SPRING Working Group R. Gandhi, Ed. Internet-Draft C. Filsfils Intended status: Standards Track Cisco Systems, Inc. Expires: August 13, 2021 N. Vaghamshi Reliance M. Nagarajah Telstra R. Foote Nokia February 09, 2021 Enhanced Performance and Liveness Monitoring in Segment Routing Networks draft-gandhi-spring-sr-enhanced-plm-04 Abstract Segment Routing (SR) leverages the source routing paradigm. SR is applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document defines procedures for Enhanced Performance and Liveness Monitoring (PLM) for end-to-end SR paths including SR Policies for both SR-MPLS and SRv6 data planes, those reduce the deployment and operational complexities in a network. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 13, 2021. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Gandhi, et al. Expires August 13, 2021 [Page 1] Internet-Draft Performance and Liveness Monitoring in SR February 2021 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Loopback Mode . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Loopback Mode Enabled with Network Programming Function . 6 3.3. Example Provisioning Model . . . . . . . . . . . . . . . 6 4. PLM Test Packet Formats . . . . . . . . . . . . . . . . . . . 7 5. PLM Procedure . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1. PLM for SR-MPLS Policies . . . . . . . . . . . . . . . . 10 5.2. PLM for SRv6 Policies . . . . . . . . . . . . . . . . . . 10 6. Enhanced PLM Procedure . . . . . . . . . . . . . . . . . . . 11 6.1. Enhanced PLM with Timestamp Label for SR-MPLS Policies . 11 6.1.1. Timestamp Label Allocation . . . . . . . . . . . . . 12 6.1.2. Node Capability for Timestamp Label . . . . . . . . . 13 6.2. Enhanced PLM with Timestamp Endpoint Function for SRv6 Policies . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2.1. Timestamp Endpoint Function Assignment . . . . . . . 14 6.2.2. Node Capability for Timestamp Endpoint Function . . . 15 7. ECMP Handling . . . . . . . . . . . . . . . . . . . . . . . . 15 8. Example PLM Failure Notifications . . . . . . . . . . . . . . 15 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . 17 11.2. Informative References . . . . . . . . . . . . . . . . . 18 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction Segment Routing (SR) leverages the source routing paradigm and greatly simplifies network operations for Software Defined Networks (SDNs). SR is applicable to both Multiprotocol Label Switching (SR- MPLS) and IPv6 (SRv6) data planes [RFC8402]. SR Policies as defined in [I-D.ietf-spring-segment-routing-policy] are used to steer traffic Gandhi, et al. Expires August 13, 2021 [Page 2] Internet-Draft Performance and Liveness Monitoring in SR February 2021 through a specific, user-defined paths using a stack of Segments. Built-in Performance Measurement as well as Liveness Monitoring for Connectivity Verification (CV) and Continuity Check (CC) are essential requirements to provide Service Level Agreements (SLAs) in SR networks. The Simple Two-way Active Measurement Protocol (STAMP) provides capabilities for the measurement of various performance metrics in IP networks [RFC8762]. It eliminates the need for control protocol by using configuration and management model to provision and manage test sessions. The STAMP can be used for Performance Measurement (PM) in SR networks as well as liveness monitoring and connectivity loss detection of SR paths. However, the STAMP requires protocol support on the Session-Reflector to process the STAMP test packets as packets need to be punted from the forwarding fast path (to slow path or control plane) on the Session-Reflector and STAMP reply test packets need to be generated. This limits the scale for number of STAMP test sessions and faster fault detection intervals. For Liveness Monitoring, Seamless Bidirectional Forwarding Detection (S-BFD) [RFC7880] can be used in SR networks. However, S-BFD requires protocol support on the BFD-Reflector to process the S-BFD packets as packets need to be punted from the forwarding fast path and generate the reply packets thereby limiting the scale for number S-BFD sessions and faster fault detection intervals. In addition, S-BFD protocol is not defined to enable performance measurement in a network. Enabling multiple protocols, S-BFD for liveness monitoring and STAMP for performance measurement increases the deployment and operational complexities a network. Also, implementing multiple protocols in a hardware significantly increases the development cost. This document defines procedures for Enhanced Performance and Liveness Monitoring (PLM) for end-to-end SR paths including SR Policies for both SR-MPLS and SRv6 data planes, those reduce the deployment and operational complexities in a network. The procedures use the new test packet formats those have the timestamps at the same locations as the base STAMP test packets to leverage the existing hardware support for STAMP. 