[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

TEAS                                                        Shaofu. Peng
Internet-Draft                                                 Ran. Chen
Intended status: Standards Track                         Gregory. Mirsky
Expires: February 21, 2020                               ZTE Corporation
                                                         August 20, 2019


              Packet Network Slicing using Segment Routing
                   draft-peng-teas-network-slicing-00

Abstract

   This document presents a mechanism aimed at providing a solution for
   network slicing in the transport network for 5G services.  The
   proposed mechanism uses a unified administrative instance identifier
   to distinguish different virtual network resources for both intra-
   domain and inter-domain network slicing scenarios.  Combined with the
   segment routing technology, the mechanism could be used for both
   best-effort and traffic engineered services for tenants.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 21, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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 extracted from this document must



Peng, et al.            Expires February 21, 2020               [Page 1]


Internet-Draft       Packet Network Slicing using SR         August 2019


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
   3.  Overview of Mechanism . . . . . . . . . . . . . . . . . . . .   4
   4.  Resource Allocation per AII . . . . . . . . . . . . . . . . .   5
     4.1.  L3 Link Resource AII Configuration  . . . . . . . . . . .   5
     4.2.  L2 Link Resource AII Configuration  . . . . . . . . . . .   6
     4.3.  Node Resource AII Configuration . . . . . . . . . . . . .   6
   5.  Interworking with SR Flex-algorithm . . . . . . . . . . . . .   7
     5.1.  Best-effort Service AII-specific  . . . . . . . . . . . .   7
     5.2.  Traffic Engineering service AII-specific  . . . . . . . .   7
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  intra-domain network slicing  . . . . . . . . . . . . . .   8
     6.2.  inter-domain network slicing via BGP-LS . . . . . . . . .   9
     6.3.  inter-domain network slicing via BGP-LU . . . . . . . . .  11
   7.  Implementation suggestions  . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   11. Normative references  . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   According to 5G context, network slicing is the collection of a set
   of technologies to create specialized, dedicated logical networks as
   a service (NaaS) in support of network service differentiation and
   meeting the diversified requirements from vertical industries.
   Through the flexible and customized design of functions, isolation
   mechanisms, and operation and management (O&M) tools, network slicing
   is capable of providing dedicated virtual networks over a shared
   infrastructure.  A Network slice instance (NSI) is the realization of
   network slicing concept.  It is an E2E logical network, which
   comprises of a group of network functions, resources, and connection
   relationships.  An NSI typically covers multiple technical domains,
   which includes a terminal, access network (AN), transport network
   (TN) and a core network (CN), as well as DC domain that hosts third-
   party applications from vertical industries.  Different NSIs may have
   different network functions and resources.  They may also share some
   of the network functions and resources.

   For a packet network, network slicing requires the underlying network
   to support partitioning of the network resources to provide the



Peng, et al.            Expires February 21, 2020               [Page 2]


Internet-Draft       Packet Network Slicing using SR         August 2019


   client with dedicated (private) networking, computing, and storage
   resources drawn from a shared pool.  The slices may be seen as
   virtual networks.  [I-D.ietf-teas-enhanced-vpn] described a framework
   to create virtual networks in a packet network.  This document
   specifies a detailed mechanism to signal association of shared
   resources required to create and manage an NSI.

   Currently there are multiple methods that could be used to identify
   the virtual network resource, such as Administrative Group (AG)
   described in [RFC3630], [RFC5329] and [RFC5305], Extended
   Administrative Groups (EAGs) described in [RFC7308], and Multi-
   Topology Routing (MTR) described in [RFC5120], [RFC4915] and
   [RFC5340].  However, all these methods are not sufficient to meet the
   requirements of network slicing service.  For example, AG or EAG are
   limited to serve as a link color scheme used in TE path computation
   to meet the requirements of TE service for a tenant.  But it is
   difficult to use them for an NSI allocation mapping (assuming that
   each bit position of AG/EAG represents an NSI) and, at the same time,
   as an IGP FIB identifier for best-effort service for the same tenant.
   MTR is limited to serve as an IGP logical topology scheme only used
   in the intra-domain scenario, and it is challenging to select inter-
   area link resource according to MT-ID when E2E inter-domain TE path
   needs to be created for a tenant.

