DetNet J. Korhonen, Ed.
Internet-Draft Broadcom
Intended status: Informational J. Farkas
Expires: March 18, 2017 G. Mirsky
Ericsson
P. Thubert
Cisco
Y. Zhuang
Huawei
L. Berger
LabN
September 14, 2016
DetNet Data Plane Protocol and Solution Alternatives
draft-dt-detnet-dp-alt-04
Abstract
This document identifies existing IP and MPLS, and other
encapsulations that run over IP and/or MPLS data plane technologies
that can be considered as the base line solution for deterministic
networking data plane definition.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on March 18, 2017.
Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DetNet Data Plane Overview . . . . . . . . . . . . . . . . . 3
3.1. Example DetNet Service Scenarios . . . . . . . . . . . . 6
4. Criteria for data plane solution alternatives . . . . . . . . 8
4.1. #1 Encapsulation and overhead . . . . . . . . . . . . . . 9
4.2. #2 Flow identification . . . . . . . . . . . . . . . . . 9
4.3. #3 Packet sequencing and duplicate elimination . . . . . 9
4.4. #4 Explicit routes . . . . . . . . . . . . . . . . . . . 10
4.5. #5 Flow duplication and merging . . . . . . . . . . . . . 10
4.6. #6 Operations, Administration and Maintenance . . . . . . 11
4.7. #8 Class and quality of service capabilities . . . . . . 11
4.8. #9 Packet traceability . . . . . . . . . . . . . . . . . 12
4.9. #10 Technical maturity . . . . . . . . . . . . . . . . . 12
5. Data plane solution alternatives . . . . . . . . . . . . . . 12
5.1. DetNet Transport layer technologies . . . . . . . . . . . 13
5.1.1. Native IPv6 transport . . . . . . . . . . . . . . . . 13
5.1.2. Native IPv4 transport . . . . . . . . . . . . . . . . 16
5.1.3. Multiprotocol Label Switching (MPLS) . . . . . . . . 19
5.1.4. Bit Indexed Explicit Replication (BIER) . . . . . . . 23
5.2. DetNet Service layer technologies . . . . . . . . . . . . 27
5.2.1. Generic Routing Encapsulation (GRE) . . . . . . . . . 27
5.2.2. MPLS-based Services for DetNet . . . . . . . . . . . 29
5.2.3. Pseudo Wire Emulation Edge-to-Edge (PWE3) . . . . . . 30
5.2.4. MPLS-Based Ethernet VPN (EVPN) . . . . . . . . . . . 34
5.2.5. Higher layer header fields . . . . . . . . . . . . . 36
6. Summary of data plane alternatives . . . . . . . . . . . . . 38
7. Security considerations . . . . . . . . . . . . . . . . . . . 40
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 41
10.1. Informative References . . . . . . . . . . . . . . . . . 41
10.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Appendix A. Examples of combined DetNet Service and Transport
layers . . . . . . . . . . . . . . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
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1. Introduction
Deterministic Networking (DetNet) [I-D.ietf-detnet-problem-statement]
provides a capability to carry unicast or multicast data flows for
real-time applications with extremely low data loss rates, timely
delivery and bounded packet delay variation
[I-D.finn-detnet-architecture]. The deterministic networking Quality
of Service (QoS) is expressed as 1) the minimum and the maximum end-
to-end latency from source (talker) to destination (listener), and 2)
probability of loss of a packet. Only the worst-case values for the
mentioned parameters are concerned.
There are three techniques to achieve the QoS required by
deterministic networks:
o Congestion protection,
o explicit routes,
o service protection.
This document identifies existing IP and Multiprotocol Label
Switching (MPLS) [RFC3031], layer-2 or layer-3 encapsulations and
transport protocols that could be considered as foundations for a
deterministic networking data plane. The full scope of the
deterministic networking data plane solution is considered including,
as appropriate: quality of service (QoS); Operations, Administration
and Maintenance (OAM); and time synchronization among other criteria
described in Section 4.
This document does not select a deterministic networking data plane
protocol. It does, however, elaborate what it would require to adapt
and use a specific protocol as the deterministic networking data
plane solution. This document is only concerned with data plane
considerations and, specifically, with topics that potentially impact
potential deterministic networking aware data plane hardware.
Control plane considerations are out of scope of this document.
2. Terminology
This document uses the terminology established in the DetNet
architecture [I-D.finn-detnet-architecture].
3. DetNet Data Plane Overview
A "Deterministic Network" will be composed of DetNet enabled nodes
i.e., End Systems, Edge Nodes, Relay Nodes and collectively deliver
DetNet services. DetNet enabled nodes are interconnected via Transit
Nodes (i.e., routers) which support DetNet, but are not DetNet
service aware. Transit nodes see DetNet nodes as end points. All
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DetNet enabled nodes are connect to sub-networks, where a point-to-
point link is also considered as a simple sub-network. These sub-
networks will provide DetNet compatible service for support of DetNet
traffic. Examples of sub-networks include IEEE 802.1TSN and OTN. Of
course, multi-layer DetNet systems may also be possible, where one
DetNet appears as a sub-network, and provides service to, a higher
layer DetNet system. A simple DetNet concept network is shown in
Figure 1.
TSN Edge Transit Relay DetNet
End System Node Node Node End System
+---------+ +.........+ +---------+
| Appl. |<---:Svc Proxy:-- End to End Service ---------->| Appl. |
+---------+ +---------+ +---------+ +---------+
| TSN | |TSN| |Svc|<-- DetNet flow ---: Service :-->| Service |
+---------+ +---+ +---+ +---------+ +---------+ +---------+
|Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +--.----.-+ +-.-+ +-.-+ +---.-----+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +........+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
Figure 1: A Simple DetNet Enabled Network
The DetNet data plane is logically divided into two layers (also see
Figure 2):
DetNet Service Layer
The DetNet service layer provides adaptation of DetNet services.
It is composed of a shim layer to carry deterministic flow
specific attributes, which are needed during forwarding and for
service protection. DetNet enabled end systems originate and
terminate the DetNet Service layer and are peers at the DetNet
Service layer. DetNet relay and edge nodes also implement DetNet
Service layer functions. The DetNet service layer is used to
deliver traffic end to end across a DetNet domain.
DetNet Transport Layer
The DetNet transport layer is required on all DetNet nodes. All
DetNet nodes are end points at the transport layer. Non-DetNet
service aware transit nodes deliver traffic between DetNet nodes.
The DetNet transport layer operates below and supports the DetNet
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Service layer and optionally provides congestion protection for
DetNet flows.
Distinguishing the function of these two DetNet data plane layers
helps to explore and evaluate various combinations of the data plane
solutions available. This separation of DetNet layers, while
helpful, should not be considered as formal requirement. For
example, some technologies may violate these strict layers and still
be able to deliver a DetNet service.
.
.
+-----------+
| Service | PW, RTP/(UDP), GRE
+-----------+
| Transport | (UDP)/IPv6, (UDP)/IPv4, MPLS LSPs, BIER
+-----------+
.
.
Figure 2: DetNet adaptation to data plane
The two logical layers defined here aim to help to identify which
data plane technology can be used for what purposes in the DetNet
context. This layering is similar to the data plane concept of MPLS,
where some part of the label stack is "Service" specific (e.g., PW
labels, VPN labels) and an other part is "Transport" specific (e.g,
LSP label, TE label(s)).
In some networking scenarios, the end system initially provides a
DetNet flow encapsulation, which contains all information needed by
DetNet nodes (e.g., Real-time Transport Protocol (RTP) [RFC3550]
based DetNet flow transported over a native UDP/IP network or
PseudoWire). In other scenarios, the encapsulation formats might
differ significantly. As an example, a CPRI "application's" I/Q data
mapped directly to Ethernet frames may have to be transported over an
MPLS-based packet switched network (PSN).
There are many valid options to create a data plane solution for
DetNet traffic by selecting a technology approach for the DetNet
Service layer and also selecting a technology approach for the DetNet
Transport layer. There are a high number of valid combinations.
Therefore, not the combinations but the different technologies are
evaluated along the criteria collected in Section 4. Different
criteria apply for the DetNet Service layer and the DetNet Transport
layer, however, some of the criteria are valid for both layers.
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One of the most fundamental differences between different potential
data plane options is the basic addressing and headers used by DetNet
end systems. For example, is the basic service a Layer 2 (e.g.,
Ethernet) or Layer 3 (i.e., IP) service. This decision impacts how
DetNet end systems are addressed, and the basic forwarding logic for
the DetNet Service layer.
3.1. Example DetNet Service Scenarios
In an attempt to illustrate a DetNet date plane, this document uses
the Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3) [RFC5254]
reference model shown in Figure 3 as the foundation for different
DetNet data plane deployment options and how layering could work.
Other reference models are possible but not covered in this document.
Note that other technologies can be also used to implement DetNet,
Multi-Segment PW is only used here to illustrate functions, features
and layering from the perspective of the architecture.
Native |<--------Multi-Segment Pseudowire----->| Native
Service | PSN PSN | Service
(AC) | |<-Tunnel->| |<-Tunnel->| | (AC)
| V V 1 V V 2 V V |
| +-----+ +-----+ +---- + |
+---+ | |T-PE1|==========|S-PE1|==========|T-PE2| | +---+
| |---|-----|........PW1...........|...PW3..........|---|----| |
|CE1| | | | | | | | | |CE2|
| |---------|........PW2...........|...PW4..........|--------| |
+---+ | | |==========| |==========| | | +---+
^ +-----+ +-----+ +-----+ ^
| Provider Edge 1 ^ Provider Edge 3 |
| | |
| PW switching point |
| |
|<------------------- Emulated Service ------------------->|
Figure 3: Pseudo Wire switching reference model
Figure 4 illustrates how DetNet can provide services for IEEE
802.1TSN end systems over a DetNet enabled network. The edge nodes
insert and remove required DetNet data plane encapsulation. The 'X'
in the edge and relay nodes represents a potential DetNet flow packet
replication and elimination point. This conceptually parallels L2VPN
services, and could leverage existing related solutions as discussed
below.