2. Conventions Used in This Document 2.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this Gandhi, et al. Expires August 13, 2021 [Page 3] Internet-Draft Performance and Liveness Monitoring in SR February 2021 document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. Abbreviations S-BFD: Seamless Bidirectional Forwarding Detection. BSID: Binding Segment ID. ECMP: Equal Cost Multi-Path. EB: Endpoint Behaviour. HMAC: Hashed Message Authentication Code. MBZ: Must be Zero. MPLS: Multiprotocol Label Switching. PLM: Performance and Liveness Monitoring. PM: Performance Measurement. PTP: Precision Time Protocol. SID: Segment ID. SL: Segment List. SR: Segment Routing. SRH: Segment Routing Header. SR-MPLS: Segment Routing with MPLS data plane. SRv6: Segment Routing with IPv6 data plane. SSID: Sender Session Identifier. STAMP: Simple Two-way Active Measurement Protocol. TC: Traffic Class. TTL: Time To Live. Gandhi, et al. Expires August 13, 2021 [Page 4] Internet-Draft Performance and Liveness Monitoring in SR February 2021 2.3. Reference Topology In the reference topology shown below, the Session-Sender R1 initiates a PLM test packet and the Session-Reflector R3 transmits a PLM return test packet. The PLM return test packet is transmitted back to the Session-Sender R1 on the same path or a different path in the reverse direction. The Session-Sender R1 and Session-Reflector R3 are connected via an SR path [RFC8402]. The SR path may be an SR Policy [I-D.ietf-spring-segment-routing-policy] on node R1 (called head-end) with destination to node R3 (called tail-end). T1 / +-------+ PLM Test Packet +-------+ | | - - - - - - - - - - - | | | R1 |======================|| R3 | | |<- - - - - - - - - - - | | +-------+ Return Test Packet +-------+ \ T4 Session-Sender Session-Reflector (Simply Forward) Reference Topology 3. Overview 3.1. Loopback Mode In loopback mode, the Session-Sender R1 initiates PLM test packets and the Session-Reflector R3 forwards them just like data packets for the regular traffic back to the Session-Sender R1. The PLM test packets are not punted at the Session-Reflector and does not process them and generate PLM return test packets. The Session-Reflector must not drop the loopback PLM test packets, for example, due to a local policy provisioned. No PLM test session is created on the Session-Reflector. The Source and Destination IP addresses in the PLM test packets are set to the Session-Reflector and the Session-Sender IP addresses, respectively (representing the reverse direction path). The Source and Destination UDP ports in the PLM test packets follow the procedure defined in [RFC8762]. The IPv4 Time To Live (TTL) and IPv6 Hop Limit (HL) are set to 255. Gandhi, et al. Expires August 13, 2021 [Page 5] Internet-Draft Performance and Liveness Monitoring in SR February 2021 3.2. Loopback Mode Enabled with Network Programming Function In loopback mode enabled with network programming function, both transmit (T1) and receive (T2) timestamps in data plane are collected by the PLM test packets transmitted in loopback mode as shown in Figure 1. The network programming function optimizes the "operations of punt and generate the PLM test packet" on the Session-Reflector as timestamping is implemented in forwarding fast path in hardware. This helps to achieve higher test session scale and faster failure detection interval. T1 T2 / \ +-------+ PLM Test Packet +-------+ | | - - - - - - - - - - - | | | R1 |======================|| R3 | | |<- - - - - - - - - - - | | +-------+ Return Test Packet +-------+ \ T4 Session-Sender Session-Reflector (Timestamp, Pop and Forward) Figure 1: Loopback Mode Enabled with Network Programming Function The Session-Sender adds transmit timestamp (T1) in the payload of the PLM test packet and clears the receive (T2) timestamp. The Session- Reflector adds the receive timestamp (T2) in the payload of the