   In summary, the following requirements would be satisfied:

   1) Uniform NSI for easy operation and maintenance;

   2) E2E network slicing, including both intra-domain and inter-domain
   case;

   3) Customization resource for QoS purpose, bandwidth and delay are
   basic constraints;

   4) Layer 2 as well as Layer 3 link resource partition;

   Thus, there needs to be a new characteristic of NSI to isolate
   underlay resources.  Firstly it could serve as TE criteria for TE
   service, and secondly, as an IGP FIB table identifier for best-effort
   service.  This document introduces a new property of NSI called
   "Administrative Instance Identifier" (AII) and corresponding method
   how to instantiate it in underlay network to match above
   requirements.








Peng, et al.            Expires February 21, 2020               [Page 3]


Internet-Draft       Packet Network Slicing using SR         August 2019


2.  Conventions used in this document

   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.

3.  Overview of Mechanism

   At the initial stage, each link in a physical network can be colored
   to conform with network slicing requirements.  As previously
   mentioned, AII can be used to color links to partition underlay
   resource.  Also, we may continue to use AG or EAG to color links for
   traditional TE purpose within a virtual network specified by an AII.
   A single or multiple AIIs could be configured on each intra-domain or
   inter-domain link regardless of IGP instance configuration.  At the
   minimum, a link always belongs to default AII (the value is 0).  The
   number of AIIs configured on a node's links determines the number of
   virtual networks the node is part of.  This document defines a new
   extension of the existing IGP-TE mechanisms [RFC3630] and [RFC5305]
   to distribute AII information in an AS as a new TE parameter of a
   link.  An SDN controller, using BGP-LS or another interface, will
   have a distinct view of each virtual network specified by AII.

   Using the CSPF algorithm, a TE path for any best-effort (BE) or
   traffic engineered (TE) service can be calculated within a virtual
   network specified by the AII.  The computation criteria could be
   <AII, min igp-metric> or <AII, traditional TE critierias> for the BE
   and TE respectively.  Combined with segment routing, the TE path
   could be represented as:

   o  a single node-SID of the destination node, for the best-effort
      service in the domain;

   o  node-SIDs of the border node and the destination node, adjacency-
      SID of inter-domain link, for the inter-domain best-effort
      service;

   o  an adjacency-SID list, for P2P traffic engineered service.

   Because packets of the best-effort service could be transported over
   an MP2P LSP without congestion control, SR best-effort FIB for each
   virtual network specified by AII to forward best-effort packets may
   be created in the IGP domain.  Thus, CSPF computation with criteria
   <AII, min igp-metric>is distributed on each node in the IGP domain.
   That is similar to the behavior in [Flex-algo], but the distributed
   CSPF computation is triggered by AII.





Peng, et al.            Expires February 21, 2020               [Page 4]


Internet-Draft       Packet Network Slicing using SR         August 2019


   To distinguish forwarding behavior of different virtual networks,
   prefix-SID need to be allocated per AII and advertised in the IGP
   domain.

   For inter-domain case, in addition to the destination node-SID,
   several node-SIDs of the domain border node and adjacency-SID of
   inter-domain link are also needed to construct the E2E segment list.
   The segment list could be computed with the help of the SDN
   controller which needs to consider AII information during the
   computation.  The head-end of the segment list maintains the
   corresponding SR-TE tunnel or
   [I-D.ietf-spring-segment-routing-policy].

   As for the prefix-SID, adjacency-SID needs to be allocated per AII to
   distinguish the forwarding behavior of different virtual networks.

   For P2P traffic engineering service, especially such as uRLLC
   service, it SHOULD not transfer over an MP2P LSP to avoid the risk of
   traffic congestion.  The segment list could consist of pure
   adjacency-SID per AII specific.  The head-end of the segment list
   maintains the corresponding SR-TE tunnel or
   [I-D.ietf-spring-segment-routing-policy].

