Deterministic Routing Header
draft-pb-6man-deterministic-crh-00
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Shaofu Peng , Ron Bonica | ||
| Last updated | 2024-02-29 | ||
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draft-pb-6man-deterministic-crh-00
Network Shaofu. Peng
Internet-Draft ZTE Corporation
Intended status: Standards Track Ron. Bonica
Expires: 2 September 2024 Juniper Networks
1 March 2024
Deterministic Routing Header
draft-pb-6man-deterministic-crh-00
Abstract
This document introduces a new IPv6 Routing Header used for
deterministic forwarding wihch is generally a strict explicit path.
This Routing Header will contain the decoupled topology instructions
and deterministic forwarding resource indications. The target is low
cost of encapasultion and less amount of allocated SIDs.
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
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This Internet-Draft will expire on 2 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The Compressed Routing Headers for DetNet (CRH-20) . . . . . 3
3. The CRH Forwarding Information Base (CRH-FIB) . . . . . . . . 6
4. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Processing on the Headend Node . . . . . . . . . . . . . 6
4.2. Processing on the Transit or Endpoint Node . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC8655] describes the architecture of deterministic network and
defines the QoS goals of deterministic forwarding: Minimum and
maximum end-to-end latency from source to destination, timely
delivery, and bounded jitter (packet delay variation); packet loss
ratio under various assumptions as to the operational states of the
nodes and links; an upper bound on out-of-order packet delivery. In
order to achieve these goals, deterministic networks use resource
reservation, explicit routing, service protection and other means.
In general, a deterministic path is generally a strictly explicit
path calculated by a centralized controller, and resources are
reserved on the nodes along the path. There is such a need that
metadata related to each hop used to provide QoS needs to be carried
in the packet to avoid network core maintenance flow states and meet
large scaling deterministic requirements.
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[RFC8200] defines the Routing Header. The source node of the IPv6
packet can include some segment information in the Routing Header to
control the packet's access to these segments before reaching the
final destination node. How to reduce the cost of Routing Header,
especially in scenarios with strict explicit deterministic forwarding
paths, is a concern. Generally, there are two categories of
optimization methods. One is to use short indexes to map to IPv6
addresses, and the other is to rely on a common prefix for all
segments. For example, [I-D.ietf-6man-comp-rtg-hdr] defines two new
routing headers called CRH-16 and CRH-32, containing a short index
for mapping to 128-bit IPv6 addresses, and retrieving all forwarding
information from the CRH-FIB entries matched by the index. And,
[RFC6554] defines Routing Type 3, where only the different parts of
each segment need to be stored in the segment list, and the common
prefix of all elements is stored in the Destination Address field of
the IPv6 header. [I-D.ietf-spring-srv6-srh-compression] also
describes another common prefixes based compression method suitable
for SRv6 network.
This document introduces a CRH varaint, called CRH-20, to meet the
requirement of deterministic forwarding. It contains the decoupled
topology instructions and deterministic forwarding resource
indications. Here, the decoupled means that the SIDs for topology
instructions and resource indications for DetNet QoS are defined,
signaled in control plane, and forwarded in data plane,
independently. Considering that there are many types of resources
and the huge amount of resource instances supported by each type,
this document does not recommend distinguishing different resource
instances by allocating different SIDs. The target of CRH-20 is low
cost of encapasultion and less amount of SIDs.
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. The Compressed Routing Headers for DetNet (CRH-20)
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ST | RT |P| | Common RI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID[0] | Individual RI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID[1] | Individual RI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// ... ... //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID[n-1] | Individual RI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: CRH-20
CRH-20 contains the following fields:
* Next Header: Defined in [RFC8200].
* Hdr Ext Len: Defined in [RFC8200].
* Routing Type: Defined in [RFC8200] (TBA for CRH-20)
* Segments Left: Defined in [RFC8200].
* Type-specific Data: Described in [RFC8200].
In the CRH-20, the Type-specific data field contains topology
instructions and forwarding resource indications. In detailed:
* ST (SID Type): 3 bits for the index type.
- 0: the SID field is 20-bit index that is the default type and
unrelated to any well-knownn index type. Implementers need to
additionally define the announcement, learning, and FIB
creation for this default index type.