received PLM test packet in forwarding fast path in hardware without punting the test packet to the slow path (or control-plane). The network programming function enables Session-Reflector to add the receive timestamp (T2) at a specific offset in the payload which is locally provisioned consistently in the network. The payload of the PLM test packet is not modified by the intermediate nodes. The Session-Reflector only adds the receive timestamp if the source IP address (in case of SR-MPLS) or destination IP address (in case of SRv6) in the PLM test packet matches the local node address to ensure that the PLM test packet reaches the intended Session-Reflector and the receive timestamp is returned by the intended Session-Reflector. 3.3. Example Provisioning Model An example provisioning model and typical measurement parameters are shown in Figure 2: Gandhi, et al. Expires August 13, 2021 [Page 6] Internet-Draft Performance and Liveness Monitoring in SR February 2021 +------------+ | Controller | +------------+ PLM Mode / \ Timestamp Label/SRV6 EB Loopback or Enhanced Mode / \ Timestamp Offset Timestamp Label/SRv6 EB / \ Timestamp Format Timestamp Format / \ Missed Packet Count (N) / \ Delay Threshold/Count (T/M) / \ Packet Loss Threshold (XofY)/ \ v v +-------+ +-------+ | | | | | R1 |==========| R3 | | | | | +-------+ +-------+ Session-Sender Session-Reflector Figure 2: Example Provisioning Model Example of PLM mode is loopback mode. The values for Timestamp Label and SRv6 Endpoint Behaviour may be provisioned as described in Section 6. Example of Timestamp Format is 64-bit PTPv2 [IEEE1588]. Example of Timestamp Offset is 16 and 32 bytes for the PLM test packet formats defined in this document. Example threshold values configured for generating notifications are: Missed Packet Count (N), Delay Exceeded Threshold and Packet Count (T/M) and Packet Loss Threshold (XofY), as described in Section 7. The mechanisms to provision the Session-Sender and Session-Reflector are outside the scope of this document. 4. PLM Test Packet Formats The PLM test packet formats for unauthenticated and authenticated modes are defined in this document as shown in Figure 3 those have the transmit and receive timestamps at the same locations as the base STAMP test packets to leverage the existing hardware support for STAMP. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit Timestamp (T1) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit Error Estimate | SSID | Gandhi, et al. Expires August 13, 2021 [Page 7] Internet-Draft Performance and Liveness Monitoring in SR February 2021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive Timestamp (T2) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MBZ (12 Octets) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive Error Estimate | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MBZ (4 Octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ PLM Test Packet Format in Unauthenticated Mode 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MBZ (12 octets) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit Timestamp (T1) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit Error Estimate | SSID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MBZ (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive Timestamp (T2) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MBZ (32 octets) | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive Error Estimate | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | MBZ (6 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MBZ (16 octets) | | | Gandhi, et al. Expires August 13, 2021 [Page 8] Internet-Draft Performance and Liveness Monitoring in SR February 2021 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | HMAC (16 octets) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ PLM Test Packet Format in Authenticated Mode Figure 3: PLM Test Packet Formats Sequence Number is the sequence number of the PLM test packet according to its transmit order. It starts with zero and is incremented by one for each subsequent PLM test packet. SSID (16-bits): PLM Sender Session Identifier. Uses the procedure for SSID defined in [RFC8762]. Transmit Timestamp and Transmit Error Estimate are the Session- Sender's transmit timestamp and error estimate for the PLM test packet, respectively. Receive Timestamp and Receive Error Estimate are the Session- Reflector's receive timestamp and error estimate, respectively. The timestamp and error estimate fields follow the definition and formats defined in Section 4.1.2 in [RFC8762]. The timestamp format used by default is 64-bit PTPv2 [IEEE1588]. HMAC: The use of the HMAC field is described in Section 4.4 of [RFC8762]. MBZ: Must be Zero. It MUST be all zeroed on the transmission and MUST be ignored on receipt. 