Internet DRAFT - draft-geng-detnet-srv6-based-bounded-latency
draft-geng-detnet-srv6-based-bounded-latency
Network Working Group X. Geng
Internet-Draft M. Mach
Intended status: Experimental Huawei
Expires: November 8, 2019 May 7, 2019
SRv6 Based Bounded Latency
draft-geng-detnet-srv6-based-bounded-latency-00
Abstract
One of the goals of DetNet is to provide bounded end-to-end latency
for critical flows. This document defines how to leverage Segment
Routing over IPv6 (SRv6) to implement bounded latency. Specifically,
new SRv6 SID function is used to specify transmission time (cycles)
of a packet. When forwarding devices along the path follow the
instructions carried in the packet, the bounded latency is achieved.
This mechanism of latency guarantee is called Cycle Specified Queuing
and Forwarding (CSQF) which is defined in
[I-D.chen-detnet-sr-based-bounded-latency].
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 8, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
3. SRv6 DetNet Data Plane Overview . . . . . . . . . . . . . . . 4
3.1. Encapsulation . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Functions . . . . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Deterministic Networking(DetNet) provides a capability to carry
specified data flows with extremely low data loss rates and bounded
latency within a network domain. DetNet is enabled by a group of
technologies, such as resource allocation, service protection and
explicit routes.([I-D.ietf-detnet-architecture])
Segment Routing(SR) leverages the source routing paradigm. A ingress
node steers a packet through an ordered list of instructions, called
"segments". SR can be applied over IPv6 data plane using Routing
Extension Header(SRH). Besides routing, the segment of SRv6 can
indicate functions which are executed locally in the node where they
are defined. SRv6 network programming makes it convenient to add
sophisticated operations in the network. ([RFC8402])
This document describes how to implement DetNet with SRv6. It can
provide : 1. Source routing, which can steer the DetNet flows go
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through the network according to an explicit route with allocated
resource by segment list in SRH; 2. Network programming, which can
give packet instructions in every node along the path to guarantee
bounded latency. DetNet SRv6 encapsulation and new SRv6 functions
for DetNet are defined in this document.
Control plane and OAM are not in the scope of this document.
2. Terminology and Conventions
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].
2.1. Terminology
Terminologies for DetNet go along with the definition in
[I-D.ietf-detnet-architecture]. Other terminologies are defined as
follows:
o NH: The IPv6 next-header field.
o SID: A Segment Identifier which represents a specific segment in a
segment routing domain([RFC8402]).
o SRH: The Segment Routing Header
([I-D.ietf-6man-segment-routing-header]).
2.2. Conventions
Conventions in the document are defined as follows:
o NH=SRH means that NH is 43 with routing type 4.
o A SID list is represented as <S1, S2, S3> where S1 is the first
SID to visit, S2 is the second SID to visit and S3 is the last SID
to visit along the SR path.
o SRH[SL] represents the SID pointed by the SL field in the first
SRH. In our example, SRH[2] represents S1, SRH[1] represents S2
and SRH[0] represents S3.
o (SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with:
IPv6 header with source and destination addresses SA and DA
respectively, and next-header SRH, with SID list <S1, S2, S3>
with SegmentsLeft = SL
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The payload of the packet is not represented
(S3, S2, S1; SL) represents the same SID list as <S1, S2, S3>,
but encoded in the SRH format where the rightmost SID in the
SRH is the first SID and the leftmost SID in the SRH is the
last SID
3. SRv6 DetNet Data Plane Overview
[I-D.chen-detnet-sr-based-bounded-latency] defines a new segment that
is called a Cycle SID, which is used to identify a cycle. .
A Cycle SID has two meanings: 1) identify an interface/link, just
like the adjacency segment does; 2) identify a cycle of the
interface/link. To specify to which interface and in which cycle a
packet should be transmitted. By attaching a list of Cycle Segments
to a packet in SRH, it can not only implement the explicit route of
the packet that is required by DetNet [I-D.ietf-detnet-architecture],
but also specify the sending cycle at each node along the path
without maintaining per-flow states at the intermediate and egress
nodes.
SRv6 Cycle SID can be represented as LOC:FUNCT:ARG::, where LOC,
abbreviated for "LOCATION", directs the explicit route, FUNCT,
abbreviated for "FUNCTION", directs the packet processing in the
local node, and ARG, abbreviated for "ARGUMENTS", provides the cycle
information. New SID functions for DetNet is defined in section 3.2.
3.1. Encapsulation
The SRH for DetNet in the outer IPv6 header is showed as follows:
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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 | Segment Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags | Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Location & Function |
| (Segment List[0] for transit node with CSQF Function) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cycle Information |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[n] |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional TLVS |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Location&Function: the 64 most significant bits that are used for
routing and function indication;
o Cycle Information : 64 bits, which are used for indicate the cycle
number in which the packet is supposed to transmit through the
output port;
3.2. Functions
New SID functions are defined as follows:
End.X.Cycle.Indication
1. IF NH=SRH and SL > 0
2. decrement SL
3. reserve the value of cycle information field
4. update the IPv6 DA with SRH[SL]
5. forward to layer-3 adjacency bound to the Location
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6. put the packet in the queue corresponding to the cycle
information reserved
7. ELSE
8. drop the packet
4. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
5. Security Considerations
TBD
6. Acknowledgements
7. Normative References
[I-D.chen-detnet-sr-based-bounded-latency]
Chen, M., Geng, X., and Z. Li, "Segment Routing (SR) Based
Bounded Latency", draft-chen-detnet-sr-based-bounded-
latency-00 (work in progress), October 2018.
[I-D.filsfils-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J.,
daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
Network Programming", draft-filsfils-spring-srv6-network-
programming-07 (work in progress), February 2019.
[I-D.ietf-6man-segment-routing-header]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-18 (work in
progress), April 2019.
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-12 (work in progress), March 2019.
[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>.
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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
Xuesong Geng
Huawei
Email: gengxuesong@huawei.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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