- 1: the SID field is 20-bit MPLS label. In this case, CRH-FIB
reuses MPLS ILM (Incoming Label Map) table.
- 2: the SID field is 20-bit SR-MPLS SID index. In this case,
CRH-FIB resuses SR-MPLS SID index table.
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- 3: the SID field is 20-bit BIER ID. In this case, CRH-FIB
resuses BIFT table.
- Other types may be defined in the future.
* RT (Resource Type): 3 bits for the forwarding resource types.
- 0: undefined. In this case, Common RI field and Individual RI
fields may also be 0 and ignored during forwarding procedure of
the packet, or other values used for user defined purposes.
- 1: Indicates that the forwarding resources is timeslot
resources. [I-D.peng-detnet-packet-timeslot-mechanism] defines
the timeslot queueing and forwarding (TQF) mechanism in IP/MPLS
network. Timeslot resources are defined as multiple equally
time slots contained within a fixed length of periodic time
(known as orchestration period). Different nodes interoperate
on the same orchestration period, but for the same
orchestration period, different nodes may configure different
timeslot lengths. In this case, Common RI field contains
orchestration period length (OPL) information, and Individual
RI field contains the specific timeslot for the corresponding
segment.
- 2: Indicates that the forwarding resources is delay resources.
[I-D.peng-detnet-deadline-based-forwarding] defines the
deadline based forwarding mechanism in IP/MPLS network. The
network may provide multiple delay levels each provided a
bounded latency according to the schedulability condition of
EDF (earliest deadline first) scheduling. In this case, Common
RI field contains the latency deviation (E) information, and
Individual RI field contains the planned residence time (D) for
the corresponding segment. All segments may have the same
planned residence time (D) by evenly dividing the total
residence time budget, but this is not mandatory.
- 3: Indicate that forwarding resources is network slice
resources, also known as Network Resource Partition (NRP)
resources. [I-D.ietf-teas-ns-ip-mpls] defines a network
slicing mechanism in IP/MPLS network. The physical network may
be partitioned into multiple slices dedicated to specific
services or customers. It is possible to directly reuse
network slices to get deterministic QoS. In this case, Common
RI field contains the default NRP-ID, and Individual RI field
contains the overrided NRP-ID when necessary.
- Other types may be defined in the future.
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* P (Pad) flag: 1 bit to indicate whether there are padding field.
If P flag is 0, there are no padding. If P flag is 1, there are
padding with 4 bytes.
* Common RI (Resource Indication): 24 bits for the common forwarding
resource information that all segments shared. The information
contained in Common RI depends on RT. Please see the above
explanation of Resource Type field.
* SID (Segment Identifier): 20 bits for the topology instruction.
Each SID identifies an entry in the CRH-FIB. Each CRH-FIB entry
identifies an interface on the path that the packet takes to its
destination.
* Individual RI (Resource Indication): 12 bits for the forwarding
resource that is specific for the corresponding segment. The
information contained in Individual RI depends on RT. Please see
the above explanation of Resource Type field.
* Padding: 0 or 4 bytes to ensure 8-octet alignment.
In CRH-20, each segment is constructed by 32-bit tuple <SID,
Individual RI>. Segments are listed in reverse order. So, the first
segment in the list represents the final interface in the path.
Because segments are listed in reverse order, the Segments Left field
can be used as an index into the SID list. In this document, the
"current Segment" is the Segment list entry referenced by the
Segments Left field.
The first segment in the path can be omitted from the list.
3. The CRH Forwarding Information Base (CRH-FIB)
Please refer to [I-D.ietf-6man-comp-rtg-hdr]. There are no
additional considerations for the topology instructions, except that
FIB may be organized by specific type of index.
4. Processing Rules
4.1. Processing on the Headend Node
The headend node is responsible for encapsulating the CRH-20 for the
packet. For a logical Segment List <S1, S2, ..., Sn>, set the SID
and RI information corresponding to each segment in CRH-20.
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According to the CRH-FIB entry matched with the SID in the segment
S1, the headend obtain the corresponding destination IPv6 address,
and copy it to the DA field of the IPv6 header. In addition, set
Segment Left to n-1, indicating that there are still n-1 segment
elements to be processed in the segment list.