5. PLM Procedure For performance and liveness monitoring of an end-to-end SR path including SR Policy, PLM test packets in loopback mode are used. For SR Policy, the PLM test packets are transmitted using the Segment List (SL) of the Candidate-Path [I-D.ietf-spring-segment-routing-policy]. When a Candidate-Path has more than one Segment Lists, multiple PLM test packets are sent, one using each Segment List. The PLM return test packets are received by the Session-Sender via IP/UDP [RFC0768] return path by default. The Segment List of the return SR path can be added in the PLM test Gandhi, et al. Expires August 13, 2021 [Page 9] Internet-Draft Performance and Liveness Monitoring in SR February 2021 packet header to receive the return test packet on a specific path using the Binding SID [I-D.ietf-pce-binding-label-sid] or Segment List of the Reverse SR Policy [I-D.ietf-pce-sr-bidir-path]. 5.1. PLM for SR-MPLS Policies The PLM test packets are transmitted using the MPLS header for each Label Stack of the SR-MPLS Policy Candidate-Path(s) as shown in Figure 4. In case of IP/UDP return path, the MPLS header is removed by the Session-Reflector. The Label Stack can contain a reverse SR- MPLS path to receive the PLM return test packet on a specific path. In this case, the MPLS header will not be removed by the Session- Reflector. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(1) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(n) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IP Header | . Source IP Address = Session-Reflector IPv4 or IPv6 Address . . Destination IP Address = Session-Sender IPv4 or IPv6 Address . . Protocol = UDP . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload as defined in Figure 3 | . . +---------------------------------------------------------------+ Figure 4: Example PLM Test Packet for SR-MPLS 5.2. PLM for SRv6 Policies The PLM test packets for SRv6 data plane are transmitted using the Segment Routing Header (SRH) [RFC8754] for each Segment List of the SRv6 Policy Candidate-Path(s) as shown in Figure 5. In case of IP/ UDP return path, the SRH is removed by the Session-Reflector. The Gandhi, et al. Expires August 13, 2021 [Page 10] Internet-Draft Performance and Liveness Monitoring in SR February 2021 Segment List can contain a reverse SRv6 path to receive the PLM return test packet on a specific path. In this case, the SRH will not be removed by the Session-Reflector. When the PLM return test packet contains an SRH at the Session-Sender, the procedure defined for upper-layer header processing for SRv6 SIDs in [I-D.ietf-spring-srv6-network-programming] is used to process the UDP header in the received PLM test packets. +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Sender IPv6 Address . . Destination IP Address = Destination IPv6 Address . . . +---------------------------------------------------------------+ | SRH as specified in RFC 8754 | . . . . +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Reflector IPv6 Address . . Destination IP Address = Session-Sender IPv6 Address . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload as defined in Figure 3 | . . +---------------------------------------------------------------+ Figure 5: Example PLM Test Packet for SRv6 6. Enhanced PLM Procedure The enhanced performance and liveness monitoring of an end-to-end SR path including SR Policy is defined using the PLM test packets in loopback mode enabled with network programming function. 6.1. Enhanced PLM with Timestamp Label for SR-MPLS Policies In this document, two new Timestamp Labels are defined for SR-MPLS data plane to enable network programming function for "timestamp, pop and forward" the received test packet. In the PLM test packets for SR-MPLS Policies, a Timestamp Label is added in the MPLS header as shown in Figure 6, to collect "Receive Gandhi, et al. Expires August 13, 2021 [Page 11] Internet-Draft Performance and Liveness Monitoring in SR February 2021 Timestamp" field in the payload of the PLM test packet. The Label Stack for the reverse SR-MPLS path can be added after the Timestamp Label to receive the PLM return test packet on a specific path. When a Session-Reflector receives a packet with Timestamp Label, after timestamping the packet at a specific offset, the Session-Reflector pops the Timestamp Label and forwards the packet using the next label or IP header in the packet (just like the data packets for the regular traffic). 