Internet DRAFT - draft-li-ippm-ioam-path-protection
draft-li-ippm-ioam-path-protection
IPPM Z.LI. Li, Ed.
Internet-Draft CAICT
Intended status: Experimental 9 January 2023
Expires: 13 July 2023
IOAM Linkage Solution for the Protection Cases of 5G Bearer Network
draft-li-ippm-ioam-path-protection-02
Abstract
In-band operation and maintenance management (IOAM, In-band OAM), as
a network performance monitoring technology, is based on the
principle of path-associated detection to perform specific field
marking/coloring and identification on actual service flows, and
perform packet loss and delay measurement. It can quickly perceive
network performance-related faults, and accurately delimit boundaries
and do troubleshooting. However, the current IOAM solution has
shortcomings too. For example, after the service traffic path
switching, the IOAM cannot continue working. This paper proposes a
scheme to achieve automatic performance monitoring through service
path switching and linkage with IOAM, which enhances the feasibility
of the IOAM scheme in large-scale deployment and the completeness of
IOAM technology.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 13 July 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. IOAM basic processing analysis . . . . . . . . . . . . . . . 3
3. The impact of service path switching on IOAM . . . . . . . . 4
3.1. Analysis of Service Protection Mechanism . . . . . . . . 4
3.2. The impact of service path switching on IOAM . . . . . . 5
3.3. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. IOAM monitoring is associated with service path . . . . . . . 7
4.1. Key points of the linkage solution . . . . . . . . . . . 7
4.1.1. Service path changes notice IOAM module . . . . . . . 7
4.1.2. Reconfigure mechanism . . . . . . . . . . . . . . . . 7
4.2. The process of the linkage solution . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
In-band operation and maintenance management (In-band OAM, IOAM) is a
flow monitoring technology with high accuracy. It does not need to
use out-of-band monitoring messages, and measures network KPIs such
as packet loss and delay directly. But there are also shortcomings:
in the current solution, performance monitoring can only be performed
based on traffic quintuple information (pre-configuration or learning
from traffic flow). If the path of this flow changes, it cannot
working in most cases. However, In real network , the service flow
path is not stable. There are many reasons for the change of the
flow path, such as the interruption of the working fiber link in the
network and the error code exceeding the threshold, or switching
traffic to the backup link temporarily because of the equipments'
upgrade. Regardless of the cause of the service traffic path
switching, it is of great significance to monitor the performance on
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the new path after the switching automatically. Service path
switching is a key event in the network. If the switched service
path is not monitored in real time, it is impossible to guarantee
that the switched path can meet the requirements of the upper-layer
service; on the contrary, if the IOAM performance monitoring of the
switched path can be used to detect the deterioration of the network
KPI after the switch in time , the operator may optimize and adjust
the service path as soon as possible. Except for the manual and
planned switching, it is difficult to predict the time for other
switching caused by network failures, which will also cause the
network operator to be unable to redeploy and start IOAM performance
monitoring in time after the switching.
1.1. 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].
1.2. Terminology
IOAM:In-band Operation And Maintenance Management
KPI:Key Performance Indicator
HSB:Hot Standby
APS:Automatic Protect Switch
Ti-LFA:Topology Independent Loop Free Alternate
SD:Signal Degrade
UNI:User Network Interface
NNI:Network Network Interface
2. IOAM basic processing analysis
IOAM Data collection and analysis process is shown in the figure1:
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+---------------------+
----------| Statistical analysis|--------
| | module for IOAM | |
| +---------------------+ |
| | |
| | |
| | |
+---------+ +---------+ +--------+
---->| Ingress |---------| Transit |---------| Egress |------>
| PE | | P | | PE |
+---------+ +---------+ +--------+
Figure 1
IOAM Data collection and analysis process
* At the ingress PE, the UNI side uses ACL to match the quintuple
information of the service flow, dyes the matched traffic packets
and sends the statistics to the statistical analysis module in the
network controller. The NNI side encapsulates the IOAM header and
service label (SR-TE/SR-BE and VPN label);
* The P device reads the IOAM header information (Flow ID and
colored bit information). The IOAM header is inside the SR label
and the VPN label, and there is no need to decapsulate and
recapsulate it to avoid too much impact on the forwarding
performance; this step only involves hop-by-hop monitoring, not
end-to-end monitoring.
