler Identifier in the Scheduler Establishment message
must be greater than 0x00FF but less than 0xFFFF. The
values 0 -- 0x00FF are reserved for use as default values.
The default values of the Scheduler Identifier are used to
specify the default settings for the scheduler. Each of the
default values maps directly to one of the scheduler
priority levels. The value 0xFFFF is reserved for use in
the QoS Connection Management message.
Net Weight
The Net Weight specifies the share of the bandwidth
available to the priority level, specified by the Priority
field, that should be given to this waiting room. The Net
Weight parameter is only valid if the priority level
specified by the Priority field supports weighted sharing.
The Net Weight is an unsigned 16-bit field specifying a
binary fraction. I.e. the bandwidth share, as a fraction
of the bandwidth available to the priority level, is given
by:
Bandwidth share = Net Weight * 2**(-16)
A Net Weight of zero indicates equal sharing between all
waiting rooms sharing this priority level that request a
Net Weight of zero. While a 16-bit field is used to
specify the Net Weight it is understood that the accuracy
of the bandwidth sharing is hardware dependent and is not
specified.
If weighted sharing is not required at a particular
priority level, a waiting room with a Net Weight value of
0xFFFF must be specified for that priority level. A
priority level that does not support weighted sharing can
only support a single waiting room.
Flags
D: Packet Discard
Bit 0 of the Flags field, if set, indicates that packet
discard is required on all connections and QoS classes
routed through this waiting room.
F: Frame-Based Scheduling
Bit 1 of the Flags field, if set, indicates that frame-
based scheduling is required on all connections and QoS
classes routed through this waiting room. In frame-based
scheduling, a connection is only scheduled for transmission
when a complete AAL-5 packet is available. When a
connection is scheduled for transmission, all cells
belonging to one or more complete packets from that
connection will be transmitted without being interleaved
with any other cells on that output port. A QoS class may
be routed through a waiting room configured with frame-
based scheduling. In this case each component connection
of the QoS class will receive frame based scheduling. For
correct distribution of bandwidth, each QoS class that
requires frame-based scheduling should have its own waiting
room.
M: VC Merging
Bit 2 of the Scheduler Flags field, if set, indicates that
VC merging is required on all connections and QoS classes
routed through this waiting room. VC merging enables the
multipoint-to-point merging of two or more incoming virtual
connections onto a single outgoing virtual connection,
without interleaving cells from different AAL-5 packets
that bear the same VPI/VCI. VC merging differs from frame-
based scheduling in that cells with a different VPI/VCI may
be interleaved with those of a multipoint-to-point VC
merging connection. Most switches achieve VC merging by
using frame-based scheduling. A QoS class may be routed
through a waiting room configured with VC merging. In this
case each component connection of the QoS class will
receive VC merging.
W: Weighted Scheduling
Bit 3 of the Flags field, if set, indicates that weighted
scheduling is required on all connections and QoS classes
routed through this waiting room. All connections and QoS
classes routed through this waiting room will require a
Connection Weight or a QoS Class Weight respectively. The
Connection Weight is specified in the QoS Connection
Management message. The QoS Class Weight is specified in
the QoS Class Establishment message. If weighted scheduling
within this waiting room is unavailable, a failure response
message must be returned indicating, "Weighted scheduling
within this waiting room is unavailable."
Bit 3 of the Flags field, if zero, indicates that this
waiting room should be configured as a single FIFO queue.
All cells arriving at this waiting room will receive
first-in-first-out service. If Frame-Based Scheduling or VC
Merging are also selected, the strict first-in-first-out
service discipline will be modified by the requirement to
support Frame-Based Scheduling or VC Merging.
x: Bits 4--7 of the Flags field are not used.
Priority
Specifies the priority level in the scheduler to which the
waiting room should be attached. Priorities are numbered
from zero, with priority level zero being the highest
priority.
Waiting Room Size
The required size of the waiting room. The size of a
waiting room specifies the maximum number of cells
permitted to wait for transmission via that waiting room.
Any further cells arriving at that waiting room beyond this
number will be discarded. If the switch is unable to grant
the size requested in the Scheduler Establishment request
message it may reply with the actual size allocated to the
waiting room in the Waiting Room Size field of the success
response message. A value of zero for the Waiting Room
Size indicates that the default value should be used.
