--- 1/draft-ietf-mpls-entropy-lsp-ping-03.txt 2016-08-11 09:15:52.795605850 -0700 +++ 2/draft-ietf-mpls-entropy-lsp-ping-04.txt 2016-08-11 09:15:52.839607071 -0700 @@ -1,43 +1,45 @@ -Internet Engineering Task Force N. Akiya +MPLS Working Group N. Akiya Internet-Draft Big Switch Networks Updates: 4379, 6424, 6790 (if approved) G. Swallow Intended status: Standards Track C. Pignataro -Expires: November 19, 2016 Cisco +Expires: February 12, 2017 Cisco A. Malis Huawei Technologies S. Aldrin Google - May 18, 2016 + August 11, 2016 Label Switched Path (LSP) and Pseudowire (PW) Ping/Trace over MPLS Network using Entropy Labels (EL) - draft-ietf-mpls-entropy-lsp-ping-03 + draft-ietf-mpls-entropy-lsp-ping-04 Abstract - The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) - Ping and Traceroute are used to exercise specific paths of Equal-Cost - Multipath (ECMP). When LSP is signaled to use Entropy Label (EL) - described in RFC 6790, the ability for LSP Ping and Traceroute - operation to discover and exercise ECMP paths has been lost in - scenarios which LSRs apply deviating load balance techniques. One - such scenario is when some LSRs apply EL based load balancing while - other LSRs apply non-EL based load balancing (ex: IP). Another - scenario is when EL based LSP is stitched with another LSP which can - be EL based or non-EL based. + Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Ping + and Traceroute are methods used to test Equal-Cost Multipath (ECMP) + paths. Ping is known as a connectivity verification method and + Traceroute as a fault isolation method, as described in RFC 4379. + When an LSP is signaled using the Entropy Label (EL) described in RFC + 6790, the ability for LSP Ping and Traceroute operations to discover + and exercise ECMP paths is lost for scenarios where LSRs apply + different load balancing techniques. One such scenario is when some + LSRs apply EL-based load balancing while other LSRs apply non-EL + based load balancing (e.g., IP). Another scenario is when an EL- + based LSP is stitched with another LSP which can be EL-based or non- + EL based. - This document extends the MPLS LSP Ping and Traceroute mechanisms to - restore the ability of exercising specific paths of ECMP over LSP - which make use of the Entropy Label. This document updates RFC 4379, - RFC 6424, and RFC 6790. + This document extends the MPLS LSP Ping and Traceroute multipath + mechanisms in RFC 6424 to allow the ability of exercising LSPs which + make use of the EL. This document updates RFC 4379, RFC 6424, and + RFC 6790. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -46,870 +48,880 @@ 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 http://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 November 19, 2016. + This Internet-Draft will expire on February 12, 2017. Copyright Notice Copyright (c) 2016 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 - 1.2. Prerequisite . . . . . . . . . . . . . . . . . . . . . . 4 - 1.3. Background . . . . . . . . . . . . . . . . . . . . . . . 4 + 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 4 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Multipath Type 9 . . . . . . . . . . . . . . . . . . . . . . 7 4. Pseudowire Tracing . . . . . . . . . . . . . . . . . . . . . 7 - 5. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 8 - 6. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 9 - 6.1. IP Based Load Balancer & Not Pushing ELI/EL . . . . . . . 10 - 6.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 11 - 6.3. Label Based Load Balancer & Not Pushing ELI/EL . . . . . 12 - 6.4. Label Based Load Balancer & Pushes ELI/EL . . . . . . . . 12 - 6.5. Flow Aware MS-PW Stitching LSR . . . . . . . . . . . . . 13 - 7. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 13 - 8. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 14 - 9. New Multipath Information Type: TBD4 . . . . . . . . . . . . 15 - 10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 16 - 11. Security Considerations . . . . . . . . . . . . . . . . . . . 18 + 5. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 8 + 6. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 9 + 7. New Multipath Information Type: TBD4 . . . . . . . . . . . . 10 + 8. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 11 + 9. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 13 + 9.1. IP Based Load Balancer & Not Pushing ELI/EL . . . . . . . 14 + 9.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 14 + 9.3. Label Based Load Balancer & Not Pushing ELI/EL . . . . . 15 + 9.4. Label Based Load Balancer & Pushes ELI/EL . . . . . . . . 16 + 9.5. Flow-Aware MS-PW Stitching LSR . . . . . . . . . . . . . 17 + 10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 17 + 11. Security Considerations . . . . . . . . . . . . . . . . . . . 19 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 - 12.1. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19 - 12.2. Multpath Type . . . . . . . . . . . . . . . . . . . . . 19 - 12.3. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19 - 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 + 12.1. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19 + 12.2. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19 + 12.3. Multipath Type . . . . . . . . . . . . . . . . . . . . . 20 + 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 14. Contributing Authors . . . . . . . . . . . . . . . . . . . . 20 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 15.1. Normative References . . . . . . . . . . . . . . . . . . 20 - 15.2. Informative References . . . . . . . . . . . . . . . . . 20 + 15.2. Informative References . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction 1.1. Terminology - The following acronyms/terminologies are used in this document: + The following acronyms and terms are used in this document: o MPLS - Multiprotocol Label Switching. o LSP - Label Switched Path. o LSR - Label Switching Router. o FEC - Forwarding Equivalent Class. o ECMP - Equal-Cost Multipath. o EL - Entropy Label. o ELI - Entropy Label Indicator. o GAL - Generic Associated Channel Label. o MS-PW - Multi-Segment Pseudowire. - o Initiating LSR - LSR which sends MPLS echo request. - - o Responder LSR - LSR which receives MPLS echo request and sends - MPLS echo reply. + o Initiating LSR - LSR which sends an MPLS echo request. - o IP Based Load Balancer - LSR which load balances on fields from IP - header (and possibly fields from upper layers), and does not - consider entropy label from label stack (i.e. Flow Label or - Entropy Label) for load balancing purpose. + o Responder LSR - LSR which receives an MPLS echo request and sends + an MPLS echo reply. - o Label Based Load Balancer - LSR which load balances on entropy - label from label stack (i.e. Flow Label or Entropy Label), and - does not consider fields from IP header (and possibly fields from - upper layers) for load balancing purpose. + o IP-Based Load Balancer - LSR which load balances on fields from an + IP header (and possibly fields from upper layers), and does not + consider an entropy label from an MPLS label stack (i.e., flow + label [RFC6391] or entropy label [RFC6790]) for load balancing + purposes. - o Label and IP Based Load Balancer - LSR which load balances on both - labels from label stack (including Flow Label or Entropy Label if - present) and fields from IP header (and possibly fields from upper - layers). + o Label-Based Load Balancer - LSR which load balances on an entropy + label from an MPLS label stack (i.e., flow label or entropy + label), and does not consider fields from an IP header (and + possibly fields from upper layers) for load balancing purposes. -1.2. Prerequisite + o Label and IP-Based Load Balancer - LSR which load balances on both + entropy labels from an MPLS label stack and fields from an IP + header (and possibly fields from upper layers). - MPLS implementations employ wide variety of load balancing techniques - in terms of fields used for hash "keys". The mechanisms in [RFC4379] - updated by [RFC6424] are designed to provide multipath support for - subset of techniques. Intent of this document is to