* At the egress PE, decapsulate the packet, read the information in
the IOAM header, report to the statistical analysis module, and
then send the original user payload from the UNI side;
* The statistical analysis module combines the topology information
to perform statistical analysis on the data sent by the network
equipments, and present it through reports or graphics.
3. The impact of service path switching on IOAM
3.1. Analysis of Service Protection Mechanism
If it is an automatic switching triggered by a network failure, it
can be divided into signal failure (SF, often caused by line fiber
break, equipment power failure), signal degradation (SD, line error
or packet loss over the threshold of performance availability, due to
aging of fiber. Switching occurs when the error rate or the
accumulated packet loss rate reaches the detection threshold). Fiber
breakage, power failure of P node, and SD error codes will trigger
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HSB or APS switching (for SR-TE tunnel) or Ti-LFA protection (for SR-
BE tunnel), the tail node power failure will trigger VPN FRR(Fast
reroute) protection.
If the switching is triggered because of network expansion, upgrade,
etc., the switching mechanism is basically the same as the network
failure trigger, and the impact on IOAM is also the same, so it will
not be analyzed separately.
3.2. The impact of service path switching on IOAM
As shown in Figure2 below, network equipments A, C, and G are PE
devices; B ,E and F are P devices, and D is CE devices. Under normal
condition, services are forwarded through the working tunnel path,
which is A-B-C-D ; The protection tunnel path is A-E-F-G-C-D (one by
one protection path of the tunnel), and the tail node protection path
is A-E-F-G-D.
+----+ +----+
+-------| B |------| C |------+
| +----+ +----+ |
+----+ | | |
gNB->| A | | | |
+----+ | | |
| | | +----+
| | | | D |---->5GC
+----+ | | +----+
| E | | | |
+----+ | | |
| +----+ +----+ |
+-------| F |------| G |------+
+----+ +----+
Figure 2
5G Bearer Network with Backup Path
1. When the working path is normal, configure IOAM end-to-end
instances on A and C respectively, or configure IOAM hop-by-hop
instances on A, B, and C to monitor the delay and packet loss.
2. Taking the L3VPN over SR-TE tunnel as an example, when the Node B
or the link between A and C fails, the HSB protection of the SR-
TE tunnel is triggered, and the service traffic switchs to
A-E-F-G-C-G, the end-to-end IOAM monitoring is not affected;
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because Node B fails , the hop-by-hop monitoring instance cannot
continue to obtain the data reported by B, so the relevant
configuration of the monitoring instance needs to be switched to
each node of the backup path, that is, the IOAM monitoring
instance needs to be newly configured at node E, F, and G.
3. When the node C fails, the VPN FRR protection is triggered.
Because the PE is switched to node G, the end-to-end and the hop
by hop monitoring instance will become invalid, and it is
impossible to continue to monitor the KPI of the service on the
protection path. IOAM monitoring needs to be newly configured at
nodes E, F, and G.
4. The statistical analysis module in the network controller
combines the topology information to perform statistical analysis
on the data sent by the network equipments, and present it
through reports or graphics.
3.3. Summary
From the above, it can be seen that the change in the flow direction
caused by the switching of the active and standby service paths will
directly affect the data collection and reporting of the IOAM
monitoring instance. Based on the existing solution, one way to
continue monitoring after the switch is to deploy IOAM monitoring on
all nodes of the active and standby paths. When there is no traffic
on the standby path, the nodes along the way do not report monitoring
data; whenever traffic reaches, the monitoring data will be reported
again. There are two issues with this solution: the first one is
that after the traffic is switched, because there is no linkage, the
upper-layer statistical analysis module in the controller does not
perceive the change of the service path, and does not know what the
real service path is, so it may not be able to calculate the result
of delay and packet loss normally; the second one is that it will
cause waste of IOAM resources configured on the device that no
traffic passes through. Therefore, if a certain linkage mechanism
can be established between the IOAM and the service path to
dynamically perceive this path change, and reconfigure in time,
continuous IOAM monitoring will be performed automatically when the
service path switches and recovers(except a short interruption during
the switching process), and no additional IOAM resources are
occupied.