Discard Threshold
The required value of the discard threshold. The discard
threshold specifies the number of cells waiting for
transmission via a waiting room after which further
arriving cells will be subject to a discard mechanism. The
value of the Discard Threshold must be less than or equal
to the value of the Waiting Room Size parameter for any
given waiting room. If the switch is unable to grant the
value of discard threshold requested in the Scheduler
Establishment request message it may reply with the actual
value of discard threshold allocated to the waiting room in
the Discard Threshold field of the success response
message. A value of zero for the Discard Threshold
indicates that the default value should be used.
9.4 QoS Class Establishment Message
The QoS Class Establishment message is used to configure a QoS class
on a specified port or to modify the parameters of an already
established QoS class. It configures the classifier and the
regulator functions for the QoS class. It also configures the QoS
class policer if a policing function is available for QoS classes.
Two styles of QoS class are available. In one style each component
connection of the QoS class may be routed independently to an output
port and waiting room specified in its connection management message.
In this case the Scheduler Identifier, and if required, the Excess
Scheduler Id, are specified in the QoS Connection Management message
that references this style of QoS class. In the alternative style of
QoS class, all component connections in the QoS class are routed to
the same waiting room on the same output port. In this case the
Output Port, the Scheduler Identifier, and if required, the Excess
Scheduler Id, are specified in the QoS Class Establishment message.
The classifier and regulator functions must be located together,
either on an input port, on an output port, or centralized. Each port
declares the location of its classifier and regulator functions at
initialization using the QoS Configuration message. If the classifier
and regulator functions are located on an input port, only
connections that arrive at that input port may join a QoS class
established on that port. However, each connection that is part of a
QoS class established on that port may be switched to a different
output port. If the classifier and regulator functions are located on
an output port, connections that arrive at any input port may join a
QoS class established on that port. However, all connections within a
QoS class established on that port must be switched to that output
port. For a centralized classifier and regulator function, there is
no restriction on the input ports on which connections in a QoS class
must arrive, or on the output ports to which connections in a QoS
class must be switched. (For the case of a centralized classifier
and regulator the actual port specified in the QoS Class
Establishment message is used only for administrative purposes. Any
valid value of Port and Port Session Number, that specifies a
centralized classifier and regulator function, may be used.)
The QoS Class Establishment message is:
Message Type = 98
The QoS Class Establishment request and success response messages
have the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Type | Result | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Session Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Regulator | Excess Action | QoS Class Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scheduler Identifier | Excess Scheduler Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Output Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ QoS Class Policer Parameters ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ QoS Class Regulator Parameters ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
QoS Class Identifier
The QoS Class Identifier is selected by the controller. It
is used to identify the QoS class being established or
modified, in future QoS Connection Management and QoS Class
Establishment messages. It is taken from a namespace that
is global across the entire switch. No two QoS classes may
have the same QoS Class Identifier regardless of the switch
ports on which they are defined. A QoS Class Identifier in
a QoS Class Establishment message must be greater than 0
and less than 0xFFFFFFFF.
Regulator
The Regulator field specifies which function is required of
the regulator. Three possible functions are currently
defined: none, policing, and shaping.
None: Regulator = 1
Policing: Regulator = 2
Shaping: Regulator = 3
If the Regulator function is specified as none, no
operations are performed by the regulator on the cells
output from the classifier. Cells output from the
classifier are transferred directly to the waiting room
specified by the Scheduler Identifier.
If policing is specified, a token bucket policer will be
applied to the QoS class. The policer determines which
cells conform to the specified policer traffic parameters
and which do not. Conforming cells are transferred directly
to the waiting room specified by the Scheduler Identifier.
The action to be taken by the policer on the excess traffic
is specified by the Excess Action field. The policer
traffic parameters are specified in the QoS Class Regulator
Parameters fields.
If shaping is specified, traffic shaping will be applied to
the QoS class. Cells in a QoS class should leave the
regulator spaced evenly apart at a rate defined by the QoS
Class Regulator Parameters fields. These cells are
transferred directly to the waiting room specified by the
Scheduler Identifier. The jitter on the conforming cell
stream on exit from the shaping function of the regulator
is not specified.
