Operations, Administration and Maintenance (OAM) for Deterministic Networks (DetNet) with IP Data Plane
Ericsson
gregimirsky@gmail.com
Huawei
mach.chen@huawei.com
Dell EMC
176 South Street
Hopkinton, MA
01748
United States of America
david.black@dell.com
Routing
DetNet Working Group
Internet-Draft
DetNet
OAM
This document defines the principles for using Operations, Administration, and Maintenance protocols and mechanisms in the
Deterministic Networking networks with the IP data plane.
Introduction
introduces and explains Deterministic Networks (DetNet)
architecture.
Operations, Administration and Maintenance (OAM) protocols are used to detect, localize defects in the network,
and monitor network performance. Some OAM functions, e.g., failure detection, work in the
network proactively, while others, e.g., defect localization, usually performed on-demand.
These tasks achieved by a combination of active and hybrid, as defined in ,
OAM methods.
lists the functional requirements toward OAM for DetNet domain.
The list can further be used for gap analysis of available OAM tools to identify
possible enhancements of existing or whether new OAM tools are required to
support proactive and on-demand path monitoring and service validation.
Also, the document defines the OAM use principals for the
DetNet networks with the IP data plane.
Conventions used in this document
Terminology
The term "DetNet OAM" used in this document interchangeably with longer version
"set of OAM protocols, methods and tools for Deterministic Networks".
DetNet Deterministic Networks
DiffServ Differentiated Services
OAM: Operations, Administration and Maintenance
PREF Packet Replication and Elimination Function
POF Packet Ordering Function
RDI Remote Defect Indication
ICMP Internet Control Message Protocol
Underlay Network or Underlay Layer: The network that provides
connectivity between the DetNet nodes. MPLS network providing LSP
connectivity between DetNet nodes is an example of the underlay layer.
DetNet Node - a node that is an actor in the DetNet domain. DetNet
domain edge node and node that performs PREF within the domain are
examples of DetNet node.
Keywords
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 BCP 14
when, and only when, they appear in all capitals, as shown here.
Active OAM for DetNet Networks with the IP Data Plane
OAM protocols and mechanisms act within the data plane of the particular networking layer.
And thus it is critical that the data plane encapsulation
supports OAM mechanisms in such a way that DetNet OAM packets are in-band with a DetNet flow
being monitored, i.e., DetNet OAM test packets follow precisely the same path as
DetNet data plane traffic both for unidirectional and bi-directional DetNet paths.
The DetNet data plane encapsulation in a transport network with IP encapsulations specified
in Section 6 of .
For the IP underlay network, DetNet flows are identified
by the ordered match to the provisioned information set that, among other elements, includes the IP protocol, source port number,
destination port number. Active IP OAM
protocols like Bidirectional Forwarding Detection (BFD) or STAMP ,
use UDP transport and the well-known UDP port numbers as the destination port. Thus a DetNet node MUST be
able to associate an IP DetNet flow with the particular test session to ensure that test packets experience the
same treatment as the DetNet flow packets.
Most of on-demand failure detection and localization in IP networks is being done by using the Internet Control Message Protocol (ICMP)
Echo Request, Echo Reply and the set of defined error messages, e.g., Destination Unreachable, with the more detailed information provided through code points.
and define the ICMP for IPv4 and IPv6 networks, respectively. Because ICMP is another IP protocol like, for example,
UDP, a DetNet node MUST able to associate an ICMP packet generated by the specified IP DetNet node and addressed to the another IP DetnNet node
with an IP DetNet flow between this pair of endpoints.
Active OAM Using DetNet-in-UDP Encapsulation
Active OAM in IP DetNet can be realized using DetNet-in-UDP encapsulation [Ed.note: Do we define it in this document or start a new one?].
Using DetNet-in-UDP tunnel between IP DetNet nodes ensures that active OAM test packets are fate-sharing with the monitored
IP DetNet flow packets. As a result, a test packet shares the tunnel with the IP DetNet flow and shares the fate, statistically speaking, of the IP DetNet flow being monitored.
Mapping Active OAM and IP DetNet flows
IP OAM protocols that use UDP transport, e.g., BFD and STAMP, can be used to detect failures or performance degradation that affects an IP DetNet flow.
When the UDP destination port number used by the OAM protocol is one of the assigned by IANA, then the UDP source port can be used to achieve co-routedness
of OAM, and the monitored IP DetNet flow in the multipath environments, e.g., LAG or ECMP. To maximize the accuracy of OAM results in detecting failures and
monitoring performance of IP DetNet, test packets should receive the same treatment by the nodes as experienced by the IP DetNet packet. Hence, the DSCP
value used for a test packet MUST be mapped to DetNet.
Active OAM Using GRE-in-UDP Encapsulation
has defined the method of encapsulating GRE (Generic Routing Encapsulation) headers
in UDP. GRE-in-UDP encapsulation can be used for IP DetNet OAM as it eases the task of mapping an OAM test session
to a particular IP DetNet flow that is identified by N-tuple. Matching a GRE-in-UDP tunnel to the monitored IP DetNet flow
enables the use of Y.1731/G.8013 as a comprehensive toolset of OAM. The Protocol Type field
in GRE header MUST be set to 0x8902 assigned by IANA to IEEE 802.1ag Connectivity Fault Management (CFM) Protocol / ITU-T Recommendation Y.1731.
Y.1731/G.8013 supports necessary for IP DetNet OAM functions, i.e., continuity check, one-way packet loss and packet delay measurement.
OAM of DetNet IP Interworking with OAM of non-IP DetNet domains
A domain in which IP data plane provides DetNet service could be used
in conjunction with a TSN and a DetNet domain with MPLS data plane to deliver end-to-end service.
In such scenarios, the ability to detect defects and monitor performance using OAM is essential.
identified two OAM interworking models - peering and tunneling.
Interworking between DetNet domains with IP and MPLS data planes analyzed in Section 6.2 of .
Also, requirements and recommendations for OAM interworking between a DetNet domain with MPLS data plane and OAM of a TSN
equally apply to a DetNet domain with an IP data plane.
IANA Considerations
This document does not have any requests for IANA allocation. This section can be deleted before the publication of the draft.
Security Considerations
This document describes the applicability of the existing Fault Management and
Performance Monitoring IP OAM protocols,
and does not raise any security concerns or issues in addition to ones common to networking or
already documented for the referenced DetNet and OAM protocols.
References
Normative References
Informational References
Operations, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks
ITU-T