Internet DRAFT - draft-wang-ffd-framework
draft-wang-ffd-framework
Network Working Group H. Wang
Internet-Draft Huawei
Intended status: Informational F. Qin
Expires: 2 September 2024 China Mobile
L. Zhao
S. Chen
H. Huang
Huawei
1 March 2024
Framework of Fast Fault Detection for IP-based Network
draft-wang-ffd-framework-02
Abstract
The IP-based distributed system and software application layer often
use heartbeat to maintain the network topology status. However, the
heartbeat setting is long, which prolongs the system fault detection
time. IP-based storage network is the typical usage of that
scenario. When the IP-based storage network fault occurs, NVMe
connections need to be switched over. Currently, no effective method
is available for quick detection, switchover is performed only based
on keepalive timeout, resulting in low performance.
This document defines the basic framework of how network assisted
host devices can quickly detect application connection failures
caused by network faults.
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].
Status of This Memo
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/.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Reference Models . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Small-scale SAN . . . . . . . . . . . . . . . . . . . . . 4
3.2. Large-scale SAN . . . . . . . . . . . . . . . . . . . . . 5
4. Functional Components . . . . . . . . . . . . . . . . . . . . 6
4.1. Storage Device . . . . . . . . . . . . . . . . . . . . . 6
4.2. Host . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.3. Network Device . . . . . . . . . . . . . . . . . . . . . 7
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Network Deployment . . . . . . . . . . . . . . . . . . . 7
5.2. Storage and Host Access . . . . . . . . . . . . . . . . . 7
5.3. Status Infomation Sync And Notification . . . . . . . . . 8
5.3.1. Access Link Failure . . . . . . . . . . . . . . . . . 8
5.3.2. Network Link or Device Failure . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Today, distributed systems based on network communication are widely
used. In order to ensure that both ends of the distributed system
can perceive faults, heartbeat is a common technology. However,
relying on the heartbeat to detect whether the peer is faulty also
faces challenges: if the heartbeat is set too short, it may be
misjudged by network disturbances; if the heartbeat is set too long,
when a fault occurs, it will not be found for a long time.
Application scenarios such as IP-based NVMe, distributed storage, and
cluster computing are typical scenarios for such technologies.
The [I-D.guo-ffd-requirement] describes the problems of the current
IP-based NVMe solution. On an IP-based storage area network, if the
access link of a storage device is faulty, hosts cannot access the
storage device. Because the host cannot directly detect the fault,
the host has to wait for the KA timeout. To speed up fault
detection, hosts and storage devices can implement fast KA or BFD.
However, this solution introdueced additional cost on hosts and
storage devices and is hard to use in large-scale IP-based storage
area network. In fact, the IP network can directly detect these
faults, so we can use the IP network to assist these access endpoints
to quickly perceive the fault, so as to perform quickly service
recovery.
2. Terminology
NoF : NVMe of Fabrics
FC : Fiber Channel
NVMe : Non-Volatile Memory Express
SAN: Storage Area Network
3. Reference Models
The frame solution here is applicable to the system where the
terminals are directly connected to the IP network.
+--------+ +-----------+ +-----------+ +--------+
|Terminal|----| IP Network|-----| IP Network|----|Terminal|
| Device | | Device | | Device | | Device |
+--------+ +-----------+ +-----------+ +--------+
Figure 1 : Basic framework
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Terminals are connected to the IP network, and they establish IP
connections through the reachability provided by the IP network.
When the connection path fails, they cannot be detected quickly.
They can only detect it after the keep-alive timeout, and then can
carry out service protection processing. This time may be relatively
long. Therefore, it is necessary to notify the terminal device of
some failures in the network, such as access port failures and
internal network failures that will cause IP connection failures
between terminals, so that the terminal device can respond quickly
and perform corresponding service processing.
As introduced in Introduction, there are scenarios such as IP-based
NVMe, distributed storage, and cluster computing. Here we take IP-
based NVME as a typical scenario for introduction, and the processing
behavior of other scenarios is similar.