restore - multipath support for those supported techniques which have been - compromised by the introduction of [RFC6790] (i.e. Entropy Labels). - Section 10 describes supported and unsupported cases, and it may be - useful for one to visit this section first. +1.2. Background -1.3. Background + MPLS implementations employ a wide variety of load balancing + techniques in terms of fields used for hash "keys". The mechanisms + in [RFC4379] and updated by [RFC6424] are designed to provide + multipath support for a subset of techniques. The intent of this + document is to provide multipath support for the supported techniques + which are compromised by the use of ELs [RFC6790]. Section 10 + describes supported and unsupported cases, and it may be useful for + the reader to first review this section. - Section 3.3.1 of [RFC4379] specifies multipath information encoding - in Downstream Mapping (DSMAP) TLV (Section 3.3 of [RFC4379]) and - Downstream Detailed Mapping (DDMAP) TLV (Section 3.3 of [RFC6424]) - which can be used by LSP Ping initiator to trace and validate all - ECMP paths between ingress and egress. While the multipath - information encoding is common to both the Downstream Mapping (DSMAP) - TLV and the Downstream Detailed Mapping (DDMAP) TLV, the former has - been deprecated by [RFC6424] and this specification only concerns - itself with the latter. The multipath information encodings are - sufficient when all the LSRs along the path(s), between ingress and - egress, consider same set of "keys" as input for load balancing - algorithm: all IP based or all label based. + The Downstream Detailed Mapping (DDMAP) TLV [RFC6424] provides + multipath information which can be used by an LSP Ping initiator to + trace and validate ECMP paths between an ingress and egress. The + multipath information encodings defined by [RFC6424] are sufficient + when all the LSRs along the path(s), between ingress and egress, + consider the same set of "keys" as input for load balancing + algorithms, e.g. either all IP-based or all label-based. - With introduction of [RFC6790], it is quite normal to see set of LSRs - performing load balancing based on EL/ELI while others still follow - the traditional way (IP based). This results in LSP Ping initiator - not be able to trace and validate all ECMP paths in following - scenarios: + With the introduction of [RFC6790], some LSRs may perform load + balancing based on labels while others may be IP-based. This results + in an LSP Ping initiator to not be able to trace and validate all the + ECMP paths in the following scenarios: - o One or more transit LSRs along LSP with ELI/EL in label stack do - not perform ECMP load balancing based on EL (hashes based on - "keys" including IP destination address). This scenario is not - only possible but quite common due transit LSRs not implementing - [RFC6790] or transit LSRs implementing [RFC6790] but not - implementing suggested transit LSR behavior in Section 4.3 of - [RFC6790]. + o One or more transit LSRs along an LSP with ELI/EL in label stack + do not perform ECMP load balancing based on EL (hashes based on + "keys" including the IP destination address). This scenario is + not only possible but quite common due to transit LSRs not + implementing [RFC6790] or transit LSRs implementing [RFC6790], but + not implementing the suggested transit LSR behavior in Section 4.3 + of [RFC6790]. - o Two or more LSPs stitched together with at least one of these LSP - pushing ELI/EL in label stack. Such scenarios are described in - [I-D.ravisingh-mpls-el-for-seamless-mpls]. + o Two or more LSPs stitched together with at least one of these LSPs + pushing ELI/EL into the label stack. - These scenarios will be quite common because every deployment of - [RFC6790] will invariably end up with nodes that support ELI/EL and - nodes that do not. There will typically be areas that support ELI/EL - and areas that do not. + These scenarios can be quite common because deployments of [RFC6790] + typically have a mixture of nodes that support ELI/EL and nodes that + do not. There will also typically be a mixture of areas that support + ELI/EL and areas that do not. - As pointed out in [RFC6790] the procedures of [RFC4379] (and + As pointed out in [RFC6790], the procedures of [RFC4379] (and consequently of [RFC6424]) with respect to multipath information type - {9} are incomplete. However [RFC6790] does not actually update - [RFC4379]. Further the specific EL location is not clearly defined, + {9} are incomplete. However, [RFC6790] does not actually update + [RFC4379]. Further, the specific EL location is not clearly defined, particularly in the case of Flow Aware Pseudowires [RFC6391]. This - document defines a new FEC Stack sub-TLV for the Entropy Label. + document defines a new FEC Stack sub-TLV for the entropy label. Section 3 of this document updates the procedures for multipath information type {9} described in [RFC4379] and applicable to [RFC6424]. The rest of this document describes extensions required - to restore ECMP discovery and tracing capabilities for scenarios + to restore ECMP discovery and tracing capabilities for the scenarios described. + [RFC4379], [RFC6424], and this document will support IP-based load + balancers and label-based load balancers which limit their hash to + the first (top-most) or only entropy label in the label stack. Other + use cases (refer to Section 10) are out of scope. + 2. Overview [RFC4379] describes LSP traceroute as an operation where the - initiating LSR send a series of MPLS echo requests towards the same - destination. The first packet in the series have the TTL set to 1. - When the echo reply is received from the LSR one hop away the second - echo request in the series is sent with the TTL set to 2, for each - echo request the TLL is incremented by one until a response is - received from the intended destination. Initiating LSR discovers and - exercises ECMP by obtaining multipath information from each transit - LSR and using specific destination IP address or specific entropy - label. + initiating LSR sends a series of MPLS echo requests towards the same + destination. The first packet in the series has the TTL set to 1. + When the echo reply is received from the LSR one hop away, the second + echo request in the series is sent with the TTL set to 2. For each + additional echo request the TLL is incremented by one until a + response is received from the intended destination. The initiating + LSR discovers and exercises ECMP by obtaining multipath information + from each transit LSR and using a specific destination IP address or + specific entropy label. - Notion of {x, y, z} from here on refers to Multipath information - types x, y or z. + From here on, the notation {x, y, z} refers to multipath information + types x, y or z. Multipath information types are defined in + Section 3.3 of [RFC4379]. - LSP Ping initiating LSR sends MPLS echo request with multipath - information. This multipath information is described in DDMAP TLV of - echo request, and may contain set of IP addresses or set of labels. - Multipath information types {2, 4, 8} carry set of IP addresses and - multipath information type {9} carries set of labels. Responder LSR - (receiver of MPLS echo request) will determine the subset of - initiator specified multipath information which load balances to each - downstream (outgoing interface). Responder LSR sends MPLS echo reply - with resulting multipath information per downstream (outgoing - interface) back to the initiating LSR. Initiating LSR is then able - to use specific IP destination address or specific label to exercise + The LSR initiating LSP Ping sends an MPLS echo request with multipath + information. This multipath information is described in the echo + request's DDMAP TLV, and may contain a set of IP addresses or a set + of labels. Multipath information types {2, 4, 8} carry a set of IP + addresses, and multipath information type {9} carries a set of + labels. The responder LSR (the receiver of the MPLS echo request) + will determine the subset of initiator-specified multipath + information which load balances to each