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TSN |<----- End to End DetNet Service ----->| TSN
Service | Transit Transit | Service
TSN (AC) | |<-Tunnel->| |<-Tunnel->| | (AC) TSN
End | V V 1 V V 2 V V | End
System | +-----+ +-----+ +---- + | System
+---+ | |T-PE1|==========|S-PE1|==========|T-PE2| | +---+
| |---|-----|.X_..DetNet Flow1..X..|...DF3........X.|---|----| |
|CE1| | | \ | | | | / | | |CE2|
| | |...X_...DF2........X..|...DF4......X_..| | |
+---+ | |==========| |==========| | +---+
^ +-----+ +-----+ +-----+ ^
| Edge Node Relay Node Edge Node |
| |
|<--------------- Emulated TSN Service ------------------->|
Figure 4: IEEE 802.1TSN over DetNet
Figure 5 illustrates how end to end native DetNet service can be
provided. In this case, the end systems are able to send and receive
native DetNet flows. For example, as PseudoWire (PW) encapsulated
IP. Like earlier the 'X' in the end systems, edge and relay nodes
represents potential DetNet flow packet replication and elimination
points. Here the relay nodes may change the underlying transport,
for example replacing IP with MPLS or tunneling IP over MPLS (e.g.,
via L3VPNs), or simply interconnect network domains.
DetNet DetNet
Service Transit Transit Service
DetNet | |<-Tunnel->| |<-Tunnel->| | DetNet
End | V 1 V V 2 V | End
System | +-----+ +-----+ +-----+ | System
+---+ | |S-PE1|==========|S-PE2|==========|S-PE3| | +---+
| X....DFa.....X_.......DF1.......X_....DF3........X.....DFa...X |
|CE1|=========| \ | | / | | / |========|CE2|
| | | | \......DF2.....X_......DF4....../ | | | |
+---+ | |==========| |==========| | +---+
^ +-----+ +-----+ +-----+ ^
| Relay Node Relay Node Relay Node |
| |
|<------------- End to End DetNet Service ---------------->|
Figure 5: Native DetNet
Figure 6 illustrates how a IEEE 802.1TSN end system could communicate
with a native DetNet end system through an edge node which provides a
TSN to DetNet inter-working capability. The edge node would add and
remove required DetNet data plane encapsulation as well as provide
any needed address mapping. As in previous figures, the 'X' in the
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end systems, edge and relay nodes represents potential DetNet flow
packet duplication and elimination points.
TSN |<----- End to End DetNet Service -------------->|
Service | Transit Transit |
TSN (AC) | |<-Tunnel->| |<-Tunnel->| DetNet | DetNet
End | V V 1 V V 2 V Service | End
System | +-----+ +-----+ +-----+ | V System
+---+ | |T-PE1|==========|S-PE1|==========|S-PE2| | +---+
| |---|-----|.X_.......DF1......X..|...DF3........X.|...DFa...X |
|CE1| | | \ | | | | / |========|CE2|
| | | \.....DF2.......X..|...DF4....../ | | | |
+---+ | |==========| |==========| | +---+
^ +-----+ +-----+ +-----+ ^
| Edge Node Relay Node Relay Node |
| |
|<----------------- End to End Service ------------------->|
Figure 6: IEEE 802.1TSN to native DetNet
4. Criteria for data plane solution alternatives
This section provides criteria to help to evaluate potential options.
Each deterministic networking data plane solution alternative is
described and evaluated using the criteria described in this section.
The used criteria enumerated in this section are selected so that
they highlight the existence or lack of features that are expected or
seen important to a solution alternative for the data plane solution.
The criteria for the DetNet Service layer:
#1 Encapsulation and overhead
#2 Flow identification (Service ID part of the DetNet flows)
#3 Packet sequencing and duplicate elimination
#5 Flow duplication and merging
#6 Operations, Administration and Maintenance (capabilities)
#8 Class and quality of service capabilities (DetNet Service
specific)
#10 Technical maturity
The criteria for the DetNet Transport layer:
#1 Encapsulation and overhead
#2 Flow identification
#4 Explicit routes (network path)
#5 Flow duplication and merging (sometimes, flow duplication and
merging is also doable at the transport layer, not just at the
service layer)
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#6 Operations, Administration and Maintenance (capabilities,
performance management, packet traceability)
#8 Class and quality of service capabilities (DetNet Transport
specific)
#9 Packet traceability (can be part of OAM)
#10 Technical maturity
[Editor's Note: numbering is off because #7 is removed.]
[Editor's Note: #9 should(?) be integrated into #6.]
Most of the criteria is relevant for both the DetNet Service and
DetNet Transport layers. However, different aspects of the same
criteria may relevant for different layers, for example, as it is the
case with criteria #5 Packet replication and elimination.
4.1. #1 Encapsulation and overhead
Encapsulation and overhead is related to how the DetNet data plane
carries DetNet flow. In several cases a DetNet flow has to be
encapsulated inside other protocols, for example, when transporting a
layer-2 Ethernet frame over an IP transport network. In some cases a
tunneling like encapsulation can be avoided by underlying transport
protocol translation, for example, translating layer-2 Ethernet frame
including addressing and flow identification into native IP traffic.
Last it is possible that sources and destinations handle
deterministic flows natively in layer-3. This criteria concerns what
is the encapsulation method the solution alternative support:
tunneling like encapsulation, protocol translation or native layer-3
transport. In addition to the encapsulation mechanism this criteria
is also concerned with the processing and specifically the
encapsulation header overhead.
4.2. #2 Flow identification
The solution alternative has to provide means to identify specific
deterministic flows. The flow identification can, for example, be an
explicit field in the data plane encapsulation header or implicitly
encoded into the addressing scheme of the used data plane protocol or
their combination. This criteria concerns the availability and
details of deterministic flow identification the data plane protocol
alternative has.
4.3. #3 Packet sequencing and duplicate elimination
The solution alternative has to provide means for end systems to
number packets sequentially and transport that sequencing information
along with the sent packets. In addition to possible reordering of
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packets other important uses for sequencing are detecting duplicates
and lost packets.
In a case of intentional packet duplication a combination of flow
identification and packet sequencing allows for detecting and
eliminating duplicates at the destination (see Section 4.5 for more
details).
4.4. #4 Explicit routes
The solution alternative has to provide a mechanism(s) for
establishing explicit routes that all packets belonging to a
deterministic flow will follow. The explicit route can be seen as a
form of source routing or a pre-reserved path e.g., using some
network management procedure. It should be noted that the explicit
route does not need to be detailed to a level where every possible
intermediate node along the path is part of the named explicit route.
RSVP-TE [RFC3209] supports explicit routes, and typically provides
pinned data paths for established LSPs. At Layer-2, the IEEE
802.1Qca [IEEE802.1Qca] specification defines how to do explicit path
control in a bridged network and its IETF counter part is defined in
[RFC7813]. This criteria concerns the available mechanisms for
explicit routes for the data plane protocol alternative.
4.5. #5 Flow duplication and merging
Flow duplication and flow merging are methods being considered to
provide DetNet service protection. The objective for supporting flow
duplication and flow merging is to enable hitless (or lossless) 1+1
protection. Other methods, if so identified, are also permissible.
The solution alternative has to provide means for end systems, relay
and edge nodes to be able to duplicate packets into duplicate flows,
and later merge the flows into one for duplicate elimination. The
duplication and merging may take place at multiple points in the
network in order to ensure that one (or more) equipment failure
event(s) still leave at least one path intact for a deterministic
networking flow. The goal is again to enable hitless 1+1 protection
in a way that no packet gets lost or there is no ramp up time when
either one of the paths fails for one reason or another.
Another concern regarding packet duplication is how to enforce
duplicated packets to take different route or path while the final
destination still remains the same. With strict source routing, all
the intermediate hops are listed and paths can be guaranteed to be
non-overlapping. Loose source routing only signals some of the
intermediate hops and it takes additional knowledge to ensure that
there is no single point of failure.
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The IEEE 802.1CB (seamless redundancy) [IEEE8021CB] is an example of
Ethernet-based solution that defines packet sequence numbering, flow
duplication, flow merging, duplicate packet identification and
elimination. The deterministic networking data plane solution
alternative at layer-3 has to provide equivalent functionality. This
criteria concerns the available mechanisms for packet replication and
duplicate deletion the data plane protocol alternative has.
4.6. #6 Operations, Administration and Maintenance
The solution alternative should demonstrate availability of
appropriate standardized OAM tools that can be extended for
deterministic networking purposes with a reasonable effort, when
required. The OAM tools do not necessarily need to be specific to
the data plane protocol as it could be the case, for example, with
MPLS-based data planes. But any OAM-related implications or
requirements on data plane hardware must be considered.
The OAM includes but is not limited to tools listed in the
requirements for overlay networks
[I-D.ooamdt-rtgwg-ooam-requirement]. Specifically, the performance
management requirements are of interest at both service and transport
layers.
4.7. #8 Class and quality of service capabilities
Class and quality of service, i.e., CoS and QoS, are terms that are
often used interchangeably and confused. In the context of DetNet,
CoS is used to refer to mechanisms that provide traffic forwarding
treatment based on aggregate group basis and QoS is used to refer to
mechanisms that provide traffic forwarding treatment based on a
specific DetNet flow basis. Examples of CoS mechanisms include
DiffServ which is enabled by IP header differentiated services code
point (DSCP) field [RFC2474] and MPLS label traffic class field
[RFC5462], and at Layer-2, by IEEE 802.1p priority code point (PCP).
Quality of Service (QoS) mechanisms for flow specific traffic
treatment typically includes a guarantee/agreement for the service,
and allocation of resources to support the service. Example QoS
mechanisms include discrete resource allocation, admission control,
flow identification and isolation, and sometimes path control,
traffic protection, shaping, policing and remarking. Example
protocols that support QoS control include Resource ReSerVation
Protocol (RSVP) [RFC2205] (RSVP) and RSVP-TE [RFC3209] and [RFC3473].
A critical DetNet service enabled by QoS (and perhaps CoS) is
delivering zero congestion loss. There are different mechanisms that
maybe used separately or in combination to deliver a zero congestion
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loss service. The key aspect of this objective is that DetNet
packets are not discarded due to congestion at any point in a DetNet
aware network.
In the context of the data plane solution there should be means for
flow identification, which then can be used to map a flow against
specific resources and treatment in a node enforcing the QoS. For
DetNet, certain aspects of CoS and QoS may be provided by the
underlying sub-net technology, e.g., actual queuing or IEEE 802.3x
priority flow control (PFC).
4.8. #9 Packet traceability
For the network management and specifically for tracing
implementation or network configuration errors any means to find out
whether a packet is a replica, which node performed replication, and
which path was intended for the replica, can be very useful. This
criteria concerns the availability of solutions for tracing packets
in the context of data plane protocol alternative. Packet
traceability can also be part of OAM.