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(1) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(n) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extension Label (15) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Timestamp Label (TBA1 or TBA2) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IP Header | . Source IP Address = Session-Reflector IPv4 or IPv6 Address . . Destination IP Address = Session-Sender IPv4 or IPv6 Address . . Protocol = UDP . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload as defined in Figure 3 | . . +---------------------------------------------------------------+ Figure 6: Example PLM Test Packet with Timestamp Label for SR-MPLS 6.1.1. Timestamp Label Allocation The timestamp Labels for unauthenticated and authenticated modes can be allocated using one of the following methods: o Labels (values TBA1 and TBA2) assigned by IANA from the "Extended Special-Purpose MPLS Values" [I-D.ietf-mpls-spl-terminology]. For Gandhi, et al. Expires August 13, 2021 [Page 12] Internet-Draft Performance and Liveness Monitoring in SR February 2021 Label (value TBA1), the timestamp offset is fixed at byte-offset 16 from the start of the payload for the unauthenticated mode, and Label (value TBA2) at byte-offset 32 from the start of the payload for the authenticated mode, both using the timestamp format 64-bit PTPv2. o Labels allocated by a Controller from the global table of the Session-Reflector. The Controller provisions the labels on both Session-Sender and Session-Reflector, as well as timestamp offsets and timestamp formats. o Labels allocated by the Session-Reflector. The signaling and IGP flooding extension for the labels (including timestamp offsets and timestamp formats) are outside the scope of this document. 6.1.2. Node Capability for Timestamp Label The PLM Session-Sender needs to know if the Session-Reflector can process the Timestamp Label to avoid dropping PLM test packets. The signaling extension for this capability exchange is outside the scope of this document. 6.2. Enhanced PLM with Timestamp Endpoint Function for SRv6 Policies The [I-D.ietf-spring-srv6-network-programming] defines SRv6 Endpoint Behaviours (EB) for SRv6 nodes. In this document, two new Timestamp Endpoint Behaviours are defined for Segment Routing Header (SRH) [RFC8754] to enable "Timestamp and Forward (TSF)" function for the received test packets. In the PLM test packets for SRv6 Policies, Timestamp Endpoint Function (End.TSF) is carried with the target Segment Identifier (SID) in SRH [RFC8754] as shown in Figure 7, to collect "Receive Timestamp" field in the payload of the PLM test packet. The Segment List for the reverse path can be added after the target SID to receive the PLM return test packet on a specific path. When a Session-Reflector receives a packet with Timestamp Endpoint (End.TSF) for the target SID which is local, after timestamping the packet at a specific offset, the Session-Reflector forwards the packet using the next SID or IP header in the packet (just like the data packets for the regular traffic). Gandhi, et al. Expires August 13, 2021 [Page 13] Internet-Draft Performance and Liveness Monitoring in SR February 2021 +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Sender IPv6 Address . . Destination IP Address = Destination IPv6 Address . . . +---------------------------------------------------------------+ | SRH as specified in RFC 8754 | . . . SRv6 Endpoint End.TSF (value TBA3 or TBA4) . . . +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Reflector IPv6 Address . . Destination IP Address = Session-Sender IPv6 Address . