Internet DRAFT - draft-shi-cats-with-real-locator
draft-shi-cats-with-real-locator
Network Working Group H. Shi
Internet-Draft X. Chen
Intended status: Informational Z. Li
Expires: 1 September 2024 Huawei Technologies
X. Yi
China Unicom
K. Yao
China Mobile
29 February 2024
CATS based on Real Locator
draft-shi-cats-with-real-locator-01
Abstract
This document describes a solution framework that adheres to the CATS
framework. The solution uses anycast IP addresses as the CATS
service identifier and real locator of the service contact instance
as the CATS Instance Selection ID.
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 [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
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This Internet-Draft will expire on 1 September 2024.
Copyright Notice
Copyright (c) 2024 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
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Realization of CATS Framework Components . . . . . . . . 4
3.2. Realization of CATS Framework Workflow . . . . . . . . . 5
3.2.1. Service Announcement . . . . . . . . . . . . . . . . 5
3.2.2. Metrics Distribution . . . . . . . . . . . . . . . . 5
3.2.3. Service Demand processing . . . . . . . . . . . . . . 6
3.2.4. Service Instance Affinity . . . . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[I-D.ldbc-cats-framework]defines a framework for Computing-Aware
Traffic Steering (CATS). Such a framework defines an approach for
making compute- and network-aware traffic steering decisions in
networking environments where services are deployed in many
locations.
[I-D.lbdd-cats-dp-sr] proposes a data plane solution for the
realization of CATS. The solution uses an anycast IP address as the
Computing-aware Service ID (CS-ID) associated with a service. Also,
the solution uses Segment Routing (SR) as the data plane
encapsulation from an ingress CATS-Router to an egress CATS-Router.
[I-D.lbdd-cats-dp-sr] describes the scenario with multiple service
sites connected to a single egress CATS-Router. To demultiplex these
sites, a specific attachment circuit must be provided to indicate the
specific target service. In order to explicitly indicate the
interface towards a site, an END.DX is encoded as the last segment in
the SRv6 encapsulation[RFC8986]. The associated END.DX is learned
from the control plane.
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In the case that there are multiple service contact instances
connected to the same interface of the egress, the selected specific
service contact instance can not be distiguished only by END.DX and
anycast IP. This document proposes real locator of the service
contact instance acting as the CIS-ID in [I-D.ldbc-cats-framework].
2. Terminology
This document makes use of the terms defined in
[I-D.ldbc-cats-framework] and [I-D.lbdd-cats-dp-sr].
3. Solution Overview
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+------+
|Client|
+------+
|
+-------------+
| C-TC |
|-------------|
| | C-PS |
......................| +-------|....................
: |CATS-Router 2| :
: +-------------+ :
: :
: Underlay :
: Infrastructure :
: SRv6 Encap 1 SRv6 Encap 2 :
: :
: +-------------+ +-------------+ :
: |CATS-Router 1| |CATS-Router 3| :
:...| |................| |......:
+-------------+ +-------------+
| C-SMA | | C-SMA |
+-------------+ +-------------+
END.DX SID1 | END.DX SID2 | | END.DX SID3
................... ...... ......
: : : : : :
................... ...... ......
| Real IP1 |Real IP2 | |
+-----------+ +----------+ +----------+ +----------+
| Service | | Service | | Service | | Service |
| contact | | contact | | contact | | contact |
| instance | | instance | | instance | | instance |
+-----------+ +----------+ +----------+ +----------+
Edge site 1 Edge site 2 Edge site 3
Figure 1: Using SRv6 and Real Locator in CATS
3.1. Realization of CATS Framework Components
The realization of CATS Framework in this document adheres to
[I-D.ldbc-cats-framework] and [I-D.lbdd-cats-dp-sr] and adds some
additional description.
As in Figure 1, there is underlay infrastructure between an egress
CATS-Router and service contact instances. One egress CATS-Router
can connect multiple service site. One service site has only one
service contact instance or multiple service contact instances.
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In the realization of CATS framework, CATS service ID is anycast IP
and CATS Instance Selector ID is the real locator of the CATS service
contact instance.
The CATS overlay encapsulation is established from an ingress CATS-
Router to an egress CATS-Router connected to a service site.To
describe conveniently in this document the tunnel between CATS-Router
assumes SRv6[RFC8986].
As in Figure 1, only one service contact instance is hosted in the
edge site2. The solution proposed in I-D.lbdd-cats-dp-sr is enough.
The solution is only use END.DX or END.DT without real locator.
But as in Figure 1, the edge site1 has two service contact instances.
