Computing Segment for Service Routing in SAN
draft-zhou-intarea-computing-segment-san-01
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| Authors | Fenlin Zhou , Dongyu Yuan , Dong Yang | ||
| Last updated | 2022-10-23 | ||
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draft-zhou-intarea-computing-segment-san-01
INTAREA F. Zhou
Internet-Draft D. Yuan
Intended status: Standards Track ZTE Corporation
Expires: 27 April 2023 D. Yang
Beijing Jiaotong University
24 October 2022
Computing Segment for Service Routing in SAN
draft-zhou-intarea-computing-segment-san-01
Abstract
Since services delivered from cloud need delicate coordination among
the client, network and cloud, this draft defines a new Segment to
provide service routing and addressing functions by leveraging SRv6
Segment programming capabilities. With Computing Segments proposed,
the network gains its capability to identify and process SAN header
in need and a complete service routing procedure can be achieved.
Status of This Memo
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This Internet-Draft will expire on 27 April 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Service Identification in SAN . . . . . . . . . . . . . . 2
1.2. Service Routing in SAN . . . . . . . . . . . . . . . . . 4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Computing Segment . . . . . . . . . . . . . . . . . . . . . . 5
4.1. When a SAN Header is Carried as an Option in the HBH . . 6
4.2. When a SAN Header is Carried as an Option in the DOH . . 6
4.3. When a SAN Header is Carried as a Type of SRH TLV . . . . 7
5. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
1.1. Service Identification in SAN
In order to deliver responsive services to clients, computing
resources continuously migrate and spread from central sites to edge
nodes. As shown in Figure 1, multiple instances located
distributedly in different resource pools are capable of providing
services. Compared with applying traditional IP routing protocols, a
fine-grained service routing policy is capable of achieving optimal
and efficient invocation of both computing power and the network.
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+-------------+ +---------+
+-+Load Balancer+-+Service 1|
| +-------------+ +---------+
|
+------+ +----------+ +---------+ | +-------------+ +---------+
|Client+---+Ingress PE+---+Egress PE+-+-+Load Balancer+-+Service 2|
+------+ +----------+ +---------+ | +-------------+ +---------+
|
| +-------------+ |---------+
+-+Load Balancer+-|Service 3|
+-------------+ +---------+
|<-Client->|<---------Network-------->|<----------Cloud---------->|
Figure 1: Computing Power Networks
In order to implement service routing, the network should be aware of
specific services and a service awareness network framework is
introduced in [I-D.huang-service-aware-network-framework]. Within
the proposed network framework, a service identification is defined
as a SAN ID(Service ID) in
[I-D.ma-intarea-identification-header-of-san] to represent a globally
unique service semantic identification.
As mentioned in [I-D.ma-intarea-encapsulation-of-san-header], a SAN
ID is encapsulated in a SAN header which can be carried as an option
in the IPv6 Hop-by-Hop Options Header, Destination Options Header and
a type of SRH TLV. Since services delivered from cloud need delicate
coordination among the client, network and cloud and thus simply
encapsulating SAN header among packets delivery can hardly satisfy
various practical situations:
* The Destination Options header is used to carry optional
information that need be examined by the destination of the path
which is defined in [RFC8200], SAN header will only be resolved by
the destination node. When a multi-layer routing protocol is
applied in the network domain, a quantity of relay nodes besides
the destination are required to identify SAN ID and forward the
received packet accordingly as well. Thus, simply carring a SAN
header can not fulfill a multi-layer service routing procedure.
* When a SAN header is carried as an option in the IPv6 Hop-by-Hop
Options Header, it may be processed by each nodes. Practically,
not all nodes along the delivery path of the packet are capable of
identifying and processing a SAN header. The SAN header may be
modified and changed and the packet may even be discarded in the
forwarding process.
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* The Segment Routing Header (SRH) and the SRH TLV is defined in
[RFC8754]. Since the segment list is encoded in order, it must be
orchestrated in advance which indicates various endpoint
behaviours in order to successively implement the designated
service routing. Previous orchestration should be regarded to be
severe restrictions.
To achieve a SAN header being processed in need in the network domain
and to preserve its identifiability along the path from the client to
the server, a new Segment to specify and standardize node behaviours
is urgently required.
1.2. Service Routing in SAN
As shown in Figure 2, a service routing table is designed to
establish a mapping relationship between the SAN ID and the
conventional IP routing table.