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload as defined in Figure 3 | . . +---------------------------------------------------------------+ Figure 7: Example PLM Test Packet with Endpoint Function for SRv6 6.2.1. Timestamp Endpoint Function Assignment The Timestamp Endpoint Functions for "Timestamp and Forward" can be signaled using one of the following methods: o Timestamp Endpoint Functions (values TBA3 and TBA4) assigned by IANA from the "SRv6 Endpoint Behaviors Registry". For endpoint behaviour (value TBA3), the timestamp offset is fixed at byte- offset 16 from the start of the payload for the unauthenticated mode, and endpoint behaviour (value TBA4) at byte-offset 32 from the start of the payload for the authenticated mode, both using the timestamp format 64-bit PTPv2. o Timestamp Endpoint Functions assigned by a Controller. The Controller provisions the values on both Session-Sender and Session-Reflector, as well as timestamp offsets and timestamp formats. o Timestamp Endpoint Functions assigned by the Session-Reflector. The signaling and IGP flooding extension for the endpoint Gandhi, et al. Expires August 13, 2021 [Page 14] Internet-Draft Performance and Liveness Monitoring in SR February 2021 functions (including timestamp offsets and timestamp formats) are outside the scope of this document. 6.2.2. Node Capability for Timestamp Endpoint Function The PLM Session-Sender needs to know if the Session-Reflector can process the Timestamp Endpoint Function to avoid dropping PLM test packets. The signaling extension for this capability exchange is outside the scope of this document. 7. ECMP Handling An SR Policy can have ECMPs between the source and transit nodes, between transit nodes and between transit and destination nodes. The PLM test packets need to be sent to traverse different ECMP paths to monitor an end-to-end SR Policy. Forwarding plane has various hashing functions available to forward packets on specific ECMP paths. In IPv4 header of the PLM test packets, sweeping of Destination Address from the 127/8 range can be used to exercise different IPv4 ECMP paths in both loopback modes as long as the forward and the return paths are SR-MPLS paths. In this case, the TTL field in the IPv4 header is set to 1. The Flow Label field in the outer IPv6 header can also be used for sweeping to exercise different IPv6 ECMP paths. 8. Example PLM Failure Notifications Liveness or connectivity success for an end-to-end SR path is initially notified as soon as one or more PLM return test packets are received at the Session-Sender. Liveness or connectivity failure for an end-to-end SR path is notified when consecutive N number of PLM return test packets are not received at the Session-Sender, where N (Missed PLM Packet Count) is a locally provisioned value. The round-trip packet loss for an end-to-end SR path is calculated using the Sequence Number in the PLM test packets. The packet loss metric is notified when X number of PLM test packets were lost out of last Y number of PLM test packets transmitted by the Session-Sender, where Threshold XofY is locally provisioned value. Similarly, the delay metrics are notified, as an example, when consecutive M number of PLM test packets have measured delay values exceed user-configured threshold T, where M (Delay Exceeded Packet Gandhi, et al. Expires August 13, 2021 [Page 15] Internet-Draft Performance and Liveness Monitoring in SR February 2021 Count) and T (Absolute and Percentage Delay Exceeded Threshold) are also locally provisioned values. In both loopback modes, the timestamps T1 and T4 are used to measure round-trip delay. In loopback mode enabled with network programming function, the timestamps T1 and T2 are used to measure one-way delay. In both loopback modes, a failure on the reverse direction path can cause the PLM return test packets to not reach the Session-Sender. This is also true in the case where the PLM return test packets were generated by the Session-Reflector e.g. to indicate Session-Sender of a failure on the forward direction path. As such, the test packet based methods have a limitation of false detection due to a reverse direction failure. 9. Security Considerations The Performance and Liveness Monitoring is intended for deployment in the well-managed private and service provider networks. As such, it assumes that a node involved in a monitoring operation has previously verified the integrity of the path and the identity of the Session- Reflector. If desired, attacks can be mitigated by performing basic validation and sanity checks, at the Session-Sender, of the timestamp fields in received PLM packets. The minimal state associated with these protocols also limits the extent of disruption that can be caused by a corrupt or invalid packet to a single test cycle. Use of HMAC-SHA-256 in the authenticated mode protects the data integrity of the test packets. Cryptographic measures may be enhanced by the correct configuration of access-control lists and firewalls. The security considerations specified in [RFC8762] also apply to the procedures defined in this document. 