Simple Two-Way Active Measurement Protocol
Extensions for Performance Measurement on LAGChina MobileNo. 29 Finance Avenue, Xicheng DistrictBeijingChinali_zhenqiang@hotmail.comHuaweiChinazhoutianran@huawei.comZTE Corp.Chinaguo.jun2@zte.com.cnEricssonUnited States of Americagregimirsky@gmail.comCiscoCanadargandhi@cisco.com
Operation and Management Area
IPPMThis document extends Simple Two-Way Active Measurement Protocol
(STAMP) to implement performance measurement on every member link of a
Link Aggregation Group (LAG). Knowing the measured metrics of each
member link of a LAG enables operators to enforce a performance based
traffic steering policy across the member links.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 when, and only when, they
appear in all capitals, as shown here.Link Aggregation Group (LAG), as defined in , provides mechanisms to combine multiple physical
links into a single logical link. This logical link offers higher
bandwidth and better resiliency, because if one of the physical member
links fails, the aggregate logical link can continue to forward traffic
over the remaining operational physical member links.Usually, when forwarding traffic over LAG, the hash-based mechanism
is used to load balance the traffic across the LAG member links. Link
delay of each member link varies because of different transport paths.
To provide low latency service for time sensitive traffic, we need to
explicitly steer the traffic across the LAG member links based on the
link delay, loss and so on. That requires a solution to measure the
performance metrics of each member link of a LAG. Hence the measured
performance metrics can work together with layer
2 bundle member link attributes advertisement for traffic
steering.Simple Two-Way Active Measurement Protocol
(STAMP) is an active measurement method according to the
classification given in , which can complement
passive and hybrid methods. It provides a mechanism to measure both
one-way and round-trip performance metrics, like delay, delay variation,
and packet loss. Running a single STAMP test session over the
aggregation without the knowledge of each member link would make it
impossible to measure the performance of a given physical member link.
The measured metrics can only reflect the performance of one member link
or an average of some/all member links of the LAG.This document extends STAMP to implement performance measurement on
every member link of a LAG. The proposed method could also potentially
apply to layer 3 ECMP (Equal Cost Multi-Path), e.g., with Segment Routing Policy.This document intends to address the scenario (e.g., ) where a LAG (e.g., the LAG includes four member
links) directly connects two nodes (A and B) . The goal is to measure
the performance of each link of the LAG.To measure the performance metrics of every member link of a LAG,
multiple sessions (one session for each member link) need to be
established between the two end points that are connected by the LAG.
These sessions are called micro sessions in the remainder of this
document.All micro sessions of a LAG share the same Sender IP Address and
Receiver IP Address. As for the UDP Port, the micro sessions may share
the same Sender Port and Receiver Port pair, or each micro session is
configured with a different Sender Port and Receiver Port pair. But from
the operational point of view, the former is simpler and is
recommended.At the Sender side, each micro STAMP session MUST be assgined with a
unique SSID. Both the micro STAMP Session
Sender and Reflector MUST use SSID to correlate the Test packet to a
micro session. If there is no such a session, or the SSID is not
correct, the Test packet MUST be discarded.Test packets MAY carry the member link information for validation
check. For example, when a micro STAMP Session-Sender receives a
reflected Test packet, it may need to check whether the Test packet is
from the expected member link. The detailed description about the member
link validation is in section 3.A micro STAMP Session-Sender MAY include the Follow-Up Telemetry TLV to request information
from the micro Session-Reflector. This timestamp might be important for
the micro Session-Sender, as it improves the accuracy of network delay
measurement by minimizing the impact of egress queuing delays on the
measurement.Test packets MAY carry the member link information for validation
check. The micro Session Sender can verify whether the test packet is
reveived from the expected member link. It can also verify whether the
packet is sent from the expected member link at the Reflector side. The
micro Session Reflector can verify whether the test packet is received
from the expected member link.STAMP TLV mechanism extends STAMP
Test packets with one or more optional TLVs. This document defines the
TLV Type (value TBA1) for the Micro-session ID TLV that carries the
micro STAMP Session-Sender member link identifier and
Session-Reflector member link identifier. The format of the
Micro-session ID TLV is shown as follows:Type: A one-octet field. Value TBA1 is allocated by IANA
(Section 5).Length: A two-octet field equal to the length of the Value
field in octets. The Length field value MUST be 4 octets.Sender Micro-session ID (2-octets in length): it is defined to
carry the Micro-session identifier of the Sender side. The value
of the Sender Member Link ID MUST be unique at the
Session-Sender.Reflector Micro-session ID (2-octets in length): it is defined
to carry the Micro-session identifier of the Reflector side. The
value of the Reflector Member ID MUST be unique at the
Session-Reflector.The micro STAMP-Test reuses the procedures as defined in Section 4
of STAMP with the following
additions.The micro STAMP Session-Sender MUST send the micro STAMP-Test
packets over the member link with which the session is associated. The
configuration and management of the mapping between a micro STAMP
session and the Sender/Reflector member link identifiers are outside
the scope of this document.When sending a Test packet, the micro STAMP Session-Sender MUST set
the Sender Micro-session ID field with the member link identifier
associated with the micro STAMP session. If the Session-Sender knows
the Reflector member link identifier, the Reflector Micro-session ID
field MUST be set. Otherwise, the Reflector Micro-session ID field
MUST be zero. The Reflector member link identifier can be obtained
from pre-configuration or learned from data plane (e.g., the reflected
Test packet). How to obtain/learn the Reflector member link identifier
is outside of this document's scope.When the micro STAMP Session-Reflector receives a Test packet, if
the Reflector Micro-session ID is not zero, the micro STAMP
Session-Reflector MUST use the Reflector member link identifier to
check whether it is associated with the micro STAMP session. If the
validation fails, the Test packet MUST be discarded. If all
validations passed, the Session-Reflector sends a reflected Test
packet to the Session-Sender. The micro STAMP Session-Reflector MUST
put the Sender and Reflector member link identifiers that are
associated with the micro STAMP session in the Sender Micro-session ID
and Reflector Micro-session ID fields respectively. The Sender member
link identifier is copied from the received Test packet.When receiving a reflected Test packet, the micro Session-Sender
MUST use the Sender Micro-session ID to validate whether the reflected
Test packet is correctly transmitted over the expected member link. If
the validation fails, the Test packet MUST be discarded. The micro
Session-Sender MUST use the Reflector Micro-session ID to validate the
Reflector's behavior. If the validation fails, the Test packet MUST be
discarded.In the "STAMP TLV Types" registry created for [RFC8972], a new STAMP
TLV Type for Micro-session ID TLV is requested from IANA as
follows:The STAMP extension defined in this document is intended for
deployment in LAG scenario where Session-Sender and Session-Reflector
are directly connnected. As such, it's assumed that a node involved in
STAMP protocol operation has previously verified the integrity of the
LAG connection and the identity of its one-hop-away peer node.This document does not introduce any additional security issues and
the security mechanisms defined in [RFC8762] and [RFC8972] apply in this
document.The authors would like to thank Mach Chen, Min Xiao, Fang Xin for the
valuable comments to this work.IEEE Standard for Local and metropolitan area networks - Link
AggregationIEEE Std. 802.1AXSegment Routing Policy Architecture