Quality of Service Parameters for Usage with Diameter
Extracted elements (23)
The Bandwidth AVP is defined as a simplified TMOD encoding (where r=p, b=large, m=large) to handle cases where only bandwidth needs to be expressed, avoiding the overhead of a full TMOD AVP.
The QoS profile extensibility mechanism uses an 8-octet vendor+specifier field to allow both IANA-registered profiles (vendor=0) and vendor-specific profiles (vendor=Enterprise Number), enabling different organizations to define their own QoS parameter sets without conflicting with the standard profile.
Two TMOD AVPs (TMOD-1 and TMOD-2) are defined because DiffServ EF traffic requires only a single token bucket, while DiffServ AF traffic requires two token buckets (one for average traffic, one for burst), enabling distinction among three levels of drop precedence as defined by the srTCM in RFC 2697.
Sets of PHBs that do not constitute a PHB Scheduling Class cannot be represented by a single PHBID with bit 14 set; they must be identified by using more than one PHBID, requiring multiple PHB-Class AVPs.
The PHB-Class AVP encoding is derived from RFC 3140 (Per Hop Behavior Identification Codes), and the registries needed for RFC 3140 already exist; therefore no new registry is required for PHB-Class values beyond what RFC 3140 established.
All bits indicated as 'reserved' in the PHB-Class AVP encoding MUST be set to zero (0).
If the four octets of the vendor field in the QoS profile are 0x00000000 (IANA reserved value), then the value in the specifier field MUST be registered with IANA.
When a single PHBID is used to identify a set of PHBs (bit 14 set to 1), that set of PHBs MUST constitute a PHB Scheduling Class, meaning use of PHBs from the set MUST NOT cause intra-microflow traffic reordering when different PHBs from the set are applied to traffic in the same microflow.
IANA allocated AVP codes 495-503 in the Diameter AVP namespace for TMOD-1, Token-Rate, Bucket-Depth, Peak-Traffic-Rate, Minimum-Policed-Unit, Maximum-Packet-Size, TMOD-2, Bandwidth, and PHB-Class AVPs defined in this document.
IANA created a QoS profile registry for the 64-bit field (4-octet vendor + 4-octet specifier). When vendor is 0x00000000, specifier values 0-511 require Standards Action, 512-32767 require Specification Required, and 32768-4294967295 are Reserved. Value 0 is allocated for the QoS profile defined in this document.
This document does not raise any security concerns as it only defines QoS parameters and does not describe how they are exchanged in an AAA protocol. Security considerations are deferred to documents that use this specification.
Bandwidth AVP (AVP Code 502) is of type Float32, measured in octets of IP datagrams per second. It is a simplified TMOD representation where token rate equals peak traffic rate, bucket depth is large, and minimum policed unit is large.
Bucket-Depth AVP (AVP Code 497) is of type Float32, representing the bucket depth (b) parameter of the token bucket model.
Maximum-Packet-Size AVP (AVP Code 500) is of type Unsigned32, representing the maximum packet size (M) parameter.
Minimum-Policed-Unit AVP (AVP Code 499) is of type Unsigned32, representing the minimum policed unit (m) parameter.
Peak-Traffic-Rate AVP (AVP Code 498) is of type Float32, representing the peak traffic rate (p) parameter of the token bucket model.
PHB-Class AVP (AVP Code 503) is of type Unsigned32 encoding a DiffServ per-hop behavior identifier. It supports three cases: a single PHB (DSCP left-justified in bits 0-5), a set of PHBs (bit 14 set to 1), and experimental/local-use PHBs (12-bit PHBID, bit 15 set to 1).
PHB-Class Case 1 encodes a single PHB as the recommended DSCP value left-justified in a 16-bit field with bits 6 through 15 set to zero, within the 32-bit Unsigned32 AVP.
PHB-Class Case 2 encodes a set of PHBs as the numerically smallest encoding of the set with bit 14 set to 1. For example, the AF1x PHB set uses the AF11 encoding with bit 14 set to 1.
PHB-Class Case 3 encodes experimental or local-use PHBs using a 12-bit PHBID assigned by IANA, left-justified in the 16-bit field, with bit 15 set to 1 and bits 12-13 reserved as zero.
TMOD-1 AVP (AVP Code 495) is a Grouped AVP containing five child AVPs: Token-Rate, Bucket-Depth, Peak-Traffic-Rate, Minimum-Policed-Unit, and Maximum-Packet-Size. It encodes a token bucket traffic model derived from RFC 2210 and RFC 2215.
TMOD-2 AVP (AVP Code 501) is a Grouped AVP with the same structure as TMOD-1, carrying a second token bucket parameter set. It is needed for DiffServ assured forwarding (AF) traffic, which requires two token buckets: one for average traffic and one for burst traffic.
Token-Rate AVP (AVP Code 496) is of type Float32, representing the token rate (r) parameter of the token bucket model.