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4. IOAM monitoring is associated with service path
4.1. Key points of the linkage solution
4.1.1. Service path changes notice IOAM module
When the service path changes, the IOAM management module in the
network controller can be notified through the alarms or events
reported by the device; in addition, after the IGP on the device
detects the network topology change, it will also notify network
controller to perform the topology refresh through the BGP-LS
protocol.
4.1.2. Reconfigure mechanism
a. Identify the equipment that needs to be configured:according to
the principle that the UNI interface on the access side(node
A,connect to gNB) will remain unchanged and the corresponding
relationship between the UNI interface -> VPN instance -> SR-TE/
SR-BE tunnel index, the corresponding tunnel path can be queried,
and then the node that needs to reconfigure the IOAM instance can
be determined; The UNI interface on the core side(node C and
G,connect to 5GC) may change due to the power failure or recovery
of the PE device(node C), so the nodes of the IOAM instance in
the downstream direction(5GC to gNB) cannot be queried in the
same way as in the upstream direction(gNB to 5GC), so how to get
the tunnel path and nodes in this direcion will be considered
later,and updated in new version of this draft. For nodes that
already have IOAM configuration, reconfiguration will not cause
problems.
b. Information and sources to be configured, as shown below:
* IOAM instance:End-to-end or hop-by-hop, unchanged before and
after switching
* Node type:PE or P, determined according to the tunnel path
information, the source and tail nodes are PE, and the others
are P
* Flow ID:The same before and after the switching
* Stream quintuple:The same before and after switching
* UNI interface and VLAN on the access side:The same before and
after switching
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* UNI interface and VLAN on the core side:To be disscussed in
new version of draft
* Telemetry configuration:Relatively fixed, generated by the
controller
c. Configuration protocol:Use Netconf protocol for configuration
delivery.
4.2. The process of the linkage solution
-------------------------------------------------------
| SDN Controller |
| -------2----------------- |
| | | |
| v v |
| +------+ +--------+ +------+ +--------------+ |
| |Alarm | |Topology| |IOAM | |IOAM statistic| |
| |manage| |manage |-2-|manage| |and analysis | |
| +------+ +--------+ +------+ +--------------+ |
|-----^----------^----------^------------^------------|
| | | |
|----------- | |
| | |
1| +----+ | +----+ |
| +---------| B |----|--| C |----|----+
v | +----+ | +----+ | |
+----+ | | |
---->| A | | | |
+----+ 3| 4| |
| | | +----+
| | | | D |---->
+----+ ------------------ +----+
| E | | |
+----+ v |
| +------+ +------+ |
+---------| F |------| G |------+
+------+ +------+
Figure 3
Process of IOAM and service path linkage scheme
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1. For link or node failure, perform the corresponding fast
switching (HSB/VPN FRR or Ti-LFA), and generate an alarm and send
it to the network controller. IGP also detects the topology
changes and reports to the controller through BGP-LS.
2. Alarm management module and topology management module in the
network controller notify the IOAM management module after
receiving the fast switching trigger event or alarm sent by
devices, or after the BGP-LS topology is refreshed.
3. The IOAM management module queries the tunnel path information
after the switching, and determines the node that needs to
reconfigure IOAM and the required information according to the
method in section 2) above: "Reconfigure mechanism", and perform
configuration provision.
4. The IOAM management module starts the monitoring instance, the
device reports the collected data with Telemetry, and the IOAM
statistical analysis module analyzes and presents the monitoring
results.
5. When the network failure recovers, the controller notifies the
IOAM management module to reconfigure according to the received
switching recovery event or BGP-LS topology refresh.
6. After the configuration of the IOAM management module is
completed, the monitoring instance is started, and the monitoring
results based on the restored path are presented.
5. Acknowledgements
TBD
6. IANA Considerations
This memo includes no request to IANA.
7. Security Considerations
TBD
8. References
8.1. Normative References
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[RFC2119] Bradner, S. and RFC Publisher, "Key words for use in RFCs
to Indicate Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
8.2. Informative References
[RFC8321] G.Fioccola, "Alternate-Marking Method for Passive and
Hybrid Performance Monitoring.", 2018,
<https://datatracker.ietf.org/doc/rfc8321/>.
[YDT38262021]
CCSA, "General Technical Requirements for Slicing Packet
Network(SPN).", 2021.
Author's Address
Zhenwen Li (editor)
CAICT
Beijing
China
Email: lizhenwen@caict.ac.cn
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