4.9. #10 Technical maturity
The technical maturity of the data plane solution alternative is
crucial, since it basically defines the effort, time line and risks
involved for the use of the solution in deployments. For example,
the maturity level can be categorized as available immediately,
available with small extensions, available with re-purposing/
redefining portions of the protocol or its header fields. Yet
another important measure for maturity is the deployment experience.
This criteria concerns the maturity of the data plane protocol
alternative as the solution alternative. This criteria is
particularly important given, as previously noted, that the DetNet
data plane solution is expected to impact, i.e., be supported in,
hardware.
5. Data plane solution alternatives
The following sections describe and rate deterministic data plane
solution alternatives. In "Analysis and Discussion" section each
alternative is evaluated against the criteria given in Section 4 and
rated using the following: (M)eets the criteria, (W)ork needed, and
(N)ot suitable or too much work envisioned.
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5.1. DetNet Transport layer technologies
5.1.1. Native IPv6 transport
5.1.1.1. Solution description
This section investigates the application of native IPv6 [RFC2460] as
the data plane for deterministic networking along the criteria
collected in Section 4.
The application of higher OSI layer headers, i.e., headers deeper in
the packet, can be considered. Two aspects have to be taken into
account for such solutions. (i) Those header fields can be encrypted.
(ii) Those header fields are deeper in the packet, therefore, routers
have to apply deep packet inspection. See further details in
Section 5.2.5.
5.1.1.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
IPv6 can encapsulate DetNet Service layer headers (and associated
DetNet flow payload) like any other upper-layer header indicated
by the Next Header. The fixed header of an IPv6 packet is 40
bytes [RFC2460]. This overhead is bigger if any Extension Header
is used, and a generic behaviour for host and forwarding nodes is
specified in [RFC7045]. However, the exact overhead (Section 4.1)
depends on what solution is actually used to provide DetNet
features, e.g., explicit routing or DetNet service protection if
any of these is applied.
IPv6 has two types of Extension Headers that are processed by
intermediate routers between the source and the final destination
and may be of interest for the data plane signaling, the Routing
Header that is used to direct the traffic via intermediate routers
in a strict or loose source routing way, and the Hop-by-Hop
Options Header that carries optional information that must be
examined by every node along a packet's delivery path. The Hop-
by-Hop Options Header, when present, must immediately follow the
IPv6 Header and it is not possible to limit its processing to the
end points of Source Routed segments.
IPv6 also provides a Destination Options Header that is used to
carry optional information to be examined only by a packet's
destination node(s). The encoding of the options used in the Hop-
by-Hop and in the Destination Options Header indicates the
expected behavior when a processing IPv6 node does not recognize
the Option Type, e.g. skip or drop; it should be noted that due to
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performance restrictions nodes may ignore the Hop-by-Hop Option
Header, drop packets containing a Hop-by-Hop Option Header, or
assign packets containing a Hop-by-Hop Option Header to a slow
processing path [I-D.ietf-6man-rfc2460bis] (e.g. punt packets from
hardware to software forwarding which is highly detrimental to the
performance).
The creation of new Extension Headers that would need to be
processed by intermediate nodes is strongly discouraged. In
particular, new Extension Header(s) having hop-by-hop behavior
must not be created or specified. New options for the existing
Hop-by-Hop Header should not be created or specified unless no
alternative solution is feasible [RFC6564].
#2 Flow identification (W)
The 20-bit flow label field of the fixed IPv6 header is suitable
to distinguish different deterministic flows. But guidance on the
use of the flow label provided by [RFC6437] places restrictions on
how the flow label can be used. In particular, labels should be
chosen from an approximation to a discrete uniform distribution.
Additionally, existing implementations generally do not open APIs
to control the flow label from the upper layers.
Alternatively, the Flow identification could be transported in a
new option in the Hop-by-Hop Options Header.
#4 Explicit routes (W)
One possibility is for a Software-Defined Networking (SDN)
[RFC7426] based approach to be applied to compute, establish and
manage the explicit routes, leveraging Traffic Engineering (TE)
extensions to routing protocols [RFC5305] [RFC7752] and evolving
to the Path Computation Element (PCE) Architecture [RFC5440],
though a number of issues remain to be solved [RFC7399].
Segment Routing (SR) [I-D.ietf-spring-segment-routing] is a new
initiative to equip IPv6 with explicit routing capabilities. The
idea for the DetNet data plane would be to apply SR to IPv6 with
the addition of a new type of routing extension header
[I-D.ietf-6man-segment-routing-header] to explicitly signal the
path in the data plane between the source and the destination,
and/or between replication points and elimination points if this
functionality is used.
#5 Flow duplication and merging (W)
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The functionality of replicating a packet exists in IPv6 but is
limited to multicast flows. In order to enforce replicated
packets to take different routes and eventually again merge flow
(bring them to a specific merging point), IP-in-IP encapsulation
and Segment Routing could be leveraged to signal a segment in a
packet. A replication point would insert a different routing
header in each copy it makes, the routing header providing
explicitly the hops to the merging point for that particular
replica of the packet, in a strict or in a loose source routing
fashion. A flow merging point would pop the routing headers from
the various copies it gets and do the rest of the required
processing for merging the two flows into one flow.
#6 Operations, Administration and Maintenance (M/W)
IPv6 enjoys the existing toolbox for generic IP network
management. However, IPv6 specific management features are still
not at the level comparable to that of IPv4. Particular areas of
concerns are those that are IPv6 specific, for example, related to
neighbor discovery protocol (ND), stateless address
autoconfiguration (SLAAC), subscriber identification, and
security. While the standards are already mostly in place the
implementations in deployed equipment can be lacking or inadequate
for commercial deployments. This is larger issue with older
existing equipment.
#8 Class and quality of service capabilities (W)
IPv6 provides support for CoS and QoS. CoS is provided by
DiffServ which is enabled by IP header differentiated services
code point (DSCP) and QoS is defined as part of RSVP [RFC2205].
DiffServ support is widely available, while RSVP for IP packets is
generally not supported.
#9 Packet traceability (W)
The traceability of replicated packets involves the capability to
resolve which replication point issued a particular copy of a
packet, which segment was intended for that replica, and which
particular packet of which particular flow this is. Sequence also
depends on the sequencing mechanism. As an example, the
replication point may be indicated as the source of the packet if
IP-in-IP encapsulation is used to forward along segments. Another
alternate to IP-in-IP tunneling along segments would be to protect
the original source address in a destination option similar to the
Home Address option [RFC6275] and then use the address of the
replication point as source in the IP header.
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The traceability also involves the capability to determine if a
particular segment is operational. While IPv6 as such has no
support for reversing a path, it appears source route extensions
such as the one defined for segment routing could be used for
tracing purposes. Though it is not a usual practice, IPv6
[RFC2460] expects that a Source Route path may be reversed, and
the standard insists that a node must not include the reverse of a
Routing Header in the response unless the received Routing Header
was authenticated.
#10 Technical maturity (M/W)
IPv6 has been around about 20 years. However, large scale global
and commercial IPv6 deployments are rather new dating only few
years back to around 2012. While IPv6 has proven itself for best
effort traffic, DiffServ usage is less common and QoS capabilities
are not currently present. Additional, there are number of small
issues to work on as they show up once operations experience
grows.
The Cisco 6Lab site [1] provides information on IPv6 deployment
per country, indicating figures for prefixes, transit AS, content
and users. Per this site, many countries, including Canada,
Brazil, the USA, Germany, France, Japan, Portugal, Sweden,
Finland, Norway, Greece, and Ecuador, achieve a deployment ratio
above 30 percent, and the overall adoption reported by Google
Statistics [2] is now above 10 percent.
5.1.1.3. Summary
IPv6 supports a significant portion of the identified DetNet data
plane criteria today. There are aspects of the DetNet data plane
that are not fully supported, notably QoS, but these can be
incrementally added or supplemented by the underlying sub-network
layer. IPv6 may be a choice as the DetNet Transport layer in
networks where other technologies such as MPLS are not deployed.
5.1.2. Native IPv4 transport
5.1.2.1. Solution description
IPv4 [RFC0791] is in principle the same as IPv6, except that it has a
smaller address space. However, IPv6 was designed around the fact
that extension headers are an integral part of the protocol and
operation from the beginning, although the practice may some times
prove differently [RFC7872]. IPv4 does support header options, but
these have historically not been supported in hardware-based
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forwarding so are generally blocked or handled at a much slower rate.
In either case, the use of IP header options is generally avoided.
In the context of deterministic networking data plane solutions the
major difference between IPv4 and IPv6 seems to be the practical
support for header extensibility. Anything below and above the IP
header independent of the version is practically the same.
5.1.2.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
The fixed header of an IPv4 packet is 20 bytes [RFC0791]. IP
options add overhead, but are not generally used and are not
considered as part of this document.
#2 Flow identification (W)
The IPv4 header has a 16-bit identification field that was
originally intended for assisting fragmentation and reassembly of
IPv4 packets as described in [RFC0791]. The identification field
has also been proposed to be used for actually identifying flows
between two IP addresses and a given protocol for detecting and
removing duplicate packets [RFC1122]. However, recent update
[RFC6864] to both [RFC0791] and [RFC1122] restricts the use of
IPv4 identification field only to fragmentation purposes.
The IPv4 also has a stream identifier option [RFC0791], which
contains a 16-bit SATNET stream identifier. However, the option
has been deprecated [RFC6814]. The conclusion is that stream
identification does not work nicely with IPv4 header alone and a
traditional 5-tuple identification might not also be enough in a
case of a flow duplication or encrypted flows. For a working
solution, upper layer protocol headers such as RTP or PWs may be
required for unambiguous flow identification. There is also
emerging work within the IETF that may provide new flow
identification alternatives.
#4 Explicit routes (W)
IPv4 has two source routing option specified: the loose source and
record route option (LSRR), and the strict source and record route
option (SSRR) [RFC0791]. The support of these options in the
Internet is questionable but within a closed network the support
may be assumed. But as both these options use IP header options,
which are generally not supported in hardware, use of these
options are questionable. Of course, the same options of SDN and
SR approaches discussed above for IPv6 may be equally applicable
to IPv4.