   However, label stack depth of the segment list MAY be optimized at a
   later time based on local policies.

   At this moment we can steer traffic of overlay service to the above
   SR best-effort FIB, SR-TE tunnel or SR policy instance, for the
   specific virtual network.  The overlay service could specify a color
   for TE purpose, for example, color 1000 means <AII=10, min igp-
   metric> to say that I need best-effort forwarding within AII 10
   resource, color 1001 means <AII=10, delay=10ms, AG=0x1> to say that I
   need traffic engineering forwarding within AII 10 resource,
   especially using link with AG equal to 0x1 to reach guarantee of not
   exceeding 10ms delay time.  Service with color 1000 will be steered
   to an SR best-effort FIB entry, or an SR-TE tunnel/policy in case of
   inter-domain.  Service with color 1001 will be steered to an SR-TE
   tunnel/policy.

4.  Resource Allocation per AII

4.1.  L3 Link Resource AII Configuration

   In IGP domain, each numbered or unnumbered L3 link could be
   configured with AII information and synchronized among IGP neighbors.
   The IGP link-state database will contain L3 links with AII
   information to support TE path computation considering AII criteria.
   For a numbered L3 link, it could be represented as a tuple <local



Peng, et al.            Expires February 21, 2020               [Page 5]


Internet-Draft       Packet Network Slicing using SR         August 2019


   node-id, remote node-id, local ip-address, remote ip-address>, for
   unnumbered it could be <local node-id, remote node-id, local
   interface-id, remote interface-id>.  Each L3 link could be configured
   to belong to a single AII or multiple AIIs, for each <L3 link, AII>
   tuple it would allocate a different adjacency-SID.  Note that an L3
   link always belongs to default AII(0).

   AII is independent of IGP instance.  An L3 link that is not part of
   the IGP domain, such as the special purpose for a static route, or an
   inter-domain link, can also be configured with AII information and
   allocate adjacency-SID per AII as the same as IGP links.  BGP-LS
   could be used to collect link state data with AII information to the
   controller.

4.2.  L2 Link Resource AII Configuration

   [I-D.ietf-isis-l2bundles] described how to encode adjacency-SID for
   each L2 member link of an L3 parent link.  It is beneficial to deploy
   LAG or another virtual aggregation interface in network slicing
   scenario.  Between two nodes, the dedicated link resources belong to
   different virtual networks could be added or removed on demand, they
   are treated as L2 member links of a single L3 virtual interface.  It
   is the single L3 virtual interface that needs to occupy IP resource
   and join to an IGP instance.  Creating a new slice-specific link on
   demand or removing the old one, is likely to affect some
   configurations.

   Each L2 member link of an L3 parent link SUGGESTED to be configured
   to belong to a single AII, and different L2 member link will have
   different single AII configuration, with different adjacency-SID.
   Note that in this case, the L3 parent link belongs to default AII(0),
   but each L2 member link belongs to the specific non-default AII.
   Routing protocol control packets follow the L3 parent link of the L2
   member link with the highest priority.  At the same time, data
   packets that belong to the specific virtual network will pass along
   the L2 member link with the specific AII value.

   TE path computation based on link-state database need view the
   detailed L2 members of an L3 adjacency to select the expected L2 link
   resource.

4.3.  Node Resource AII Configuration

   For topology resource, each node needs to allocate node-SID per AII
   when it joins the related virtual network.  All nodes in the IGP
   domain can run CSPF algorithm with criteria <AII, min IGP metric> to
   compute best-effort next-hop to any other destination nodes for a
   virtual network AII-specific, based on the link-state database that



Peng, et al.            Expires February 21, 2020               [Page 6]


Internet-Draft       Packet Network Slicing using SR         August 2019


   containing AII information so that SR best-effort FIB can be
   constructed for each AII.

   An intra-domain overlay best-effort service belongs to a virtual
   network could directly match in the above SR best-effort FIB for the
   specific AII, while an inter-domain overlay best-effort service
   belongs to a virtual network could be over a segment list containing
   domain border node-SID and destination node-SID which could match in
   the above SR best-effort FIB for the specific AII.

