| Network Work group | N. Kumar |
| Internet-Draft | C. Pignataro |
| Intended status: Standards Track | Cisco Systems, Inc. |
| Expires: October 26, 2019 | N. Akiya |
| Big Switch Networks | |
| L. Zheng | |
| M. Chen | |
| Huawei Technologies | |
| G. Mirsky | |
| ZTE Corp. | |
| April 24, 2019 |
BIER Ping and Trace
draft-ietf-bier-ping-05
Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast related per- flow state. BIER also does not require any explicit tree-building protocol for its operation. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. The BIER header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by setting the bits that correspond to those routers in the BIER header.
This document describes the mechanism and basic BIER OAM packet format that can be used to perform failure detection and isolation on BIER data plane.
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 October 26, 2019.
Copyright (c) 2019 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 (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.
[RFC8279] introduces and explains BIER architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast related per-flow state. BIER also does not require any explicit tree-building protocol for its operation. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. The BIER header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by setting the bits that correspond to those routers in the BIER header.
This document describes the mechanism and basic BIER OAM packet format that can be used to perform failure detection and isolation on BIER data plane without any dependency on other layers like IP layer.
BFER - Bit Forwarding Egress Router
BFIR - Bit Forwarding Ingress Router
BIER - Bit Index Explicit Replication
ECMP - Equal Cost Multi-Path
OAM - Operation, Administration and Maintenance
SI - Set Identifier
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 [RFC2119].
BIER OAM is defined in a way that it stays within BIER layer by following directly the BIER header without mandating the need for IP header. [RFC8296] defines a 4-bit field as "Proto" to identify the payload following BIER header. When the payload is BIER OAM, the "Proto" field will be set to 5 as defined in [RFC8296]
The BIER OAM packet header format that follows BIER header is as follows:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ver | Message Type | Proto | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OAM Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Message Type Dependent Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Ver
Message Type
Type Value Field -------- --------------- 1 BIER Echo Request 2 BIER Echo Reply
Proto
OAM Message Length
The Echo Request/Reply header format is as follows:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ver | Echo Req/Rep | Proto | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | QTF | RTF | Reply mode | Return Code | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender's Handle | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TimeStamp Sent | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TimeStamp Sent | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TimeStamp Received | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TimeStamp Received | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ TLVs ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Proto
QTF
RTF
Reply mode
Value Meaning -------- --------------- 1 Do not Reply 2 Reply via IPv4/IPv6 UDP packet. 3 Reply via BIER packet
When Reply mode is set to 1, the receiver will not send any reply. This is used for unidirectional path validation. The Reply mode by default would be set to 2 and the Responder BFR will encapsulate the Echo reply payload with IP header. When the Initiator intend to validate the return BIER path, the Reply mode is set to 3 so that the Responder BFR will encapsulate the Echo Reply with BIER header.
Return Code
Reserved
Sender's Handle, Sequence number and Timestamp
TLVs
Responder uses Return Code field to reply with validity check or other error message to Initiator. It does not carry any meaning in Echo Request and MUST be set to zero.
The Return Code can be one of the following:
Value Value Meaning -------- --------------- 0 No return code 1 Malformed Echo Request received 2 One or more of the TLVs was not understood 3 Replying BFR is the only BFER in header Bitstring 4 Replying BFR is one of the BFER in header Bitstring 5 Packet-Forward-Success 6 Invalid Multipath Info Request 8 No matching entry in forwarding table. 9 Set-Identifier Mismatch 10 DDMAP Mismatch
"No return code" will be used by Initiator in the Echo Request. This Value MUST NOT be used in Echo Reply.
"Malformed Echo Request received" will be used by any BFR if the received Echo Request packet is not properly formatted.
When any TLV included in the Echo Request is not understood by receiver, the Return code will be set to "One or more of the TLVs was not understood" carrying the respective TLVs.
When the received header BitString in Echo Request packet contains only its own Bit-ID, "Replying BFR is the only BFER in header BitString" is set in the reply. This implies that the receiver is BFER and the packet is not forwarded to any more neighbors.
When the received header BitString in Echo Request packet contains its own Bit-ID in addition to other Bit-IDs, "Replying BFR is one of the BFER in header BitString" is set in the reply. This implies that the responder is a BFER and the packet is further forwarded to one or more neighbors.
Any transit BFR will send the Echo Reply with "Packet-Forward-Success", if the TLV in received Echo Request are understood and forwarding table have forwarding entries for the BitString. This is used by transit BFR during traceroute mode.
