Internet Engineering Task Force                         D. Joachimpillai
Internet-Draft                                                   Verizon
Intended status: Standards Track                           J. Hadi Salim
Expires: July 8, September 7, 2015                             Mojatatu Networks
                                                         January 4,
                                                           March 6, 2015

                          ForCES Inter-FE LFB


   This document describes extending the ForCES LFB topology across FEs
   i.e inter-FE connectivity without needing any changes to the ForCES
   specification by defining the Inter-FE LFB.  The Inter-FE LFB
   provides ability to pass data, metadata and exceptions across FEs.
   The document describes a generic way to transport the mentioned
   details but focuses on ethernet transport.

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Table of Contents

   1.  Terminology and Conventions  . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
     1.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Problem Scope And Use Cases  . . . . . . . . . . . . . . . . .  4
     3.1.  Basic Router . . . . . . . . . . . . . . . . . . . . . . .  4
       3.1.1.  Distributing The LFB Topology  . . . . . . . . . . . .  6
     3.2.  Arbitrary Network Function . . . . . . . . . . . . . . . .  7
       3.2.1.  Distributing The Arbitrary Network Function  . . . . .  8
   4.  Proposal Overview  . . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  Inserting The Inter-FE LFB . . . . . . . . . . . . . . . .  9
   5.  Generic Inter-FE connectivity  . . . . . . . . . . . . . . . . 11
     5.1.  Inter-FE Ethernet connectivity Connectivity . . . . . . . . . . . . . . 13
       5.1.1.  Inter-FE Ethernet Connectivity Issues  . . . . . . . . 15
   6.  Detailed Description of the Ethernet inter-FE LFB  . . . . . . 16
     6.1.  Data Handling  . . . . . . . . . . . . . . . . . . . . . . 16
       6.1.1.  Egress Processing  . . . . . . . . . . . . . . . . . . 17
       6.1.2.  Ingress Processing . . . . . . . . . . . . . . . . . . 18
     6.2.  Components . . . . . . . . . . . . . . . . . . . . . . . . 19
     6.3.  Inter-FE LFB XML Model . . . . . . . . . . . . . . . . . . 19
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
   9.  IEEE Assignment Considerations . . . . . . . . . . . . . . . . 24
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 24
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     11.2. Informative References . . . . . . . . . . . . . . . . . . 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 26

1.  Terminology and Conventions

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

1.2.  Definitions

   This document reiterates the terminology defined in several ForCES
   documents [RFC3746], [RFC5810], [RFC5811], and [RFC5812] for the sake
   of contextual clarity.

      Control Engine (CE)

      Forwarding Engine (FE)

      FE Model

      LFB (Logical Functional Block) Class (or type)

      LFB Instance

      LFB Model

      LFB Metadata

      ForCES Component

      LFB Component

      ForCES Protocol Layer (ForCES PL)

      ForCES Protocol Transport Mapping Layer (ForCES TML)

2.  Introduction

   In the ForCES architecture, a packet service can be modelled by
   composing a graph of one or more LFB instances.  The reader is
   referred to the details in the ForCES Model [RFC5812].

   The FEObject LFB capabilities in the ForCES Model [RFC5812] define
   component ModifiableLFBTopology which, when advertised by the FE,
   implies that the advertising FE is capable of allowing creation and
   modification the of LFB graph graph(s) by the control plane.  Details on how a
   graph of LFB class instances can be created can be derived by the
   control plane by looking at the FE's FEObject LFB class table
   component SupportedLFBs.  The SupportedLFBs table contains
   information about each LFB class that the FE supports.  For each LFB
   class supported, details are provided on how the supported LFB class
   may be connected to other LFB classes.  The SupportedLFBs table
   describes which LFB class a specified LFB class may succeed or
   precede in an LFB class instance topology.  Each link connecting two
   LFB class instances is described in the LFBLinkType dataTypeDef and
   has sufficient details to identify precisely the end points of a link
   of a service graph.

   The CE may therefore create a packet service by describing an LFB
   instance graph connection; this is achieved by updating the FEOBject
   LFBTopology table.

   Often there are requirements for the packet service graph to cross FE
   boundaries.  This could be from a desire to scale the service or need
   to interact with LFBs which reside in a separate FE (eg lookaside
   interface to a shared TCAM, an interconnected chip, or as coarse
   grained functionality as an external NAT FE box being part of the
   service graph etc).