downstream (outgoing + interface). The responder LSR sends an MPLS echo reply with + resulting multipath information per downstream (outgoing interface) + back to the initiating LSR. The initiating LSR is then able to use a + specific IP destination address or a specific label to exercise a specific ECMP path on the responder LSR. Current behavior is problematic in following scenarios: - o Initiating LSR sends IP multipath information, but responder LSR - load balances on labels. + o The initiating LSR sends IP multipath information, but the + responder LSR load balances on labels. - o Initiating LSR sends label multipath information, but responder - LSR load balances on IP addresses. + o The initiating LSR sends label multipath information, but the + responder LSR load balances on IP addresses. - o Initiating LSR sends existing multipath information to LSR which - pushes ELI/EL in label stack, but the initiating LSR can only - continue to discover and exercise specific path of ECMP, if the - LSR which pushes ELI/EL responds with both IP addresses and - associated EL corresponding to each IP address. This is because: + o The initiating LSR sends existing multipath information to an LSR + which pushes ELI/EL in the label stack, but the initiating LSR can + only continue to discover and exercise specific paths of the ECMP, + if the LSR which pushes ELI/EL responds with both IP addresses and + the associated EL corresponding to each IP address. This is + because: - * ELI/EL pushing LSR that is a stitching point will load balance - based on IP address. + * An ELI/EL pushing LSR that is a stitching point will load + balance based on the IP address. - * Downstream LSR(s) of ELI/EL pushing LSR may load balance based - on ELs. + * Downstream LSR(s) of an ELI/EL pushing LSR may load balance + based on ELs. - o Initiating LSR sends one of existing multipath information to ELI/ - EL pushing LSR, but initiating LSR can only continue to discover - and exercise specific path of ECMP if ELI/EL pushing LSR responds - with both labels and associated EL corresponding to label. This - is because: + o The initiating LSR sends existing multipath information to an ELI/ + EL pushing LSR, but the initiating LSR can only continue to + discover and exercise specific paths of ECMP, if the ELI/EL + pushing LSR responds with both labels and associated EL + corresponding to the label. This is because: - * ELI/EL pushing LSR that is a stitching point will load balance - based on EL from previous LSP and pushes new EL. + * An ELI/EL pushing LSR that is a stitching point will load + balance based on EL from the previous LSP and pushes a new EL. * Downstream LSR(s) of ELI/EL pushing LSR may load balance based on new ELs. - The above scenarios point to how the existing multipath information - is insufficient when LSP traceroute is operated on an LSP with - Entropy Labels described by [RFC6790]. Therefore, this document - defines a multipath information type to be used in the DDMAP of MPLS - echo request/reply packets in Section 9. + The above scenarios demonstrate the existing multipath information is + insufficient when LSP traceroute is used on an LSP with entropy + labels [RFC6790]. This document defines a new multipath information + type to be used in the DDMAP of MPLS echo request/reply packets for + [RFC6790] LSPs. - In addition, responder LSR can reply with empty multipath information - if no IP address set or label set from received multipath information - matched load balancing to a downstream. Empty return is also - possible if initiating LSR sends multipath information of one type, - IP address or label, but responder LSR load balances on the other - type. To disambiguate between the two results, this document - introduces new flags in the DDMAP TLV to allow responder LSR to - describe the load balance technique being used. + The responder LSR can reply with empty multipath information if no IP + address is set or label set is received with the multipath + information. An empty return is also possible if an initiating LSR + sends multipath information of one type, IP address or label, but the + responder LSR load balances on the other type. To disambiguate + between the two results, this document introduces new flags in the + DDMAP TLV to allow the responder LSR to describe the load balancing + technique being used. - It is required that all LSRs along the LSP understand new flags as - well as new multipath information type. It is also required that - initiating LSR can select both IP destination address and label to - use on transmitting MPLS echo request packets. Two additional DS - Flags are defined for the DDMAP TLV in Section 8. These two flags + All LSRs along the LSP need to be able to understand the new flags + and the new multipath information type. It is also required that the + initiating LSR can select both the IP destination address and label + to use when transmitting MPLS echo request packets. Two additional + DS Flags are defined for the DDMAP TLV in Section 6. These two flags are used by the responder LSR to describe its load balance behavior - on received MPLS echo request. + on a received MPLS echo request. - Note that the terms "IP Based Load Balancer", "Label Based Load - Balancer" and "Label Based Load Balancer" are in context of how - received MPLS echo request is handled by the responder LSR. + Note that the terms "IP-Based Load Balancer" and "Label-Based Load + Balancer" are in context of how a received MPLS echo request is + handled by the responder LSR. 3. Multipath Type 9 - This section defines to which labels multipath type {9} applies. - [RFC4379] defined multipath type {9} for tracing of LSPs where label - based load-balancing is used. However, as pointed out in [RFC6790], + based load balancing is used. However, as pointed out in [RFC6790], the procedures for using this type are incomplete as the specific location of the label was not defined. It was assumed that the presence of multipath type {9} implied the value of the bottom-of- stack label should be varied by the values indicated by multipath to - determine their respective out-going interfaces. + determine the respective outgoing interfaces. - Section 7 defines a new FEC-Stack sub-TLV to indicate an entropy - label. These labels may appear anywhere in a label stack. + Section 5 defines a new FEC-Stack sub-TLV to indicate an entropy + label. These labels MAY appear anywhere in a label stack. - Multipath type {9} applies to the first label in the label-stack that + Multipath type {9} applies to the first label in the label stack that corresponds to an EL-FEC. If no such label is found, it applies to the label at the bottom of the label stack. 4. Pseudowire Tracing This section defines procedures for tracing pseudowires. These procedures pertain to the use of multipath information type {9} as well as type {TBD4}. In all cases below, when a control word is in - use the N-flag in the DDMAP MUST be set. Note that when a control - word is not in use the returned DDMAPs may not be accurate. + use, the N-flag in the DDMAP MUST be set. Note that when a control + word is not in use, the returned DDMAPs may not be accurate. - In order to trace a non Flow-Aware Pseudowire the initiator includes - an EL-FEC instead of the appropriate PW-FEC at the bottom of the FEC- - Stack. Tracing in this way will cause compliant routers to return + In order to trace a non-flow-aware Pseudowire, the initiator includes + an EL-FEC instead of the appropriate PW-FEC at the bottom of the FEC + stack. Tracing in this way will cause compliant routers to return the proper outgoing interface. Note that this procedure only traces to the end of the MPLS LSP that is under test and will not verify the - PW FEC. To actually verify the PW-FEC or in the case of a MS-PW, to + PW FEC. To actually verify the PW FEC or in the case of a MS-PW, to determine the next pseudowire label value, the initiator MUST repeat - that step of the trace, (i.e., repeating the TTL value used) but with - the FEC-Stack modified to contain the appropriate PW-FEC. Note that - these procedures are applicable to scenarios which an initiator is - able to vary the bottom label (i.e. pseudowire label). Possible - scenarios are tracing multiple non Flow-Aware Pseudowires on the same - endpoints or tracing a non Flow-Aware Pseudowire provisioned with - multiple pseudowire labels. + that step of the trace (i.e., repeating the TTL value used) but with + the FEC Stack modified to contain the appropriate PW FEC. Note that + these procedures are applicable to scenarios where an initiator is + able to vary the bottom label (i.e., Pseudowire label). Possible + scenarios are tracing multiple non-flow-aware Pseudowires on the same + endpoints or tracing a non-flow-aware Pseudowire provisioned with + multiple Pseudowire labels. - In order to trace a Flow Aware Pseudowire, the initiator includes an - EL-FEC at the bottom of the FEC-Stack and pushes the appropriate PW- - FEC onto the FEC-Stack. + In order to trace a flow-aware Pseudowire [RFC6391], the initiator + includes an EL FEC at the bottom of the FEC Stack and pushes the + appropriate PW FEC onto the FEC Stack. - In order to trace through non-compliant routers the initiator forms + In order to trace through non-compliant routers, the initiator forms an MPLS echo request message and includes a DDMAP with multipath type - {9}. For a non Flow-Aware Pseudowire it includes the appropriate PW- - FEC in the FEC-Stack. For a Flow Aware Pseudowire, the initiator - includes a NIL-FEC at the bottom of the FEC-Stack and pushes the - appropriate PW-FEC onto the FEC-Stack. + {9}. For a non-flow-aware Pseudowire it includes the appropriate PW + FEC in the FEC Stack. For a flow-aware Pseudowire, the initiator + includes a Nil FEC at the bottom of the FEC Stack and pushes the + appropriate PW FEC onto the FEC Stack. -5. Initiating LSR Procedures +5. Entropy Label FEC - In order to facilitate the flow of the following text we speak in - terms of a boolean called EL_LSP maintained by the initiating LSR. - This value controls the multipath information type to be used in - transmitted echo request packets. When the initiating LSR is - transmitting an echo request packet with DDMAP with a non-zero - multipath information type, then EL_LSP boolean MUST be consulted to - determine the multipath information type to use. + The entropy label indicator (ELI) is a reserved label that has no + explicit FEC associated, and has label value 7 assigned from the + reserved range. Use the Nil FEC as the Target FEC Stack sub-TLV to + account for ELI in a Target FEC Stack TLV. - In addition to procedures described in [RFC4379] as updated by - Section 3 and [RFC6424], initiating LSR MUST operate with following - procedures. + The entropy label (EL) is a special purpose label with the label + value being discretionary (i.e., the label value is not from the + reserved range). For LSP verification mechanics to perform its + purpose, it is necessary for a Target FEC Stack sub-TLV to clearly + describe the EL, particularly in the scenario where the label stack + does not carry ELI (e.g., flow-aware Pseudowire [RFC6391]). + Therefore, this document defines an EL FEC sub-TLV (TBD1, see + Section 12.1) to allow a Target FEC Stack sub-TLV to be added to the + Target FEC Stack to account for EL. + + The Length is 4. Labels are 20-bit values treated as numbers. + + 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 | MBZ | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 1: Entropy Label FEC + + Label is the actual label value inserted in the label stack; the MBZ + field MUST be zero when sent and ignored on receipt. + +6. DS Flags: L and E + + Two flags, L and E, are added to the DS Flags field of the DDMAP TLV. + Both flags MUST NOT be set in echo request packets when sending, and + SHOULD be ignored when received. Zero, one or both new flags MUST be + set in echo reply packets. + + DS Flags + -------- + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + | MBZ |L|E|I|N| + +-+-+-+-+-+-+-+-+ + + RFC-Editor-Note: Please update the above figure to place the flag E + in the bit number TBD2 and the flag L in the bit number TBD3. + + Flag Name and Meaning + ---- ---------------- + L Label-based load balance indicator + This flag MUST be set to zero in the echo request. An LSR + which performs load balancing on a label MUST set this + flag in the echo reply. An LSR which performs load + balancing on IP MUST NOT set this flag in the echo + reply. + + E ELI/EL push indicator + This flag MUST be set to zero in the echo request. An LSR + which pushes ELI/EL MUST set this flag in the echo + reply. An LSR which does not push ELI/EL MUST NOT set + this flag in the echo reply. + + The two flags result in four load balancing techniques which the echo + reply generating LSR can indicate: + + o {L=0, E=0} LSR load balances based on IP and does not push ELI/EL. + + o {L=0, E=1} LSR load balances based on IP and pushes ELI/EL. + + o {L=1, E=0} LSR load balances based on labels and does not push + ELI/EL. + + o {L=1, E=1} LSR load balances based on labels and pushes ELI/EL. + +7. New Multipath Information Type: TBD4 + + One new multipath information type is added to be used in DDMAP TLV. + This new multipath type has the value of TBD4. + + Key Type Multipath Information + --- ---------------- --------------------- + TBD4 IP and label set IP addresses and label prefixes + + Multipath type TBD4 is comprised of three sections. The first + section describes the IP address set. The second section describes + the label set. The third section describes another label set which + associates to either the IP address set or the label set specified in + the other sections. + + Multipath information type TBD4 has following format: + + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |IPMultipathType| IP Multipath Length | Reserved(MBZ) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ + | (IP Multipath Information) | + ~ ~ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |LbMultipathType| Label Multipath Length | Reserved(MBZ) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ + | (Label Multipath Information) | + ~ ~ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Assoc Label Multipath Length | Reserved(MBZ) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ + | (Associated Label Multipath Information) | + ~ ~ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 2: Multipath Information Type TBD4 + + o IPMultipathType + + * 0 when "IP Multipath Information" is omitted. Otherwise, one + of the IP multipath information values: {2, 4, 8}. + + o IP Multipath Information + * This section is omitted when "IPMultipathType" is 0. + Otherwise, this section reuses IP multipath information from + [RFC4379]. Specifically, multipath information for values {2, + 4, 8} can be used. + + o LbMultipathType + + * 0 when "Label Multipath Information" is omitted. Otherwise, + label multipath information value {9}. + + o Label Multipath Information + + * This section is omitted when "LbMultipathType" is 0. + Otherwise, this section reuses label multipath information from + [RFC4379]. Specifically, multipath information for value {9} + can be used. + + o Associated Label Multipath Information + + * "Assoc Label Multipath Length" is a 16 bit field of multipath + information which indicates the length in octets of the + associated label multipath information. + + * "Associated Label Multipath Information" is a list of labels + with each label described in 24 bits. This section MUST be + omitted in an MPLS echo request message. A midpoint which + pushes ELI/EL labels SHOULD include "Assoc Label Multipath + Information" in its MPLS echo reply message, along with either + "IP Multipath Information" or "Label Multipath Information". + Each specified associated label described in this section maps + to a specific IP address OR label described in the "IP + Multipath Information" section or "Label Multipath Information" + section. For example, if three IP addresses are specified in + the "IP Multipath Information" section, then there MUST be + three labels described in this section. The first label maps + to the first IP address specified, the second label maps to the + second IP address specified, and the third label