5.  Interworking with SR Flex-algorithm

   [I-D.ietf-lsr-flex-algo] introduced a mechanism to do label stack
   depth optimization for an SR policy in IGP domain part.  As the color
   of SR policy defined a TE purpose, traditionally the headend or SDN
   controller will compute an expected TE path to meet that purpose.  It
   is necessary to map a color (32 bits) to an FA-ID (8 bits) when SR
   flex-algorithm enabled for an SR policy, besides that, it is
   necessary to enable the FA-ID on each node that will join the same FA
   plane manually.  However, the FAD could copy the TE constraints
   contained in the color template.  We need to consider the cost of
   losing the flexibility of color when executing the flex-algo
   optimization, and also consider the gap between P2P TE requirements
   and MP2P SR FA LSP capability, to reach the right balance when
   deciding which SR policy need optimization.

5.1.  Best-effort Service AII-specific

   As described above, for best-effort service we have already
   constructed SR best-effort FIB per AII, that is mostly like [Flex-
   algo].  Thus, it is not necessary to map to FA-ID again for a color
   template which has defined a best-effort behavior within the
   dedicated AII.  Of course, if someone forced to remap it, there is no
   downside for the operation, the overlay best-effort service (with a
   color which defined specific AII, best-effort requirement, and
   mapping FA-ID) in IGP domain will try to recurse over <AII, prefix>
   or <FA-ID, prefix> FIB entry.

5.2.  Traffic Engineering service AII-specific

   An SR-TE tunnel/policy that served for traffic engineering service of
   a virtual network specified by an AII was generated and computed
   according to the relevant color template, which contained specific
   AII and some other traditional TE constraints.  If we config mapping
   FA-ID under the color template, the SR-TE tunnel/policy instance
   could inherit forwarding information from corresponding SR Flex-Algo
   FIB entry.




Peng, et al.            Expires February 21, 2020               [Page 7]


Internet-Draft       Packet Network Slicing using SR         August 2019


6.  Examples

   In this section, we will further illustrate the point through some
   examples.  All examples share the same figure below.



                  .-----.                               .-----.
                 (       )                             (       )
             .--(         )--.                     .--(         )--.
        +---+----link A1----+---+             +---+----link A1----+---+
        |PE1|----link A2----|PE2|---link A1---|PE3|----link A2----|PE2|
        |   |----link B1----|   |---link B1---|   |----link B1----|   |
        +---+----link B2----+---+             +---+----link B2----+---+
            (                  )                  (                  )
              '--(  AS1    )--'                    '--(   AS2    )--'
                  (       )                            (       )
                   '-----'                              '-----'

                     Figure 1 Network Slicing via AII

   Suppose that each link belongs to separate virtual network, e.g.,
   link Ax belongs to the virtual network colored by AII A, link Bx
   belongs to the virtual network colored by AII B. link x1 has an IGP
   metric smaller than link x2, but TE metric lager.

   To simplify the use case, each AS just contained a single IGP area.

6.1.  intra-domain network slicing

   From the perspective of node PE1 in AS1, it will calculate best-
   effort forwarding entry for each AII instance (including default AII)
   to destinations in the same IGP area.  For example:

   For <AII=0, destination=ASBR1> entry, forwarding information could be
   ECMP during link A1 and link B1, with destination node-SID 100 for
   <AII=0, destination=ASBR1>.

   For <AII=A, destination=ASBR1> entry, forwarding information could be
   link A1, with destination node-SID 200 for <AII=A,
   destination=ASBR1>.

   For <AII=B, destination=ASBR1> entry, forwarding information could be
   link B1, with destination node-SID 300 for <AII=B,
   destination=ASBR1>.






Peng, et al.            Expires February 21, 2020               [Page 8]


Internet-Draft       Packet Network Slicing using SR         August 2019


   It could also initiate an SR-TE instance (SR tunnel or SR policy)
   with the particular color template on PE1, PE1 is headend and ASBR1
   is destination node.  For example:

   For SR-TE instance 1 with color template which defined criteria
   including {default AII, min TE metric}, forwarding information could
   be ECMP during two segment list {adjacency-SID 1002 for <AII=0, link
   A2>@PE1} and {adjacency-SID 1004 for <AII=0, link B2>@PE1}.