An IP-based storage area network mainly includes three types of
roles:
o Initiator, the terminal device, is also called the host.
o Switch, which is a network device used to access terminal devices.
o Target is also a terminal device, also known as a storage device.
The host and storage devices use the Ethernet-based NVMe protocol to
transmit data through the IP network to provide high-performance
storage services.
3.1. Small-scale SAN
+--+ +--+
Host |H1| |H2|
(Initiator) +-,+ +_.+
| `', _-` |
| _-` |
| _-` `', |
IP +----+ +----+
Network | SW1| | SW2|
+---,+ +_.--+
| `', _-` |
| `', |
| _-` `', |
Storage +-`+ +`'+
(Target) |S1| |S2|
+--+ +--+
Figure 1 : Small-scale SAN
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This is the basic model for small-scale storage access networks.
Hosts and storage devices are dual-homed to different switches.
When the access link of the storage device is faulty, the host needs
to quickly detect the fault so that the NVMe connection can be
quickly switched to the standby path.
3.2. Large-scale SAN
+--+ +--+ +--+ +--+
Host |H1| |H2| |H3| |H4|
(Initiator) +/-+ +-,+ +.-+ +/-+
| | '. ,-`| |
| | `', | |
| | ,-` '. | |
+-\--+ +--`-+ +`'--+ +-\--+
| SW1| | SW2| | SW3| | SW4|
+--,-+ +---,, +,.--+ +-.--+
`. `'.,` .`
`. _,-'` ``'., .`
IP +--'`+ +`-`-+
Network | SW5| | SW6|
+--,,+ +,.,-+
.` `'., ,.-`` ',
.` _,-'` `.
+--`-+ +--'`+ `'---+ +-`'-+
| SW7| | SW8| | SW9| |SW10|
+-.,-+ +-..-+ +-.,-+ +-_.-+
| '. ,-` | | `., .' |
| `', | | '.` |
| ,-` '. | | ,-` `', |
Storage +-`+ `'\+ +-`+ +`'+
(Target) |S1| |S2| |S3| |S4|
+--+ +--+ +--+ +--+
Figure 2 : Large-scale SAN
This is a relatively large-scale storage network which applies to a
large-scale storage device access network.
When the access link of the storage device is faulty, the host needs
to quickly detect the fault so that the NVMe connection can be
quickly switched to the standby path.
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4. Functional Components
The NVMe IP-based SANs consists of storage devices, hosts and
switches. Hosts and storage devices need to obtain required fault
information from the IP network. Switches need to synchronize
locally detected fault information on the IP network so that other
switches can obtain the faults and notify hosts or storage devices
that require the fault infomation.
4.1. Storage Device
As the server side, storage devices provide storage access services
for hosts. If a storage device is connected to an IP network and is
interested in the status of other devices, the storage device can
initiate a subscription request to the connected switch to obtain
status notifications of other devices from the access switch.
To reduce the complexity of storage devices, it's suggest to extend
the LLDP protocol to support subscription from storage devices to
switches and use the new L2-based protocol to notify the switch of
status to the storage device.
+-------+ +------+
|Storage| |Switch|
+-------+ +------+
| Subscribe Msg |
| ----------------------->|
| |
| Notification Msg |
| <-----------------------|
| |
| |
Figure 3 : Storage Device
4.2. Host
The host is the client of the storage device. As the client side, a
host needs to quickly obtain the service status of the storage device
that provides services. When the host receives a notification
message from the switch indicating that the storage device is faulty,
the host will quickly disconnect from the storage device and switch
to a redundant one.
The recommended protocol on the host side is the same as that on the
storage device.
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+-------+ +------+
| HOST | |Switch|
+-------+ +------+
| Subscribe Msg |
| ----------------------->|
| |
| Notification Msg |
| <-----------------------|
| |
| |
Figure 4 : Host Device
4.3. Network Device
Switches can quickly detect local faults and synchronize the faults
to other switches on the IP network. After detecting a fault, the
switch needs to notify the required host or storage device of the
fault.