maps to the + third IP address specified. + + When a section is omitted, the length for that section MUST BE set to + zero. + +8. Initiating LSR Procedures + + The following procedure is described in terms of an EL_LSP boolean + maintained by the initiating LSR. This value controls the multipath + information type to be used in the transmitted echo request packets. + When the initiating LSR is transmitting an echo request packet with + DDMAP with a non-zero multipath information type, then the EL_LSP + boolean MUST be consulted to determine the multipath information type + to use. + + In addition to procedures described in [RFC4379], as updated by + Section 3 and [RFC6424], the initiating LSR MUST operate with the + following procedures: o When the initiating LSR pushes ELI/EL, initialize EL_LSP=True. Else set EL_LSP=False. - o When the initiating LSR is transmitting non-zero multipath + o When the initiating LSR is transmitting a non-zero multipath information type: * If (EL_LSP), the initiating LSR MUST use multipath information - type {TBD4} unless same responder LSR cannot handle type - {TBD4}. When the initiating LSR is transmitting multipath - information type {TBD4} in this case, both "IP Multipath - Information" and "Label Multipath Information" MUST be - included, and "IP Associated Label Multipath Information" MUST - be omitted (NULL). + type {TBD4} unless the responder LSR cannot handle type {TBD4}. + When the initiating LSR is transmitting multipath information + type {TBD4}, both "IP Multipath Information" and "Label + Multipath Information" MUST be included, and "IP Associated + Label Multipath Information" MUST be omitted (NULL). * Else the initiating LSR MAY use multipath information type {2, 4, 8, 9, TBD4}. When the initiating LSR is transmitting multipath information type {TBD4} in this case, "IP Multipath Information" MUST be included, and "Label Multipath Information" and "IP Associated Label Multipath Information" MUST be omitted (NULL). o When the initiating LSR receives echo reply with {L=0, E=1} in DS flags with valid contents, set EL_LSP=True. - In following conditions, the initiating LSR may have lost the ability - to exercise specific ECMP paths. The initiating LSR MAY continue - with "best effort". + In the following conditions, the initiating LSR may have lost the + ability to exercise specific ECMP paths. The initiating LSR MAY + continue with "best effort" in the following cases: o Received echo reply contains empty multipath information. o Received echo reply contains {L=0, E=} DS flags, but does not contain IP multipath information. o Received echo reply contains {L=1, E=} DS flags, but does not contain label multipath information. o Received echo reply contains {L=, E=1} DS flags, but does not contain associated label multipath information. o IP multipath information types {2, 4, 8} sent, and received echo reply with {L=1, E=0} in DS flags. o Multipath information type {TBD4} sent, and received echo reply with multipath information type other than {TBD4}. -6. Responder LSR Procedures +9. Responder LSR Procedures Common Procedures: o The responder LSR receiving an MPLS echo request packet MUST first determine whether or not the initiating LSR supports this LSP Ping and Traceroute extension for Entropy Labels. If either of the following conditions are met, the responder LSR SHOULD determine that the initiating LSR supports this LSP Ping and Traceroute - extension for Entropy Labels. + extension for entropy labels. 1. Received MPLS echo request contains the multipath information type {TBD4}. 2. Received MPLS echo request contains a Target FEC Stack TLV - that includes the Entropy Label FEC. + that includes the entropy label FEC. If the initiating LSR is determined to not support this LSP Ping - and Traceroute extension for Entropy Labels, then the responder + and Traceroute extension for entropy labels, then the responder LSR MUST NOT follow further procedures described in this section. Specifically, MPLS echo reply packets: * MUST have following DS Flags cleared (i.e., not set): "ELI/EL - push indicator" and "Label based load balance indicator". + push indicator" and "Label-based load balance indicator". * MUST NOT use multipath information type {TBD4}. o The responder LSR receiving an MPLS echo request packet with - multipath information type {TBD4} MUST validate following + multipath information type {TBD4} MUST validate the following contents. Any deviation MUST result in the responder LSR to - consider the packet as malformed and return code 1 (Malformed echo - request received) in the MPLS echo reply packet. + consider the packet as malformed and return code 1 ("Malformed + echo request received") in the MPLS echo reply packet. * IP multipath information MUST be included. * Label multipath information MAY be included. * IP associated label multipath information MUST be omitted (NULL). - Following subsections describe expected responder LSR procedures when - echo reply is to include DDMAP TLVs, based on local load balance - technique being employed. In case the responder LSR performs - deviating load balance techniques per downstream basis, appropriate - procedures matching to each downstream load balance technique MUST be - operated. + The following subsections describe expected responder LSR procedures + when the echo reply is to include DDMAP TLVs, based on the local load + balance technique being employed. In case the responder LSR performs + deviating load balance techniques on a per downstream basis, + appropriate procedures matched to each downstream load balance + technique MUST be followed. -6.1. IP Based Load Balancer & Not Pushing ELI/EL +9.1. IP Based Load Balancer & Not Pushing ELI/EL o The responder MUST set {L=0, E=0} in DS flags. o If multipath information type {2, 4, 8} is received, the responder MUST comply with [RFC4379] and [RFC6424]. o If multipath information type {9} is received, the responder MUST reply with multipath type {0}. - o If multipath information type {TBD4} is received, following + o If multipath information type {TBD4} is received, the following procedures are to be used: * The responder MUST reply with multipath information type {TBD4}. - * "Label Multipath Information" and "Associated Label Multipath - Information" sections MUST be omitted (NULL). + * The "Label Multipath Information" and "Associated Label + Multipath Information" sections MUST be omitted (NULL). - * If no matching IP address is found, then "IPMultipathType" - field MUST be set to multipath information type {0} and "IP + * If no matching IP address is found, then the "IPMultipathType" + field MUST be set to multipath information type {0} and the "IP Multipath Information" section MUST also be omitted (NULL). - * If at least one matching IP address is found, then + * If at least one matching IP address is found, then the "IPMultipathType" field MUST be set to appropriate multipath - information type {2, 4, 8} and "IP Multipath Information" + information type {2, 4, 8} and the "IP Multipath Information" section MUST be included. -6.2. IP Based Load Balancer & Pushes ELI/EL +9.2. IP Based Load Balancer & Pushes ELI/EL o The responder MUST set {L=0, E=1} in DS flags. o If multipath information type {9} is received, the responder MUST reply with multipath type {0}. - o If multipath type {2, 4, 8, TBD4} is received, following + o If multipath type {2, 4, 8, TBD4} is received, the following procedures are to be used: * The responder MUST respond with multipath type {TBD4}. See - Section 9 for details of multipath type {TBD4}. - - * "Label Multipath Information" section MUST be omitted (i.e. is - it not there). + Section 7 for details of multipath type {TBD4}. - * IP address set specified in received IP multipath information - MUST be used to determine the returning IP/Label pairs. + * The "Label Multipath Information" section MUST be omitted + (i.e., it is not there). - * If received multipath information type was {TBD4}, received - "Label Multipath Information" sections MUST NOT be used to - determine the associated label portion of returning IP/Label + * The IP address set specified in the received