One document matched: draft-bryant-filsfils-fat-pw-03.xml
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<rfc category="std" docName="draft-bryant-filsfils-fat-pw-03"
ipr="trust200902">
<front>
<title abbrev="FAT-PW">Flow Aware Transport of MPLS Pseudowires</title>
<author fullname="Stewart Bryant" initials="S" role="editor"
surname="Bryant">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>250 Longwater Ave</street>
<city>Reading</city>
<code>RG2 6GB</code>
<country>United Kingdom</country>
</postal>
<phone>+44-208-824-8828</phone>
<email>stbryant@cisco.com</email>
</address>
</author>
<author fullname="Clarence Filsfils" initials="C" surname="Filsfils">
<organization>Cisco Systems</organization>
<address>
<postal>
<street></street>
<city>Brussels</city>
<code></code>
<country>Belgium</country>
</postal>
<email>cfilsfil@cisco.com</email>
</address>
</author>
<author fullname="Ulrich Drafz" initials="U" surname="Drafz">
<organization>Deutsche Telekom</organization>
<address>
<postal>
<street></street>
<city>Muenster</city>
<region></region>
<code></code>
<country>Germany</country>
</postal>
<phone></phone>
<facsimile></facsimile>
<email>Ulrich.Drafz@t-com.net</email>
<uri></uri>
</address>
</author>
<author fullname="Vach Kompella" initials="V" surname="Kompella">
<organization>Alcatel-Lucent</organization>
<address>
<postal>
<street></street>
<city></city>
<region></region>
<code></code>
<country></country>
</postal>
<phone></phone>
<facsimile></facsimile>
<email>Alcatel-Lucent vach.kompella@alcatel-lucent.com</email>
<uri></uri>
</address>
</author>
<author fullname="Joe Regan" initials="J" surname="Regan">
<organization>Alcatel-Lucent</organization>
<address>
<postal>
<street></street>
<city></city>
<region></region>
<code></code>
<country></country>
</postal>
<phone></phone>
<facsimile></facsimile>
<email>joe.regan@alcatel-lucent.comRegan</email>
<uri></uri>
</address>
</author>
<author fullname="Shane Amante " initials="S" surname="Amante">
<organization>Level 3 Communications</organization>
<address>
<postal>
<street></street>
<city></city>
<region></region>
<code></code>
<country></country>
</postal>
<phone></phone>
<facsimile></facsimile>
<email>shane@castlepoint.net</email>
<uri></uri>
</address>
</author>
<date year="2009" />
<area>Internet</area>
<workgroup>PWE3</workgroup>
<keyword></keyword>
<keyword>pseudowire</keyword>
<keyword>MPLS</keyword>
<keyword>Internet-Draft</keyword>
<abstract>
<t>Where the payload carried over a pseudowire carries a number of
identifiable flows it can in some circumstances be desirable to carry
those flows over the equal cost multiple paths (ECMPs) that exist in the
packet switched network. Most forwarding engines are able to hash based
on label stacks and use this to balance flows over ECMPs. This draft
describes a method of identifying the flows, or flow groups, to the
label switched routers by including an additional label in the label
stack.</t>
</abstract>
<note title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref
target="RFC2119">RFC2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>A pseudowire <xref target="RFC3985"></xref> is normally transported
over one single network path, even if multiple Equal Cost Multiple Paths
(ECMP) exit between the ingress and egress PEs<xref target="RFC4385">
</xref> <xref target="RFC4928"></xref>. This is required to preserve the
characteristics of the emulated service (e.g. to avoid misordering SAToP
pseudowire’s <xref target="RFC4553"></xref>). The use of a single
path to preserve order remains the default mode of operation of a
pseudowire (PW). The new capability proposed in this document is an
OPTIONAL mode which may be used when the use of ECMP paths for is known
to be beneficial (and not harmful) to the operation of the PW.</t>
<t>Some pseudowires are used to transport large volumes of IP traffic
between routers at two locations. One example of this is the use of an
Ethernet pseudowire to create a virtual direct link between a pair of
routers. Such pseudowire’s may carry from hundred’s of Mbps
to Gbps of traffic. Such pseudowire’s do not require strict
ordering to be preserved between packets of the pseudowire. They only
require ordering to be preserved within the context of each individual
transported IP flow. Some operators have requested the ability to
explicitly configure such a pseudowire to leverage the availability of
multiple ECMP paths. This allows for better capacity planning as the
statistical multiplexing of a larger number of smaller flows is more
efficient than with a smaller set of larger flows. Although Ethernet is
used as an example above, the mechanisms described in this draft are
general mechanisms that may be applied to any pseudowire type in which
