Operations, Administration and Maintenance (OAM) for Overlay Networks: Gap Analysis

Operations, Administration, and Maintenance (OAM) toolset provides methods for fault management and performance monitoring in each layer of the network, in order to improve their ability to support services with guaranteed and strict Service Level Agreements (SLAs) while reducing operational costs. provided detailed analysis of OAM protocols. Since its completion several new protocols that define data plane encapsulation were introduced. That presented both need to re-evaluate existing set of OAM tools and opportunity to build it into set of tools that can be used and re-used for different data plane protocols. Overlay OAM Requirements define the set of requirements for OAM in Overlay networks. The OAM solution for Overlay networks, developed by the design team, has two objectives: The Overlay OAM toolset should be developed based on existing IP and IP/MPLS architecture, technology, and toolsets. The Overlay OAM operational experience should be similar to that in other, e.g. IP and IP/MPLS, networks. The Overlay OAM toolset may use some or all of the following OAM protocols designed at IETF: proactive continuity check: Bidirectional Forwarding Detection (BFD) for point-to-point as defined in , , , , , and ; BFD for multipoint network as defined in and ; S-BFD as defined in and ; on-demand continuity check and connectivity verification: MPLS Echo Request/Reply, a.k.a. LSP Ping, as defined in and its numerous extensions; LSP Self-ping, as defined in ; is a good example of generic troubleshooting and defect localization tool that can be extended and suited for more specific requirements of the particular type of an overlay network; performance measurement: packet loss and delay measurement in MPLS networks, as defined in with ability to export measurement results for post-processing ; Two-Way Active Measurement Protocol (TWAMP), as defined in , , and ; use of the Marking Method that, if accordingly supported by the overlay layer, can behave as close as technically possible to a passive method to measure performance, e.g. .

Term "Overlay OAM" used in this document interchangeably with longer version "set of OAM protocols, methods and tools for Overlay networks". BFD Bidirectional Forwarding Detection FM Fault Management OAM Operations, Administration, and Maintenance PM Performance Measurement SLA Service Level Agreement TWAMP Two-Way Active Measurement Protocol

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in .

Protocols that enable Fault Management functions of OAM toolset are comprised of protocols that perform proactive and on-demand defect detection and failure localization.

Bidirectional Forwarding Detection (BFD) is the protocol of choice for proactive Continuity Check and Connectivity Verification .

. Bit-Indexed Explicit Replication (BIER) provides the multicast service. For that BFD over multipoint network and are the most suitable of BFD family presents IP/UDP format of BFD over BIER in MPLS network.

Proto field MUST be set to IPv4 or IPv6 vlalue. Note that IP Destination address in must follow Section 7 , i.e. ?the destination IP address MUST be randomly chosen from the 127/8 range for IPv4 and from the 0:0:0:0:0:FFFF:7F00/104 range for IPv6.? BFD packets in the reverse direction of the BFD session will be transmitted on IP network to the IP address mapped to the BFIR-id and the destination UDP port number set as source UDP port number of the received BFD packet. IP/UDP format presents overhead, particularly in case of IPv6 address family. Thus option to avoid use of extra headers for OAM seems attractive. presents G-ACh format of BFD over BIER in MPLS network. Proto field of the BIER header MUST be set to OAM value. BFD control packet follows the BIER OAM header as defined in . According to the Section 3.1 of , Ver is set to 1; BFD control packet over multi-point without or with active tail accordingly identified in Message Type Field. The Proto field ?is used to define if there is any data packet immediately following the OAM payload?.

defines format of Echo Request/Reply control packet and set of TLVs that can be used to perform failure detection and isolation in BIER domain over MPLS network.

describes how the Marking Method can be used in BIER domain over MPLS networks.

Excessive use of the in-band OAM channel may affect user flow and thus change network behavior. For example, if operator uses passive measurement exporting massive amount of data over the OAM channel may affect network. I think that a management channel should be used in such case. Obviously it may traverse the same nodes and links but may not require the same QoS. We can refer to LMAP Reference Model with Controller, Measurement Agent and Data Collector. proposes transport independent generic telemetry probe structure.

This document does not propose any IANA consideration. This section may be removed.

This document list the OAM requirement for BIER-enabled domain and does not raise any security concerns or issues in addition to ones common to networking.

TBD