   Given that the ForCES inter-LFB architecture calls out for ability to
   pass metadata between LFBs, it is imperative therefore to define
   mechanisms to extend that existing feature and allow passing the
   metadata between LFBs across FEs.

   This document describes extending the LFB topology across FEs i.e
   inter-FE connectivity without needing any changes to the ForCES
   definitions.  It focusses on using Ethernet as the interconnection as
   a starting point while leaving room for other protocols (such as
   directly on top of IP, UDP, VXLAN, etc) to be addressed by other
   future documents.

3.  Problem Scope And Use Cases

   The scope of this document is to solve the challenge of passing
   ForCES defined metadata and exceptions across FEs (be they physical
   or virtual).  To illustrate the problem scope we present two use
   cases where we start with a single FE running all the functionality
   then split it into multiple FEs.

3.1.  Basic Router

   A sample LFB topology Figure 1 demonstrates a service graph for
   delivering basic IPV4 forwarding service within one FE.  For the
   purpose of illustration, the diagram shows LFB classes as graph nodes
   instead of multiple LFB class instances.

   Since the illustration is meant only as an exercise to showcase how
   data and metadata are sent down or upstream on a graph of LFBs, it
   abstracts out any ports in both directions and talks about a generic
   ingress and egress LFB.  Again, for illustration purposes, the
   diagram does not show exception or error paths.  Also left out are
   details on Reverse Path Filtering, ECMP, multicast handling etc.  In
   other words, this is not meant to be a complete description of an
   IPV4 forwarding application; for a more complete example, please
   refer to the LFBlib document [RFC6956] . [RFC6956].

   The output of the ingress LFB(s) coming into the IPv4 Validator LFB
   will have both the IPV4 packets and, depending on the implementation,
   a variety of ingress metadata such as offsets into the different
   headers, any classification metadata, physical and virtual ports
   encountered, tunnelling information etc.  These metadata are lumped
   together as "ingress metadata".

   Once the IPV4 validator vets the packet (example ensures that no
   expired TTL etc), it feeds the packet and inherited metadata into the
   IPV4 unicast LPM LFB.

                      |    |
           IPV4 pkt   |    | IPV4 pkt     +-----+             +---+
       +------------->|    +------------->|     |             |   |
       |  + ingress   |    | + ingress    |IPv4 |   IPV4 pkt  |   |
       |   metadata   |    | metadata     |Ucast+------------>|   +--+
       |              +----+              |LPM  |  + ingress  |   |  |
     +-+-+             IPv4               +-----+  + NHinfo   +---+  |
     |   |             Validator                   metadata   IPv4   |
     |   |             LFB                                    NextHop|
     |   |                                                     LFB   |
     |   |                                                           |
     |   |                                                  IPV4 pkt |
     |   |                                               + {ingress  |
     +---+                                                  + NHdetails}
     Ingress                                                metadata |
      LFB                                +--------+                  |
                                         | Egress |                  |
                                      <--+        |<-----------------+
                                         |  LFB   |

             Figure 1: Basic IPV4 packet service LFB topology

   The IPV4 unicast LPM LFB does a longest prefix match lookup on the
   IPV4 FIB using the destination IP address as a search key.  The
   result is typically a next hop selector which is passed downstream as

   The Nexthop LFB receives the IPv4 packet with an associated next hop
   info metadata.  The NextHop LFB consumes the NH info metadata and
   derives from it a table index to look up the next hop table in order
   to find the appropriate egress information.  The lookup result is
   used to build the next hop details to be used downstream on the
   egress.  This information may include any source and destination
   information (MAC address to use, if ethernet;) as well egress ports.
   [Note: It is also at this LFB where typically the forwarding TTL
   decrement and IP checksum recalculation occurs.]

   The details of the egress LFB are considered out of scope for this
   discussion.  Suffice it is to say that somewhere within or beyond the
   Egress LFB the IPV4 packet will be sent out a port (ethernet, virtual
   or physical etc).