In order to further save the cost of CRH-20, because the destination
IPv6 address corresponding to the first segment has already been
copied to the DA field of the IPv6 header, the headend node may
exclude the first segment from the segment list of CRH-20. If this
is the case, only n-1 segments (from [0] to [n-2]) need to be
included in the list, and the segment [n-2] field stores the segment
S2. The Segment Left is still set to n-1, indicating that there are
still n-1 segment elements to be processed in the segment list. The
headend node must ensure that when forwarding packets to the first
segment S1, it accesses the specified forwarding resource (although
it is also not included in the list). Note that this attempting to
reduce overhead may not be meaningful due to the need for 8-octet
alignment.
4.2. Processing on the Transit or Endpoint Node
When a transit or endpoint node receives an IPv6 packet, if the DA in
the IPv6 header matches the local IP address, and the Next Header
field of the IPv6 header indicates that the next layer header is CRH-
20, then continue to process CRH-20 as below:
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S01. When a CRH-20 is processed {
S02. if (Segments Left == 0) {
S03. Stop processing the CRH-20, and proceed to process the
next header in the packet, whose type is identified by
the Next Header field in the routing header.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), interrupt
packet processing, and discard the packet.
S07. }
S08. Decrement IPv6 Hop Limit by 1
S09. Decrement Segments Left by 1
S10. Read the next 32-bit segment by Segment List[Segments Left].
Match CRH-FIB entry by ST field and segment.SID field.
S11. If there is no matched FIB entry, discard the packet and send
an ICMPv6 Parameter Problem, Code 0, message to the Source
Address, pointing to the current segment.
S12. Get the destinatoin IPv6 address and output interface from
the matched FIB entry, and copy the destinatoin IPv6
address to the DA field in the IPv6 header.
S13. Transmit the packet to the output interface, and access the
forwarding resource indicated by Common RI field and
Individual RI field.
S14. }
5. IANA Considerations
TBD
6. Security Considerations
TBD
7. Acknowledgements
TBD
8. Normative References
[I-D.ietf-6man-comp-rtg-hdr]
Bonica, R., Kamite, Y., Alston, A., Henriques, D., and L.
Jalil, "The IPv6 Compact Routing Header (CRH)", Work in
Progress, Internet-Draft, draft-ietf-6man-comp-rtg-hdr-03,
18 January 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-6man-comp-rtg-hdr-03>.
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[I-D.ietf-spring-srv6-srh-compression]
Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, "Compressed SRv6 Segment List Encoding", Work in
Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
compression-13, 29 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
srv6-srh-compression-13>.
[I-D.ietf-teas-ns-ip-mpls]
Saad, T., Beeram, V. P., Dong, J., Wen, B., Ceccarelli,
D., Halpern, J. M., Peng, S., Chen, R., Liu, X.,
Contreras, L. M., Rokui, R., and L. Jalil, "Realizing
Network Slices in IP/MPLS Networks", Work in Progress,
Internet-Draft, draft-ietf-teas-ns-ip-mpls-03, 26 November
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
teas-ns-ip-mpls-03>.
[I-D.peng-detnet-deadline-based-forwarding]
Peng, S., Du, Z., Basu, K., cheng, Yang, D., and C. Liu,
"Deadline Based Deterministic Forwarding", Work in
Progress, Internet-Draft, draft-peng-detnet-deadline-
based-forwarding-08, 14 December 2023,
<https://datatracker.ietf.org/doc/html/draft-peng-detnet-
deadline-based-forwarding-08>.
[I-D.peng-detnet-packet-timeslot-mechanism]
Peng, S., Liu, P., Basu, K., Liu, A., Yang, D., and G.
Peng, "Timeslot Queueing and Forwarding Mechanism", Work
in Progress, Internet-Draft, draft-peng-detnet-packet-
timeslot-mechanism-05, 14 December 2023,
<https://datatracker.ietf.org/doc/html/draft-peng-detnet-
packet-timeslot-mechanism-05>.
[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>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<https://www.rfc-editor.org/info/rfc6554>.
[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>.
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[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
Authors' Addresses
Shaofu Peng
ZTE Corporation
China
Email: peng.shaofu@zte.com.cn
Ron Bonica
Juniper Networks
United States of America
Email: rbonica@juniper.net
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