   For SR-TE instance 2 with the color template which defined criteria
   including {AII=A, min TE metric}, forwarding information could be
   presented as the segment list {adjacency-SID 2002 for <AII=A, link
   A2>@PE1}.

   For SR-TE instance 3 with the color template which defined criteria
   including {AII=B, min TE metric}, forwarding information could be
   presented as the segment list {adjacency-SID 3004 for <AII=B, link
   B2>@PE1}.

   Furthermore, we can use SR Flex-algo to optimize the above SR-TE
   instance.  For example, for SR-TE instance 1, we can define FA-ID 201
   with FAD that contains the same information as the color template, in
   turn, FA-ID 202 for SR-TE instance 2, FA-ID 203 for SR-TE instance 3.
   Note that each FA-ID also needs to be enabled on ASBR1.  So that the
   corresponding SR FA entry could be:

   For <FA-ID=201, destination=ASBR1> entry, forwarding information
   could be ECMP during link A2 and link B2, with destination node-SID
   600 for <FA-ID=201, destination=ASBR1>.

   For <FA-ID=202, destination=ASBR1> entry, forwarding information
   could be link A2, with destination node-SID 700 for <FA-ID=202,
   destination=ASBR1>.

   For <FA-ID=203, destination=ASBR1> entry, forwarding information
   could be link B2, with destination node-SID 800 for <FA-ID=203,
   destination=ASBR1>.

6.2.  inter-domain network slicing via BGP-LS

   [RFC7752] BGP-LS describes the methodology that using BGP protocol to
   transfer the Link-State information that maybe originated from IGP
   instance (for intra-domain topology information) or from local direct
   interface or static configuration(for inter-domain topology
   information).  [I-D.ietf-idr-bgpls-inter-as-topology-ext] also
   describes a method to firstly put inter-domain interconnections to
   IGP instance, then always import data from IGP protocol source to




Peng, et al.            Expires February 21, 2020               [Page 9]


Internet-Draft       Packet Network Slicing using SR         August 2019


   BGP-LS.  In any case BGP-LS need extend to transfer the Link-State
   data with AII information.

   An E2E inner-AS SR-TE instance with particular color template could
   be initiated on PE1, PE1 is head-end and PE2 is destination node.
   BGP-LS could be used to inform the SDN controller about the underlay
   network topology information including AII attribute.  Thus the
   controller could calculate E2E TE path within the particular virtual
   network.

   o For best-effort service, for example:

   For SR-TE instance 4 with color template which defined criteria
   including {default AII, min IGP metric}, forwarding information could
   be segment list {node-SID 100 for <AII=0, destination=ASBR1>,
   adjacency-SID 1001 for <AII=0, link A1>@ASBR1, node-SID 400 for <
   AII=0, destination=PE2>}.

   For SR-TE instance 5 with color template which defined criteria
   including {AII=A, min IGP metric}, forwarding information could be
   segment list {node-SID 200 for <AII=A, destination=ASBR1>, adjacency-
   SID 1001 for <AII=A, link A1>@ASBR1, node-SID 500 for <AII=A,
   destination=PE2>}.

   For SR-TE instance 6 with color template which defined criteria
   including {AII=B, min IGP metric}, forwarding information could be
   segment list {node-SID 300 for <AII=B, destination=ASBR1>, adjacency-
   SID 1003 for <AII=B, link B1>@ASBR1, node-SID 600 for <AII=B,
   destination=PE2>}.

   o For TE service, for example:

   For SR-TE instance 7 with color template which defined criteria
   including {default AII, min TE metric}, forwarding information could
   be ECMP during two segment list {adjacency-SID 1002 for <AII=0, link
   A2>@PE1, adjacency-SID 1001 for <AII=0, link A1>@ASBR1, adjacency-SID
   1002 for <AII=0, link A2>@ASBR2} and {adjacency-SID 1004 for <AII=0,
   link B2>@PE1, adjacency-SID 1003 for <AII=0, link B1>@ASBR1,
   adjacency-SID 1004 for <AII=0, link B2>@ASBR2}.