3.1.1.  Distributing The LFB Topology

   Figure 2 demonstrates one way the router LFB topology in Figure 1 may
   be split across two FEs (eg two ASICs).  Figure 2 shows the LFB
   topology split across FEs after the IPV4 unicast LPM LFB.

    |                            +----+                           |
    | +----------+               |    |                           |
    | | Ingress  |    IPV4 pkt   |    | IPV4 pkt     +-----+      |
    | |  LFB     +-------------->|    +------------->|     |      |
    | |          |  + ingress    |    | + ingress    |IPv4 |      |
    | +----------+    metadata   |    |   metadata   |Ucast|      |
    |      ^                     +----+              |LPM  |      |
    |      |                      IPv4               +--+--+      |
    |      |                     Validator              |         |
    |                             LFB                   |         |
                                                   IPv4 packet +
                                                 {ingress + NHinfo}
      FE2                                               |
    |                                                   V         |
    |             +--------+                       +--------+     |
    |             | Egress |     IPV4 packet       | IPV4   |     |
    |       <-----+  LFB   |<----------------------+NextHop |     |
    |             |        |{ingress + NHdetails}  | LFB    |     |
    |             +--------+      metadata         +--------+     |

             Figure 2: Split IPV4 packet service LFB topology

   Some proprietary inter-connect (example Broadcom Higig over XAUI
   (XXX: ref needed)) maybe
   [brcm-higig]) are known to exist to carry both the IPV4 packet and
   the related metadata between the IPV4 Unicast LFB and IPV4 NextHop
   LFB across the two FEs.

   The purpose of the inter-FE LFB is to define standard mechanisms for
   interconnecting FEs and for that reason we are not going to touch
   anymore on proprietary chip-chip interconnects other than state the
   fact they exist and that it is feasible to have translation to and
   from proprietary approaches.  The document focus is the FE-FE
   interconnect where the FE could be physical or virtual and the
   interconnecting technology runs a standard protocol such as ethernet,
   IP or other protocols on top of IP.

3.2.  Arbitrary Network Function

   In this section we show an example of an arbitrary network function
   which is more coarse grained in terms of functionality.  Each Network
   function may constitute more than one LFB.

    |                            +----+                           |
    | +----------+               |    |                           |
    | | Network  |   pkt         |NF2 |    pkt       +-----+      |
    | | Function +-------------->|    +------------->|     |      |
    | |    1     |  + NF1        |    | + NF1/2      |NF3  |      |
    | +----------+    metadata   |    |   metadata   |     |      |
    |      ^                     +----+              |     |      |
    |      |                                         +--+--+      |
    |      |                                            |         |
    |                                                   |         |

         Figure 3: A Network Function Service Chain within one FE

   The setup in Figure 3 is atypical a typical of most packet processing boxes
   where we have functions like DPI, NAT, Routing, etc connected in such
   a topology to deliver a packet processing service to flows.

3.2.1.  Distributing The Arbitrary Network Function

   The setup in Figure 3 can be split out across 3 FEs instead as
   demonstrated in Figure 4.  This could be motivated by scale out
   reasons or because different vendors provide different functionality
   which is plugged-in to provide such functionality.  The end result is
   to have the same packet service delivered to the different flows
   passing through.

      FE1                        FE2
      +----------+               +----+               FE3
      | Network  |   pkt         |NF2 |    pkt       +-----+
      | Function +-------------->|    +------------->|     |
      |    1     |  + NF1        |    | + NF1/2      |NF3  |
      +----------+    metadata   |    |   metadata   |     |
           ^                     +----+              |     |
           |                                         +--+--+

       Figure 4: A Network Function Service Chain Distributed Across
                               Multiple FEs

4.  Proposal Overview

   We address the inter-FE connectivity requirements by proposing the
   inter-FE LFB class.  Using a standard LFB class definition implies no
   change to the basic ForCES architecture in the form of the core LFBs
   (FE Protocol or Object LFBs).  This design choice was made after
   considering an alternative approach that would have required changes
   to both the FE Object capabilities (SupportedLFBs) as well
   LFBTopology component to describe the inter-FE connectivity
   capabilities as well as runtime topology of the LFB instances.

4.1.  Inserting The Inter-FE LFB

   The distributed LFB topology described in Figure 2 is re-illustrated
   in Figure 5 to show the topology location where the inter-FE LFB
   would fit in.

