Internet Engineering Task Force D. Joachimpillai
Internet-Draft Verizon
Intended status: Standards Track J. Hadi Salim
Expires: September 7, 2015 Mojatatu Networks
March 6, 2015
ForCES Inter-FE LFB
draft-ietf-forces-interfelfb-01
Abstract
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.
Status of this Memo
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This Internet-Draft will expire on September 7, 2015.
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the Trust Legal Provisions and are provided without warranty as
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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 . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Terminology and Conventions
1.1. 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 [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 of LFB graph(s) by the control plane. Details on how a
graph of LFB class instances can be created can be derived by the
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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
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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].
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
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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
metadata.
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.
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FE1
+-------------------------------------------------------------+
| +----+ |
| +----------+ | | |
| | Ingress | IPV4 pkt | | IPV4 pkt +-----+ |
| | LFB +-------------->| +------------->| | |
| | | + ingress | | + ingress |IPv4 | |
| +----------+ metadata | | metadata |Ucast| |
| ^ +----+ |LPM | |
| | IPv4 +--+--+ |
| | Validator | |
| LFB | |
+---------------------------------------------------|---------+
|
IPv4 packet +
{ingress + NHinfo}
metadata
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
[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.
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FE1
+-------------------------------------------------------------+
| +----+ |
| +----------+ | | |
| | Network | pkt |NF2 | pkt +-----+ |
| | Function +-------------->| +------------->| | |
| | 1 | + NF1 | | + NF1/2 |NF3 | |
| +----------+ metadata | | metadata | | |
| ^ +----+ | | |
| | +--+--+ |
| | | |
| | |
+---------------------------------------------------|---------+
V
Figure 3: A Network Function Service Chain within one FE
The setup in Figure 3 is 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 | |
^ +----+ | |
| +--+--+
|
V
Figure 4: A Network Function Service Chain Distributed Across
Multiple FEs
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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.
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FE1
+-------------------------------------------------------------+
| +----------+ +----+ |
| | 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
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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.
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+-- 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.
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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 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
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 to be used is
0xFEFE (XXX: Note to editor, to 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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
identification.
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 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
length).
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.
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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
encapsulation.
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 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 ForCES control of the port 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 xref
to be more flexible on the settings of the ethertype value used.
We make the 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 [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)
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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 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 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
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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 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 that the additional overhead of the outer header and
encapsulated metadata will not exceed MTU. If it does, increment
the error packet count statistics and return allowing the packet
to pass through.
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
updated).
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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.
o Increment statistics for packet and byte count observed.
o Look at the metadata length field and walk the packet data
extracting from the TLVs the metadata values. For each metadatum
extracted, the metaid is compared against the relevant IFETable
row metafilter list. If the metadatum is 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 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 appropriate error id. Note that the
EXCEPTIONOUT LFB port is merely an abstraction and implementation may
in fact drop packets as described above.
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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
metadatum.
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
EthernetAny
Packet with any Ethernet type
InterFEFrame
Packet with an encapsulate IFE Ethernet type
bstats
Basic stats
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bytes
The total number of bytes seen
uint64
packets
The total number of packets seen
uint32
errors
The total number of packets with errors
uint32
IFEInfo
Describing IFE table row Information
NEID
The VLAN Id 12 bits part of the 802.1q TCI field.
uint16
IFETYPE
the ethernet type to be used for outgoing IFE frame
uint16
DSTFE
the destination MAC address of destination FE
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byte[6]
SRCFE
the source MAC address used for the source FE
byte[6]
MetaFilterList
the allowed metadata filter table
uint32
InterFEid
Metadata identifying the index of the NexFE table
16
uint32
IFE
This LFB describes IFE connectivity parameterization
1.0
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IN1
The input port of the egress side.
It expects any type of Ethernet frame.
[EthernetAny]
IN2
The input port of the ingress side.
It expects an inter-FE encapsulated Ethernet frame
with associated metadata.
[InterFEFrame]
[InterFEid]
OUT1
The output port of the egress side.
[InterFEFrame]
[InterFEid]
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OUT2
The output port of the Ingress side.
[EthernetAny]
[InterFEid]
EXCEPTIONOUT
The exception handling path
[EthernetAny]
[ExceptionID]
[InterFEid]
IFETable
the table of all InterFE relations
IFEInfo
IFEStats
the stats corresponding to the IFETable table
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bstats
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
https://www.iana.org/assignments/forces
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
1.0.
The second request is for the sub-registry "Metadata ID" to request
for the InterFEid metadata the value 0x00000010.
9. 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
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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.
[brcm-higig]
"Higig", .
[linux-tc]
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.
[vxlan-udp]
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"iproute2 and kernel code (drivers/net/vxlan.c)",
.
Authors' Addresses
Damascane M. Joachimpillai
Verizon
60 Sylvan Rd
Waltham, Mass. 02451
USA
Email: damascene.joachimpillai@verizon.com
Jamal Hadi Salim
Mojatatu Networks
Suite 400, 303 Moodie Dr.
Ottawa, Ontario K2H 9R4
Canada
Email: hadi@mojatatu.com
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