| Internet-Draft | DLEP Traffic Classification | July 2023 |
| Cheng, et al. | Expires 11 January 2024 | [Page] |
This document defines a new Dynamic Link Exchange Protocol (DLEP) Data Item that is used to support traffic classification. Traffic classification information is used to identify traffic flows based on frame/packet content such as destination address. The Data Item is defined in an extensible and reusable fashion. Its use will be mandated in other documents defining specific DLEP extensions. This document also introduces DLEP Sub-Data Items, and Sub-Data Items are defined to support DiffServ and Ethernet traffic classification.¶
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The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175]. It provides the exchange of link related control information between DLEP peers. DLEP peers are comprised of a modem and a router. DLEP defines a base set of mechanisms as well as support for possible extensions. DLEP defines Data Items which are sets of information that can be reused in DLEP messaging. The base DLEP specification does not include any flow identification beyond DLEP endpoints. This document defines DLEP Data Item formats which provide flow identification on a more granular basis. Specifically it enables a router to use traffic flow classification information provided by the modem to identify traffic flows. In this case, a flow is identified based on information found in a data plane header and one or more matches are associated with a single flow. (For general background on traffic classification see [RFC2475] Section 2.3.) The Data Item is structured to allow for use of the defined traffic classification information with applications such as credit window control as specified in [I-D.ietf-manet-dlep-da-credit-extension]¶
This document defines traffic classification based on a DLEP destination and flows identified by either DiffServ [RFC2475] DSCPs (differentiated services codepoints) or IEEE 802.1Q [IEEE.802.1Q_2014] Ethernet Priority Code Points (PCP). The defined mechanism allows for flows to be described in a flexible fashion and when combined with applications such as credit window control, allows credit windows to be shared across traffic sent to multiple DLEP destinations and as part of multiple flows, or used exclusively for traffic sent to a particular destination and/or belonging to a particular flow. The extension also supports the "wildcard" matching of any flow (DSCP or PCP). Traffic classification information is provided such that it can be readily extended to support other traffic classification techniques, or be used by non-credit window related extensions, such as [RFC8651] or even 5-tuple IP flows.¶
This document defines support for traffic classification using a single new Data Item in Section 2.1 for general support and two new Sub-Data Items are defined to support identification of flows based on DSCPs and PCPs.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The Traffic Classification Data Item is used to represent a list of flows that may be used at the same time for traffic sent from a router to a modem. The data plane information used to identify each flow is represented in a separate Sub-Data Item. The Data Item and Sub-Data Item structure is intended to be independent of any specific usage of the flow identification, e.g., flow control. The Sub-Data Item structure is also intended to allow for future traffic classification types, e.g., 5-tuple flows. While the structure of the Data Items is extensible, actual flow information is expected to be used in an extension dependent manner. Support for DSCP and PCP-based flows are defined via individual Sub-Data Items below. Other types of flow identification, e.g., based on IP protocol and ports, may be defined in the future via new Sub-Data Items. Note that when extensions supporting multiple Sub-Data Item types are negotiated, these types MAY be combined in a single Data Item.¶
Each list of flows is identified using a "Traffic Classification Identifier" or "TID" and is expected to represent a valid combination of data plane identifiers that may be used at the same time. Each flow is identified via a "Flow Identifier" or "FID". Each FID is defined in a Sub-Data Item which carries the data plane identifier or identifiers used to associate traffic with the flow. A DLEP destination address is also needed to complete traffic classification information used in extensions such as flow control. This information is expected to be provided in an extension specific manner. For example, this address can be provided by a modem when it identifies the traffic classification set in a Destination Up Message using the Credit Window Associate Data Item defined in [I-D.ietf-manet-dlep-credit-flow-control]. TID and FID values have modem-local scope.¶
This sections defines the Traffic Classification Data Item. This Data Item is used by a modem to provide a router with traffic classification information. When an extension requires use of this Data Item the Traffic Classification Data Item SHOULD be included by a modem in any Session Initialization Response Message, e.g., see [I-D.ietf-manet-dlep-da-credit-extension]. Updates to previously provided traffic classifications or new traffic classifications MAY be sent by a modem by including the Data Item in Session Update Messages. More than one Data Item MAY be included in a message to provide information on multiple traffic classifiers.¶
The set of traffic classification information provided in the data item is identified using a Traffic Classification Identifier, or TID. The actual data plane related information used in traffic classification is provided in a variable list of Traffic Classification Sub-Data Items.¶
The format of the Traffic Classification Data Item is:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Traffic Class. Identifier (TID)| Num SDIs | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Classification Sub-Data Item 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Classification Sub-Data Item n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
Variable¶
Per [RFC8175] Length is the number of octets in the Data Item, excluding the Type and Length fields.¶
A router receiving the Traffic Classification Data Item MUST locate the traffic classification information that is associated with the TID indicated in each received Data Item. If no associated traffic classification information is found, the router MUST initialize a new information set using the values carried in the Data Item. When associated traffic classification information is found, the router MUST replace the corresponding information using the values carried in the Data Item. In both cases, a router MUST also ensure that any data plane state, e.g., [I-D.ietf-manet-dlep-credit-flow-control], that is associated with the TID is updated as needed.¶