As described in [I-D.ldbc-cats-framework] if the egress CATS-Router
executes per-instance computing-related metric distribution the real
locator should be advertised with the service ID too. And when the
packet is forwarded according to the computing result of CATS PATH
Selector the real locator of selected service contact instance should
be carried besides END.DX or END.DT. The following section will
describe the detail of process.
3.2. Realization of CATS Framework Workflow
As described in Section 3.4 of [I-D.ldbc-cats-framework], CATS can be
deployed in a distributed model, centralized model, or a hybrid
model. The following description is about distributed model.
3.2.1. Service Announcement
This section is the same as Section 3.2.1 of [I-D.lbdd-cats-dp-sr].
3.2.2. Metrics Distribution
As per the CATS framework, CS-ID routes with metrics and CIS-ID are
distributed among the overlay CATS-Routers for per-instance metric
distribution. The detailed control plane solutions of metrics
distribution are out of the scope of this document. However, a
sample procedure is provided for the readers convenience.
For example, BGP can be used to distribute anycast IP route of the
service with additional metrics and real locator.
In the case of the C-SMA running as stand alone outside an egress
CATS-Router, the C-SMA collects the metrics of computing resource for
the service per one service contact instance and distributes the
anycast IP route of the service with the collected metrics and real
locator to the egress CATS-Router. Egress CATS-Routers will generate
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new metrics combining the network metrics and computing-related
metrics, and redistribute the anycast IP route with the new metrics
and real locator to ingress CATS-Routers. In the case of the C-SMA
running as a logic entity on an egress CATS-Router, the same process
will be performed inside the egress CATS-Router.
3.2.3. Service Demand processing
In a distributed model an ingress CATS-Router receives the packet
with destination address being anycast IP of the service. The
ingress CATS-Router determines the special service contact instance
to serve this packet and get the IP address of the egress CATS-Router
the service contact instance is connected to, END.DX or END.DT for
SRv6 and real locator.
The ingress CATS-Router generates SRv6 encapsulations from itself to
the egress CATS-Router with real locator carried in the outer IPv6
extension header. Egress CATS-Router decapsulates the outer tunnel
header and get the real locator. It determines the service site
according to END.DX or END.DT and forwards the packet to the specific
service contact instance according to the real locator.
There are two typical ways to forward the packet from the egress
CATS-Router to the service contact instance:
1. Tunnel mode: The packet with destination IP being anycast IP is
encapsulated to the tunnel with destination address set to real
locator.
2. IP mode: The packet should be IPv6 packet with the real locator
carried in the IPv6 extension header. The CATS-Router and the
underlay infrastructure should forward the packet according to
the real locator. And the real locator in the IPv6 extension
header can be inserted to the packet in the ingress or egress
CATS-Router.
3.2.4. Service Instance Affinity
This section is the same as Section 3.2.4 of [I-D.lbdd-cats-dp-sr].
4. Requirements
This section describes the requirements of protocol extensions about
the real locator used in CATS .
[REQ01] IPv6 extension header should be used to carry real locator.
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[REQ02] Protocol extensions should be defined to advertise real
locator from C-SMA running as stand alone to an egress CATS-Router.
[REQ03] Protocol extensions should be defined to advertise real
locator from an egress CATS-Router to an ingress CATS-Router in a
distributed model.
5. Security Considerations
TBD
6. IANA Considerations
There are no IANA considerations in this document.
7. Normative References
[I-D.lbdd-cats-dp-sr]
Li, C., Boucadair, M., Du, Z., and J. Drake, "Computing-
Aware Traffic Steering (CATS) Using Segment Routing", Work
in Progress, Internet-Draft, draft-lbdd-cats-dp-sr-01, 11
January 2024, <https://datatracker.ietf.org/doc/html/
draft-lbdd-cats-dp-sr-01>.
[I-D.ldbc-cats-framework]
Li, C., Du, Z., Boucadair, M., Contreras, L. M., and J.
Drake, "A Framework for Computing-Aware Traffic Steering
(CATS)", Work in Progress, Internet-Draft, draft-ldbc-
cats-framework-06, 8 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ldbc-cats-
framework-06>.
[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>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
Authors' Addresses
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Hang Shi
Huawei Technologies
Beijing
China
Email: shihang9@huawei.com
Xia Chen
Huawei Technologies
Beijing
China
Email: jescia.chenxia@huawei.com
Zhenbin Li
Huawei Technologies
Beijing
China
Email: lizhenbin@huawei.com
Xinxin Yi
China Unicom
Beijing
China
Email: yixx3@chinaunicom.cn
Kehan Yao
China Mobile
Beijing
China
Email: yaokehan@chinamobile.com
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