    | +----------+               +----+                           |
    | | Ingress  |    IPV4 pkt   |    | IPV4 pkt     +-----+      |
    | |  LFB     +-------------->|    +------------->|     |      |
    | |          |  + ingress    |    | + ingress    |IPv4 |      |
    | +----------+    metadata   |    |   metadata   |Ucast|      |
    |      ^                     +----+              |LPM  |      |
    |      |                      IPv4               +--+--+      |
    |      |                     Validator              |         |
    |      |                      LFB                   |         |
    |      |                                  IPv4 pkt + metadata |
    |      |                        {ingress + NHinfo + InterFEid}|
    |      |                                            |         |
    |                                              +----V----+    |
    |                                              | InterFE |    |
    |                                              |   LFB   |    |
    |                                              +----+----+    |
                                         IPv4 packet and metadata
                                {ingress + NHinfo + Inter FE info}
     FE2                                                |
    |                                              +----V----+    |
    |                                              | InterFE |    |
    |                                              |   LFB   |    |
    |                                              +----+----+    |
    |                                                   |         |
    |                                         IPv4 pkt + metadata |
    |                                          {ingress + NHinfo} |
    |                                                   |         |
    |             +--------+                       +----V---+     |
    |             | Egress |     IPV4 packet       | IPV4   |     |
    |       <-----+  LFB   |<----------------------+NextHop |     |
    |             |        |{ingress + NHdetails}  | LFB    |     |
    |             +--------+      metadata         +--------+     |

         Figure 5: Split IPV4 forwarding service with Inter-FE LFB

   As can be observed in Figure 5, the same details passed between IPV4
   unicast LPM LFB and the IPV4 NH LFB are passed to the egress side of
   the Inter-FE LFB.  In addition an index for the inter-FE LFB
   (interFEid) is passed as metadata.

   The egress of the inter-FE LFB uses the received Inter-FE index
   (InterFEid metadata) to select details for encapsulation when sending
   messages towards the selected neighboring FE.  These details will
   include what to communicate as the source and destination FEID; in
   addition the original metadata and any exception IDs may be passed
   along with the original IPV4 packet.

   On the ingress side of the inter-FE LFB the received packet and its
   associated details are used to decide the packet graph continuation.
   This includes what of the of the original metadata and exception IDs
   to restore and what next LFB class instance to continue processing
   on.  In the illustrated case above, an IPV4 Nexthop LFB is selected
   and metadata is passed on to it.

   The ingress side of the inter-FE LFB consumes some of the information
   passed (eg the destination FEID) and passes on the IPV4 packet
   alongside with the ingress + NHinfo metadata to the IPV4 NextHop LFB
   as was done earlier in both Figure 1 and Figure 2.

5.  Generic Inter-FE connectivity

   In this section we describe the generic encapsulation format in
   Figure 6 as extended from the ForCES redirect packet format.  We
   intend for the described encapsulation to be a generic guideline of
   the different needed fields to be made available by any used
   transport for inter-FE LFB connectivity.  We expect that for any
   transport mechanism used, a description of how the different fields
   will be encapsulated to be correlated to the information described in
   Figure 6.  The goal of this document is to provide ethernet
   encapsulation, and to that end in Section 5.1 we illustrate how we
   use the guidelines provided in this section to describe the fit for
   inter-FE LFB interfacing over ethernet.

            +-- Main ForCES header
            |   |
            |   +---- msg type = REDIRECT
            |   +---- Destination FEID
            |   +---- Source FEID
            |   +---- NEID (first word of Correlator)
            +-- T = ExceptionID-TLV
               |  |
               |  +-- +-Exception Data ILV (I = exceptionID , L= length)
               |  |   |  |
               |  |   |  +----- V= Metadata value
               |  .   |
               |  .   |
               |  .   +-Exception Data ILV
               +- T = METADATA-TLV
               |  |
               |  +-- +-Meta Data ILV (I = metaid, L= length)
               |  |   |  |
               |  |   |  +----- V= Metadata value
               |  .   |
               |  .   |
               |  .   +-Meta Data ILV
               +- T = REDIRECTDATA-TLV
                  +--  Redirected packet Data

                    Figure 6: Packet format suggestion

   o  The ForCES main header as described in RFC5810 is used as a fixed
      header to describe the Inter-FE encapsulation.

      *  The Source FEID field is mapped to the originating FE and the
         destination FEID is mapped to the destination FEID.

      *  The first 32 bits of the correlator field are used to carry the
         NEID.  The 32-bit NEID defaults to 0.

   o  The ExceptionID TLV carries one or more exception IDs within ILVs.
      The I in the ILV carries a globally defined exceptionID as per-
      ForCES specification defined by IANA.  This TLV is new to ForCES
      and sits in the global ForCES TLV namespace.

   o  The METADATA and REDIRECTDATA TLV encapsulations are taken
      directly from [RFC5810] section 7.9.