When Echo Request is received with multipath info for more than one BFER, the return-code is set to "Invalid Multipath Info Request".
If the BitString cannot be matched in local forwarding table, the BFR will use "No matching entry in forwarding table" in the reply.
If the BIER-MPLS label in received Echo Request is not the one assigned for SI in Original SI-BitString TLV, "Set-Identifier Mismatch" is set inorder to report the mismatch.
This section defines various TLVs that can be used in BIER OAM packet. The TLVs (Type-Length-Value tuples) have the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Value ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Types are defined below; Length is the length of the Value field in octets. The Value field depends on the TLV Type.
The Original SI-BitString TLV carries the set of BFER and carries the same BitString that Initiator includes in BIER header.This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 1 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Set ID | Sub-domain ID |BS Len| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Set ID field is set to the Set Identifier to which the BitString belongs to. This value is derived as defined in [RFC8279]
Sub-domain ID is set to the Sub domain value to which BFER in BitString belongs to.
BS Len is set based on the length of BitString as defined in [RFC8296]
The BitString field carries the set of BFR-IDs that Initiator will include in the BIER header. This TLV MUST be included by Initiator in Echo Request packet
The Target SI-BitString TLV carries the set of BFER from which the Initiator expects the reply from.This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 2 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Set ID | Sub-domain ID |BS Len| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Set ID field is set to the Set Identifier to which the BitString belongs to. This value is derived as defined in [RFC8279]
Sub-domain ID is set to the Sub domain value to which BFER in BitString belongs to.
BS Len is set based on the length of BitString as defined in [RFC8296]
The BitString field carries the set of BFR-IDs of BFER(s) that Initiator expects the response from. The BitString in this TLV may be different from the BitString in BIER header and allows to control the BFER responding to the Echo Request. This TLV MUST be included by Initiator in BIER OAM packet if the Downstream Mapping TLV (section 3.3.4) is included.
The Incoming SI-BitString TLV will be included by Responder BFR in Reply message and copies the BitString from BIER header of incoming Echo Request message. This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 3 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Set ID | Sub-domain ID |BS Len| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Set ID field is set to the Set Identifier to which the BitString belongs to. This value is derived as defined in [RFC8279]
Sub-domain ID is set to the Sub domain value to which BFER in BitString belongs to.
BS Len is set based on the length of BitString as defined in [RFC8296]
The BitString field copies the BitString from BIER header of the incoming Echo Request. A Responder BFR SHOULD include this TLV in Echo Reply if the Echo Request is received with I flag set in Downstream Mapping TLV.
An Initiator MUST NOT include this TLV in Echo Request.
This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 4 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MTU | Address Type | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Downstream Address (4 or 16 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Downstream Interface Address (4 or 16 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-tlv Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . List of Sub-TLVs . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MTU
Type Addr. Type DA Length DIA Length ------- --------------- ---------- ---------- 1 IPv4 Numbered 4 4 2 IPv4 Unnumbered 4 4 3 IPv6 Numbered 16 16 4 IPv6 Unnumbered 16 4 DA Length - Downstream Address field Length DIA Length - Downstream Interface Address field Length
Address Type
Flags
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Rsvd |I|
+-+-+-+-+-+-+-+-+
When I flag is set, the Responding BFR MUST include the Incoming SI-BitString TLV in Echo Reply message.
Downstream Address and Downstream Interface Address
This section defines the optional Sub-TLVs that can be included in Downstream Mapping TLV.
Sub-TLV Type Value --------------- -------------- 1 Multipath Entropy Data 2 Egress BitString
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M| Reserved | |
+-+-+-+-+-+-+-+-+-+ |
| |
| (Multipath Information) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M Flag
Multipath Information
Responder BFR MAY include this Sub-TLV with the rewritten BitString in the outgoing interface as defined in section 6.1 of [RFC8279]
0 1 2 3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Set ID | Sub-domain ID |BS Len| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BFER replying to the request MAY include the Responder BFER TLV. This is used to identify the originator of BIER Echo Reply. This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 5 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | BFR-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
BFR-ID
Any transit BFR replying to the request MAY include the Responder BFR TLV. This is used to identify the replying BFR without BFR-ID. This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV Type = 6 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Address Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ BFR-Prefix (4 or 16 bytes) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length
Address Type
BFR-Prefix
The BFR replying to the request will include the Upstream Interface TLV. This is used to identify the incoming interface and the BIER-MPLS label in the incoming Echo Request. This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV Type = 7 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Address Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Upstream Address (4 or 16 bytes) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length
Address Type
Upstream Address
The Initiator BFR MAY include Reply-To TLV in the Echo Request. This is used by transit BFR or BFER when the reply mode is 2. The IP address will be used to generate the Echo Reply. This TLV has the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV Type = 8 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Address Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Reply-To Address (4 or 16 bytes) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length
Address Type
Reply-To Address
The size of Entropy field in BIER header is 20 bits as defined in section 2 of [RFC8296]. This is similar to Multipath Type 9 encoding defined in Section 3.4.1.1.1 of [RFC8029].
