Network Working Group W. Cheng
Internet-Draft W. Jiang
Intended status: Standards Track China Mobile
Expires: March 30, 2022 C. Lin
New H3C Technologies
September 30, 2021
Encapsulation and Processing of Network Slice Selector in IPv6 Data
Plane
draft-cheng-teas-ipv6-network-slice-selector-00
Abstract
Packets belong to a network slice need to be forwarded using the
specific network resources. A network slice selector is carried in
each packet to identify the network slice that it belongs to.
This document proposes a new Network Slice Selector Option, and
describes the encapsulation and processing of network slice selector
in IPv6 data plane using the proposed option.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Carrying Network Slice Selector in IPv6 Data Plane . . . . . 3
3. Definition of Network Slice Selector Option . . . . . . . . . 3
4. Processing of Network Slice Selector Option . . . . . . . . . 4
5. Usage of Network Slice Selector Option . . . . . . . . . . . 5
5.1. IP Backbone of Network Slice . . . . . . . . . . . . . . 5
5.2. IP Fast-Reroute of Network Slice . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Network slicing provides the ability to partition a physical network
into multiple isolated logical networks of varying sizes, structures,
and functions so that each slice can be dedicated to specific
services or customers. [I-D.ietf-teas-ietf-network-slices] defines
the term "IETF Network Slice" and establishes the general principles
of network slicing in the IETF context.
[I-D.cheng-teas-network-slice-usecase] describes several use cases of
IETF Network Slice. [I-D.bestbar-teas-ns-packet] proposes a solution
to realize network slicing in IP/MPLS networks. Network nodes need
to identify a packet belonging to a network slice before it can apply
the proper forwarding treatment, so a Network Slice Selector must be
carried in each packet.
This document proposes a new Network Slice Selector Option, and
describes the encapsulation and processing of the network slice
selector in IPv6 data plane using the proposed option.
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
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14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Terminology
IETF Network Slice: An IETF Network Slice is a logical network
topology connecting a number of endpoints using a set of shared or
dedicated network resources that are used to satisfy specific Service
Level Objectives. See [I-D.ietf-teas-ietf-network-slices].
Service Level Objectives (SLO): Define a set of measurable network
attributes and characteristics that describe an IETF Network Slice
service. See [I-D.ietf-teas-ietf-network-slices].
Network Slice Selector (NSS): An identifier carried in each packet to
indicate the network slice that it belongs to.
2. Carrying Network Slice Selector in IPv6 Data Plane
As specified in [RFC8200], the Hop-by-Hop Options header is used to
carry optional information that may be examined and processed by
every node along a packet's delivery path.
Therefore, in IPv6 data plane, the Network Slice Selector can be
carried as a Hop-by-Hop option in the Hop-by-Hop options header.
Each node along the path will process the IPv6 Hop-by-Hop options
header and apply the specific Per Hop Behavior (PHB) that is
associated with the network slice.
3. Definition of Network Slice Selector Option
A new Network Slice Selector Option is defined to encapsulate the
network slice selector in IPv6 data plane. It identifies the network
slice which the packet belongs to.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Slice Selector |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Option Type: 8-bit identifier of the type of option. The value is
to be assigned by IANA. The highest-order 2 bits are set to 00 to
indicate that a node which does not recognize the option type will
skip over this option and continue processing the header. The
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third highest-order bit is set to 0 to indicate the option data
does not change en route.
o Opt Data Len: 8-bit unsigned integer. Length of the Option Data
field of this option, in octets. The Value is 6.
o Flags: 16 bits of flags. The following flags are defined:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|B U U U U U U U U U U U U U U U|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* B: Best-effort. When the forwarding behavior of the specific
network slice identified by the Network Slice Selector filed is
not configured or available, if B-Flag is set, the packet
should be transmitted ignoring the Network Slice Selector
Option, otherwise it should be discarded.
* U: Unused and for future use. MUST be 0 on transmission and
ignored on receipt.
o Network Slice Selector: 32-bit identifier of the network slice
which the packet belongs to.