   It is expected that a variety of transport encapsulations would be
   applicable to carry the format described in Figure 6.  In such a
   case, a description of a mapping to intepret interpret the inter-FE details
   and translate into proprietary or legacy formatting would need to be
   defined.  For any mapping towards these definitions a different
   document to describe the mapping, one per transport, is expected to
   be defined.

5.1.  Inter-FE Ethernet connectivity Connectivity

   In this document, we describe a format that is to be used over
   Ethernet.  An existing implementation of this specification on top of
   Linux Traffic Control [linux-tc] is described in [tc-ife].

   The following describes the mapping from Figure 6 to ethernet wire
   encapsulation illustrated in Figure 7.

   o  When an NE tag is needed, a VLAN tag will be used.  Note: that the
      NEID as per Figure 6 is described as being 32 bits while a vlan
      tag is 12 bits.  It is however thought to be sufficient to use 12
      bits within the scope of a LAN NE cluster.

   o  An ethernet type will be used to imply that a wire format is
      carrying an inter-FE LFB packet.  The ethernet type will to be
      requested from the appropriate IEEE Standards Association
      (preferred value used is
      0xFEFE because it maps nicely (XXX: Note to the term
      FE-FE editor, to imply inter-FE connectivity). be updated when issued by IEEE
      Standards Association).

   o  The destination FEID will be mapped to the destination MAC address
      of the target FEID.

   o  The source FEID will be mapped to the source MAC address of the
      originating FEID.

   o  In this version of the specification, we only focus on data and
      metadata.  Therefore we are not going to describe how to carry the
      ExceptionID information (future versions may).  We are also not
      going to use METADATA-TLV or REDIRECTDATA-TLV in order to save
      shave off some overhead bytes.  Figure 7 describes the payload.

       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
      |  Outer Destination MAC Address  (Destination FEID)            |
      | Outer Destination MAC Address | Outer Source MAC Address      |
      |  Outer Source MAC Address  (Source FEID)                      |
      | Optional 802.1Q info (NEID)   | Inter-FE ethertype            |
      | Metadata length               | TLV encoded Metadata          |
      | TLV encoded Metadata ~~~..............~~                      |
      | Original Ethernet payload ~~................~~                |

                    Figure 7: Packet format suggestion

   An outer Ethernet header is introduced to carry the information on
   Destination FEID, Source FEID and optional NEID.

   o  The Outer Destination MAC Address carries the Destination FEID

   o  Outer Source MAC Address carries the Source FEID identification.

   o  When an NEID is needed, an optional 802.1Q is carried with 12-bit
      VLANid representing the NEID.

   o  The ethernet type is used to identify the frame as inter-FE LFB
      type.  Ethertype 0xFEFE is to be used (XXX: Note, to be requested). editor update
      when available).

   o  The 16-bit metadata length is used to described the total encoded
      metadata length (including the 16 bits used to encode the metadata

   o  One or more TLV encoded metadatum follows the metadata length
      field.  The TLV type identifies the Metadata id.  ForCES IANA-
      defined Metadata ids will be used.  We recognize that using a 16
      bit TLV restricts the metadata id to 16 bits instead of ForCES
      define space of 32 bits.  However, at the time of publication we
      believe this is sufficient to carry all the info we need and
      approach taken would save us 4 bytes per Metadatum transferred.
      XXX: If there is objection from the we could convert this to an

   o  The original ethernet payload is appended at the end of the
      metadata as shown.

5.1.1.  Inter-FE Ethernet Connectivity Issues

   There are several issues that may arise due to using direct ethernet

   o  Because we are adding data to existing ethernet frames, MTU issues
      may arise.  We recommend:

      *  To use large MTUs when possible (example with jumbo frames).

      *  Limit the amount of metadata that could be transmitted; our
         definition allows for filtering of which metadata is to be
         encapsulated in the frame.  We recommend complementing implementing this by
         setting the egress port MTU to allow space for maximum size of
         the metadata total size you wish to allow between FEs.  In such
         a setup, the port is configured to "lie" to the upper layers by
         claiming to have a lower MTU than it is capable of.  MTU
         setting can be achieved by configuration or ForCES control of the port LFB. LFB(or
         other config).  In essence, the control plane making a decision
         for the MTU settings of the egress port is implicitly deciding
         how much metadata will be allowed.