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#5 Flow duplication and merging (W/N)
The functionality of replicating a packet exists in IPv4 but is
limited to multicast flows. In general the issue regarding the
IPv6 packet replication also applies to IPv4. Duplicate packet
detection for IPv4 is studied in [RFC6621] to a great detail in
the context of simplified multicast forwarding. In general there
is no good way to detect duplicated packets for IPv4 without
additional upper layer protocol support.
#6 Operations, Administration and Maintenance (M)
IPv4 enjoys the extensive and "complete" existing toolbox for
generic IP network management.
#8 Class and quality of service capabilities (M/W)
IPv4 provides support for CoS and QoS. CoS is provided by
DiffServ which is enabled by IP header differentiated services
code point (DSCP) and QoS is defined as part of RSVP [RFC2205].
DiffServ support is widely available, while RSVP for IP packets is
generally not supported.
#9 Packet traceability (W)
The IPv4 has similar needs and requirements for traceability as
IPv6 (see Section 5.1.1.2). The IPv4 has a traceroute option
[RFC6814] that could be used to record the route the packet took.
However, the option has been deprecated [RFC6814].
#10 Technical maturity (M/W)
IPv4 can be considered mature technology with over 30 years of
implementation, deployment and operations experience. As with
IPv6, today's commercial implementations and deployments of IPv4
generally lack any support for QoS.
5.1.2.3. Summary
The IPv4 has specifications to support most of the identified DetNet
data plane criteria today. However, several of those have already
been deprecated or their wide support is not guaranteed. The DetNet
data plane criteria that are not fully supported could be
incrementally added or supplemented by the underlying sub-network
layer. Unfortunately, the IPv4 has had limited success getting its
extensions deployed at large. However, introducing new extensions
might have a better success in closed networks (like DetNet) than in
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Internet. Due to the popularity of the IPv4, it should be considered
as a potential choice for the DetNet Transport layer.
5.1.3. Multiprotocol Label Switching (MPLS)
Multiprotocol Label Switching Architecture (MPLS) [RFC3031] and its
variants, MPLS with Traffic Engineering (MPLS-TE) [RFC3209] and
[RFC3473], and MPLS Transport Profile (MPLS-TP) [RFC5921] is a widely
deployed technology that switches traffic based on MPLS label stacks
[RFC3032] and [RFC5960]. MPLS is the foundation for Pseudowire-based
services Section 5.2.3 and emerging technologies such as Bit-Indexed
Explicit Replication (BIER) Section 5.1.4 and Source Packet Routing
[3].
MPLS supports the equivalent of both the DetNet Service and DetNet
Transport layers, and provides a very rich set of mechanisms that can
be reused directly, and perhaps augmented in certain cases, to
deliver DetNet services. At the DetNet Transport layer, MPLS
provides forwarding, protection and OAM services. At the DetNet
Service Layer it provides client service adaption, directly, via
Pseudowires Section 5.2.3 and via other label-like mechanisms such as
EPVN Section 5.2.4. A representation of these options are shown in
Figure 7.
PW-Based EVPN Labeled IP
Services Services Transport
|------------| |-----------------------------| |------------|
Emulated EVPN over LSP EVPN w/ ESI ID IP
Service
+------------+
| Payload |
+------------+ +------------+ +------------+ (Service)
| PW Payload | | Payload | |ESI Lbl(S=1)|
+------------+ +------------+ +------------+ +------------+
|PW Lbl(S=1) | |VPN Lbl(S=1)| |VPN Lbl(S=0)| | IP |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|LSP Lbl(S=0)| |LSP Lbl(S=0)| |LSP Lbl(S=0)| |LSP Lbl(S=1)|
+------------+ +------------+ +------------+ +------------+
. . . .
. . . . (Transport)
. . . .
~~~~~~~~~~~ denotes DetNet Service <-> DetNet Transport layer boundary
Figure 7: MPLS-based Services
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MPLS can be controlled in a number of ways including via a control
plane, via the management plane, or via centralized controller (SDN)
based approaches. MPLS also provides standard control plane
reference points. Additional information on MPLS architecture and
control can be found in [RFC5921]. A summary of MPLS control plane
related functions can be found in [RFC6373]. The remainder of this
section will focus on the MPLS transport data plane, additional
information on the MPLS service data plane can be found below in
Section 5.2.2.
5.1.3.1. Solution description
The following draws heavily from [RFC5960].
Encapsulation and forwarding of packets traversing MPLS LSPs follows
standard MPLS packet encapsulation and forwarding as defined in
[RFC3031], [RFC3032], [RFC5331], and [RFC5332].
Data plane Quality of Service capabilities are included in the MPLS
in the form of Traffic Engineered (TE) LSPs [RFC3209] and the MPLS
Differentiated Services (DiffServ) architecture [RFC3270]. Both
E-LSP and L-LSP MPLS DiffServ modes are defined. The Traffic Class
field (formerly the EXP field) of an MPLS label follows the
definition of [RFC5462] and [RFC3270].
Except for transient packet reordering that may occur, for example,
during fault conditions, packets are delivered in order on L-LSPs,
and on E-LSPs within a specific ordered aggregate.
The Uniform, Pipe, and Short Pipe DiffServ tunneling and TTL
processing models are described in [RFC3270] and [RFC3443] and may be
used for MPLS LSPs.
Equal-Cost Multi-Path (ECMP) load-balancing is possible with MPLS
LSPs and can be avoided using a number of techniques. The same holds
for Penultimate Hop Popping (PHP).
MPLS includes the following LSP types:
o Point-to-point unidirectional
o Point-to-point associated bidirectional
o Point-to-point co-routed bidirectional
o Point-to-multipoint unidirectional
Point-to-point unidirectional LSPs are supported by the basic MPLS
architecture [RFC3031].
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A point-to-point associated bidirectional LSP between LSRs A and B
consists of two unidirectional point-to-point LSPs, one from A to B
and the other from B to A, which are regarded as a pair providing a
single logical bidirectional transport path.
A point-to-point co-routed bidirectional LSP is a point-to-point
associated bidirectional LSP with the additional constraint that its
two unidirectional component LSPs in each direction follow the same
path (in terms of both nodes and links). An important property of
co-routed bidirectional LSPs is that their unidirectional component
LSPs share fate.
A point-to-multipoint unidirectional LSP functions in the same manner
in the data plane, with respect to basic label processing and packet-
switching operations, as a point-to-point unidirectional LSP, with
one difference: an LSR may have more than one (egress interface,
outgoing label) pair associated with the LSP, and any packet it
transmits on the LSP is transmitted out all associated egress
interfaces. Point-to-multipoint LSPs are described in [RFC4875] and
[RFC5332]. TTL processing and exception handling for point-to-
multipoint LSPs is the same as for point-to-point LSPs.
Additional data plane capabilities include Linear Protection,
[RFC6378] and [RFC7271]. And the in progress work on MPLS support
for time synchronization [I-D.ietf-mpls-residence-time].
5.1.3.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
There are two perspectives to consider when looking at
encapsulation. The first is encapsulation to support services.
These considerations are part of the DetNet service layer and are
covered below, see Sections 5.2.3 and 5.2.4.
The second perspective relates to encapsulation, if any, which is
needed to transport packets across network. In this case, the
MPLS label stack, [RFC3032] is used to identify flows across a
network. MPLS labels are compact and highly flexible. They can
be stacked to support client adaptation, protection, network
layering, source routing, etc.
The number of DetNet Transport layer specific labels is flexible
and support a wide range of applicable functions and MPLS domain
characteristics (e.g., TE-tunnels, Hierarchical-LSPs, etc.).
#2 Flow identification (M)
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MPLS label stacks provide highly flexible ways to identify flows.
Basically, they enable the complete separation of traffic
classification from traffic treatment and thereby enable arbitrary
combinations of both.
For the DetNet flow identification the MPLS label stack can be
used to support n-layers of DetNet flow identification. For
example, using dedicated LSP per DetNet flow would simplify flow
identification for intermediate transport nodes, and additional
hierarchical LSPs could be used to facilitate scaling.
#4 Explicit routes (M)
MPLS supports explicit routes based on how LSPs are established,
e.g., via TE explicit routes [RFC3209]. Additional, but not
required, capabilities are being defined as part of Segment
Routing (SR) [I-D.ietf-spring-segment-routing].
#5 Flow duplication and merging (M/W)
MPLS as DetNet Transport layer supports the replication via point-
to-multipoint LSPs. At the MPLS LSP level, there are mechanisms
defined to provide 1+1 protection, which could help in realizing
the flow merging function. The current definitions [RFC6378] and
[RFC7271] use OAM mechanisms to support and coordinate protection
switching and packet loss is possible during a switch. While such
this level of protection may be sufficient for many DetNet
applications, when truly hitless (i.e., zero loss) switching is
required, additional mechanisms will be needed. It is expected
that these additional mechanisms will be defined at a DetNet
layer.
#6 Operations, Administration and Maintenance (M)
MPLS already includes a rich set of OAM functions at both the
Service and Transport Layers. This includes LSP ping [ref] and
those enabled via the MPLS Generic Associated Channel [RFC5586]
and registered by IANA [4].
#8 Class and quality of service capabilities (M/W)
As previously mentioned, Data plane Quality of Service
capabilities are included in the MPLS in the form of Traffic
Engineered (TE) LSPs [RFC3209] and the MPLS Differentiated
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Services (DiffServ) architecture [RFC3270]. Both E-LSP and L-LSP
MPLS DiffServ modes are defined. The Traffic Class field
(formerly the EXP field) of an MPLS label follows the definition
of [RFC5462] and [RFC3270]. One potential open area of work is
synchronized, time based scheduling. Another is shaping, which is
generally not supported in shipping MPLS hardware.
#9 Packet traceability (M)
MPLS supports multiple tracing mechanisms. A control based one is
defined in [RFC3209]. An OAM based mechanism is defined in MPLS
On-Demand Connectivity Verification and Route Tracing [RFC6426].
#10 Technical maturity (M)
MPLS as a mature technology that has been widely deployed in many
networks for many years. Numerous vendor products and multiple
generations of MPLS hardware have been built and deployed.
5.1.3.3. Summary
MPLS is a mature technology that has been widely deployed. Numerous
vendor products and multiple generations of MPLS hardware have been
built and deployed. MPLS LSPs support a significant portion of the
identified DetNet data plane criteria today. Aspects of the DetNet
data plane that are not fully supported can be incrementally added.
It's worth noting that a number of limitations are in shipping
hardware, versus at the protocol specification level, e.g., shaping.