there are identifiable flows, and in which the there is no requirement
to preserve the order between those flows.</t>
<t>Typically, forwarding hardware can deduce that an IP payload is being
directly carried by an MPLS label stack, and is capable of looking at
some fields in packets to construct hash buckets for conversations or
flows. However, an intermediate node has no information on the type
pseudowire being carried in the packet. This limits the forwarder at the
intermediate node to only being able to make an ECMP choice based on a
hash of the label stack. In the case of a pseudowire emulating a high
bandwidth trunk, the granularity obtained by hashing the default label
stack is inadequate for satisfactory load-balancing. The ingress node,
however, is in the special position of being able to look at the
un-encapsulated packet and spread flows amongst an available ECMP paths,
or even Loop-Free Alternates <xref
target="I-D.ietf-rtgwg-ipfrr-spec-base">I</xref> . This draft proposes a
method to introduce granularity on the hashing of traffic running over
pseudowires by introducing an additional label, chosen by the ingress
node, and placed at the bottom of the label stack.</t>
<t>In addition to providing an indication of the flow structure for use
in ECMP forwarding decisions, the mechanism described in the document
may also be used to select flows for distribution over an 802.1ad link
aggregation group that has been used in an MPLS network.</t>
<section title="ECMP in Label Switched Routers">
<t>Label switched routers commonly hash the label stack or some
elements of the label stack as a method of discriminating between
flows, in order to distribute those flows over the available equal
cost multiple paths that exist in the network. Since the label at the
bottom of stack is usually the label most closely associated with the
flow, this normally provides the greatest entropy, and hence is
usually included in the hash. This draft describes a method of adding
an additional label at the bottom of stack in order to facilitate the
load balancing of the flows within a pseudowire over the available
ECMPs. A similar design for general MPLS use has also been proposed
<xref target="I-D.kompella-mpls-entropy-label"></xref>, however that
is outside the scope of this draft.</t>
<t>An alternative method of load balancing by creating a number of
pseudowires and distributing the flows amongst them was considered,
but was rejected because:<list style="symbols">
<t>It did not introduce as much entropy as the load balance label
method.</t>
<t>It required additional pseudowires to be set up and
maintained.</t>
</list></t>
</section>
<section title="Flow Label">
<t>An additional label is interposed between the pseudowire label and
the control word, or if the control word is not present, between the
pseudowire label and the pseudowire payload. This additional label is
called the Flow label. Indivisible flows within the pseudowire MUST be
mapped to the same Flow label by the ingress PE. The flow label
stimulates the correct ECMP load balancing behaviour in the PSN. On
receipt of the pseudowire packet at the egress PE (which knows this
additional label is present) the flow label is discarded without
processing.</t>
<t>Note that the flow label MUST NOT be an MPLS reserved label (values
in the range 0..15) <xref target="RFC3032"></xref>, but is otherwise
unconstrained by the protocol.</t>
<t>Considerations of the TTL value are described in the Security
section of this document. In the case of a pseudowire there are no
lower restrictions on the label value since the TTL is never the top
label. The designers of the generalized solution <xref
target="I-D.kompella-mpls-entropy-label"></xref>.</t>
</section>
</section>
<section title="Native Service Processing Function">
<t>The Native Service Processing (NSP) function is a component of a PE
that has knowledge of the structure of the emulated service and is able
to take action on the service outside the scope of the pseudowire. In
this case it is required that the NSP in the ingress PE identify flows,
or groups of flows within the service, and indicate the flow (group)
identity of each packet as it is passed to the pseudowire forwarder.
Since this is an NSP function, by definition, the method used to
identify a flow is outside the scope of the pseudowire design.
Similarly, since the NSP is internal to the PE, the method of flow
indication to the pseudowire forwarder is outside the scope of this
document</t>
</section>
<section title="Pseudowire Forwarder">
<t>The pseudowire forwarder must be provided with a method of mapping
flows to load balanced paths.</t>
<t>The forwarder must generate a label for the flow or group of flows.