   For SR-TE instance 8 with color template which defined criteria
   including {AII=A, min TE metric}, forwarding information could be
   segment list {adjacency-SID 2002 for <AII=A, link A2>@PE1, adjacency-
   SID 2001 for <AII=A, link A1>@ASBR1, adjacency-SID 2002 for <AII=A,
   link A2>@ASBR2}.

   For SR-TE instance 9 with color template which defined criteria
   including {AII=B, min TE metric}, forwarding information could be



Peng, et al.            Expires February 21, 2020              [Page 10]


Internet-Draft       Packet Network Slicing using SR         August 2019


   segment list {adjacency-SID 3004 for <AII=B, link B2>@PE1, adjacency-
   SID 3003 for <AII=B, link B1>@ASBR1, adjacency-SID 3004 for <AII=B,
   link B2>@ASBR2}.

   For TE service, if we use SR Flex-algo to do optimizaztion, the above
   forwarding information of each TE instance could inherit the
   corresponding SR FA entry, it would look like this:

   For SR-TE instance 7, forwarding information could be ECMP during two
   segment list {node-SID 600 for <FA-ID=201, destination=ASBR1>,
   adjacency-SID 1001 for <AII=0, link A1>@ASBR1, node-SID 600 for < FA-
   ID=201, destination=PE2>} and {adjacency-SID 1004 for <AII=0, link
   B2>@PE1, adjacency-SID 1003 for <AII=0, link B1>@ASBR1, adjacency-SID
   1004 for <AII=0, link B2>@ASBR2}.

   For SR-TE instance 8 with color template which defined criteria
   including {AII=A, min TE metric}, forwarding information could be
   segment list {node-SID 700 for <FA-ID=202, destination=ASBR1>,
   adjacency-SID 2001 for <AII=A, link A1>@ASBR1, node-SID 700 for <FA-
   ID=202, destination=PE2>}.

   For SR-TE instance 9 with color template which defined criteria
   including {AII=B, min TE metric}, forwarding information could be
   segment list {node-SID 800 for <FA-ID=203, destination=ASBR1>,
   adjacency-SID 3003 for <AII=B, link B1>@ASBR1, node-SID 800 for <FA-
   ID=203, destination=PE2>}.

6.3.  inter-domain network slicing via BGP-LU

   In some deployments, operators adopt BGP-LU to build inter-domain
   MPLS LSP, overlay service will be directly over BGP-LU LSP.  If
   overlay service has TE requirements that defined by a color, that
   means that BGP-LU LSP needs to have a sense of color too, i.e., BGP-
   LU label could be allocated per color.  At entry node of each domain,
   BGP-LU LSP generated for specific color will be over intra-domain SR-
   TE or SR Best-effort path generated for that color again.  At exit
   node of each domain, BGP-LU LSP generated for specific color will
   select inter-domain forwarding resource per color.

   [RFC7911] defined that multiple paths UPDATE message for the same
   destination prefix can be advertised in BGP, each UPDATE can contain
   the Color Extended Community ([I-D.ietf-idr-tunnel-encaps]) with
   different color value.

   In figure 1, PE2 can allocate and advertise six labels for its
   loopback plus color 1, 2, 3, 4, 5, 6 respectively.  Suppose color 1
   defines {default AII, min IGP metric}, color 2 defines {AII=A, min
   IGP metric}, color 3 defines {AII=B, min IGP metric}, and color 4



Peng, et al.            Expires February 21, 2020              [Page 11]


Internet-Draft       Packet Network Slicing using SR         August 2019


   defines {default AII, min TE metric}, color 5 defines {AII=A, min TE
   metric}, color 6 defines {AII=B, min TE metric}. PE2 will advertise
   these labels to ASBR2 and ASBR2 then continues to allocate six labels
   each for prefix PE2 plus different color.  Other nodes will have the
   same operation.  Ultimately PE1 will maintain six BGP-LU LSP.