5.1.4. Bit Indexed Explicit Replication (BIER)
Bit Indexed Explicit Replication [I-D.ietf-bier-architecture] (BIER)
is a network plane replication technique that was initially intended
as a new method for multicast distribution. In a nutshell, a BIER
header includes a bitmap that explicitly signals the destinations
that are intended for a particular packet, which means that 1) the
source is aware of the individual destinations and 2) the BIER
control plane is a simple extension of the unicast routing as opposed
to a dedicated multicast data plane, which represents a considerable
reduction in OPEX. For this reason, the technology is getting a lot
of traction from Service Providers. In the context of DetNet, BIER
may be applicable for implementing packet replication, as described
in Section 5.1.4.
The encapsulation of a BIER packet in an MPLS network is shown in
Figure 8
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Stack Element |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Stack Element |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BIER-MPLS label | |1| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 0 1| Ver | Len | Entropy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM| Reserved | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: BIER packet in MPLS encapsulation
5.1.4.1. Solution description
A distinctive BIER payload type (with its own Proto(col) ID) would be
created for DetNet, providing a header that would identify:
o Version;
o Sequence Number;
o Timestamp;
o Payload type, e.g. data vs. OAM.
A DetNet node, collocated with a BFIR (Bit-Forwarding Ingress Router)
may use multiple BIER sub-domains to create replicated flows.
Downstream DetNet nodes, collocated with BFER (Bit-Forwarding Ingress
Router) would terminate redundant flows based on Sequence Number and/
or Timestamp information. Thus a DetNet node may be collocated with
a BFER in one BIER sub- domain and with a BFIR in another, and a
DetNet flow could traverse several BIER sub-domains.
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+-----+
| A |
+-----+
/ \
. .
/ .
. \
/ .
. .
/ \
+-----+ +-----+
| B | | C |
+-----+ +-----+
/ \ / \
. . . .
/ \ . .
. . / \
/ \ . .
. . . .
/ \ / \
+-----+ +-----+ +-----+
| D | | E | | F |
+-----+ +-----+ +-----+
\ . . /
. . . .
\ . . .
. . . /
\ . . .
. . . .
\ . . /
+-----+ +-----+
| G | | H |
+-----+ +-----+
Figure 9: DetNet in BIER domain
Consider a DetNet flow that must traverse BIER enabled domain from A
to G and H. DetNet may use three BIER subdomains:
o A-B-D-E-G (dash-dot): A is BFIR, E and G are BFERs,
o A-C-E-F-H (dash-double-dot): A is BFIR, E and H are BFERs,
o E-G-H (dotted): E is BFIR, G and H are BFERs.
DetNet node A sends DetNet into red and purple BIER sub-domains.
DetNet node E receives DetNet packet and sends into green sub-domain
while terminating duplicates and those that are deemed "too-late".
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DetNet nodes G and H receive DetNet flows, terminate duplicates and
those that are too-late.
5.1.4.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
BIER over MPLS network encapsulation ("BIER over MPLS"), Figure 8,
is being defined [I-D.ietf-bier-mpls-encapsulation] within the
BIER working group.
#2 Flow identification (M)
Flow identification and separation can be achieved through use of
BIER domains and/or Entropy value in the BIER over MPLS, Figure 8.
#4 Explicit routes (M)
Explicit routes may be used as underlay for BIER domain. BIER
underlay may be calculated using PCE and instantiated using any
southbound mechanism.
#5 Flow duplication and merging (M/W)
Packet replication, as indicated by its name, is a core function
of the Bit-Indexed Explicit Replication. Elimination of the
duplicates and/or too-late packets cannot be done within BIER sub-
domain but may be done at DetNet overlay at the edge of the BIER
sub-domain.
[Editor's note: how about the flow merging?]
#6 Operations, Administration and Maintenance (M/W)
BIER over MPLS guarantees that OAM is fate-sharing, i.e. in-band
with a data flow being monitored or measured. Additionally, BIER
over MPLS enables passive performance measurement, e.g. with the
marking method [I-D.mirsky-bier-pmmm-oam]. Existing OAM protocols
can be applied and used in BIER over MPLS as demonstrated in
[I-D.ooamdt-rtgwg-oam-gap-analysis], while new protocols are being
worked on, e.g. ping/traceroute [I-D.kumarzheng-bier-ping] or Path
MTU Discovery [I-D.mirsky-bier-path-mtu-discovery].
#8 Class and quality of service capabilities (M/W)
Class of Service can be inherited from the underlay of the
particular BIER sub-domain. Quality of Service, i.e. scheduling
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and bandwidth reservations can be used among other constraints in
calculating explicit paths for the BIER sub-domain's underlay.
#9 Packet traceability (W)
Ability to do passive performance measurement by using OAM field
of the BIER over MPLS, Figure 8, is unmatched and significantly
simplifies truly passive tracing of selected flows and packets
within them.
#10 Technical maturity (W)
The BIER over MPLS is nearing finalization within the BIER WG and
several experimental implementations are expected soon.
5.1.4.3. Summary
BIER over MPLS supports a significant portion of the identified
DetNet data plane requirements, including controlled packet
replication, traffic engineering, while some requirements, e.g.
duplicate and too-late packet elimination may be realized as function
of the DetNet overlay. BIER over MPLS is a viable candidate as the
DetNet Transport layer in MPLS networks.
5.2. DetNet Service layer technologies
5.2.1. Generic Routing Encapsulation (GRE)
5.2.1.1. Solution description
Generic Routing Encapsulation (GRE) [RFC2784] provides an
encapsulation of an arbitrary network layer protocol over another
arbitrary network layer protocol. The encapsulation of a GRE packet
can be found in Figure 10.
+-------------------------------+
| Delivery Header |
+-------------------------------+
| GRE Header |
+-------------------------------+
| Payload packet |
+-------------------------------+
Figure 10: Encapsulation of a GRE packet
Based on RFC2784, [RFC2890] further includes sequencing number and
Key in optional fields of the GRE header, which may help to transport
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DetNet traffic flows over IP networks. The format of a GRE header is
presented in Figure 11.
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type |
+-----------------------------------------------------------------+
| Checksum (optional) | Reserved1 (Optional) |
+-----------------------------------------------------------------+
| Key (optional) |
+-----------------------------------------------------------------+
| Sequence Number (optional) |
+-----------------------------------------------------------------+
Figure 11: Format of a GRE header
5.2.1.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
GRE can provide encapsulation at the service layer over the
transport layer. A new protocol type for DetNet traffic should be
allocated as an "Ether Type" in [RFC3232] and in IANA Ethernet
Numbers [5]. The fixed header of a GRE packet is 4 octets while
the maximum header is 16 octets with optional fields in Figure 11.
#2 Flow identification (W)
There is no flow identification field in GRE header. However, it
can rely on the flow identification mechanism applied in the
delivery protocols, such as flow identification stated in IP
Sections 5.1.1 and 5.1.2 when the delivery protocols are IPv6 and
IPv4 respectively. Alternatively, the Key field can also be
extended to carry the flow identification. The size of Key field
is 4 octets.
#3 Packet sequencing and duplicate elimination (M/W)
As stated in Section 5.2.1, GRE provides an optional sequencing
number in its header to provide sequencing services for packets.
The size of the sequencing number is 32 bits. The GRE header
could be extended to indicate the duplicated packets by defining a
flag in reserved fields or using the sequencing number of a flow.
#5 Flow duplication and merging (W/N)
GRE has no flow/packet replication and merging support in its
header. It can use the transport IPv4/IPv6 protocols at the
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transport layer to replicate the packets and take the different
routes as discussed in Section 5.1.1 and Section 5.1.2.
#6 Operations, Administration and Maintenance (M)
GRE uses the network management provided by the IP protocols as
transport layer.
#8 Class and quality of service capabilities (W)
For the class of service capability, an optional code point field
to indicate CoS of the traffic could be added into the GRE header.
Otherwise, GRE can reuse the class and quality of service of
delivery protocols at transport layer such as IPv6 and IPv4 stated
in Section 5.1.1 and Section 5.1.2.
#10 Technical maturity (M)
GRE has been developed over 20 years. The delivery protocol
mostly used is IPv4, while the IPv6 support for GRE is to be
standardized now in IETF as [RFC7676]. Due to its good
extensibility, GRE has also been extended to support network
virtualization in Data Center, which is NVGRE [RFC7637].
5.2.1.3. Summary
As a tunneling protocol, GRE can encapsulate a wide variety of
network layer protocols over another network layer, which can
naturally serve as the service layer protocol for DetNet. Currently,
it supports a portion of the Detnet service layer criteria, and still
some are not fully supported but can be incrementally added or
supported by delivery protocols at as the transport layer. In
general, GRE can be a choice as the DetNet service layer and can work
with IPv6 and IPv4 as the DetNet Transport layer.
5.2.2. MPLS-based Services for DetNet
MPLS based technologies support both the DetNet Service and DetNet
Transport layers. This, as well as a general overview of MPLS, is
covered above in Section 5.1.3. Following sections focus on the
DetNet Service Layer which provides client service adaption, via
Pseudowires Section 5.2.3 and via native and other label-like
mechanisms such as EPVN in Section 5.2.4. A representation of these
options was previously discussed and is shown in Figure 7.
The following text is adapted from [RFC5921]:
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The MPLS native service adaptation functions interface the client
layer network service to MPLS. For Pseudowires, these adaptation
functions are the payload encapsulation described in Section 4.4
of [RFC3985] and Section 6 of [RFC5659]. For network layer client
services, the adaptation function uses the MPLS encapsulation
format as defined in [RFC3032].
The purpose of this encapsulation is to abstract the data plane of
the client layer network from the MPLS data plane, thus
contributing to the independent operation of the MPLS network.
MPLS may itself be a client of an underlying server layer. MPLS
can thus also be bounded by a set of adaptation functions to this
server layer network, which may itself be MPLS. These adaptation
functions provide encapsulation of the MPLS frames and for the
transparent transport of those frames over the server layer
network.
While MPLS service can provided on a true end-system to end-system
basis, it's more likely that DetNet service will be provided over
Pseudowires as described in Section 5.2.3 or via an EPVN-based
service described in Section 5.2.4 .
MPLS labels in the label stack may be used to identify transport
paths, see Section 5.1.3, or as service identifiers. Typically a
single label is used for service identification.
Packet sequencing mechanisms are added in client-related
adaptation processing, see Sections 5.2.3 and 5.2.4.