IP multipath + information MUST be used to determine the returning IP/Label pairs. - * If no matching IP address is found, then "IPMultipathType" - field MUST be set to multipath information type {0} and "IP + * If the received multipath information type was {TBD4}, the + received "Label Multipath Information" sections MUST NOT be + used to determine the associated label portion of returning IP/ + Label pairs. + + * If no matching IP address is found, then the "IPMultipathType" + field MUST be set to multipath information type {0} and the "IP Multipath Information" section MUST be omitted. In addition, - "Assoc Label Multipath Length" MUST be set to 0, and + the "Assoc Label Multipath Length" MUST be set to 0, and the "Associated Label Multipath Information" section MUST also be omitted. - * If at least one matching IP address is found, then + * If at least one matching IP address is found, then the "IPMultipathType" field MUST be set to appropriate multipath - information type {2, 4, 8} and "IP Multipath Information" - section MUST be included. In addition, "Associated Label - Multipath Information" section MUST be populated with list of - labels corresponding to each IP address specified in "IP + information type {2, 4, 8} and the "IP Multipath Information" + section MUST be included. In addition, the "Associated Label + Multipath Information" section MUST be populated with a list of + labels corresponding to each IP address specified in the "IP Multipath Information" section. "Assoc Label Multipath Length" - MUST be set to a value representing length in octets of + MUST be set to a value representing the length in octets of the "Associated Label Multipath Information" field. -6.3. Label Based Load Balancer & Not Pushing ELI/EL +9.3. Label Based Load Balancer & Not Pushing ELI/EL o The responder MUST set {L=1, E=0} in DS flags. o If multipath information type {2, 4, 8} is received, the responder MUST reply with multipath type {0}. o If multipath information type {9} is received, the responder MUST comply with [RFC4379] and [RFC6424] as updated by Section 3. - o If multipath information type {TBD4} is received, following + o If multipath information type {TBD4} is received, the following procedures are to be used: * The responder MUST reply with multipath information type {TBD4}. - * "IP Multipath Information" and "Associated Label Multipath + * The "IP Multipath Information" and "Associated Label Multipath Information" sections MUST be omitted (NULL). - * If no matching label is found, then "LbMultipathType" field - MUST be set to multipath information type {0} and "Label + * If no matching label is found, then the "LbMultipathType" field + MUST be set to multipath information type {0} and the "Label Multipath Information" section MUST also be omitted (NULL). - * If at least one matching label is found, then "LbMultipathType" - field MUST be set to appropriate multipath information type {9} - and "Label Multipath Information" section MUST be included. + * If at least one matching label is found, then the + "LbMultipathType" field MUST be set to the appropriate + multipath information type {9} and the "Label Multipath + Information" section MUST be included. -6.4. Label Based Load Balancer & Pushes ELI/EL +9.4. Label Based Load Balancer & Pushes ELI/EL o The responder MUST set {L=1, E=1} in DS flags. o If multipath information type {2, 4, 8} is received, the responder MUST reply with multipath type {0}. - o If multipath type {9, TBD4} is received, following procedures are - to be used: + o If multipath type {9, TBD4} is received, the following procedures + are to be used: * The responder MUST respond with multipath type {TBD4}. - * "IP Multipath Information" section MUST be omitted. + * The "IP Multipath Information" section MUST be omitted. - * Label set specified in received label multipath information - MUST be used to determine the returning Label/Label pairs. + * The label set specified in the received label multipath + information MUST be used to determine the returning Label/Label + pairs. * If received multipath information type was {TBD4}, received "Label Multipath Information" sections MUST NOT be used to determine the associated label portion of returning Label/Label pairs. - * If no matching label is found, then "LbMultipathType" field + * If no matching label is found, then the "LbMultipathType" field MUST be set to multipath information type {0} and "Label Multipath Information" section MUST be omitted. In addition, - "Assoc Label Multipath Length" MUST be set to 0, and + "Assoc Label Multipath Length" MUST be set to 0, and the "Associated Label Multipath Information" section MUST also be omitted. - * If at least one matching label is found, then "LbMultipathType" - field MUST be set to appropriate multipath information type {9} - and "Label Multipath Information" section MUST be included. In - addition, "Associated Label Multipath Information" section MUST - be populated with list of labels corresponding to each label - specified in "Label Multipath Information" section. "Assoc - Label Multipath Length" MUST be set to a value representing - length in octets of "Associated Label Multipath Information" - field. + * If at least one matching label is found, then the + "LbMultipathType" field MUST be set to the appropriate + multipath information type {9} and the "Label Multipath + Information" section MUST be included. In addition, the + "Associated Label Multipath Information" section MUST be + populated with a list of labels corresponding to each label + specified in the "Label Multipath Information" section. "Assoc + Label Multipath Length" MUST be set to a value representing the + length in octets of the "Associated Label Multipath + Information" field. -6.5. Flow Aware MS-PW Stitching LSR +9.5. Flow-Aware MS-PW Stitching LSR - Stitching LSR that cross-connects Flow Aware Pseudowires behave in + A stitching LSR that cross-connects flow-aware Pseudowires behaves in one of two ways: - o Load balances on previous Flow Label, and carries over same Flow - Label. For this case, stitching LSR is to behave as procedures - described in Section 6.3. - - o Load balances on previous Flow Label, and replaces Flow Label with - newly computed. For this case, stitching LSR is to behave as - procedures described in Section 6.4. - -7. Entropy Label FEC - - Entropy Label Indicator (ELI) is a reserved label that has no - explicit FEC associated, and has label value 7 assigned from the - reserved range. Use Nil FEC as Target FEC Stack sub-TLV to account - for ELI in a Target FEC Stack TLV. - - Entropy Label (EL) is a special purpose label with label value being - discretionary (i.e. label value may not be from the reserved range). - For LSP verification mechanics to perform its purpose, it is - necessary for a Target FEC Stack sub-TLV to clearly describe EL, - particularly in the scenario where label stack does not carry ELI - (ex: Flow Aware Pseudowire [RFC6391]). Therefore, this document - defines a EL FEC to allow a Target FEC Stack sub-TLV to be added to - the Target FEC Stack to account for EL. - - The Length is 4. Labels are 20-bit values treated as numbers. - - 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 | MBZ | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - - Figure 1: Entropy Label FEC - - Label is the actual label value inserted in the label stack; the MBZ - fields MUST be zero when sent and ignored on receipt. - -8. DS Flags: L and E - - Two flags, L and E, are added in DS Flags field of the DDMAP TLV. - Both flags MUST NOT be set in echo request packets when sending, and - ignored when received. Zero, one or both new flags MUST be set in - echo reply packets. - - DS Flags - -------- - - 0 1 2 3 4 5 6 7 - +-+-+-+-+-+-+-+-+ - | MBZ |L|E|I|N| - +-+-+-+-+-+-+-+-+ - - RFC-Editor-Note: Please update above figure to place the flag E in - the bit number TBD2 and the flag L in the bit number TBD3. - - Flag Name and Meaning - ---- ---------------- - L Label based load balance indicator - This flag MUST be set to zero in the echo request. LSR - which performs load balancing on a label MUST set this - flag in the echo