How the load balance label values are determined is outside the scope of
this document, however the load balance label allocated to a flow MUST
NOT be an MPLS reserved label and SHOULD remain constant for the life of
the flow. It is recommended that the method chosen to generate the load
balancing labels introduces a high degree of entropy in their values, to
maximise the entropy presented to the ECMP path selection mechanism in
the LSRs in the PSN, and hence distribute the flows as evenly as
possible over the available PSN ECMP paths. The forwarder at the ingress
PE prepends the pseudowire control word (if applicable), and then pushes
the flow label, followed by the pseudowire label.</t>
<t>The forwarder at the egress PE uses the pseudowire label to identify
the pseudowire. From the context associated with the pseudowire label,
the egress PE can determine whether a flow label is present. If a flow
label is present, the label is discarded.</t>
<t>All other pseudowire forwarding operations are unmodified by the
inclusion of the flow label.</t>
<section title="Encapsulation ">
<t>The PWE3 Protocol Stack Reference Model modified to include flow
label is shown in <xref target="PStack"></xref> below</t>
<figure anchor="PStack" title="PWE3 Protocol Stack Reference Model">
<artwork><![CDATA[
+-------------+ +-------------+
| Emulated | | Emulated |
| Ethernet | | Ethernet |
| (including | Emulated Service | (including |
| VLAN) |<==============================>| VLAN) |
| Services | | Services |
+-------------+ +-------------+
| Flow | | Flow |
+-------------+ Pseudowire +-------------+
|Demultiplexer|<==============================>|Demultiplexer|
+-------------+ +-------------+
| PSN | PSN Tunnel | PSN |
| MPLS |<==============================>| MPLS |
+-------------+ +-------------+
| Physical | | Physical |
+-----+-------+ +-----+-------+
]]></artwork>
<postamble></postamble>
</figure>
<t></t>
<t>The encapsulation of a pseudowire with a flow label is shown in
<xref target="Encap"></xref> below</t>
<figure anchor="Encap"
title="Encapsulation of a pseudowire with a pseudowire load balancing label">
<artwork><![CDATA[
+-------------------------------+
| MPLS Tunnel label(s) | n*4 octets (four octets per label)
+-------------------------------+
| PW label | 4 octets
+-------------------------------+
| Flow label | 4 octets
+-------------------------------+
| Optional Control Word | 4 octets
+-------------------------------+
| Payload |
| |
| | n octets
| |
+-------------------------------+
]]></artwork>
<postamble></postamble>
</figure>
<t></t>
</section>
</section>
<section title="Signaling the Presence of the Flow Label">
<t>When using the signalling procedures in <xref
target="RFC4447"></xref>, there is a Pseudowire Interface Parameter
Sub-TLV type used to synchronize the flow label states between the
ingress and egress PEs.</t>
<t>The absence of a flow label (FL) TLV by either party indicates that
the PE concerned is unable to recognize this TLV and the sender of the
FL TLV MUST send a new label mapping without the FL TLV. This preserves
backwards compatibility with existing PEs that do not understand the FL
TLV or that cannot, do not wish to, process the flow label.</t>
<t>A PE that wishes to use a flow label sends an FL TLV with the F bit
set. A PE that can correctly process a flow label and is willing to
receive on, but does not wish to send a flow label sends an FL TLV with
the F bit clear. A PE that sends an FL TLV with the F bit set and
receives an FL TLV with or without the F bit set MUST include the flow
label between the pseudowire label and the control word (or is the
control word is not present between the pseudowire label and the
pseudowire payload).</t>
<t>If PWE3 signalling <xref target="RFC4447"></xref> is not in use for a
pseudowire, then whether the flow label is used MUST be identically
provisioned in both PEs at the pseudowire endpoints. If there is no
provisioning support for this option, the default behaviour is not to
include the flow label.</t>
<t>Note that what is signalled is the desire to include the flow label
in the label stack. The value of the label is a local matter for the
ingress PE, and the label value itself is not signalled.</t>
<section title="Structure of Flow Label TLV">
<t>The structure of the flow label TLV is shown in <xref
target="MultipleVCTLV"></xref>.</t>
<figure anchor="MultipleVCTLV" title="Multiple VC TLV">
<preamble></preamble>
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FL | Length |F| must be zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
<postamble></postamble>
</figure>
<t></t>
<t>Where:</t>
<t><list style="symbols">
<t>FL is the flow label TLV identifier assigned by IANA.</t>
<t>Length is the length of the TLV in octets and is 4.</t>
<t>When F=1 a flow label will be pushed. When F=0 a flow label
will not be pushed.</t>
</list></t>
</section>
</section>
<section title="OAM">
<t>The following OAM considerations apply to this method of load
balancing.</t>
<t>Where the OAM is only to be used to perform a basic test that the