10. IANA Considerations IANA maintains the "Special-Purpose Multiprotocol Label Switching (MPLS) Label Values" registry (see ). IANA is requested to allocate Timestamp Label value from the "Extended Special-Purpose MPLS Label Values" registry: Gandhi, et al. Expires August 13, 2021 [Page 16] Internet-Draft Performance and Liveness Monitoring in SR February 2021 +-------------+---------------------------------+---------------+ | Value | Description | Reference | +-------------+---------------------------------+---------------+ | TBA1 | Timestamp Label | This document | | | for offset 16 | | | | for Unauthenticated Mode | | +-------------+---------------------------------+---------------+ | TBA2 | Timestamp Label | This document | | | for offset 32 | | | | for Authenticated Mode | | +-------------+---------------------------------+---------------+ IANA is requested to allocate, within the "SRv6 Endpoint Behaviors Registry" sub-registry belonging to the top-level "Segment Routing Parameters" registry [I-D.ietf-spring-srv6-network-programming], the following allocation: +-------------+---------------------------------+---------------+ | Value | Endpoint Behavior | Reference | +-------------+---------------------------------+---------------+ | TBA3 | End.TSF (Timestamp and Forward) | This document | | | for offset 16 | | | | for Unauthenticated Mode | | +-------------+---------------------------------+---------------+ | TBA4 | End.TSF (Timestamp and Forward) | This document | | | for offset 32 | | | | for Authenticated Mode | | +-------------+---------------------------------+---------------+ 11. References 11.1. Normative References [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Gandhi, et al. Expires August 13, 2021 [Page 17] Internet-Draft Performance and Liveness Monitoring in SR February 2021 [RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple Two-Way Active Measurement Protocol", RFC 8762, DOI 10.17487/RFC8762, March 2020, . [I-D.ietf-spring-srv6-network-programming] Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "SRv6 Network Programming", draft-ietf-spring-srv6-network-programming-28 (work in progress), December 2020. 11.2. Informative References [IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", March 2008. [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. Pallagatti, "Seamless Bidirectional Forwarding Detection (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016, . [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, . [I-D.ietf-spring-segment-routing-policy] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", draft- ietf-spring-segment-routing-policy-09 (work in progress), November 2020. [I-D.ietf-mpls-spl-terminology] Andersson, L., Kompella, K., and A. Farrel, "Special Purpose Label terminology", draft-ietf-mpls-spl- terminology-06 (work in progress), January 2021. Gandhi, et al. Expires August 13, 2021 [Page 18] Internet-Draft Performance and Liveness Monitoring in SR February 2021 [I-D.ietf-pce-binding-label-sid] Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID in PCE-based Networks.", draft-ietf-pce-binding-label- sid-05 (work in progress), October 2020. [I-D.ietf-pce-sr-bidir-path] Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong, "Path Computation Element Communication Protocol (PCEP) Extensions for Associated Bidirectional Segment Routing (SR) Paths", draft-ietf-pce-sr-bidir-path-05 (work in progress), January 2021. Acknowledgments The authors would like to thank Greg Mirsky, Mach Chen, Kireeti Kompella, and Adrian Farrel for providing the review comments. Authors' Addresses Rakesh Gandhi (editor) Cisco Systems, Inc. Canada Email: rgandhi@cisco.com Clarence Filsfils Cisco Systems, Inc. Email: cfilsfil@cisco.com Navin Vaghamshi Reliance Email: Navin.Vaghamshi@ril.com Moses Nagarajah Telstra Email: Moses.Nagarajah@team.telstra.com Gandhi, et al. Expires August 13, 2021 [Page 19] Internet-Draft Performance and Liveness Monitoring in SR February 2021 Richard Foote Nokia Email: footer.foote@nokia.com Gandhi, et al. Expires August 13, 2021 [Page 20]