reply. LSR which performs load - balancing on IP MUST NOT set this flag in the echo - reply. - - E ELI/EL push indicator - This flag MUST be set to zero in the echo request. LSR - which pushes ELI/EL MUST set this flag in the echo - reply. LSR which does not push ELI/EL MUST NOT set - this flag in the echo reply. - - Two flags result in four load balancing techniques which echo reply - generating LSR can indicate: - - o {L=0, E=0} LSR load balances based on IP and does not push ELI/EL. - - o {L=0, E=1} LSR load balances based on IP and pushes ELI/EL. - - o {L=1, E=0} LSR load balances based on label and does not push ELI/ - EL. - - o {L=1, E=1} LSR load balances based on label and pushes ELI/EL. - -9. New Multipath Information Type: TBD4 - - One new multipath information type is added to be used in DDMAP TLV. - New multipath type has value of TBD4. - - Key Type Multipath Information - --- ---------------- --------------------- - TBD4 IP and label set IP addresses and label prefixes - - Multipath type TBD4 is comprised of three sections. One section to - describe IP address set. One section to describe label set. One - section to describe another label set which associates to either IP - address set or label set specified in the other section. - - Multipath information type TBD4 has following format: - - 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 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - |IPMultipathType| IP Multipath Length | Reserved(MBZ) | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ~ ~ - | (IP Multipath Information) | - ~ ~ - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - |LbMultipathType| Label Multipath Length | Reserved(MBZ) | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ~ ~ - | (Label Multipath Information) | - ~ ~ - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Assoc Label Multipath Length | Reserved(MBZ) | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ~ ~ - | (Associated Label Multipath Information) | - ~ ~ - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - - Figure 2: Multipath Information Type TBD4 - - o IPMultipathType - * 0 when "IP Multipath Information" is omitted. Otherwise one of - IP multipath information values: {2, 4, 8}. - - o IP Multipath Information - - * This section is omitted when "IPMultipathType" is 0. Otherwise - this section reuses IP multipath information from [RFC4379]. - Specifically, multipath information for values {2, 4, 8} can be - used. - - o LbMultipathType - - * 0 when "Label Multipath Information" is omitted. Otherwise - label multipath information value {9}. - - o Label Multipath Information - - * This section is omitted when "LbMultipathType" is 0. Otherwise - this section reuses label multipath information from [RFC4379]. - Specifically, multipath information for value {9} can be used. - - o Associated Label Multipath Information - - * "Assoc Label Multipath Length" is a 16 bit field of multipath - information which indicates length in octets of the associated - label multipath information. + o Load balances on the previous flow label, and carries over the + same flow label. For this case, the stitching LSR is to behave as + described in Section 9.3. - * "Associated Label Multipath Information" is a list of labels - with each label described in 24 bits. This section MUST be - omitted in an MPLS echo request message. A midpoint which - pushes ELI/EL labels SHOULD include "Assoc Label Multipath - Information" in its MPLS echo reply message, along with either - "IP Multipath Information" or "Label Multipath Information". - Each specified associated label described in this section maps - to specific IP address OR label described in the "IP Multipath - Information" section or "Label Multipath Information" section. - For example, if 3 IP addresses are specified in the "IP - Multipath Information" section, then there MUST be 3 labels - described in this section. First label maps to the lowest IP - address specified, second label maps to the second lowest IP - address specified and third label maps to the third lowest IP - address specified. + o Load balances on the previous flow label, and replaces the flow + label with a newly computed label. For this case, the stitching + LSR is to behave as described in Section 9.4. 10. Supported and Unsupported Cases - MPLS architecture never defined strict rules on how implementations - are to identify hash "keys" for load balancing purpose. As result, - implementations may be of following load balancer types: + The MPLS architecture does not define strict rules on how + implementations are to identify hash "keys" for load balancing + purpose. As a result, implementations may be of the following load + balancer types: - 1. IP Based Load Balancer. - 2. Label Based Load Balancer. - 3. Label and IP Based Load Balancer. + 1. IP-based load balancer. + 2. Label-based load balancer. + 3. Label- and IP-based load balancer. - For cases (2) and (3), implementation can include different sets of - labels from the label stack for load balancing purpose. Thus + For cases (2) and (3), an implementation can include different sets + of labels from the label stack for load balancing purpose. Thus the following sub-cases are possible: a. Entire label stack. - b. Top N labels from label stack where number of labels in label - stack is >N. - c. Bottom N labels from label stack where number of labels in label + b. Top N labels from label stack where the number of labels in label stack is >N. + c. Bottom N labels from label stack where the number of labels in + label stack is >N. - In a scenario where there is one Flow Label or Entropy Label present - in the label stack, following further cases are possible for (2b), - (2c), (3b) and (3c): + In a scenario where there is one flow label or entropy label present + in the label stack, the following further cases are possible for + (2b), (2c), (3b) and (3c): - 1. N labels from label stack include Flow Label or Entropy Label. - 2. N labels from label stack does not include Flow Label or Entropy - Label. + 1. N labels from label stack include flow label or entropy label. + 2. N labels from label stack do not include flow label or entropy + label. - Also in a scenario where there are multiple Entropy Labels present in + Also in a scenario where there are multiple entropy labels present in the label stack, it is possible for implementations to employ deviating techniques: - o Search for entropy stops at the first Entropy Label. - o Search for entropy includes any Entropy Label found plus continues + o Search for entropy stops at the first entropy label. + + o Search for entropy includes any entropy label found plus continues to search for entropy in the label stack. - Furthermore, handling of reserved (i.e. special) labels varies among + Furthermore, handling of reserved (i.e., special) labels varies among implementations: o Reserved labels are used in the hash as any other label would be - (a bad practice). + (not a recommended practice). o Reserved labels are skipped over and, for implementations limited to N labels, the reserved labels do not count towards the limit of N. o Reserved labels are skipped over and, for implementations limited to N labels, the reserved labels count towards the limit of N. - It is important to point this out since presence of GAL will affect - those implementations which include reserved labels for load - balancing purpose. + It is important to point this out since the presence of GAL will + affect those implementations which include reserved labels for load + balancing purposes. - As can be seen from above, there are many flavors of potential load + As can be seen from the above, there are many types of potential load balancing implementations. Attempting for any OAM tools to support - ECMP discovery and traversal over all flavors of such will require - fairly complex procedures and implementations to support those - complex procedures. Complexities in OAM tools will produce minimal - benefits if majority of implementations are expected to employ small - subset of cases described above. + ECMP discovery and traversal over all types would require