Internet DRAFT - draft-zzhang-bier-slicing-and-differentiation
draft-zzhang-bier-slicing-and-differentiation
bier Z. Zhang
Internet-Draft A. Przygienda
Intended status: Standards Track Juniper Networks
Expires: April 2, 2022 September 29, 2021
BIER with Network Slicing and Flow Differentiation
draft-zzhang-bier-slicing-and-differentiation-00
Abstract
This document specifies how BIER works in the context of IETF Network
slicing, with or without fined-grained traffic differentiation.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BIER with IETF Network Slicing . . . . . . . . . . . . . . . 3
3. BIER with Slice Aggregates . . . . . . . . . . . . . . . . . 4
4. Specifications . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. ISIS Signaling . . . . . . . . . . . . . . . . . . . . . 4
4.1.1. OSPF Signaling . . . . . . . . . . . . . . . . . . . 5
4.1.2. BGP Signaling . . . . . . . . . . . . . . . . . . . . 5
4.2. BIER Extension Header . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Network slicing has been a topic widely discussed in and beyond IETF.
According to [I-D.ietf-teas-ietf-network-slices]:
"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
(SLOs).
An IETF Network Slice combines the connectivity resource requirements
and associated network behaviors such as bandwidth, latency, jitter,
and network functions with other resource behaviors such as compute
and storage availability."
It is expected that traffic associated with an IETF network slice is
identified with a slice identifier (e.g. an MPLS label) and each node
in the path uses the slice identifier to identify the slice in which
the traffic is forwarded.
[I-D.bestbar-teas-ns-packet] introduces the notion of Slice Aggregate
which comprises of one of more IETF network slice traffic streams. A
Slice Aggregate is identified by a Slice Selector (SS), and packets
carry the SS so that associated forwarding treatment or S-PHB (Slice
policy Per Hop Behavior - the externally observable forwarding
behavior applied to a specific packet belonging to a slice aggregate)
- can be applied along the path.
[I-D.li-apn-problem-statement-usecases] describes challenges faced by
network operators when attempting to provide fine-grained traffic
operations to satisfy the various requirements demanded by new
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applications that require differentiated service treatment and
[I-D.li-apn-framework] proposes a framework for solution:
"... proposes a new framework, named Application-aware
Networking (APN), where application-aware information (i.e. APN
attribute) including APN identification (ID) and/or APN parameters
(e.g. network performance requirements) is encapsulated at network
edge devices and carried in packets traversing an APN domain in order
to facilitate service provisioning, perform fine-granularity traffic
steering and network resource adjustment."
The authors of this document believe that the IETF Network Slicing
framework, when augmented by the Slice Aggregate, addresses the APN
problem domain very well. This documents describes how BIER
[RFC8279] works together with IETF network slicing, with or without
Slice Aggregate to provide fine granularity traffic differentiation
(e.g. down to per-flow level) that is demanded in the APN problem
statement.
2. BIER with IETF Network Slicing
Since an IETF Network Slice is a logical network topology, each slice
may have its BIRT (which maps to a set of BIFTs when BitStringLength
and SetID are considered). While it is tempting and seems logical to
map a slice to a BIER sub-domain, and it is straightforward to do so
when the number of slices is smaller than 256 (the max number of sub-
domains), this document allows to map a slice directly to a BIRT
instead of a sub-domain.
Now a BIRT corresponds to a <sub-domain, slice> tuple, and each BIFT
corresponds to a <subdomain-id, slice-id, bitstring length, set-id>
tuple. In forwarding plane a BIFT is only identified by a 20-bit
opaque number locally on a BFR, which could be an MPLS label or just
a plain number in case of non-MPLS data plane. Therefore, it is
feasible to have many slices in the same sub-domain - each slice will
have its own BIRT so that the same BFER in the same sub-domain can be
reached via different nexthop BFRs according to different BIRTs (i.e.
different set of corresponding BIFTs) for different slices.
With this, up to 2^20 slices could be supported in theory - the only
limit is the number of BIFT entries that a BFR can hold.
Mapping a slice directly to a BIRT instead of a sub-domain not only
allows more than 256 slices but also reduces the burden of sub-domain
related provisioning (e.g. a BFR-ID is needed for each <sub-domain,
BFIR/BFER>). Of course, as mentioned earlier, if the number of
slices is smaller than 256 then a slice can map to a sub-domain as
well.
