--- 1/draft-ietf-mpls-entropy-lsp-ping-02.txt 2016-05-18 14:16:39.649020401 -0700 +++ 2/draft-ietf-mpls-entropy-lsp-ping-03.txt 2016-05-18 14:16:39.689021420 -0700 @@ -1,25 +1,25 @@ Internet Engineering Task Force N. Akiya Internet-Draft Big Switch Networks Updates: 4379, 6424, 6790 (if approved) G. Swallow Intended status: Standards Track C. Pignataro -Expires: July 7, 2016 Cisco +Expires: November 19, 2016 Cisco A. Malis Huawei Technologies S. Aldrin Google - January 4, 2016 + May 18, 2016 Label Switched Path (LSP) and Pseudowire (PW) Ping/Trace over MPLS Network using Entropy Labels (EL) - draft-ietf-mpls-entropy-lsp-ping-02 + draft-ietf-mpls-entropy-lsp-ping-03 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 @@ -46,21 +46,21 @@ 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 July 7, 2016. + This Internet-Draft will expire on November 19, 2016. 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 @@ -142,38 +142,42 @@ upper layers) for load balancing purpose. 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). 1.2. Prerequisite MPLS implementations employ wide variety of load balancing techniques - in terms of fields used for hash "keys". [RFC4379] and [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. + 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. 1.3. Background Section 3.3.1 of [RFC4379] specifies multipath information encoding - in Downstream Mapping TLV (Section 3.3 of [RFC4379]) and Downstream - Detailed Mapping 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. These 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. + 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. 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: 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 @@ -184,58 +188,60 @@ 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]. 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. - As pointed out in [RFC6790] the procedures of [RFC4379] 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, particularly in the case of Flow Aware - Pseudowires [RFC6391]. This 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]. - Rest of this document describes extensions required to restore ECMP - discovery and tracing capabilities for scenarios described. + 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, + particularly in the case of Flow Aware Pseudowires [RFC6391]. This + 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 + described. 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. Notion of {x, y, z} from here on refers to Multipath information types x, y or z. LSP Ping initiating LSR sends MPLS echo request with multipath - information. This multipath information is described in DSMAP/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 specific ECMP path on the responder LSR. + 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 + 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 Initiating LSR sends label multipath information, but responder LSR load balances on IP addresses. o Initiating LSR sends existing multipath information to LSR which @@ -258,39 +264,39 @@ * ELI/EL pushing LSR that is a stitching point will load balance based on EL from previous LSP and pushes 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 DSMAP/DDMAP of - MPLS echo request/reply packets in Section 9. + defines a multipath information type to be used in the DDMAP of MPLS + echo request/reply packets in Section 9. 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 DSMAP/DDMAP TLV to allow responder LSR to + introduces new flags in the DDMAP TLV to allow responder LSR to describe the load balance 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 DSMAP and DDMAP TLVs in Section 8. These - two flags are used by the responder LSR to describe its load balance - behavior on received MPLS echo request. + Flags are defined for the DDMAP TLV in Section 8. These two flags + are used by the responder LSR to describe its load balance behavior + on 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. 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 @@ -306,23 +312,22 @@ 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 or DSMAP MUST be set. Note that when a - control word is not in use the returned DDMAPs or DSMAPs 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 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 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 @@ -330,33 +335,33 @@ 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 through non-compliant routers the initiator forms - an MPLS echo request message and includes a DDMAP or DSMAP 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. + 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. 5. Initiating LSR Procedures 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 DSMAP/DDMAP with a non-zero + 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. In addition to procedures described in [RFC4379] as updated by Section 3 and [RFC6424], initiating LSR MUST operate with following procedures. o When the initiating LSR pushes ELI/EL, initialize EL_LSP=True. Else set EL_LSP=False. @@ -436,22 +441,22 @@ 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 DSMAP/DDMAP TLVs, based on local load - balance technique being employed. In case the responder LSR performs + 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. 6.1. 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]. @@ -621,24 +626,24 @@ | 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 DSMAP/DDMAP - TLVs. 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. + 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 @@ -666,22 +671,22 @@ 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 DSMAP/DDMAP - TLVs. New multipath type has value of 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.