+-------+ +-------+
|Service| | I P |
SAN ID<---->|Routing|<->|Routing|
| Table | | Table |
+-------+ +-------+
+--------+ +-----------+ +----------+ +-----+
| Client +--------+Ingress PE+----------+Egress PE+--------+ L B |
+--------+ +-----------+ +----------+ +-----+
Figure 2: Service Routing in SAN
A service routing table can be published from a control and
management system to the network domain within a centralized control
plane while it can also be calculated and generated by the Ingress PE
itself under a distributed control plane.
With considerations of both path metrics and service SLA
requirements, a specific service routing table is introduced,
including mutiple attributes, SAN ID and outer gateway for instance.
Afterwards, a corresponding IP routing table should be indexed which
further determines the next hop or an SRv6 policy.
In order to describe and standardize the mentioned behaviours, a new
Computing Segment is proposed. With Computing Segments, multiple
nodes in the network domain can be informed to locate and identify
SAN header in need and to implement a referred forwarding behaviour
through the complete procedure.
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2. 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.
3. Terminology
* SAN: Service Aware Network
* SAN ID: Service Aware Network Identification, an identification
designed to indicate the fundamental and common service types
* SAN header: Encapsulation format of the SAN ID
* DOH: Destination Options Header
* HBH: Hop-by-Hop Options Header
* SRH: Segment Routing Header
* SID: Segment Identifier
* FIB: Forwarding Information Base
* DA: Destination Address
* LB: Load Balancer
4. Computing Segment
This draft introduces a new SRv6 Segment, namely Computing Segment,
aiming to describe the behaviour of querying service routing table
and corresponding packet forwarding.
Computing Segment is the identifier of packets in which a
corresponding SAN header should be identified and further being
forwarded via the matched service routing table entity, indicating
the following operations:
* Identify the SAN ID encapsulated in DOH, HBH or SRH TLV.
* Query the forwarding table entry indexed by SAN ID.
* Forward the packet to the new destination.
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In the case of SRv6, a new behavior End.C for Computing Segment is
defined. An instance of a Computing SID is associated with a service
routing table and a source address.
Behaviours of End.C when a SAN header is carried as an option in the
HBH, DOH or a type of SRH TLV are described in the following
sections.
4.1. When a SAN Header is Carried as an Option in the HBH
When an IPv6 node (N) receives an IPv6 packet whose destination
address matches a local IPv6 address instantiated as a SID (S), and S
is a Computing SID, N does:
S01. When an IPv6 packet is processed {
S02. Identify the SAN ID encapsulated in the option of the HBH
S03. Query the forwarding table entry indexed by SAN ID
S04. Set the packet's associated FIB table to the specific FIB
S05. Set the IPv6 DA to the next hop
S06. Maintain the TLVs in the HBH
S07. Resubmit the packet and transmit to the new destination
S08. }
Figure 3: When a SAN Header is Carried as an Option in the HBH
4.2. When a SAN Header is Carried as an Option in the DOH
When an IPv6 node (N) receives an IPv6 packet whose destination
address matches a local IPv6 address instantiated as a SID (S), and S
is a Computing SID, N does:
S01. When an IPv6 packet is processed {
S02. Identify the SAN ID encapsulated in the option of the DOH
S03. Query the forwarding table entry indexed by SAN ID
S04. Set the packet's associated FIB table to the specific FIB
S05. Set the IPv6 DA to the next hop
S06. Maintain the TLVs in the DOH
S07. Resubmit the packet and transmit to the new destination
S08. }
Figure 4: When a SAN Header is Carried as an Option in the DOH
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4.3. When a SAN Header is Carried as a Type of SRH TLV
When an SRv6-capable node (N) receives an IPv6 packet whose
destination address matches a local IPv6 address instantiated as an
SRv6 SID (S), and S is a Computing SID, N does:
S01. When an SRH is processed {
S02. If (Segments Left>0) {
S03. Decrement IPv6 Hop Limit by 1
S04. Decrement Segments Left by 1
S05. Update IPv6 DA with Segment List[Segments Left]
S06. Identify the SAN ID encapsulated in the SRH TLV
S07. Query the forwarding table entry indexed by SAN ID
S08. Set the packet's associated FIB table to the specific FIB
S09. Maintain the TLVs in the SRH
S10. Resubmit the packet transmit to the new destination
S11. }
S12. }
Figure 5: When a SAN Header is Carried as a Type of SRH TLV
When a SAN header is carried as a type of SRH TLV, Computing SIDs in
Segment List are required to be orchestrated in advance which
previously indicates the the determinism of a multi-segment routing
policy. Therefore, Computing Segment does not cooperate well with
the circumstances when a SAN header is carried as a type of SRH TLV.
5. Use Case
When a SAN header is carried as an option in the DOH, a typical
service addressing procedure is shown in Figure 6.