The MPLS client inherits its Quality of Service (QoS) from the
MPLS transport layer, which in turn inherits its QoS from the
server (sub-network) layer. The server layer therefore needs to
provide the necessary QoS to ensure that the MPLS client QoS
commitments can be satisfied.
5.2.3. Pseudo Wire Emulation Edge-to-Edge (PWE3)
5.2.3.1. Solution description
Pseudo Wire Emulation Edge-to-Edge (PWE3) [RFC3985] or simply
PseudoWires (PW) provide means of emulating the essential attributes
and behaviour of a telecommunications service over a packet switched
network (PSN) using IP or MPLS transport. In addition to traditional
telecommunications services such as T1 line or Frame Relay, PWs also
provide transport for Ethernet service [RFC4448] and for generic
packet service [RFC6658]. Figure 12 illustrate the reference PWE3
stack model.
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+----------------+ +----------------+
|Emulated Service| |Emulated Service|
|(e.g., Eth, ...)|<= Emulated Service =>|(e.g., Eth, ...)|
+----------------+ +----------------+
| Payload | | Payload | CW,
| Encapsulation |<=== Pseudo Wire ====>| Encapsulation | Timing,
| | | | Seq., ..
+----------------+ +----------------+
|PW Demultiplexer| |PW Demultiplexer|
| PSN Tunnel, |<==== PSN Tunnel ====>| PSN Tunnel, | MPLS.
| PSN & Physical | | PSN & Physical | L2TP,
| Layers | | Layers | IP, ..
+-------+--------+ ___________ +---------+------+
| / \ |
+============/ PSN \==============+
\ /
\___________/
Figure 12: PWE3 protocol stack reference model
PWs appear as a good data plane solution alternative for a number of
reasons. PWs are a proven and deployed technology with a rich OAM
control plane [RFC4447], and enjoy the toolbox developed for MPLS
networks in a case of MPLS-based PSN. Furthermore, PWs may have an
optional Control Word (CW) as part of the payload encapsulation
between the PSN and the emulated service that is, for example,
capable of frame sequencing and duplicate detection. The
encapsulation layer may also provide timing using RTP as described in
Sections 5.2.2, 5.4.1 and 5.4.2 of [RFC3985] and utilized by
[RFC4553][RFC5087]. Furthermore, advanced DetNet node functions are
conceptually already supported by PW framework (with some added
functional required), such as the DetNet Relay node modeled after the
Multi-Segment PWE3 [RFC5254].
PWs can be also used if the PSN is IP, which enables the application
of PWs in networks that do not have MPLS enabled in their core
routers. One approach to provide PWs over IP is to provide MPLS over
IP in some way and then leverage what is available for PWs over MPLS.
The following standard solutions are available both for IPv4 and IPv6
to follow this approach. The different solutions have different
overhead as discussed in the following subsection. The MPLS-in-IP
encapsulation is specified by [RFC4023]. The IPv4 Protocol Number
field or the IPv6 Next Header field is set to 137, which indicates an
MPLS unicast packet. (The use of the MPLS-in-IP encapsulation for
MPLS multicast packets is not supported.) The MPLS-in-GRE
encapsulation is specified in [RFC4023], where the IP header (either
IPv4 or IPv6) is followed by a GRE header, which is followed by an
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MPLS label stack. The protocol type field in the GRE header is set
to MPLS Unicast (0x8847) or Multicast (0x8848). MPLS over L2TPv3
over IP encapsulation is specified by [RFC4817]. The MPLS-in-UDP
encapsulation is specified by [RFC7510], where the UDP Destination
Port indicates tunneled MPLS packet and the UDP Source Port is an
entropy value that is generated by the encapsulator to uniquely
identify a flow. MPLS-in-UDP encapsulation can be applied to enable
UDP-based ECMP (Equal-Cost Multipath) or Link Aggregation. All these
solutions can be secured with IPsec [RFC4303].
5.2.3.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
PWs offer encapsulation services practically for practically any
type of payload over any PSN. New PW types need a code point
allocation [RFC4446] and in some cases an emulated service
specific document.
Specifically in the case of the MPLS PSN the PW encapsulation
overhead is minimal. Typically minimum two labels and a CW is
needed, which totals to 12 octets. PW type specific handling
might, however, allow optimizations on the emulated service in the
provider edge (PE) device's native service processing (NSP) /
forwarder function. These optimizations could be used, for
example, to reduce header overhead. Ethernet PWs already have
rather low overhead [RFC4448]. Without a CW and VLAN tags the
Ethernet header gets reduced to 14 octets (minimum Ethernet header
overhead is 26).
The overhead is somewhat bigger in case of IP PSN if an MPLS over
IP solution is applied to provide PWs. IP adds at least 20 (IPv4)
or 40 (IPv6) bytes overhead to the PW over MPLS overhead;
furthermore, the GRE, L2TPv3, or UDP header has to be taken into
account if any of these further encapsulations is used.
#2 Flow identification (M)
PWs provide multiple layers of flow identification, especially in
the case of the MPLS PSN. The PWs are typically prepended with an
endpoint specific PW label that can be used to identify a specific
PW per endpoint. Furthermore, the MPLS PSN also uses one or more
labels to transport packets over specific label switched paths
(that then would carry PWs). So, a DetNet flow can be identified
in this example by the service and transport layer labels. IP
(and other) PSNs may need other mechanisms, such as, UDP port
numbers, upper layer protocol header (like RTP) or some IP
extension header to provide required flow identification.
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#3 Packet sequencing and duplicate elimination (M)
As mentioned earlier PWs may contain an optional CW that is able
to provide sequencing services. The size of the sequence number
in the generic CW is 16 bits, which might be, depending on the
used link and DetNet flow speed be too little. The PW duplicate
detection mechanism is already conceptually specified [RFC3985]
but no emulated service makes use of it currently.
#5 Flow duplication and merging (W)
PWs could use a (extended) version of existing transport layer
provided protection mechanisms (e.g., hitless 1+1 protection) for
both flow duplication and flow merging. The service layer has to
provide the functionality to map DetNet flows into appropriate
transport layer connection.
#6 Operations, Administration and Maintenance (M/W)
PWs have rich control plane for OAM and in a case of the MPLS PSN
enjoy the full control plane toolbox developed for MPLS network
OAM likewise IP PSN has the full toolbox of IP network OAM tools.
There could be, however, need for deterministic networking
specific extensions for the mentioned control planes.
#8 Class and quality of service capabilities (M/W)
In a case of IP PSN the 6-bit differentiated services code point
(DSCP) field can be used for indicating the class of service
[RFC2474] and 2-bit field reserved for the explicit congestion
notification (ECN) [RFC3168]. Similarly, in a case of MPLS PSN,
there are 3-bit traffic class field (TC) [RFC5462] in the label
reserved for for both Explicitly TC-encoded-PSC LSPs (E-LSP)
[RFC3270] and ECN [RFC5129]. Due to the limited number of bits in
the TC field, their use for QoS and ECN functions is restricted
and intended to be flexible. Although the QoS/CoS mechanism is
already in place some clarifications may be required in the
context of deterministic networking flows, for example, if some
specific mapping between bit fields have to be done.
When PWs are used over MPLS, MPLS LSPs can be used to provide both
CoS (E-LSPs and L-LSPs) and QoS (dedicated TE LSPS).
#10 Technical maturity (M)
PWs, IP and MPLS are proven technologies with wide variety of
deployments and years of operational experience. Furthermore, the
estimated work for missing functionality (packet replication and
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elimination) does not appear to be extensive, since the existing
protection mechanism already gets close to what is needed from the
deterministic networking data plane solution.
5.2.3.3. Summary
PseudoWires appear to be a strong candidate as the deterministic
networking data plane solution alternative for the DetNet Service
layer. The strong points are the technical maturity and the
extensive control plane for OAM. This holds specifically for MPLS-
based PSN.
Extensions are required to realize the packet replication and
duplicate detection features of the deterministic networking data
plane.
5.2.4. MPLS-Based Ethernet VPN (EVPN)
5.2.4.1. Solution description
MPLS-Based Ethernet VPN (EVPN), in the form documented in [RFC7432]
and [RFC7209], is an increasingly popular approach to delivering
MPLS-based Ethernet services and is designed to be the successor to
Virtual Private LAN Service (VPLS), [RFC4664].
EVPN provides client adaptation and reuses the MPLS data plane
discussed above in Section 5.2.2. While not required, the PW Control
Word is also used. EVPN control is via BGP, [RFC7432], and may use
TE-LSPs, e.g., controlled via [RFC3209] for MPLS transport.
Additional EVPN related RFCs and in progress drafts are being
developed by the BGP Enabled Services Working Group [6].
5.2.4.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
EVPN generally uses a single MPLS label stack entry to support its
client adaptation service. The optional addition of a second
label is also supported. In certain cases PW Control Word may
also be used.
#2 Flow identification (W)
EVPN currently uses labels to identify flows per {Ethernet Segment
Identifier, VLAN} or per MAC level. Additional definition will be
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needed to standardize identification of finer granularity DetNet
flows as well as mapping of TSN services to DetNet Services.
#3 Packet sequencing and duplicate elimination (M)
Like MPLS, EVPN generally orders packets similar to Ethernet.
Reordering is possible primarily during path changes and
protection switching. In order to avoid misordering due to ECMP,
EVPN uses the "Preferred PW MPLS Control Word" [RFC4385] (in which
case EVPN inherits this function from PWs) or the entropy labels
[RFC6790].
If additional ordering mechanisms are required, such mechanisms
will need to be defined.
#5 Flow duplication and merging (M/W)
EVPN relies on the MPLS layer for all protection functions. See
Section 5.1.3 and Section 5.2.2. Some extensions, either at the
EVPN or MPLS levels, will be need to support those DetNet
applications which require true hitless (i.e., zero loss) 1+1
protection switching. (Network coding may be an interesting
alternative to investigate to delivering such hitless loss
protection capability.)
#6 Operations, Administration and Maintenance (M/W)
Nodes supporting EVPN may participate in either or both Ethernet
level and MPLS level OAM. It is likely that it may make sense to
map or adapt the OAM functions at the different levels, but such
has yet to be defined. [RFC6371] provides some useful background
on this topic.
#8 Class and quality of service capabilities (M/W)
EVPN is largely silent on the topics of CoS and QoS, but the 802.1
TSN Ethernet and existing MPLS TE mechanisms can be directly used.
The inter-working of such is new work and within the scope of
DetNet. The existing MPLS mechanisms include both CoS (E-LSPs and
L-LSPs) and QoS (dedicated TE LSPs).