Excess Action
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|T|D|S|x x x x x|
+-+-+-+-+-+-+-+-+
T: Tagging
If bit 0 of the Excess Action field is set, all cells
transferred to the waiting room specified by the Excess
Scheduler Id will have their CLP bit set. If bit 0 of the
Excess Action field is zero, the CLP bit of cells
transferred to the waiting room specified by the Excess
Scheduler Id will remain unchanged.
D: Discard
This function is only available if policing is selected as
the regulator function. If the Regulator field specifies
Policing, and bit 1 of the Excess Action field is set, all
cells determined by the policer to be in excess of the
traffic parameters must be discarded. In this case the
Excess Scheduler Id is not used and bit 0 of the Excess
Action field should be ignored.
S: Differentiated Scheduling
This function operates differently according to whether
policing or shaping is selected as the regulator function.
If the Regulator field specifies Policing, and bit 1 of the
Excess Action field is zero, and bit 2 of the Excess Action
field is set, all cells determined by the policer to be in
excess of the traffic parameters must be transferred to the
waiting room specified by the Excess Scheduler Id. In this
case care must be taken in the implementation to ensure
that within each virtual path connection or virtual channel
connection, cells depart in the same order that they
arrived. If the Regulator field specifies Policing, and
bit 1 of the Excess Action field is zero, and bit 2 of the
Excess Action field is zero, all cells determined by the
policer to be in excess of the traffic parameters must be
transferred to the waiting room specified by the Scheduler
Identifier. In this case the Excess Scheduler Id is not
used.
If the Regulator field specifies Shaping, and bit 2 of the
Excess Action field is zero, cells will be transferred from
the QoS class to the waiting room pointed to by the
Scheduler Identifier at a rate defined by the QoS Class
Regulator Parameters. In this case the Excess Scheduler Id
is not used. If the Regulator field specifies Shaping, and
bit 2 of the Excess Action field is set, additional cells
will be scheduled for transmission by the waiting room
pointed to by the Excess Scheduler Id. This permits a
minimum cell rate to be allocated to the QoS class using
the QoS Class Regulator Parameters and additional bandwidth
to be shared by the QoS class. The additional share of
bandwidth is determined according to the parameters of the
waiting room pointed to by the Excess Scheduler Id. If the
Excess Scheduler Id is specified in the QoS Class
Establishment message, the additional bandwidth will be
shared by the entire QoS class. If the Excess Scheduler Id
is specified in each individual QoS Connection Management
message, the additional bandwidth is specific to that
connection and not shared by the entire QoS class. Care
must be taken in the implementation to ensure that within
each virtual path connection or virtual channel connection,
cells depart in the same order that they arrived.
x: Bits 3--7 of the Excess Action field are not used.
QoS Class Weight
If bit 1 of the Scheduler Flags field of the QoS
Configuration message indicates that weighted service may
be applied to a QoS class, the QoS Class Weight parameter
specifies the share of the bandwidth available to the
waiting room that should be given to this QoS class.
The QoS Class Weight is an unsigned 16-bit field specifying
a binary fraction. I.e. the bandwidth share, as a fraction
of the bandwidth available to the waiting room, is given
by:
Bandwidth share = QoS Class Weight * 2**(-16)
A QoS Class Weight of zero indicates equal sharing between
all QoS classes sharing this waiting room that request a
QoS Class Weight of zero. While a 16-bit field is used to
specify the QoS Class Weight it is understood that the
accuracy of the bandwidth sharing is hardware dependent and
is not specified.
If the Regulator field of the QoS Class Establishment
message indicates None, or Policer, the QoS Class Weight
should be applied to the waiting room pointed to by the
Scheduler Identifier. If the Regulator field of the QoS
Class Establishment message indicates Shaper, the QoS Class
Weight should be applied to the waiting room pointed to by
the Excess Scheduler Id.
If the specified waiting room is unable to offer weighted
sharing for a QoS class, a failure response message should
be returned with the failure code indicating: "This waiting
room is unable to offer weighted sharing for a QoS class."