4. Processing of Network Slice Selector Option
In an IPv6 network which deploys network slicing, the ingress node
encapsulates an outer IPv6 Header with the Network Slice Selector
Option into each packet that belongs to a certain network slice. The
Network Slice Selector is carried in the Hop-by-Hop Options Header,
and needs to be processed by each node along the delivery path.
Nodes should be able to process the Network Slice Selector Option in
the forwarding plane.
When forwarding a packet with the Network Slice Selector Option, a
node performs an IPv6 fib lookup on the Destination Address in IPv6
Header, and determines the next hop to the destination. Then it
processes the Network Slice Selector Option in the Hop-by-Hop Options
Header with the following logic:
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Perform network slice lookup using the Network Slice Selector
and determine the forwarding behavior
IF (the network slice or the forwarding behavior is not
configured or available) {
IF (B-Flag is set) {
Transmit the packet to next hop indicated by Destination
Address, ignoring the Network Slice Selector Option
}
ELSE {
Discard the packet
}
}
ELSE {
Transmit the packet to next hop indicated by Destination
Address, using the forwarding behavior for the specific
network slice
}
Nodes which do not recognize the Network Slice Selector Option should
ignore the Network Slice Selector Option and continue to forward the
packet.
The egress node decapsulates the outer IPv6 Header carrying the
Network Slice Selector Option.
5. Usage of Network Slice Selector Option
5.1. IP Backbone of Network Slice
In Figure 1, the network operator has created two network slices in
the IP Backbone for IETF network slices, which are NS1 and NS2. The
SLO of NS1 is guaranteed bandwidth of 100Mbps, and the SLO of NS2 is
guaranteed bandwidth of 200Mbps. Two network slice selectors, NSS1
and NSS2, are assigned for NS1 and NS2 respectively. SRv6 is applied
in the IP Backbone.
Along with the forwarding path <PE1-P1-P2-PE2>, dedicated queues with
guaranteed bandwidth for NS1 and NS2 are configured at corresponding
interfaces of each router. Taking the interface P1-P2 of router P1
as an example, which is shown in Figure 2, Queue 1 is configured with
network slice selector NSS1 and guaranteed bandwidth of 100Mbps, and
Queue 2 is configured with NSS2 and 200Mbps. When P1 transmits a
packet through interface P1-P2, the network slice selector carried in
the packet header is checked. If NSS1 appears in Hop-by-Hop Options
Header, P1 uses Queue 1 to transmit the packet. If NSS2 appears in
Hop-by-Hop Options Header, P1 uses Queue 2 to transmit the packet.
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When the traffic flows of NS1 or NS2 enter the IP Backbone, PE1 and
PE2 encapsulate the received packet with an outer IPv6 header. The
outer IPv6 header has a Hop-by-Hop Options Header which contains a
Network Slice Selector Option carrying NSS1 or NSS2, along with a SRH
header which contains the SIDs of path <PE1-P1-P2-PE2>.
In packet forwarding, P1 and P2 use the SID in IPv6 destination
address and SRH to determine the next-hop and the outgoing interface,
and then, according to the Hop-by-Hop Options Header, use the
dedicated queue related with NSS1 or NSS2 to transmit the packet.
.................................
: IP Backbone :
CPE PE1 P1 P2 PE2 ......
|----| |---| NS1 |---| NS1 |---| NS1 |---| : DC :
| o---|o-o|-----|o-o|-----|o-o|-----|o-o|--o :
| o---|o-o|-----|o-o|-----|o-o|-----|o-o|--o :
|----| |---| NS2 |---| NS2 |---| NS2 |---| :....:
: :
:...............................:
+-------+ +-------+
| IPv6 | | IPv6 |
+-------+ +-------+
| HBH | | HBH |
+-------+ +-------+
| SRH | | SRH |
+-------+ +-------+ +-------+ +-------+
| IPv6 | | IPv6 | | IPv6 | | IPv6 |
+-------+ <-> +-------+ <...> +-------+ <-> +-------+
|Payload| |Payload| |Payload| |Payload|
+-------+ +-------+ +-------+ +-------+
Figure 1
|----| Interface: P1-P2
| | ----------------------------------
| | >>>>>>Queue 1: NSS1, 100Mbps>>>>>>
| P1 | >>>>>>Queue 2: NSS2, 200Mbps>>>>>>
| | >>>>>> ... >>>>>>
| | ----------------------------------
|----|
Figure 2
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5.2. IP Fast-Reroute of Network Slice
In Figure 3, the network operator has created a network slice NS1. A
forwarding path <PE1-P1-P2-PE2> is selected to transmit the traffic
flows of NS1. On the links of PE1-P1, P1-P2 and P2-PE2, dedicated
resources are allocated for NS1.
