Update of the Simple Two-way Active Measurement Protocol (STAMP) Class-of-Service Optional Extension

Introduction defined several extensions to Simple Two-way Active Measurement Protocol (STAMP). Among those is Class of Service TLV that enables monitoring of the Differential Services Code Point (DSCP) marking in downstream and upstream directions. Also, Class of Service TLV supports downstream monitoring of the Explicit Congestion Notification (ECN). Experience deploying STAMP and its extensions demonstrated that it is helpful to an operator to monitor ECN's consistency in the upstream direction. This specification defines the extension of the Class of Service TLV in a backward compatible manner to support monitoring of ECN in the upstream direction of the STAMP test session.

Conventions Used in This Document

Acronyms CoS Class of Service DSCP Differentiated Services Code Point ECN Explicit Congestion Notification STAMP Simple Two-way Active Measurement Protocol

Requirements Language 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 when, and only when, they appear in all capitals, as shown here.

TLV Extensions to STAMP

Class of Service TLV The STAMP Session-Sender MAY include a Class of Service (CoS) TLV in the STAMP test packet. The format of the CoS TLV is presented in .

Class of Service TLV where fields are defined as the following:

STAMP TLV Flags - is an eight-bit-long field. Its format is presented in Section 4 of .
CoS (Class of Service) Type - is a one-octet-long field, the value MUST be set to 4.
Length - two-octet-long field, set equal to the value 4.
DSCP1 - The Differentiated Services Code Point (DSCP) intended by the Session-Sender to be used as the DSCP value of the reflected test packet.
DSCP2 - The received value in the DSCP field at the ingress of the Session-Reflector.
ECN - is a two-bit-long field. The received value in the ECN field at the ingress of the Session-Reflector.
RP (Reverse Path) - is a two-bit-long field. A Session-Sender MUST set the value of the RP field to 0 on transmission.
REC - is a two-bit-long field. The value intended by the Session-Sender to be used as the ECN value of the reflected test packet.
Reserved - 14-bit-long field. It MUST be zeroed on transmission and ignored on receipt.

Processing and handling of DSCP1, DSCP2, and ECN fields as defiend in Section 4.4 of . A system that supports this specification MUST set the ECN value in the data plane encapsulation of the reflected STAMP test packet to the value of the REC field. Furthermore, such a system MUST add 0b10 to the value of the RP field in the Class of Service TLV in the reflected test packet. As a result, the Session-Sender can detect whether the recommended values for DSCP and ECN fields in the reflected packets were used by inspecting the value of the RP field in the received reflected test packet. The extended Class of Service TLV defined in this dradft s backward compatible with the specification in Section 4.4 of . Consider a case when implementation that supports this specification performs as Session-Sender, nd the intended Session-Reflector support of the Class of Service TLV is according to Session 4.4 of . If the operator requires monitoring ECN in the upstream direction, the value of the REC field will be set to a non-zero value. Because the Session-Reflector would treat the REC field as part of the Reserved field and ignore its value, the Session-Reflector would not add 0b10 to the value of the RP field in the reflected STAMP packet. Consequently, the Session-Sender will determine that the ECN value in the IP/UDP encapsulation of the reflected test packet was not set to the requested value.

IANA Considerations This document makes no requests to IANA.

Security Considerations This document extends the functionality of the Class of Service TLV () and inherits all the security considerations applicable to the base STAMP specification and . As this specification defined the mechanism to test ECN mapping, this document inherits all the security considerations discussed in . Monitoring and optional control of ECN for a reflected STAMP test packet using the extended CoS TLV may be used across the Internet so that the Session-Sender and the Session-Reflector are located in different domains.

Acknowledgments TBA