Scheduler Identifier
If all conforming traffic from this QoS class is directed
to the same waiting room, on the same output port, this
field specifies the Scheduler Identifier for the entire QoS
class. The Scheduler Identifier points to the waiting room,
on the output port specified by the Output Port field, to
which all conforming traffic should be sent. If this field
is not used it should be set to 0xFFFF. If each component
connection of the QoS class specifies its own output port
and waiting room, the Scheduler Identifier must be
specified in the QoS Connection Management message and this
field must be set to 0xFFFF.
Excess Scheduler Id
If all conforming traffic from this QoS class is directed
to the same waiting room, on the same output port, this
field specifies the Excess Scheduler Id for the entire QoS
class. The Excess Scheduler Id points to the waiting room,
on the output port specified by the Output Port field, to
which all excess traffic should be sent. If this field is
not used it should be set to 0xFFFF. If each component
connection of the QoS class specifies its own output port
and waiting room, the Excess Scheduler Id must be specified
in the QoS Connection Management message and this field
must be set to 0xFFFF. If the Scheduler Id is specified in
the QoS Class Establishment message, the Excess Scheduler
Id must also be specified in the QoS Class Establishment
message (or not used). If the Scheduler Id is specified in
the QoS Connection Management message, the Excess Scheduler
Id must also be specified in the QoS Connection Management
message (or not used). The Excess Scheduler Id must not
point to the same waiting room on the same output port as
the Scheduler Identifier.
Output Port
If the Scheduler Identifier field in the QoS Establishment
message is not 0xFFFF the Output Port field specifies the
Output Port to which traffic from this QoS class should be
routed. If the Scheduler Identifier field in the QoS
Establishment message is 0xFFFF, this field is not used.
QoS Class Policer Parameters
A policer function may be applied to a QoS class on output
from the classifier independently of the regulator
function. The QoS class policer function is identical to
the connection policer function defined in the QoS
Connection Management message with the exception that it
applies to all cells that belong to the QoS class rather
than just cells that belong to a single connection.
The QoS Class Policer Parameters have the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Increment-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Limit-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Increment-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Limit-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |C|A|x x x x x x|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The definition of these fields is given in the UPC
Parameters section of the QoS Connection Management
message.
QoS Class Regulator Parameters
The QoS class regulator function is identical to the
regulator function defined in the QoS Connection Management
message with the exception that it applies to all cells
that belong to the QoS class rather than just cells that
belong to a single connection.
The QoS Class Regulator Parameters have the following
format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Regulator Increment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS Class Regulator Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The definition of these fields is given in the Regulator
Parameters section of the QoS Connection Management
message.
9.5 QoS Release Message The QoS Release message is used to delete a Scheduler Identifier or a QoS Class Identifier and to release all resources associated with it. The QoS Release message is: Message Type = 99 The QoS Release request and success response messages have the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Message Type | Result | Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transaction Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Port Session Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Scheduler Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | QoS Class Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Port If the QoS Release message contains a Scheduler Identifier, the Port field must contain the Port Number of the switch output port to which the Scheduler Identifier applies. If the QoS Release message contains a QoS Class Identifier, any valid Port number may be used. (The QoS Class Identifier has a global namespace.) Port Session Number The current Port Session Number for the port specified in the Port field. Scheduler Identifier If the Scheduler Identifier contains the value 0xFFFF the QoS Class Identifier specified in the QoS Class Identifier field should be released. Else, if the value of the Scheduler Identifier lies in the range 0x0100 -- 0xFFFE inclusive, the Scheduler Identifier specified by the Scheduler Identifier field should be released. A Scheduler
Identifier with a value less than 0x0100 is invalid in a
QoS Release message. (It specifies a default value which
may not be released.)
QoS Class Identifier
If the Scheduler Identifier contains the value 0xFFFF the
QoS Class Identifier field specifies the QoS Class
Identifier to be released.
If the QoS Release message requests that a Scheduler Identifier be
released, and the Scheduler Identifier is still in use by one or more
established connections, a failure response must be returned with the
failure code indicating: "Scheduler Identifier still in use." If the
QoS Release message requests that a QoS Class Identifier be released,
and the QoS Class Identifier is still in use by one or more
established connections, a failure response must be returned with the
failure code indicating: "QoS Class Identifier still in use."
(page 86 continued on part 4)