fairly + complex procedures. Complexities in OAM tools have minimal benefit + if the majority of implementations are expected to employ only a + small subset of the cases described above. - o Section 4.3 of [RFC6790] states that implementations, for load - balancing purpose, parsing beyond the label stack after finding - Entropy Label is "limited incremental value". Therefore, it is - expected that most implementations will be of types "IP Based Load - Balancer" or "Label Based Load Balancer". + o Section 4.3 of [RFC6790] states that in implementations, for load + balancing purposes, parsing beyond the label stack after finding + an entropy label has "limited incremental value". Therefore, it + is expected that most implementations will be of types "IP-based + load balancer" or "Label-based load balancer". - o Section 2.4.5.1 of [RFC7325] recommends that search for entropies - from the label stack should terminate upon finding the first - Entropy Label. Therefore, it is expected that implementations - will only include the first (top-most) Entropy Label when there - are multiple Entropy Labels in the label stack. + o Section 2.4.5.1 of [RFC7325] recommends that searching for entropy + labels in the label stack should terminate upon finding the first + entropy label. Therefore, it is expected that implementations + will only include the first (top-most) entropy label when there + are multiple entropy labels in the label stack. - o It is expected that, in most cases, number of labels in the label - stack will not exceed number of labels (N) which implementations - can include for load balancing purpose. + o It is expected that, in most cases, the number of labels in the + label stack will not exceed number of labels (N) which + implementations can include for load balancing purposes. - o It is expected that labels in the label stack, besides Flow Label - and Entropy Label, are constant for the lifetime of a single LSP - multipath traceroute operation. Therefore, deviating load + o It is expected that labels in the label stack, besides the flow + label and entropy label, are constant for the lifetime of a single + LSP multipath traceroute operation. Therefore, deviating load balancing implementations with respect to reserved labels should not affect this tool. - Thus [RFC4379], [RFC6424] and this document will support cases (1) - and (2a1), where only the first (top-most) Entropy Label is included - when there are multiple Entropy Labels in the label stack. + Thus [RFC4379], [RFC6424], and this document supports cases (1) and + (2a1), where only the first (top-most) entropy label is included when + there are multiple entropy labels in the label stack. 11. Security Considerations - This document extends LSP Traceroute mechanism to discover and - exercise ECMP paths when LSP uses ELI/EL in label stack. Additional - processings are required for responder and initiator nodes. - Responder node that pushes ELI/EL will need to compute and return - multipath data including associated EL. Initiator node will need to - store and handle both IP multipath and label multipath information, - and include destination IP addresses and/or ELs in MPLS echo request - packet as well as in carried multipath information to downstream - nodes. Due to additional processing, it is critical that proper - security measures described in [RFC4379] and [RFC6424] are followed. + This document extends the LSP Ping and Traceroute mechanisms to + discover and exercise ECMP paths when an LSP uses ELI/EL in the label + stack. Additional processing is required for responder and initiator + nodes. The responder node that pushes ELI/EL will need to compute + and return multipath data including associated EL. The initiator + node will need to store and handle both IP multipath and label + multipath information, and include destination IP addresses and/or + ELs in MPLS echo request packets as well as in multipath information + sent to downstream nodes. This document does not itself introduce + any new security considerations. The security measures described in + [RFC4379], [RFC6424], and [RFC6790] are applicable. [RFC6424] + provides guidelines if a network operator wants to prevent tracing or + does not want to expose details of the tunnel and [RFC6790] provides + guidance on the use of the EL. 12. IANA Considerations -12.1. DS Flags +12.1. Entropy Label FEC + + The IANA is requested to assign a new sub-TLV from the "Sub-TLVs for + TLV Types 1, 16, and 21" section from the "Multi-Protocol Label + Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" + registry ([IANA-MPLS-LSP-PING]). + + Sub-Type Sub-TLV Name Reference + -------- ------------ --------- + TBD1 Entropy label FEC this document + +12.2. DS Flags The IANA is requested to assign new bit numbers from the "DS flags" sub-registry from the "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" registry ([IANA-MPLS-LSP-PING]). Note: the "DS flags" sub-registry is created by [RFC7537]. Bit number Name Reference ---------- ---------------------------------------- --------- TBD2 E: ELI/EL push indicator this document - TBD3 L: Label based load balance indicator this document + TBD3 L: Label-based load balance indicator this document -12.2. Multpath Type +12.3. Multipath Type The IANA is requested to assign a new value from the "Multipath Type" sub-registry from the "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" registry ([IANA-MPLS-LSP-PING]). - Note: the "Multipath Type" sub-registry is created by [RFC7537]. + Note: The "Multipath Type" sub-registry is created by [RFC7537]. Value Meaning Reference ---------- ---------------------------------------- --------- TBD4 IP and label set this document -12.3. Entropy Label FEC - - The IANA is requested to assign a new sub-TLV from the "Sub-TLVs for - TLV Types 1 and 16" section from the "Multi-Protocol Label Switching - (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" registry - ([IANA-MPLS-LSP-PING]). - - Sub-Type Sub-TLV Name Reference - -------- ------------ --------- - TBD1 Entropy Label FEC this document - 13. Acknowledgements - Authors would like to thank Loa Andersson, Curtis Villamizar, Daniel - King, Sriganesh Kini and Victor Ji for performing thorough review and - providing valuable comments. + The authors would like to thank Loa Andersson, Curtis Villamizar, + Daniel King, Sriganesh Kini, Victor Ji, and Acee Lindem for + performing thorough reviews and providing valuable comments. 14. Contributing Authors Nagendra Kumar Cisco Systems, Inc. Email: naikumar@cisco.com 15. References 15.1. Normative References @@ -917,54 +929,49 @@ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, DOI 10.17487/RFC4379, February 2006, . + [RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for + Performing Label Switched Path Ping (LSP Ping) over MPLS + Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011, + . + [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L. Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC 6790, DOI 10.17487/RFC6790, November 2012, . [RFC7537] Decraene, B., Akiya, N., Pignataro, C., Andersson, L., and S. Aldrin, "IANA Registries for LSP Ping Code Points", RFC 7537, DOI 10.17487/RFC7537, May 2015, . 15.2. Informative References - [I-D.ravisingh-mpls-el-for-seamless-mpls] - Singh, R., Shen, Y., and J. Drake, "Entropy label for - seamless MPLS", draft-ravisingh-mpls-el-for-seamless- - mpls-04 (work in progress), October 2014. - [IANA-MPLS-LSP-PING] IANA, "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters", . [RFC6391] Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V., Regan, J., and S. Amante, "Flow-Aware Transport of Pseudowires over an MPLS Packet Switched Network", RFC 6391, DOI 10.17487/RFC6391, November 2011, . - [RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for - Performing Label Switched Path Ping (LSP Ping) over MPLS - Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011, - . - [RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A., and C. Pignataro, "MPLS Forwarding Compliance and Performance Requirements", RFC 7325, DOI 10.17487/RFC7325, August 2014, . Authors' Addresses Nobo Akiya Big Switch Networks