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3. BIER with Slice Aggregates
Per [I-D.bestbar-teas-ns-packet], a Slice Aggregate may be the
aggregation of several entire slices, or just a particular flow in a
slice. With a Slice Aggregate for several entire slices, the
different slices (of the same Slice Aggregate) also map to the same
BIRT. In that case, for the same destination BFER, traffic in those
different slices are forwarded to the same (set of ECMP) nexthop BFER
according to the shared BIRT, yet other forwarding treatment (e.g.
queuing) could still be different.
In [RFC8279], a sub-domain is associated with only one topology and
each sub-domain has its own BIRT calculated using the topology
information. When multiple slices are associated with a single sub-
domain, each slice (or a set of slices) also has its own BIRT
calculated based on the slice's (or the set of slices') topology
information. Therefore, having a sub-domain with multiple slices
does not violate the underlying principle of BIER architecture, i.e.,
a BIRT is calculated on a corresponding topology, whether the
topology is for a sub-domain as in [RFC8279] or for a <sub-domain,
slice or set of slices> tuple as in this document.
The BIER header has a 6-bit DSCP field. If that is not enough to
identify different slices or slice aggregates that share the same
BIRT, an explicit Slice Selector can be carried in "BIER Extension
Header" [I-D.zzhang-intarea-generic-delivery-functions].
This means that, even for a transit BFR, if provisioned to support
slice aggregates identified by a Slice Selector in the extension
header, it must check if the "Proto" field is set to a value for BIER
Extension Header.
Note: while the concept of "BIER Extension Header" is first brought
up in that Generic Delivery Functions draft
[I-D.zzhang-intarea-generic-delivery-functions] in intarea WG, it is
expected that BIER specific work will be brought to the BIER WG.
4. Specifications
BIER signaling for OSPF/ISIS/BGP is extended to include slice
information so that slice-specific BIRTs can be built.
4.1. ISIS Signaling
A BIER MPLS Encapsulation Extended Sub-sub-TLV is defined with a new
type to allow sub-sub-sub-TLVs in it. Besides the new type and
additional sub-sub-sub-TLVs, the rest are the same as original BIER
MPLS Encapsulation Sub-sub-TLV [RFC8401].
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub-sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: Value of TBD indicating Extended sub-sub-TLV for MPLS
Length: Variable
Sub-sub-sub-TLVs: for information like Slice Selector
Sub-sub-sub-TLVs will be defined to include Slice Selector
information [I-D.bestbar-teas-ns-packet] that identifies a slice or a
Slice Aggregate, and potentially other information. Note that the
Slice Aggregate here is for a set of slices instead of a flow in a
slice. Future revisions will have more details.
Similar encoding will be defined for non-MPLS encapsulation in future
revisions.
4.1.1. OSPF Signaling
Similar encoding will be defined for OSPF signaling in future
revisions.
4.1.2. BGP Signaling
Similar encoding will be defined for BGP signaling in future
revisions.
4.2. BIER Extension Header
This will be tracked by a separate BIER draft. For now, please refer
to [I-D.zzhang-intarea-generic-delivery-functions].
5. Security Considerations
To be provided.
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6. IANA Considerations
To be provided.
7. References
7.1. Normative References
[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.zzhang-intarea-generic-delivery-functions]
Zhang, Z., Bonica, R., Kompella, K., and G. Mirsky,
"Generic Delivery Functions", draft-zzhang-intarea-
generic-delivery-functions-02 (work in progress), August
2021.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
Zhang, "Bit Index Explicit Replication (BIER) Support via
IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
<https://www.rfc-editor.org/info/rfc8401>.
7.2. Informative References
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Gray, E., Drake, J., Rokui, R., Homma, S.,
Makhijani, K., Contreras, L. M., and J. Tantsura,
"Framework for IETF Network Slices", draft-ietf-teas-ietf-
network-slices-04 (work in progress), August 2021.
[I-D.li-apn-framework]
Li, Z., Peng, S., Voyer, D., Li, C., Liu, P., Cao, C.,
Mishra, G., Ebisawa, K., Previdi, S., and J. N. Guichard,
"Application-aware Networking (APN) Framework", draft-li-
apn-framework-03 (work in progress), May 2021.
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[I-D.li-apn-problem-statement-usecases]
Li, Z., Peng, S., Voyer, D., Xie, C., Liu, P., Qin, Z.,
Mishra, G., Ebisawa, K., Previdi, S., and J. N. Guichard,
"Problem Statement and Use Cases of Application-aware
Networking (APN)", draft-li-apn-problem-statement-
usecases-04 (work in progress), June 2021.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
Email: zzhang@juniper.net
Antoni Przygienda
Juniper Networks
Email: prz@juniper.net
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