This section describes aspects of Ping and traceroute operations.
A BIER OAM packet MUST be sent to BIER control plane for OAM processing if one of the following conditions is true:
As defined in [RFC8279], BIER follows the unicast forwarding path and allows load balancing over ECMP paths between BFIR and BFER. BIER OAM MUST support ECMP path discovery between a BFIR and a given BFER and MUST support path validation and failure detection of any particular ECMP path between BFIR and BFER.
[RFC8296] proposes the BIER header with Entropy field that can be leveraged to exercise all ECMP paths. The Initiator/BFIR will use traceroute message to query each hop about the Entropy information for each downstream paths. To avoid complexity, it is suggested that the ECMP query is performed per BFER by carrying required information in BIER OAM message.
The Initiator MUST include Multipath Entropy Data Sub-TLV in Downstream Mapping TLV. It MUST also include the BFER in BitString TLV to which the Multipath query is performed.
Any transit BFR will reply with Bit-masked Entropy for each downstream path as defined in [RFC8029]
The Initiator MUST set the Message Type as 1 and Return Code as 0. The Proto field in OAM packet MUST be set to 0. The choice of Sender's Handle and Sequence number is a local matter to the Initiator and SHOULD increment the Sequence number by 1 for every subsequent Echo Request. The QTF field is set to Initiator's local timestamp format and TimeStamp Sent field is set to the time that the Echo Request is sent.
The Initiator MUST include Original SI-BitString TLV. The Initiator MUST NOT include more than one Original SI-BitString TLV. The Initiator infers the Set Identifier value and Sub-domain ID value from the respective BitString that will be included in BIER header of the packet and includes the values in "SI" and Sub-Domain ID fields respectively.
In Ping mode, the Initiator MAY include Target SI-BitString TLV to control the responding BFER(s) by listing all the BFERs from which the Initiator expects a response. In trace route mode, the Initiator MAY include Target SI-Bitstring TLV to control the path trace towards any specific BFER or set of BFERs. The Initiator on receiving a reply with Return code as "Replying BFR is the only BFER in header Bitstring" or "Replying router is one of the BFER in header Bitstring", SHOULD unset the respective BFR-id from Target SI-BitString for any subsequent Echo Request.
When the Reply mode is set to 2, the Initiator MUST include Reply-To TLV (section 3.3.8) in the Echo Request. The Initiator MUST also listen to the UDP port defined in this TLV and process any segment received with destination port as the value defined in the TLV and sent to control plane for BIER OAM payload processing.
The Initiator MAY include Downstream Mapping TLV (section 3.3.4) in the Echo Request to query additional information from transit BFRs and BFERs. In case of ECMP discovery, the Initiator MUST include the Multipath Entropy Data Sub-TLV and SHOULD set the Target SI-BitString TLV carrying a specific BFER ID.
The Initiator MUST encapsulate the OAM packet with BIER header and MUST set the Proto as 5 and further encapsulates with BIER-MPLS label. In ping mode, the BIER-MPLS Label TTL MUST be set to 255. In traceroute mode, the BIER-MPLS Label TTL is set successively starting from 1 and MUST stop sending the Echo Request if it receives a reply with Return code as "Replying router is the only BFER in BIER header Bitstring" from all BFER listed in Target SI-BitString TLV.
Sending a BIER OAM Echo Request to control plane for payload processing is triggered as mentioned in section 4.1.
Any BFR on receiving Echo Request MUST perform the basic sanity check. If the BFR cannot parse the OAM Dependent data payload completely if the OAM Message Length is incorrect. BFR MUST send Echo Reply with Return Code set to "Malformed Echo Request received" if the OAM Message Length is incorrect. If the packet sanity check is fine, it SHOULD initiate the below set of variables:
Reply-Flag
Interface-I
BIER-Label-L
Header-H
BFR MUST initialize Best-return-code variable to null value.