When the traffic flows of NS1 enter the network via PE1, PE1
encapsulates the received packet with an outer IPv6 header. The
outer IPv6 header has a Hop-by-Hop Options Header which contains a
Network Slice Selector Option carrying NSS1, along with a SRH header
which contains the SIDs of path <PE1-P1-P2-PE2>. The B-Flag in the
Network Slice Selector Option is set. The packets are forwarded
along the selected path, using the dedicated resources.
Then, a failure occurs on P2. The fast re-route technology on P1
works, and P1 will send the packets to P3 and make the packet
forwarding along the path <P3-P4-PE2>. However, on the links of
P1-P3, P3-P4 and P4-PE2, there is no dedicated resource allocated for
NS1. The B-Flag in the Network Slice Selector Option indicates the
routers to transmit the packets with best-effort service rather than
discard them. Since the lack of dedicated resource along the new
path, the SLO of NS1 may not be satisfied during the failure, but NS1
remains available.
|---| |---| |---| |---|
--|PE1|*****|P1 |*****|P2 |*****|PE2|--
|---| |---| |---| |---|
| | | |
| | | |
| | | |
| |---| |---| |
+-------|P3 |-----|P4 |-------+
|---| |---|
*****: links with dedicated resource for NS1
-----: links without dedicated resource for NS1
Figure 3
For another example as shown in Figure 4, the network operator has
assigned a main path <PE1-P1-P2-PE2> and a hot-standby backup path
<PE1-P3-P4-PE2> for NS1. Dedicated resources are allocated both on
the main and backup paths. In this case, the B-Flag in the Network
Slice Selector Option can be unset. When PE1 detects a failure on
the main path, the traffic flows of NS1 will be steered to the backup
path and forwarded with dedicated resource.
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|---| |---| |---| |---|
--|PE1|*****|P1 |*****|P2 |*****|PE2|--
|---| |---| |---| |---|
* | | *
* | | *
* | | *
* |---| |---| *
********|P3 |*****|P4 |********
|---| |---|
*****: links with dedicated resource for NS1
-----: links without dedicated resource for NS1
Figure 4
6. IANA Considerations
This document requests IANA to assign a new option type for Network
Slice Selector Option.
7. Security Considerations
TBD.
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>.
[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>.
[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>.
8.2. Informative References
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[I-D.bestbar-teas-ns-packet]
Saad, T., Beeram, V. P., Wen, B., Ceccarelli, D., Halpern,
J., Peng, S., Chen, R., Liu, X., Contreras, L. M., and R.
Rokui, "Realizing Network Slices in IP/MPLS Networks",
draft-bestbar-teas-ns-packet-03 (work in progress), July
2021.
[I-D.cheng-teas-network-slice-usecase]
Cheng, W., Jiang, W., Chen, R., Gong, L., and S. Peng,
"IETF Network Slice use cases", draft-cheng-teas-network-
slice-usecase-01 (work in progress), August 2021.
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Gray, E., Drake, J., Rokui, R., Homma, S.,
Makhijani, K., Contreras, L., and J. Tantsura, "Framework
for IETF Network Slices", draft-ietf-teas-ietf-network-
slices-04 (work in progress), August 2021.
Authors' Addresses
Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com
Wenying Jiang
China Mobile
Email: jiangwenying@chinamobile.com
Changwang Lin
New H3C Technologies
Email: linchangwang.04414@h3c.com
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