Network Working Group J. Li
Internet Draft China Mobile
Intended status: Standards Track C. Lin
Expires: August 18, 2025 New H3C Technologies
March 4, 2025
BGP-Link State (BGP-LS) Advertisement of Flow Queue
draft-li-idr-bgpls-flow-queue-00
Abstract
In the traffic congestion management of routers, queueing technology
is generally used to classify and transmit traffic. Therefore, queue
information indirectly reflects the congestion status of the router.
This document makes the necessary expansion of the BGP-LS mechanism
to send queue information to the network controller in a scalable
way, enabling the network controller to understand the router's
traffic congestion status and make appropriate adjustments to the
network traffic.
Status of this Memo
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This Internet-Draft will expire on August 18, 2025.
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Table of Contents
1. Introduction...................................................2
1.1. Requirements Language.....................................3
2. BGP-LS Extensions for Queue Information Advertisement..........3
2.1. BGP-LS Queue Link NLRI....................................4
2.1.1. Queue Descriptors Sub-TLVs...........................5
2.2. Queue Attribute TLVs......................................5
2.2.1. Queue Depth TLV......................................5
2.2.2. Queue Precedence TLV.................................6
2.2.3. Queue Length TLV.....................................6
3. Operational Considerations.....................................7
4. Security Considerations........................................7
5. IANA Considerations............................................7
6. References.....................................................8
6.1. Normative References......................................8
Author's Address..................................................9
1. Introduction
In complex network forwarding processes, when the maximum resources
supported by network equipment cannot meet the resources required
for normal forwarding, a phenomenon known as traffic congestion
occurs, causing negative impacts such as latency and jitter in
traffic transmission, leading to a decline in network service
quality.
As networks become increasingly complex, traffic congestion within
the network is inevitable. To alleviate congestion, a scheduler
policy needs to be formulated to determine the processing order of
packet forwarding. This scheduler policy generally adopts queue
technology, using a queue algorithm to classify traffic and a
precedence algorithm to send traffic. Several queue algorithms
exist, such as First-In First-Out (FIFO) queue, Priority Queue (PQ),
and Custom Queue (CQ), each addressing specific network traffic
issues. In other words, queue information can reflect the congestion
status of network nodes.
When congestion occurs in the network, network managers need to
promptly detect and respond to it by collecting traffic queue
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information from network nodes and reporting it to the network
controller. When the network controller receives queue information
indicating congestion at network nodes, it can execute some actions
like traffic engineering. However, specific actions are not
designated in this document.
This document specifies the BGP-LS mechanism with necessary
expansions for scalable transmission of queue information to the
network controller. Queue information is sent using a separate type
of BGP-LS NLRI, allowing flexible updates of queue information
without affecting the based link state information.
1.1. Requirements Language
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. BGP-LS Extensions for Queue Information Advertisement
BGP-LS [RFC9552] defines the mechanisms to advertise Node, Link, and
Prefix Link-State NLRI types and their associated attributes via
BGP.
Each queue functions on the corresponding interface of a network
node (NN) for the traffic forwarding of that interface. Therefore, a
queue can be defined as network link information, and queue-specific
information can be advertised in two possible ways.
The first method is to publish queue information as the link
attribute of a Layer 3 link using existing BGP-LS link NLRI.
However, this method has scalability issues when the number of
queues on Layer 3 links becomes large. Firstly, as the number of
queues on a link increases, the number of associated queue
information also increases, and in some cases, the queue information
may not fit into a single BGP update message. Secondly, for a
specific link, when only one queue information changes, the link
NLRI and all link attributes, along with all related queue
attributes, need to be updated. This can lead to unnecessary route
advertisement.
The second method is to introduce a dedicated BGP-LS NLRI type to
advertise queue-specific information. This approach allows the
related information of each queue to be independently advertised and
updated. This also reduces the load and overhead issues caused by
the first method.
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Therefore, for better scalability, this document proposes the
mechanism of the second method and BGP-LS expansion. Queue
information related to a link is advertised through a new BGP-LS
NLRI and related BGP-LS attributes. The queue identify (ID)
information and the link identify associated with the queue are
carried using a new BGP-LS Queue Link NLRI, and the queue attribute
of the related link is carried in the form of relevant BGP-LS
attribute TLVs.
2.1. BGP-LS Queue Link NLRI
A new BGP-LS NLRI type called "Queue-link" is defined to advertise
Queue-specific link information. The NLRI-Type is to be assigned by
IANA (TBD1). Its format is shown as below:
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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+ (8 octets) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors TLV (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Remote Node Descriptors TLV (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Link Descriptors TLVs (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Queue Descriptors TLV (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Encoding of NRP-Link NLRI
The encoding and semantics of Protocol-ID, Identifier, Local Node
Descriptors and Remote Node Descriptors are the same as defined in
[RFC9552]. If interface and neighbor addresses, either IPv4 or IPv6,
are present, then the interface/neighbor address TLVs MUST be
included in the Link Descriptors. If the link borrows the address
from another interface, then both the Link Local/Remote Identifiers
and the interface/neighbor address TLVs MUST be included.
