Chapter 3: Traffic Management

Table Of Contents

Traffic Management

Service Categories

Connection Admission Control

G-CAC and A-CAC

A-CAC

Qbin for AutoRoute and PNNI

Usage Parameter Control

Available Bit Rate

ABR VS/VD Control

Frame Discard for AAL5

Traffic Management

---

The following traffic management functions are supported on the PNNI node:

•Asymmetrical traffic requirements.

•Connection Admission Control (CAC).

•Qbin for AutoRoute and PNNI

•Mapping of SVC/SPVC Traffic Parameters to UPC capabilities.

•Dual leaky bucket UPC (GCRA 1 and GCRA2).

•ABR EFCI marking, Relative Rate marking, Explicit Rate marking and VS/VD control.

•Frame Discard for AAL5.

Service Categories

The following service categories as defined in ATM Forum Traffic Management 4.0 are supported:

•constant bit rate (CBR)

•real-time VBR (rt-VBR)

•non-real-time VBR (nrt-VBR)

•unspecified bit rate (UBR)

•available bit rate (ABR)

---

Note ABR is currently only supported in SPVCs. ABR will be supported in SVCs when UNI 4.0 is supported.

---

Table 3-1 Supported Service Categories 

Attribute	CBR	rt-VBR	nrt-VBR	UBR	ABR
PCR, CDVT	yes	yes	yes	yes	yes
SCR, MBS	N/A	yes	yes	N/A	N/A
MCR (UNI 4.0)	N/A	N/A	N/A	N/A	yes
RAIG CLP (PNNI 1.0)	Yes	yes	yes	N/A	N/A
peak-to-peak CDV (UNI 4.0)	yes	yes	no	no	no
max CTD (UNI 4.0)	yes	yes	no	no	no
CLR (UNI 4.0)	yes	yes	yes	no	network specific

Connection Admission Control

Each connection between an ATM CPE (ATM end user) and the WAN switching network establishes a contract with the network based on Quality of Service (QoS) parameters. This contract specifies an envelope that describes the intended traffic flow, including values for peak bandwidth, average sustained bandwidth, and burst size.

The ATM CPE device is responsible for adhering to the contract by means of traffic shaping. Traffic shaping is the use of queues to constrain data bursts, limit peak data rate, and smooth jitter so that the traffic complies with the criteria specified in the envelope.

The SES PNNI nodes have the option of using traffic policing to enforce the networking contract. The SES PNNI node uses the following two methods to police traffic from ATM CPE into the network:

•Connection Admission Control

•Usage Parameter Control

Connection Admission Control (CAC) verifies that sufficient network resources are available to accept the call. The desired ATM traffic contract is specified in the Bearer Capability, the Traffic Descriptor, and Quality of Service (QoS) information elements of the Setup message. These UNI signaling Setup message elements are mapped to Usage Parameter Control (UPC) parameters in the SES PNNI node.

G-CAC and A-CAC

CAC functions are performed on each individual node. G-CAC (Generic CAC) is performed by the routing protocol when it selects a routing path for a call. The PNNI routing protocol needs to make sure that the routing path it selected will satisfy the basic traffic parameter requirement specified by the call. The checking performed by the routing protocol at border node is called G-CAC. For G-CAC description, refer to "ATM Forum PNNI 1.0 Spec. af-pnni-0055.000". A routing path which satisfied the G-CAC checking may not guarantee the call will have traffic resource on each node of its routing path. This is attributed to the routing data base synchronization delay in the network. To ensure a call has traffic resource it requested on each node of its routing path, a local CAC (A-CAC) must be performed when the call arrived on the node. A call will be released or cranked back if it fails on A-CAC. A-CAC performance is described in the section below.

A-CAC

Both resource-related criteria and policy-related criteria are used for CAC. And the CAC is performed per service category. The CAC is applied to all types of interfaces, UNI, NNI, and IISP.

Resource-based CAC

For resource-related CAC, the CAC algorithm calculates the Equivalent Cell Rate (ECR) of a connection prior to establishing the connection, and ensures high efficiency of network resources in accordance with the following criteria:

•Requested service category

•Requested conformance definition

•Traffic descriptor, PCR, SCR, MCR, and MBS

•CDVT

•Requested UPC conformance

•QoS parameters (namely, CDV, CTD, and CLR)

•Buffer size at each of the QBIN

•Line speed at each port

•Policy-related parameters, minimum and maximum bandwidth, booking factor for a service category

When a call is admitted with the ECR, the requested QoS for the connection is guaranteed even under the worst scenario as described by the traffic descriptors of the connection.

Policy-based CAC

For policy-related CAC, the following parameters are configurable per service category.

•Booking factor per service category per interface

•Guaranteed minimum bandwidth per service category per interface

•Maximum bandwidth allowed per service category per interface

•Guaranteed minimum number of connections per service category per interface

•Maximum number of connections allowed per service category per interface

•Maximum bandwidth allowed for a single connection per service category per interface

Qbin for AutoRoute and PNNI

BPX/SES support per CoS queuing. The BXM supports 16 qbin for each port. Qbin 0 to Qbin 9 are reserved for AutoRoute. Qbin 10 to Qbin 15 are reserved for VSI applications such as PNNI and MPLS service. For detail Qbin description and configuration, refer to Appendix D, Virtual Switch Interface, and Chapter 10, Configuring ATM SVCs, PNNI Routing, and SPVCs.