BFR will populate Interface-I with interface over which the Echo Request is received, the top label in the MPLS stack of the received Echo Request to BIER-Label-L, and the BIER header to BIER-Header. If the received Echo Request carries Target SI-BitString TLV, a BFR SHOULD run boolean AND operation between BitString in Header-H and BitString in Target SI-BitString TLV. If the resulting BitString is all-zero, reset Reply-Flag=0 and go to section 4.5. Else:
If Reply-Flag=0; BFR MUST release the variables and MUST not send any response to the Initiator. If Reply-Flag=1, proceed as below:
The Responder BFR SHOULD include the BitString from Header-H to Incoming SI-BitString TLV and include the Set ID, Sub-domain ID and BS Len that corresponds to BIER-Label-L. Responder BFR SHOULD include the Upstream Interface TLV and populate the address from Interface-I.
When the Best-return-code is "Replying BFR is one of the BFER in header Bitstring", it MUST include Responder BFER TLV.
When the Best-return-code is "Replying BFR is the only BFER in header Bitstring", it MUST include Responder BFER TLV.
Responder MUST set the Message Type as 2 and Return Code as Best-return-code. The Proto field MUST be set to 0.
The Echo Reply can be sent either as BIER-encapsulated or IP/UDP encapsulated depending on the Reply mode in received Echo Request. When the Reply mode in received Echo Request is set to 3, Responder appends BIER header listing the BitString with BFIR ID (from Header-H), set the Proto to 5 and set the BFIR as 0. When the Reply mode in received Echo Request is set to 2, Responder encapsulates with IP/UDP header. The UDP destination port MUST be set to TBD1 and source port MAY be set to TBD1 or other random local value. The source IP is any local address of the responder and destination IP is derived from Reply-To TLV.
The Initiator on receiving Echo Reply will use the Sender's Handle to match with Echo Request sent. If no match is found, the Initiator MUST ignore the Echo Reply.
If receiving Echo Reply have Downstream Mapping, the Initiator SHOULD copy the same to subsequent Echo Request(s).
If one of the Echo Reply is received with Return Code as "Replying BFR is one of the BFER in header Bitstring", it SHOULD reset the BFR-id of the responder from Target SI-BisString TLV in subsequent Echo Request.
This document request UDP port TBD1 to be allocated by IANA for BIER Echo.
This document request the IANA for creation and management of below registries and sub-registries:
IANA is requested to create and maintain "BIER OAM Parameters" registry.
IANA is requested to create "Message Type" sub-registry under "BIER OAM Parameters" registry and assign the Message Types defined in section 3.1
IANA is requested to also create "Echo Reply Mode" sub-registry under "BIER OAM Parameters" registry and assign the Echo Reply Modes defined in section 3.1
IANA is requested to create "Echo Return Codes" sub-registry under "BIER OAM Parameters" registry and assign the Return Codes defined in section 3.2
The TLVs and Sub-TLVs defined in this document is not limited to Echo Request or Reply message types and is applicable for other message types. The TLVs and Sub-TLVs requested by this document for IANA consideration are the following:
Type Sub-Type Value Field
------- -------- -----------
1 Original SI-BitString
2 Target SI-BitString
3 Incoming SI-BitString
4 Downstream Mapping
4 1 Multipath Entropy Data
4 2 Egress BitString
5 Responder BFER
6 Responder BFR
7 Upstream Interface
The security consideration for BIER Ping is similar to ICMP or LSP Ping. As like ICMP or LSP ping, BFR may be exposed to Denial-of-Service (DoS) attacks and it is RECOMMENDED to regulate the BIER Ping packet flow to control plane. A rate limiter SHOULD be applied to avoid any attack.
As like ICMP or LSP Ping, a traceroute can be used to obtain network information. It is RECOMMENDED that the implementation checks the integrity of BFIR of the Echo messages against any local secured list before processing the message further
The authors would like to thank Antoni Przygienda, Eric Rosen, Faisal Iqbal Jeffrey (Zhaohui) Zhang and Shell Nakash for their review and comments.
The authors would like to thank Mankamana Mishra for this thorough review and comments.
| [RFC0792] | Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, September 1981. |
| [RFC6291] | Andersson, L., van Helvoort, H., Bonica, R., Romascanu, D. and S. Mansfield, "Guidelines for the Use of the "OAM" Acronym in the IETF", BCP 161, RFC 6291, DOI 10.17487/RFC6291, June 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. |
| [RFC6425] | Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa, S. and T. Nadeau, "Detecting Data-Plane Failures in Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011. |