   o  The frame may be dropped if there is congestion on the receiving
      FE side.  One approach to mitigate this issue is to make sure that
      inter-FE LFB frames receive the highest priority treatment when
      scheduled on the wire.  Typically protocols that tunnel in the
      middle box do not care and depend on the packet originator to
      resend if the originator cares about reliability.  We do not
      expect to be any different.

   o  While we expect to use a unique IEEE-issued ethertype for the
      inter-FE traffic, we use lessons learnt from VXLAN deployment[XXX:
      ref] deployment xref
      to be more flexible on the settings of the ethertype value used.
      We make the etherype ether type an LFB read-write component.  Linux VXLAN
      implementation uses UDP port 8472 because the deployment happened
      much earlier than the point of RFC publication where the IANA
      assigned udp port issued was 4789. 4789 [vxlan-udp].  For this reason we
      make it possible to define at control time what ethertype to use
      and default to the IEEE issued ethertype.  We justify this by
      assuming that a given ForCES NE is likely to be owned by a single
      organization and that the organization's CE(or CE cluster) could
      program all participating FEs via the inter-FE LFB (described in
      this document) to recognize a private ethernet type used for
      inter-LFB traffic (possibly those defined as available for private
      use by the IEEE, namely: IDs 0x88B5 and 0x88B6)

6.  Detailed Description of the Ethernet inter-FE LFB

   The ethernet inter-FE LFB has two LFB input ports and three LFB
   output ports.

    Inter-FE LFB   |                 |
    Encapsulated   |             OUT2+--> decapsulated Packet + metadata
    -------------->|IN2              |
    Packet         |                 |
                   |                 |
    raw Packet +   |             OUT1+--> encapsulated Packet
    -------------->|IN1              |
    Metadata       |                 |
                   |    EXCEPTIONOUT +--> ExceptionID, packet + metadata
                   |                 |

                          Figure 8: Inter-FE LFB

6.1.  Data Handling

   The Inter-FE LFB can be positioned at the egress of a source FE.  In
   such a case an Inter-FE LFB instance receives via port IN1, raw
   packet and metadata IDs from the preceeding preceding LFB instance.  The
   InterFEid metadatum MAY be present on the incoming raw data.  The
   processed encapsulated packet will go out on either LFB port OUT1 to
   a downstream LFB or EXCEPTIONOUT port in the case of a failure.

   The Inter-FE LFB can be positioned at the ingress of a receiving FE.
   In such a case an Inter-FE LFB receives, via port IN2, an
   encapsulated packet.  Successful processing of the packet will result
   in a raw packet with associated metadata IDs going downstream to an
   LFB connected on OUT2.  On failure the data is sent out EXCEPTIONOUT.

   The Inter-FE LFB may use the InterFEid metadatum on egress of an FE
   to lookup the IFETable table.  The interFEid in such a case will be
   generated by an upstream LFB instance (i.e one preceeding preceding the Inter-FE
   LFB).  The output result constitutes a matched table row which has
   the InterFEinfo details i.e. the tuple {NEID,Destination FEID,Source
   FEID, inter FE type, metafilters}.  The metafilters lists define
   which Metadatum are to be passed to the neighboring FE.

   The component names used in describing processing are defined in
   Section 6.2

6.1.1.  Egress Processing

   The egress Inter-FE LFB will receive an ethernet frame and
   accompanying metadatum (including optionally the InterFEid metadatum)
   at LFB port IN1.  The ethernet frame may be 802.1Q tagged.

   The InterFEid may be used to lookup IFETable table.  If lookup is
   successful, the inter-FE LFB will perform the following actions using
   the resulting tuple:

   o  Increment statistics for packet and byte count observed.

   o  Walk each passed packet metadatum and apply against the relevant
      MetaFilterList.  If no legitimate metadata is found that needs to
      be passed downstream then the processing stops and the packet is
      allowed through as is.

   o  check  Check that the additional overhead of the outer header and
      encapsulated metadata will not exceed MTU.  If it does does, increment
      the error packet count statistics and return allowing the packet
      to pass through.  (XXX: Should it be dropped because it cannot
      send the required metadata?)

   o  create the outer ethernet header which is a duplicate of the
      incoming frame's ethernet header.  The outer ethernet header may
      have an optional 802.1q header (if one was included in the
      original frame).

   o  If the NEID field is present (not 0) and the original header had a
      vlan tag, replace the vlan tag on the outer header with the value
      from the matched NEID field.  If the NEID field is present (not 0)
      and the original header did not have a vlan tag, create one that
      matches the NEID field and appropriately add it to the outer
      header.  If the NEID field is absent or 0, do nothing.