Usage Parameter Control

Usage Parameter Control (UPC) may be performed at the ingress of network edge nodes only, or alternatively may be performed at every intermediate node. UPC is enabled on a per interface basis as specified by a service class template on the switches. The traffic contracts are defined in the ATM Forum Traffic Management Specification 4.0 and UNI 3.x, and are summarized in the following table.

Table 3-2 Traffic Contracts

Service Category	CBR	CBR	rt, nrt, VBR	rt, nrt VBR	CBR	rt, nrt VBR	UBR	UBR	ABR
UNI 4.0 Conform-ance	1 CBR.2	CBR.3	VBR.2	VBR.3	CBR.1	VBR.1	UBR.1	UBR.2	ABR
Parameters
PCR (0+1)	x	x	x	x	x	x	x	x	x
PCR (0)	x	x
CDVT(0+1)	x	x	x	x	x	x	x	x	x
CDVT(0)	x	x
SCR (0+1)						x
SCR (0)			x	x
MBS (0+1)						x
MBS(0)			x	x
Tagging		x		x				x
Best Effort							x	x
MCR									x
Transmit ATC2	5	5	9, 10	9, 10	7	19, 11	10	10	12
ILMI Traffic Descriptor Type	NoClpNoScr	NoClpNoScr	ClpNoTaggingScr	ClpTaggingScr	NoClpNoScr	NoClpScr	NoClpNoScr	NoClpNoScr	ClpNoTagi-Mcr
ILMI Best Effort Indicator	false	false	false	false	false	false	true	true	false
Specification	3.x	3.x	3.x 4.0	3.x 4.0	3.x 4.0	3.x 4.0	3.x 4.0	4.0	4.0

1 This traffic definition applies to the CBR traffic sets specified in TM 3.x. 2 Transmit ATC is defined in TM 4.0, which is not supported in the current release.

Available Bit Rate

Available Bit Rate (ABR) can operate in the following modes, all of which are supported by the
BPX switch:

•EFCI marking

•Relative Rate marking

•Explicit Rate marking

•VS/VD control.

EFCI marking and VS/VD control are configured by the service template for an interface. SPVC supports VS/VD on a per connection basis. Relative Rate marking (CI control) and Explicit Rate marking are configured on a per slot basis, and this configuration applies to both AutoRoute and
PNNI ABR connections on the slot.

ABR VS/VD Control

The ABR closed loop virtual source/virtual destination (VS/VD) control is set up between the originating and terminating UNIs which are set up as VSVD endpoints. An interface is provisioned so that ABR endpoints on that interface operate as a VSVD endpoints.

Figure 3-1 ABR VS/VD Control Loop

The ABR parameters (Table 3-3) are obtained from the following SETUP message information:

•Broadband Bearer Capability	Bearer Class must be set to ABR and User Plane Connection Configuration must be point-to-point.
•Traffic Descriptor	IE contains the forward and backward MCR and PCR values.
•ABR Setup Parameters	Mandatory IE contains the forward and backward ICR, TBE, RIF and RDF values, and the CRM value.
•ABR Additional Parameters	Optional IE contains the forward and backward Nrm, Trm, CDF and ADTF parameters.

If ABR parameters are not supplied in the SETUP message then default values are used.

Table 3-3 ABR Signal Parameters  

Parameter	Default	Value Range	Units	Description	IE
PCR	mandatory	50 - Line Rate	cells/s	Peak Cell Rate	Traffic Descriptor
MCR	0	50 - Line Rate	cells/s	Minimum Cell Rate	Traffic Descriptor
ICR	PCR	MCR - PCR	cells/s	Initial Cell Rate	ABR Setup Parameters
RIF	1/16	Power of 2: 1/32768 - 1	-	Rate Increase Factor	ABR Setup Parameters
RDF	1/16	Power of 2: 1/32768 - 1	-	Rate Decrease Factor	ABR Setup Parameters
TBE	16777215	0 - 16777215	cells	Transient Buffer Exposure	ABR Setup Parameters
FRTT	-	0 - 16777215	usec	Fixed Round Trip Time	ABR Setup Parameters
Nrm	32	Power of 2: 2 - 256	cells	Maximum cells per forward RM-cell	ABR Additional Parameters
ADTF	0.55	0.01-10.23	sec	ACR Decrease Time Factor	ABR Additional Parameters
Trm	100	100 times power of 2: 100*2-7 - 100*20	msec	Time between Forward RM-cells	ABR Additional Parameters
CDF	1/16	Power of 2: 1/64 - 1	-	Cutoff Decrease Factor	ABR Additional Parameters
CRM	TBE/Nrm	1 - 4095	cells	Cumulative RM-cell Count	Computed

When the SES node receives a Setup message, the following processing, which includes Connection Admission Control (CAC), occurs:

•Validate the Bearer Class and Traffic Descriptor combinations.

•Determine the SES PNNI controller Service Category from the Bearer Capability information element and the Traffic Descriptor information element. The SES PNNI controller Service Category is either CBR, rt-VBR, nrt-VBR, ABR, or UBR.

•Verify that the required bandwidth is less than the Available Cell Rate. CAC is performed on the BXM.

•Verify that a channel is available on the port by obtaining a free LCN.

•Verify that a VPCI is available.

•Map the Traffic Parameters to the port UPC capabilities.

Frame Discard for AAL5

BPX/SES support frame discard for AAL5 on PNNI 1.0 signaling to support SPVC applications. For frame discard for AAL5 in SVC, it will be supported in later release when UNI4.0 is supported.