+------+ +------+
|Switch| |Switch|
+------+ +------+
| Information Sync |
| ----------------------->|
| |
| |
| |
Figure 5 : Network Device
5. Procedures
5.1. Network Deployment
The IP-based SAN uses the standard Ethernet technolog. Network
deployments typically use the current IP technologies. For example,
OSPF is usually deployed as an underlay protocol.
5.2. Storage and Host Access
Hosts and storage devices are connected to the ethernet network. The
administrator assigns access IP addresses to the hosts and storage
devices. In most scenarios, these routes can be advertised through
the underlay protocol. In addition, after hosts and storage devices
go online, they needs to send subscription requests to the switch to
obtain the status information of the target device.
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To prevent hosts or storage devices from being aware of extra IP
address, it is recommended that LLDP be used to implement this
message.
5.3. Status Infomation Sync And Notification
When hosts and storage devices go online, the switch can calculates
an initial state of these devices and synchronizes the state on the
IP network.
After detecting a local fault, the switch needs to notify other
access devices that need the fault information. In addition, the
switch needs to synchronize the fault information to other switches
on the network. To ensure that synchronization messages can be
reliably synchronized to other switches, a reliable transmission
protocol, such as TCP or Quic, must be used. For large-scale IP
networks, hierarchical synchronization can be used to reduce the
number of sessions between switches.
The synchronization information about the host and storage devices
belongs to the application layer's information.
+-------+ +----+ +------+ +----+ +-------+
| HOST |-----------|TOR1|------|Spine1|------|TOR3|---------|Storage|
+---/---+ +-/--+ +--/---+ +-/--+ +---/---+
|---------------->| Info Sync | Info Sync |<---------------|
| SubscribeMsg |----------->|<-----------| Subscribe Msg |
| |<-----------|----------->| |
|<----------------| Info Sync | Info Sync | |
|Notification Msg | | | |
| | | | |
Figure 7 : Information Advertisement
5.3.1. Access Link Failure
When an access link is faulty, the access switch detects the fault.
Based on the faulty link, the access switch can calculate the devices
whose IP addresses are affected. The access switch advertises the
faulty IP address information on other access links. The switch
synchronizes the faulty IP address information on the IP network
based on the computation result. After receiving the synchronized
fault information, other switches notify the access host or storage
device of the fault information.
5.3.2. Network Link or Device Failure
ECMP or redundant link protection is usually deployed to prevent this
failure.
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6. Security Considerations
In order to control the communication range of information and reduce
the negative impact of possible information flooding, the Subscribe
Msg and Notification Msg considered in this framework are suggested
to be implemented through the L2 extension protocol, so that the
sending and receiving of this information will only be controlled by
the access network device within the domain. At the same time, the
network device is not allowed to forward this message, only allowed
to receive or send such message as needed.
For the communication protocol between network devices, in order to
ensure its security, it can be encrypted by commonly used encryption
technology, including but not limited to TCP-AO, TLS and other
technologies.
7. IANA Considerations
This document makes no request of IANA.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "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
[I-D.guo-ffd-requirement]
Guo, L., Feng, Y., Zhao, J., Qin, F., Zhao, L., Wang, H.,
and W. Quan, "Requirement of Fast Fault Detection for IP-
based Network", Work in Progress, Internet-Draft, draft-
guo-ffd-requirement-01, 9 March 2023,
<https://datatracker.ietf.org/doc/html/draft-guo-ffd-
requirement-01>.
Authors' Addresses
Haibo Wang
Huawei
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: rainsword.wang@huawei.com
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Fengwei Qin
China Mobile
Beijing
China
Email: qinfengwei@chinamobile.com
Lily Zhao
Huawei
No. 3 Shangdi Information Road
Beijing
100085
P.R. China
Email: Lily.zhao@huawei.com
Shuanglong Chen
Huawei
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: chenshuanglong@huawei.com
Hongyi Huang
Huawei
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: hongyi.huang@huawei.com
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