   o  If the optional DSTFE is present, set the Destination MAC address
      of the outer header with value found in the DSTFE field.  When
      absent, then the inner destination MAC address is used (at this
      point already copied).

   o  If the optional SRCFE is present, set the Source MAC address of
      the outer header with value found in the SRCFE field.  If SRCFE is
      absent then the inner source MAC address is used (at this point
      already copied).

   o  If the optional IFETYPE is present, set the outer ethernet type to
      the value found in IFETYPE.  If IFETYPE is absent then the
      standard ethernet type is used (XXX: Note to editor, to be requested from IEEE).

   o  encapsulate each allowed metadatum in a TLV.  Use the Metaid as
      the "type" field in the TLV header.  The TLV should be aligned to
      32 bits.  This means you may need to add padding of zeroes to
      ensure alignment.

   o  Update the Metadata length to the sum of each TLV's space + 2
      bytes (for the Metadata length field 16 bit space).

   The resulting packet is sent to the next LFB instance connected to
   the OUT1 LFB-port; typically a port LFB.

   In the case of a failed lookup or a zero-value InterFEid, (or absence
   of InterFEid when needed by the implementation) the packet is sent
   out unchanged via the OUT1 LFB Class instance port (typically towards
   a Port LFB).

6.1.2.  Ingress Processing

   An inter-FE LFB packet is recognized by looking at the etherype
   received on LFB instance port IN2.  The IFETable table may be
   optionally utilized to provide metadata filters (XXX: Should we allow
   for the interFEid metadata to be sent by the neighbor FE and use it
   here?  Implementations dont need it to associate a specific port/MAC/
   VLAN etc with the IFETable LFB). filters.

   o  Increment statistics for packet and byte count observed.

   o  The inter-FE LFB instance looks  Look at the metadata length field and
      walks walk the packet data
      extracting from the TLVs the metadata values.  For each metadatum
      extracted, optionally the metaid is compared against the relevant IFETable
      row metafilter list.  If the metadatum is recognized recognized, and is
      allowed by the filter the corresponding implementation metadatum
      field is set.  If an unknown metadatum id is encountered, or if
      the metaid is not found in the option allowed filter list the
      implementation is expected to ignore it, increment the packet
      error statistic and proceed processing other metadatum.

   o  Upon completion of processing all the metadata, the inter-FE LFB
      instance resets the header to point to the original (inner)
      ethernet header i.e skips the metadata IFE header information.  At this
      point the the original ethernet frame that was passed to the
      egress Inter-FE LFB at the source FE is reconstructed.  This data
      is then passed along with the reconstructed metadata downstream to
      the next LFB instance in the graph.

   In the case of processing failure of either ingress or egress
   positioning of the LFB, the packet and metadata are sent out the
   EXCEPTIONOUT LFB port with proper appropriate error id (XXX: More description to
   be added). id.  Note that the
   EXCEPTIONOUT LFB port is merely an abstraction and implementation may
   in fact drop packets as described above.

6.2.  Components

   There are two LFB component populated by the CE.

   The CE optionally programs LFB instances in a service graph that
   require inter-FE connectivity with InterFEid values to correspond to
   the inter-FE LFB IFETable table entries to use.

   The first component is an array known as the IFETable table.  The
   array rows are made up of IFEInfo structure.  The IFEInfo structure
   constitutes: optional NEID, optional IFETYPE, optional Destination
   FEID(DSTFE), optional Source FEID (SRCFE), optional array of allowed
   Metaids (MetaFilterList).  The table is looked up by a 32 bit index
   passed from an upstream LFB class instance in the form of InterFEid

   The second component(ID 2) is IFEStats table which carries the basic
   stats structure bstats.  The table index value used to lookup this
   table is the same one as in IFETable table; in other words for a
   table row index 10 in the IFETable table, its corresponding stats
   will be found in row index of the IFEStats table.

6.3.  Inter-FE LFB XML Model

   XXX: metadata definition requires clarification.  We expect to use
   IANA defined metadatum.  How do we describe them here in the model?