The Queue Descriptors TLV includes descriptions of the Queue which
the link is associated with. This is a mandatory TLV for Queue-Link
NLRIs. Its type is to be assigned by IANA (TBD2). The length of this
TLV is variable. The value contains one or more Queue Descriptor
sub-TLSs defined in Section 2.1.1.
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2.1.1. Queue Descriptors Sub-TLVs
In this document, one Queue Descriptors sub-TLV is defined as below:
+====================+=============+========+
| Sub-TLV Code Point | Description | Length |
+====================+=============+========+
| TBD3 | Queue ID | 4 |
+--------------------+-------------+--------+
Table 1: Queue Descriptor Sub-TLVs
Queue ID: A 32-bit link-interface-wide unique identifier, which is
used to identify a Queue that the link is associated with.
The Queue ID sub-TLV is mandatory in the Queue Descriptors. There
MUST be only one instance of Queue ID sub-TLV present in the Queue
Descriptors.
2.2. Queue Attribute TLVs
The Queue Attribute TLVs are a set of TLVs which may be encoded in
the BGP-LS Attribute associated with a Queue-Link NLRI.
The following Queue Attribute TLVs can be defined in this document.
+================+========================+========+
| TLV Code Point | Description | Length |
+================+========================+========+
| TBD4 | Queue Depth | 4 |
+----------------+------------------------+--------+
| TBD5 | Queue Precedence | 1 |
+----------------+------------------------+--------+
| TBD6 | Queue Length | 4 |
+----------------+------------------------+--------+
Table 2: Queue Attribute TLVs
2.2.1. Queue Depth TLV
A new Queue Attribute TLV is defined to carry the Queue Depth
information, which indicates the upper limit of the queue capacity.
The form of the Queue Depth TLV is as below:
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 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Depth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Encoding of Queue Depth TLV
Type (16 bits): TBD4.
Length (16 bits): Length of the value field in octets. The value is
4.
Depth: Indicates the upper limit of the queue capacity.
2.2.2. Queue Precedence TLV
When there are multiple queues on a specified link, the Queue
Precedence TLV is used to determine the order in which the queues
are scheduled. The format of the Queue Precedence TLV is as below:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Precedence |
+-+-+-+-+-+-+-+-+
Figure 3: Encoding of Queue Precedence TLV
Type (16 bits): TBD5.
Length (16 bits): Length of the value field in octets. The value is
1.
Precedence: The Precedence of the Queue. The larger the value, the
higher the priority.
2.2.3. Queue Length TLV
A new Queue Attribute TLV is defined to carry the Queue Length
information, which indicates the number of packets actually waiting
to be forwarded in the current queue. The form of the Queue Length
TLV is as below:
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 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Encoding of Queue Length TLV
Type (16 bits): TBD6.
Length (16 bits): Length of the value field in octets. The value is
4.
Queue Length: The number of packets actually waiting to be forwarded
in the current queue. If the queue length exceeds the queue depth,
packets will be discarded.
3. Operational Considerations
It SHOULD implement the functionality to allow the operator to
globally control whether to send link-related queue information. It
SHOULD also allow the operator to control whether to send queue
information for a specified link.
It MUST implement the functionality to allow the operator to
configure the queue length threshold, where the queue information is
only triggered and sent after reaching this threshold, ensuring that
queue information is sent only during actual link congestion and
reducing the frequency of advertisements.
After reaching the queue length threshold, it MUST allow the
operator to configure the queue length variation threshold, where
updated queue information is sent only when the queue length
variation reaches this threshold, to avoid frequent advertisements.
4. Security Considerations
This document introduces no additional security vulnerabilities in
addition to the ones as described in [RFC9552].
5. IANA Considerations
There is a need to request IANA to assign a new code point for
"Queue-Link NLRI" under the "BGP-LS NLRI Types" Registry.
+======+=================+===============+
| Type | NLRI Type | Reference |
+======+=================+===============+
| TBD1 | Queue Link NLRI | This document |
+------+-----------------+---------------+
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Table 3: Queue NLRI Type
There also is a need to request IANA to assign the following new
code points for under the "BGP-LS NLRI and Attribute TLVs" Registry.
+================+===================+===============+
| TLV Code Point | Description | Reference |
+================+===================+===============+
| TBD2 | Queue Descriptors | This document |
+----------------+-------------------+---------------+
| TBD3 | Queue ID | This document |
+----------------+-------------------+---------------+
| TBD4 | Queue Depth | This document |
+----------------+-------------------+---------------+
| TBD5 | Queue Precedence | This document |
+----------------+-------------------+---------------+
| TBD6 | Queue Length | This document |
+----------------+-------------------+---------------+
Table 4: Queue related TLV/Sub-TLVs
6. References
6.1. 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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552, DOI
10.17487/RFC9552, December 2023, <https://www.rfc-
editor.org/info/rfc9552>.
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Author's Address
Jinming Li
China Mobile
32 Xuanwumen West Street
Beijing
Xicheng District, 100053
China
Email: lijinming@chinamobile.com
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
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