All Traffic Classification Sub-Data Items share a common format that is patterned after the standard DLEP Data Item format, see [RFC8175] Section 11.3. There is no requirement on, or meaning to Sub-Data Item ordering. Any errors or inconsistencies encountered in parsing Sub-Data Items are handled in the same fashion as any other Data Item parsing error encountered in DLEP.¶
The format of the Traffic Classification Sub-Data Item is:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
Variable¶
Copying [RFC8175], Length is a 16-bit unsigned integer that is the number of octets in the Sub-Data Item, excluding the Type and Length fields.¶
The DiffServ Traffic Classification Sub-Data Item is used to identify the set of DSCPs that should be treated as a single flow, i.e., receive the same traffic treatment. DSCPs are identified in a list of DiffServ fields. An implementation that does not support DSCPs and wants the same traffic treatment for all traffic to a destination or destinations would indicate 0 DSCPs.¶
The format of the DiffServ Traffic Classification Sub-Data Item is:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must be one (1) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow Identifier (FID) | Num DSCPs | DS Field 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DS Field 2 | ... | DS Field n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
Variable¶
Length is defined above. For this Sub-Data Item, it is equal to three (3) plus the value of the Num DSCPs field.¶
Each DS Field is an 8-bit that carries the DSCP field defined in [RFC2474].¶
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| DSCP | MBZ |
+---+---+---+---+---+---+---+---+
DSCP: differentiated services codepoint
MBZ: MUST be zero
¶
A router receiving the Traffic Classification Sub-Data Item MUST validate the information on receipt, prior to using the carried information, including potentially updating the data behavior as determined by the extension requiring the use of the Sub-Data Item. Validation failures MUST be treated as an error as described above.¶
Once validated, the receiver MUST ensure that each DS Field value is listed only once across the whole Traffic Classification Data Item. Note, this check is across the Data Item and not the individual Sub-Data Item. If the same DS Field value is listed more than once within the same Traffic Classification Data Item, the Data Item MUST be treated as an error as described above.¶
The Ethernet Traffic Classification Sub-Data Item is used to identify the VLAN and PCPs that should be treated as a single flow, i.e., receive the same traffic treatment. Ethernet Priority Code Point support is defined as part of the IEEE 802.1Q [IEEE.802.1Q_2014] tag format and includes a 3 bit "PCP" field. The tag format also includes a 12 bit VLAN identifier (VID) field. PCPs are identified in a list of priority fields. An implementation that does not support PCPs and wants the same traffic treatment for all traffic to a destination or destinations would indicate 0 PCPs. Such an implementation could identify a VLAN to use per destination.¶
The format of the Ethernet Traffic Classification Sub-Data Item is:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must be two (2) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow Identifier (FID) |NumPCPs| VLAN Identifier (VID) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pri. 1| Pri. 2| ..... | ..... | ..... | Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
Variable¶
Length is defined above. For this Sub-Data Item, it is equal to four (4) plus the number of octets needed to accommodate the number of Priority fields indicated by the NumPCPs field. Note that as length is in octets and each Priority field is 4 bits, the additional length is the value carried in the NumPCPs field divided by two and rounded up to the next higher integer quantity.¶
Each Priority Field is 4-bits long and indicates a PCP field defined in [IEEE.802.1Q_2014]. Note that zero (0) is a valid value for either PCP.¶
0 1 2 3
+---+---+---+---+
| PCP |MBZ|
+---+---+---+---+
PCP: Priority code point
MBZ: MUST be zero
¶
A router receiving the Traffic Classification Sub-Data Item MUST validate the information on receipt, prior to the using the carried information, including potentially updating the data behavior as determined by the extension requiring the use of the Sub-Data Item. Validation failures MUST be treated as an error as described above.¶
Once validated, the receiver MUST ensure that each Priority Field value is listed only once across the whole Traffic Classification Data Item. Note, this check is across the Data Item and not the individual Sub-Data Item. If the same Priority Field value is listed more than once within the same Traffic Classification Data Item, the Data Item MUST be treated as an error as described above.¶
If a packet matches both a DiffServ Traffic Classification Sub-Data Item (Section 2.2), e.g., DSCP match, and an Ethernet Traffic Classification Sub-Data Item (see Section 2.3), e.g., PCP match, then the TID with which the DiffServ Traffic Classification Sub-Data Item is associated MUST take precedence.¶
The formats defined in this document will only be used when extensions require their use.¶
This document introduces finer grain flow identification mechanisms to DLEP. These mechanisms do not inherently introduce any additional vulnerabilities above those documented in [RFC8175]. The approach taken to Security in that document applies equally to the mechanism defined in this document.¶
This document requests the assignment of several values by IANA. All assignments are to registries defined by [RFC8175].¶
This document requests the following new assignments to the DLEP Data Item Registry named "Data Item Type Values" in the range with the "Specification Required" policy. The requested values are as follows:¶
| Type Code | Description |
|---|---|
| TBA1 | Traffic Classification |
Upon approval of this document, IANA is requested to create a new DLEP registry, named "Traffic Classification Sub-Data Item Type Values".¶
The following table provides initial registry values and the [RFC8126] defined policies that should apply to the registry:¶
| Type Code | Description |
|---|---|
| 0 | Reserved |
| 1 | DiffServ Traffic Classification |
| 2 | Ethernet Traffic Classification |
| 3-65407 | Specification Required |
| 65408-65534 | Private Use |
| 65535 | Reserved |
The Sub-Data Item format was inspired by Rick Taylor's "Data Item Containers". He also proposed the separation of credit windows from traffic classification at IETF98. Many useful comments were received from contributors to the MANET working group. This document was derived from [I-D.ietf-manet-dlep-da-credit-extension] as a result of discussions at IETF 101. Many useful comments were received from contributors to the MANET working group, notably Ronald in't Velt and David Black.¶