   <LFBLibrary xmlns="urn:ietf:params:xml:ns:forces:lfbmodel:1.0"

             <synopsis>Packet with any Ethernet type</synopsis>
                    Packet with an encapsulate IFE Ethernet type



          <synopsis>Basic stats</synopsis>

           <component componentID="1">
            <synopsis>The total number of bytes seen</synopsis>

           <component componentID="2">
            <synopsis>The total number of packets seen</synopsis>

           <component componentID="3">
            <synopsis>The total number of packets with errors</synopsis>


           <synopsis>Describing IFE table row Information</synopsis>
              <component componentID="1">
                     The VLAN Id 12 bits part of the 802.1q TCI field.
              <component componentID="2">
                    the ethernet type to be used for outgoing IFE frame
              <component componentID="3">
                        the destination MAC address of destination FE
              <component componentID="4">
                        the source MAC address used for the source FE
              <component componentID="5">
                        the allowed metadata filter table
                <array type="variable-size">



                   Metadata identifying the index of the NexFE table

       <LFBClassDef LFBClassID="6612">
            This LFB describes IFE connectivity parametrization parameterization

                      The input port of the egress side.
                      It expects any type of Ethernet frame.
                      The input port of the ingress side.
                      It expects an inter-FE encapsulated Ethernet frame
                      with associated metadata.



                    The output port of the egress side.
                    The output port of the Ingress side.

                    The exception handling path



            <component componentID="1" access="read-write">
                  the table of all InterFE relations
               <array type="variable-size">
            <component componentID="2">
                        the stats corresponding to the IFETable table




                        Figure 9: Inter-FE LFB XML

7.  Acknowledgements

   The authors would like to thank Joel Halpern and Dave Hood for the
   stimulating discussions.  Evangelos Haleplidis contributed to
   improving this document.

8.  IANA Considerations

   This memo includes two IANA requests within the registry

   The first request is for the sub-registry "Logical Functional Block
   (LFB) Class Names and Class Identifiers" to request for the
   reservation of LFB class name IFE with LFB classid 6112 with version

   The second request is for the sub-registry "Metadata ID" to request
   for the InterFEid metadata the value 0x00000010.

9.  Security  IEEE Assignment Considerations


   This memo includes a request for a new ethernet protocol type as
   described in Section 5.1.

10.  Security Considerations

   This document does not alter either the ForCES model the ForCES Model
   [RFC5812] or the ForCES Protocol [RFC5810] As such, it has no impact
   on their security considerations.  This document simply defines the
   operational parameters and capabilities of an LFB that performs LFB
   class instance extensions across nodes under a single administrative
   control. this document does not attempt to analyze the presence or
   possibility of security interactions created by allowing LFB graph
   extension on packets.  Any such issues, if they exist, are for the
   designers of the particular data path, not the general mechanism.

11.  References

11.1.  Normative References

   [RFC3746]  Yang, L., Dantu, R., Anderson, T., and R. Gopal,
              "Forwarding and Control Element Separation (ForCES)
              Framework", RFC 3746, April 2004.

   [RFC5810]  Doria, A., Hadi Salim, J., Haas, R., Khosravi, H., Wang,
              W., Dong, L., Gopal, R., and J. Halpern, "Forwarding and
              Control Element Separation (ForCES) Protocol
              Specification", RFC 5810, March 2010.

   [RFC5811]  Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport Mapping
              Layer (TML) for the Forwarding and Control Element
              Separation (ForCES) Protocol", RFC 5811, March 2010.

   [RFC5812]  Halpern, J. and J. Hadi Salim, "Forwarding and Control
              Element Separation (ForCES) Forwarding Element Model",
              RFC 5812, March 2010.


11.2.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC6956]  Wang, W., Haleplidis, E., Ogawa, K., Li, C., and J.
              Halpern, "Forwarding and Control Element Separation
              (ForCES) Logical Function Block (LFB) Library", RFC 6956,
              June 2013.

              "Higig", <>.

              Hadi Salim, J., "Linux Traffic Control Classifier-Action
              Subsystem Architecture", netdev 01, Feb 2015.

   [tc-ife]   Hadi Salim, J. and D. Joachimpillai, "Distributing Linux
              Traffic Control Classifier-Action Subsystem", netdev 01,
              Feb 2015.

              "iproute2 and kernel code (drivers/net/vxlan.c)",

Authors' Addresses

   Damascane M. Joachimpillai
   60 Sylvan Rd
   Waltham, Mass.  02451


   Jamal Hadi Salim
   Mojatatu Networks
   Suite 400, 303 Moodie Dr.
   Ottawa, Ontario  K2H 9R4