#10 Technical maturity (M)
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EVPN is a second (or third) generation MPLS-based L2VPN service
standard. From a data plane standpoint it makes uses of existing
MPLS data plane mechanisms. The mechanisms have been widely
implemented and deployed.
5.2.4.3. Summary
EVPN is the emerging successor to VPLS. EVPN is standardized,
implemented and deployed. It makes use of the mature MPLS data
plane. While offering a mature and very comprehensive set of
features, certain DetNet required features are not fully/directly
supported and additional standardization in these areas are needed.
Examples include: mapping CoS and QoS; use of labels per DetNet flow,
and hitless 1+1 protection.
5.2.5. Higher layer header fields
Fields of headers belonging to higher OSI layers can be used to
implement functionality that is not provided e.g., by the IPv6 or
IPv4 header fields. However, this approach cannot be always applied,
e.g., due to encryption. Furthermore, even if this approach is
applicable, it requires deep packet inspection from the routers and
switches. There are implementation dependent limits how far into the
packet the lookup can be done efficiently in the fast path. When
encryption is not used, a safe bet is generally between 128 and 256
octets for the maximum lookup depth. Various higher layer protocols
can be applied. Some examples are provided here for the sequence
numbering feature (Section 4.3).
5.2.5.1. TCP
The TCP header includes a sequence number parameter, which can be
applied to detect and eliminate duplicate packets if DetNet service
protection is used. As the TCP header is right after the IP header,
it does not require very deep packet inspection; the 4-byte sequence
number is conveyed by bits 32 through 63 of the TCP header. In
addition to sequencing, the TCP header also contain source and
destination port information that can be used for assisting the flow
identification.
5.2.5.2. RTP
5.2.5.2.1. Solution Description
Real-time Transport Protocol (RTP) [RFC3550] is often used to deliver
time critical traffic in IP networks. RTP is typically carried on
top of UDP/IP. However, as noted earlier in Section 5.2.3
PseudoWires also have a well-defined way of embedding and
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transposting RTP headers as part of its payload encapsulation
headers/sub-layer. RTP is also augmented by its own control protocol
RTCP, which monitors the data delivery and provides minimal control
and identification functionality. RTCP packets do not carry "media
payload". Although both RTP and RTCP are typically used with UDP/IP
transport they are designed to be independent of the underlying
transport and network layers.
The RTP header includes a 2-byte sequence number, which can be used
to detect and eliminate duplicate packets if DetNet service
protection is used. The sequence number is conveyed by bits 16
through 31 of the RTP header. In addition to the sequence number the
RTP header has also timestamp field (bits 32 through 63) that can be
useful for time synchronization purposes. Furthermore, the RTP
header has also one or more synchronization sources (bits starting
from 64) that can potentially be useful for flow identification
purposes.
5.2.5.2.2. Analysis and Discussion
#1 Encapsulation and overhead (M)
RTP adds minimum 12 octets of header overhead. Typically 8 octets
overhead of UDP header has to be also added, at least in a case
when RTP is transported over IP. Although RTCP packets do not
contribute to the media payload transport they still consume
overall network capacity, since all participants to an RTP session
including sourcess and multicast session destinations are expected
to send RTCP reports.
#2 Flow identification (M)
The RTP header contains a synchronization source (SSRC)
identifier. The intent is that no two synchronization sources
within the same RTP session have the same SSRC identifier.
#3 Packet sequencing and duplicate elimination (M)
The RTP header contains a 16 bit sequence number. The sequence
number can be also used to detect duplicate packets.
#5 Flow duplication and merging (M/W)
RTP has precedence of being used for hitless protection switching
[ST20227], which essentially is equivalent to DetNet service
protection. Furthermore, recent work in IETF for RTP stream
duplication [RFC7198] as a mechanism to protect media flows from
packet loss is again equivalent to Detnet service protection.
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#6 Operations, Administration and Maintenance (M)
RTP has its own control protocol RTCP for (minimal) management and
stream monitoring purposes. Existing IP OAM tools can directly
leveraged when RTP is deployed over IP transport.
#8 Class and quality of service capabilities (M/W)
TBD. [Editor's note: relies on lower layers to provide CoS/QoS]
#10 Technical maturity (M)
RTP has been deployed and used in large commercial systems for
over ten years and can be considered a mature technology.
5.2.5.2.3. Summary
RTP appears to be a good candidate as the deterministic networking
data plane solution alternative for the DetNet Service layer. The
strong points are the technical maturity and the fact it was designed
for transporting time-sensitive payload from the beginning. RTP is
specifically well suited to be used with (UDP)/IP transport.
Extensions may be required to realize the packet replication and
duplicate detection features of the deterministic networking data
plane. However, there is already precedence of similar solutions
that could potentially be leveraged [ST20227][RFC7198].
6. Summary of data plane alternatives
The following table summarizes the criteria (Section 4) used for the
evaluation of data plane options.
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Applicability per Alternative
+--------+---------------------------------------------+
| Item # | Meaning |
+--------+---------------------------------------------+
| #1 | Encapsulation and overhead |
| #2 | Flow identification |
| #3 | Packet sequencing and duplicate elimination |
| #4 | Explicit routes |
| #5 | Flow duplication and merging |
| #6 | Operations, Administration and Maintenance |
| #8 | Class and quality of service capabilities |
| #9 | Packet traceability |
| #10 | Technical maturity |
+--------+---------------------------------------------+
Table 1: Evaluation criteria
There is no single technology that could meet all the criteria on its
own. Distinguishing the DetNet Service and the DetNet Transport, as
explained in (Section 3), allows a number of combinations, which can
meet most of the criteria. There is no room here to evaluate all
possible combinations. Therefore, only some combinations are
highlighted here, which are selected based on the number of criteria
that are met and the maturity of the technology (#10).
The following table summarizes the evaluation of the data plane
options that can be used for the DetNet Transport Layer against the
evaluation criteria. Each value in the table is from the
corresponding section.
Applicability per Transport Alternative
+----------+----+----+----+-----+-----+-----+----+-----+
| Solution | #1 | #2 | #4 | #5 | #6 | #8 | #9 | #10 |
+----------+----+----+----+-----+-----+-----+----+-----+
| IPv6 | M | W | W | W | M | W | W | M/W |
| IPv4 | M | W | W | W/N | M | M/W | W | M/W |
| MPLS | M | M | M | M/W | M | M/W | M | M |
| BIER | M | M | M | M/W | M/W | M/W | M | W |
+----------+----+----+----+-----+-----+-----+----+-----+
Summarizing Transport capabilities
Table 2: DetNet Transport Layer
The following table summarizes the evaluation of the data plane
options that can be used for the DetNet Service Layer against the
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criteria evaluation criteria. Each value in the table is from the
corresponding section.
Applicability per Service Alternative
+----------+----+----+-----+-----+-----+-----+-----+
| Solution | #1 | #2 | #3 | #5 | #6 | #8 | #10 |
+----------+----+----+-----+-----+-----+-----+-----+
| GRE | M | W | M/W | W/N | M | W | M |
| PWE3 | M | M | M | W | M/W | M/W | M |
| EVPN | M | W | M | M/W | M/W | M/W | M |
| RTP | M | M | M | M/W | M | M/W | M |
+----------+----+----+-----+-----+-----+-----+-----+
Summarizing Service capabilities
Table 3: DetNet Service Layer
PseudoWire (Section 5.2.3) is a technology that is mature and meets
most of the criteria for the DetNet Service layer as shown in the
table above. From upper layer protocols PWs or RTP can be a
candidate for non-MPLS PSNs. The identified work for PWs is to
figure out how to implement duplicate detection for these protocols
(e.g., based on [RFC3985]). In a case of RTP there is precedence of
implementing packet duplication and duplicate elimination
[ST20227][RFC7198].
PWs can be carried over MPLS or IP. MPLS is the most common
technology that is used as PSN for PseudoWires; furthermore, MPLS is
a mature technology and meets most DetNet Transport layer criteria.
IPv[46] can be also used as PSN and both are mature technologies,
although both generally only support CoS (DiffServ) in deployed
networks. RTP is independent of the underlying transport technology
and network. However, it is well suited for UDP/IP transport or
embedded as a part of the PseudoWire timing sub-layer.
7. Security considerations
This document does not add any new security considerations beyond
what the referenced technologies already have.
8. IANA Considerations
This document has no IANA considerations.
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9. Acknowledgements
The author(s) ACK and NACK.
The following people were part of the DetNet Data Plane Design Team:
Jouni Korhonen
Janos Farkas
Norman Finn
Olivier Marce
Gregory Mirsky
Pascal Thubert
Zhuangyan Zhuang
Substantial contributions were received from:
Balazs Varga (service model)
The DetNet chairs serving during the DetNet Data Plane Design Team:
Lou Berger
Pat Thaler
10. References
10.1. Informative References
[I-D.finn-detnet-architecture]
Finn, N. and P. Thubert, "Deterministic Networking
Architecture", draft-finn-detnet-architecture-08 (work in
progress), August 2016.
[I-D.ietf-6man-rfc2460bis]
Hinden, R., "Internet Protocol, Version 6 (IPv6)
Specification", draft-ietf-6man-rfc2460bis-06 (work in
progress), September 2016.
[]
Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
J., Aries, E., Kosugi, T., Vyncke, E., and D. Lebrun,
"IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
segment-routing-header-01 (work in progress), March 2016.
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-04 (work in
progress), July 2016.
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[I-D.ietf-bier-mpls-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
Explicit Replication in MPLS Networks", draft-ietf-bier-
mpls-encapsulation-05 (work in progress), July 2016.
[I-D.ietf-detnet-problem-statement]
Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", draft-ietf-detnet-problem-statement-00 (work
in progress), April 2016.
[I-D.ietf-mpls-residence-time]
Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
and S. Vainshtein, "Residence Time Measurement in MPLS
network", draft-ietf-mpls-residence-time-11 (work in
progress), July 2016.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-09 (work in progress), July 2016.
[I-D.kumarzheng-bier-ping]
Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
and G. Mirsky, "BIER Ping and Trace", draft-kumarzheng-
bier-ping-03 (work in progress), July 2016.
[I-D.mirsky-bier-path-mtu-discovery]
Mirsky, G., Przygienda, T., and A. Dolganow, "Path Maximum
Transmission Unit Discovery (PMTUD) for Bit Index Explicit
Replication (BIER) Layer", draft-mirsky-bier-path-mtu-
discovery-01 (work in progress), April 2016.