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+--------+ +-----------+ +----------+ +-----+
| Client +---------+Ingress PE+--------+Egress PE+---------+ L B |
+--------+ +-----------+ +----------+ +-----+
+-----------+ +-----------+ +-----------+
| SIP | | SIP | | SIP |
+-----------+ +-----------+ +-----------+
|END.C(SID1)| |END.C(SID2)| | DIP |
+-----------+ +-----------+ +-----------+
| DOH | | DOH | | DOH |
+-----------+ +-----------+ +-----------+
| PAYLOAD | | PAYLOAD | | PAYLOAD |
+-----------+ +-----------+ +-----------+
DOH:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Opt Length |Opt Data Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SAN Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Service Routing Table: v
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (SRv6 Policy) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Gateway |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
IP ROUTING TABLE: v
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Gateway |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Typical Service Addressing Procedure with Service ID
Encapsulated in the DOH
Suppose the Endpoint behaviour of END.C is configured at Ingress PE
and Egress PE, namely SID 1 and SID 2 respectively. SID1 and SID2
are advertised to the nodes in the network by IGP. The service
addressing procedure from the client to the cloud is described below:
The Computing SID of Ingress PE (SID1) is configured as DA by the
client. The packet carrying the SAN header as the option of the DOH
is forwarded to Ingress PE.
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When Ingress PE receives the packet, it queries the local routing
table in accordance with DA and identifys that DA is a Computing SID
(SID1). As defined in 4.2, the Ingress PE continues to forward the
packet carrying the DOH.
When Egress PE receives the packet, it queries the local routing
table in accordance with DA and identifys that DA is a Computing SID
(SID2). As defined in 4.2, the Egress PE continues to forward the
packet carrying the DOH.
When an intra-cloud LB receives the packet, the packet can be
forwarded in accordance with the Endpoint behaviour defined in 4.2.
or be processed as a normal IPV6 packet, depending on the practical
circumstances.
|<-Client->|<-------------------Network----------------->|<-Cloud->|
+------+ +----------+ +---------+ +-----+
|Client+-----+Ingress PE+-------------------+Egress PE+-----+ L B |
+------+ +----------+ | +---------+ +-----+
BE: v TE:
+-----------+ +-----------+
| IIP | | IIP |
+-----------+ +-----------+
| EIP | | SID |
+-----------+ +-----------+
| SIP | | SRH |
+-----------+ +-----------+
|END.C(SID2)| | SIP |
+-----------+ +-----------+
| DOH | |END.C(SID2)|
+-----------+ +-----------+
| PAYLOAD | | DOH |
+-----------+ +-----------+
| PAYLOAD |
+-----------+
Figure 7: Outer Headers Encapsulated between Ingress PE and Egress PE
As shown in Figure 7, between Ingress PE and Egress PE, an outer
header including SRH should be encapsulated when the traffic follows
a specific SRv6 TE policy. Otherwise, a normal IPv6 header should be
encapsulated under a BE condition. In the introduced case, the SAN
header is not perceived by relay devices between Ingress PE and
Egress PE.
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6. Security Considerations
TBA
7. Acknowledgements
TBA
8. IANA Considerations
This document requires registration of End.C behavior in "SRv6
Endpoint Behaviors" sub-registry of "Segment Routing Parameters"
registry.
9. Normative References
[I-D.huang-service-aware-network-framework]
Huang, D. and B. Tan, "Service Aware Network Framework",
Work in Progress, Internet-Draft, draft-huang-service-
aware-network-framework-00, 24 May 2022,
<https://www.ietf.org/archive/id/draft-huang-service-
aware-network-framework-00.txt>.
[I-D.ma-intarea-encapsulation-of-san-header]
Ma, L., Zhao, D., Zhou, F., and D. Yang, "Encapsulation of
SAN Header", Work in Progress, Internet-Draft, draft-ma-
intarea-encapsulation-of-san-header-00, 23 October 2022,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ma-intarea-encapsulation-of-san-header/>.
[I-D.ma-intarea-identification-header-of-san]
Ma, L., Zhou, F., Li, H., and D. Yang, "Service
Identification Header of Service Aware Network", Work in
Progress, Internet-Draft, draft-ma-intarea-identification-
header-of-san-00, 24 October 2022,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ma-intarea-identification-header-of-san/>.
[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>.
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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>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
Authors' Addresses
Fenlin Zhou
ZTE Corporation
No.50 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: zhou.fenlin@zte.com.cn
Dongyu Yuan
ZTE Corporation
No.50 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: yuan.dongyu@zte.com.cn
Dong Yang
Beijing Jiaotong University
No.3 Shangyuancun Haidian District
Beijing
100044
China
Email: dyang@bjtu.edu.cn
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