   For example, the BGP-LU LSP for color 1 will be over SR best-effort
   FIB entry node-SID 100 for <AII=0, destination=ASBR1> to pass through
   AS1, over adjacency-SID 1001 for <AII=0, link A1>@ASBR1 to pass
   inter-AS, over SR best-effort FIB entry node-SID 400 for <AII=0,
   destination=PE2> to pass through AS2.

   For example, The BGP-LU LSP for color 4 will over SR-TE instance 1
   (see section 6.1), or SR best-effort FIB entry node-SID 600 for <FA-
   ID=201, destination=ASBR1> (see section 6.1) to pass through AS1,
   over adjacency-SID 1001 for <AII=0, link A1>@ASBR1 to pass inter-AS,
   over SR-TE instance 1' or corresponding SR FA entry to pass through
   AS2.  Note that ASBR1 need also understand the meaning of a specific
   color and select forwarding resource between two AS.

7.  Implementation suggestions

   As a node often contains control plane and forwarding plane, a
   suggestion is that only default AII specific FTN entry need be
   installed on forwarding plane, so that there are not any modification
   and upgrade requirement for hardware and existing MPLS forwarding
   mechanism.  FTN entry for non-default AII instance will only be
   maintained on the control plane and be used for overlay service
   iteration according to next-hop plus color (color will give AII
   information and mapping FA-ID information).  Note that ILM entry for
   all AII need be installed on forwarding plane.

   The same suggestion is also appropriate for SR Flex-algo.

   SR NHLFE need contain AII information for expected packet scheduling.

8.  IANA Considerations

   TBD.

9.  Security Considerations

   TBD.








Peng, et al.            Expires February 21, 2020              [Page 12]


Internet-Draft       Packet Network Slicing using SR         August 2019


10.  Acknowledgements

   TBD.

11.  Normative references

   [I-D.ietf-idr-bgpls-inter-as-topology-ext]
              Wang, A., Chen, H., Talaulikar, K., and S. Ma, "BGP-LS
              Extension for Inter-AS Topology Retrieval", draft-ietf-
              idr-bgpls-inter-as-topology-ext-03 (work in progress),
              July 2019.

   [I-D.ietf-idr-tunnel-encaps]
              Patel, K., Velde, G., Ramachandra, S., and E. Rosen, "The
              BGP Tunnel Encapsulation Attribute", draft-ietf-idr-
              tunnel-encaps-13 (work in progress), July 2019.

   [I-D.ietf-isis-l2bundles]
              Ginsberg, L., Bashandy, A., Filsfils, C., Nanduri, M., and
              E. Aries, "Advertising L2 Bundle Member Link Attributes in
              IS-IS", draft-ietf-isis-l2bundles-07 (work in progress),
              May 2017.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-03 (work in progress), July 2019.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-03 (work in progress), May 2019.

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Service", draft-ietf-teas-enhanced-vpn-02 (work in
              progress), July 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>.







Peng, et al.            Expires February 21, 2020              [Page 13]


Internet-Draft       Packet Network Slicing using SR         August 2019


   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
              "Traffic Engineering Extensions to OSPF Version 3",
              RFC 5329, DOI 10.17487/RFC5329, September 2008,
              <https://www.rfc-editor.org/info/rfc5329>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [RFC7308]  Osborne, E., "Extended Administrative Groups in MPLS
              Traffic Engineering (MPLS-TE)", RFC 7308,
              DOI 10.17487/RFC7308, July 2014,
              <https://www.rfc-editor.org/info/rfc7308>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <https://www.rfc-editor.org/info/rfc7911>.







Peng, et al.            Expires February 21, 2020              [Page 14]


Internet-Draft       Packet Network Slicing using SR         August 2019


Authors' Addresses

   Shaofu Peng
   ZTE Corporation

   Email: peng.shaofu@zte.com.cn


   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn


   Gregory Mirsky
   ZTE Corporation

   Email: gregimirsky@gmail.com

































Peng, et al.            Expires February 21, 2020              [Page 15]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/