[I-D.mirsky-bier-pmmm-oam]
Mirsky, G., Zheng, L., Chen, M., and G. Fioccola,
"Performance Measurement (PM) with Marking Method in Bit
Index Explicit Replication (BIER) Layer", draft-mirsky-
bier-pmmm-oam-01 (work in progress), March 2016.
[I-D.ooamdt-rtgwg-oam-gap-analysis]
Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N., Kumar,
D., Chen, M., Yizhou, L., Mozes, D., Networks, J., and I.
Bagdonas, "Operations, Administration and Maintenance
(OAM) for Overlay Networks: Gap Analysis", draft-ooamdt-
rtgwg-oam-gap-analysis-02 (work in progress), July 2016.
Korhonen, et al. Expires March 18, 2017 [Page 42]
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[I-D.ooamdt-rtgwg-ooam-requirement]
Kumar, N., Pignataro, C., Kumar, D., Mirsky, G., Chen, M.,
Nordmark, E., Networks, J., and D. Mozes, "Overlay OAM
Requirements", draft-ooamdt-rtgwg-ooam-requirement-01
(work in progress), July 2016.
[IEEE802.1Qca]
IEEE 802.1, "IEEE 802.1Qca Bridges and Bridged Networks -
Amendment 24: Path Control and Reservation", IEEE
P802.1Qca/D2.1 P802.1Qca, June 2015,
<https://standards.ieee.org/findstds/standard/802.1Qca-
2015.html>.
[IEEE8021CB]
Finn, N., "Draft Standard for Local and metropolitan area
networks - Seamless Redundancy", IEEE P802.1CB
/D2.1 P802.1CB, December 2015,
<http://www.ieee802.org/1/files/private/cb-drafts/
d2/802-1CB-d2-1.pdf>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<http://www.rfc-editor.org/info/rfc1122>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<http://www.rfc-editor.org/info/rfc2474>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
Korhonen, et al. Expires March 18, 2017 [Page 43]
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[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, DOI 10.17487/RFC2890, September 2000,
<http://www.rfc-editor.org/info/rfc2890>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<http://www.rfc-editor.org/info/rfc3032>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
January 2002, <http://www.rfc-editor.org/info/rfc3232>.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
<http://www.rfc-editor.org/info/rfc3270>.
[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
in Multi-Protocol Label Switching (MPLS) Networks",
RFC 3443, DOI 10.17487/RFC3443, January 2003,
<http://www.rfc-editor.org/info/rfc3443>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
Korhonen, et al. Expires March 18, 2017 [Page 44]
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[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<http://www.rfc-editor.org/info/rfc3985>.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<http://www.rfc-editor.org/info/rfc4023>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <http://www.rfc-editor.org/info/rfc4385>.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", BCP 116, RFC 4446,
DOI 10.17487/RFC4446, April 2006,
<http://www.rfc-editor.org/info/rfc4446>.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447,
DOI 10.17487/RFC4447, April 2006,
<http://www.rfc-editor.org/info/rfc4447>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<http://www.rfc-editor.org/info/rfc4448>.
[RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
Agnostic Time Division Multiplexing (TDM) over Packet
(SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
<http://www.rfc-editor.org/info/rfc4553>.
Korhonen, et al. Expires March 18, 2017 [Page 45]
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[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<http://www.rfc-editor.org/info/rfc4664>.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March
2007, <http://www.rfc-editor.org/info/rfc4817>.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
DOI 10.17487/RFC4875, May 2007,
<http://www.rfc-editor.org/info/rfc4875>.
[RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
"Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
DOI 10.17487/RFC5087, December 2007,
<http://www.rfc-editor.org/info/rfc5087>.
[RFC5129] Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January
2008, <http://www.rfc-editor.org/info/rfc5129>.
[RFC5254] Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed.,
"Requirements for Multi-Segment Pseudowire Emulation Edge-
to-Edge (PWE3)", RFC 5254, DOI 10.17487/RFC5254, October
2008, <http://www.rfc-editor.org/info/rfc5254>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
Label Assignment and Context-Specific Label Space",
RFC 5331, DOI 10.17487/RFC5331, August 2008,
<http://www.rfc-editor.org/info/rfc5331>.
[RFC5332] Eckert, T., Rosen, E., Ed., Aggarwal, R., and Y. Rekhter,
"MPLS Multicast Encapsulations", RFC 5332,
DOI 10.17487/RFC5332, August 2008,
<http://www.rfc-editor.org/info/rfc5332>.
Korhonen, et al. Expires March 18, 2017 [Page 46]
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[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <http://www.rfc-editor.org/info/rfc5462>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<http://www.rfc-editor.org/info/rfc5586>.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-
Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
DOI 10.17487/RFC5659, October 2009,
<http://www.rfc-editor.org/info/rfc5659>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<http://www.rfc-editor.org/info/rfc5921>.
[RFC5960] Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
Transport Profile Data Plane Architecture", RFC 5960,
DOI 10.17487/RFC5960, August 2010,
<http://www.rfc-editor.org/info/rfc5960>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <http://www.rfc-editor.org/info/rfc6275>.
[RFC6371] Busi, I., Ed. and D. Allan, Ed., "Operations,
Administration, and Maintenance Framework for MPLS-Based
Transport Networks", RFC 6371, DOI 10.17487/RFC6371,
September 2011, <http://www.rfc-editor.org/info/rfc6371>.
[RFC6373] Andersson, L., Ed., Berger, L., Ed., Fang, L., Ed., Bitar,
N., Ed., and E. Gray, Ed., "MPLS Transport Profile (MPLS-
TP) Control Plane Framework", RFC 6373,
DOI 10.17487/RFC6373, September 2011,
<http://www.rfc-editor.org/info/rfc6373>.
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[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
October 2011, <http://www.rfc-editor.org/info/rfc6378>.
[RFC6426] Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
On-Demand Connectivity Verification and Route Tracing",
RFC 6426, DOI 10.17487/RFC6426, November 2011,
<http://www.rfc-editor.org/info/rfc6426>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437,
DOI 10.17487/RFC6437, November 2011,
<http://www.rfc-editor.org/info/rfc6437>.
[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
RFC 6564, DOI 10.17487/RFC6564, April 2012,
<http://www.rfc-editor.org/info/rfc6564>.
[RFC6621] Macker, J., Ed., "Simplified Multicast Forwarding",
RFC 6621, DOI 10.17487/RFC6621, May 2012,
<http://www.rfc-editor.org/info/rfc6621>.
[RFC6658] Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
"Packet Pseudowire Encapsulation over an MPLS PSN",
RFC 6658, DOI 10.17487/RFC6658, July 2012,
<http://www.rfc-editor.org/info/rfc6658>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>.
[RFC6814] Pignataro, C. and F. Gont, "Formally Deprecating Some IPv4
Options", RFC 6814, DOI 10.17487/RFC6814, November 2012,
<http://www.rfc-editor.org/info/rfc6814>.
[RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field",
RFC 6864, DOI 10.17487/RFC6864, February 2013,
<http://www.rfc-editor.org/info/rfc6864>.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013,
<http://www.rfc-editor.org/info/rfc7045>.
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[RFC7198] Begen, A. and C. Perkins, "Duplicating RTP Streams",
RFC 7198, DOI 10.17487/RFC7198, April 2014,
<http://www.rfc-editor.org/info/rfc7198>.
[RFC7209] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
Henderickx, W., and A. Isaac, "Requirements for Ethernet
VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,
<http://www.rfc-editor.org/info/rfc7209>.
[RFC7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of Synchronous Digital Hierarchy,
Optical Transport Network, and Ethernet Transport Network
Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,
<http://www.rfc-editor.org/info/rfc7271>.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399,
DOI 10.17487/RFC7399, October 2014,
<http://www.rfc-editor.org/info/rfc7399>.
[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <http://www.rfc-editor.org/info/rfc7426>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <http://www.rfc-editor.org/info/rfc7432>.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<http://www.rfc-editor.org/info/rfc7510>.
[RFC7637] Garg, P., Ed. and Y. Wang, Ed., "NVGRE: Network
Virtualization Using Generic Routing Encapsulation",
RFC 7637, DOI 10.17487/RFC7637, September 2015,
<http://www.rfc-editor.org/info/rfc7637>.
[RFC7676] Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
for Generic Routing Encapsulation (GRE)", RFC 7676,
DOI 10.17487/RFC7676, October 2015,
<http://www.rfc-editor.org/info/rfc7676>.
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[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,
<http://www.rfc-editor.org/info/rfc7752>.
[RFC7813] Farkas, J., Ed., Bragg, N., Unbehagen, P., Parsons, G.,
Ashwood-Smith, P., and C. Bowers, "IS-IS Path Control and
Reservation", RFC 7813, DOI 10.17487/RFC7813, June 2016,
<http://www.rfc-editor.org/info/rfc7813>.
[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu,
"Observations on the Dropping of Packets with IPv6
Extension Headers in the Real World", RFC 7872,
DOI 10.17487/RFC7872, June 2016,
<http://www.rfc-editor.org/info/rfc7872>.
[ST20227] SMPTE 2022, "Seamless Protection Switching of SMPTE ST
2022 IP Datagrams", ST 2022-7:2013, 2013,
<https://www.smpte.org/digital-library>.
10.2. URIs
[1] http://6lab.cisco.com/stats/
[2] https://www.google.com/intl/en/ipv6/statistics.html
[3] https://datatracker.ietf.org/wg/spring/charter/
[4] http://www.iana.org/assignments/g-ach-parameters/g-ach-
parameters.xhtml
[5] http://ftp.isi.edu/in-notes/iana/assignments/ethernet-numbers
[6] https://tools.ietf.org/wg/bess/
Appendix A. Examples of combined DetNet Service and Transport layers
Authors' Addresses
Jouni Korhonen (editor)
Broadcom
3151 Zanker Road
San Jose, CA 95134
USA
Email: jouni.nospam@gmail.com
Korhonen, et al. Expires March 18, 2017 [Page 50]
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Janos Farkas
Ericsson
Konyves Kalman krt. 11/B
Budapest 1097
Hungary
Email: janos.farkas@ericsson.com
Gregory Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Pascal Thubert
Cisco
Email: pthubert@cisco.com
Yan Zhuang
Huawei
Email: zhuangyan.zhuang@huawei.com
Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Korhonen, et al. Expires March 18, 2017 [Page 51]