pseudowires have been configured at the PEs, <xref
target="RFC5085">VCCV</xref> messages may be sent using any load balance
pseudowire path, i.e. using any value for the flow label.</t>
<t>Where it is required to verify that a pseudowire is fully functional
for all flows<xref target="RFC5085">, VCCV</xref> connection
verification message MUST be sent over each ECMP path to the pseudowire
egress PE. This problem is difficult to solve and scales poorly. We
believe that this problem is addressed by the following two methods:</t>
<t><list counter="" style="numbers">
<t>If a failure occurs within the PSN, this failure will normally be
detected by the PSN's IGP (link/node failure, link or BFD or IGP
hello detection), and the IGP convergence will naturally modify the
ECMP set of network paths between the Ingress and Egress PE's. Hence
the PW is only impacted during the normal IGP convergence time.</t>
<t>If the failure is related to the individual corruption of an LFIB
entry in a router, then only the network path using that specific
entry is impacted. If the PW is load balanced over multiple network
paths, then this failure can only be detected if, by chance, the
transported OAM flow is mapped onto the impacted network path, or
all paths are tested. This type of error may be better solved be
solved by other means such as LSP self test <xref
target="I-D.ietf-mpls-lsr-self-test"></xref>.</t>
</list>To troubleshoot the MPLS PSN, including multiple paths, the
techniques described in <xref target="RFC4378"></xref> and <xref
target="RFC4379"></xref> can be used.</t>
<t>Where the pseudowire OAM is carried out of band (VCCV Type 2) it is
necessary to insert an "MPLS Router Alert Label" in the label stack. The
resultant label stack is a follows:</t>
<t><figure anchor="OBVCCV" title="Use of Router Alert LAbel">
<preamble></preamble>
<artwork><![CDATA[ +-------------------------------+
| MPLS Tunnel label(s) | n*4 octets (four octets per label)
+-------------------------------+
| Router Alert label | 4 octets
+-------------------------------+
| PW label | 4 octets
+-------------------------------+
| Flow label | 4 octets
+-------------------------------+
| Optional Control Word | 4 octets
+-------------------------------+
| Payload |
| |
| | n octets
| |
+-------------------------------+]]></artwork>
<postamble></postamble>
</figure></t>
</section>
<section title="Applicability">
<t>A node within the PSN is not able to perform deep-packet-inspection
(DPI) of the PW as the PW technology is not self-describing: the
structure of the PW payload is only known to the ingress and egress PE
devices. The method proposed in this document provides a statistical
mitigation of the problem of load balance in those cased where a PE is
able to discern flows embedded in the traffic received on the attachment
circuit.</t>
<t>The methods describe in this document are transparent to the PSN and
as such do not require any new capability from the PSN.</t>
<t>The requirement to load-balance over multiple PSN paths occurs when
the ratio between the PW access speed and the PSN’s core link
bandwidth is large (e.g. >= 10%). ATM and FR are unlikely to meet
this property. Ethernet does and this is the reason why this document
focuses on Ethernet. Applications for other high-access-bandwidth
PW’s (fiber-channel) may be defined in the future.</t>
<t>This design applies to MPLS pseudowires where it is meaningful to
deconstruct the packets presented to the ingress PE into flows. The
mechanism described in this document promotes the distribution of flows
within the pseudowire over different network paths. This in turn means
that whilst packets within a flow are delivered in order (subject to
normal IP delivery perturbations due to topology variation), order is
not maintained amongst packets of different flows. It is not proposed to
associate a different sequence number with each flow. If sequence number
support is required this mechanism is not applicable.</t>
<t>Where it is known that the traffic carried by the Ethernet pseudowire
is IP the method of identifying the flows are well known and can be
applied. Such methods typically include hashing on the source and
destination addresses, the protocol ID and higher-layer flow-dependent
fields such as TCP/UDP ports, L2TPv3 Session ID’s etc.</t>
<t>Where it is known that the traffic carried by the Ethernet pseudowire
is non-IP, techniques used for link bundling between Ethernet switches
may be reused. In this case however the latency distribution would be
larger than is found in the link bundle case. The acceptability of the
increased latency is for further study. Of particular importance the
Ethernet control frames SHOULD always be mapped to the same PSN path to
ensure in-order delivery.</t>
<section title="ECMP">
<t>ECMP in packet switched networks is statistical in nature. The
mapping of flows to a particular path does not take into account the
bandwidth of the flow being mapped or the current bandwidth usage of
the members of the ECMP set. This simplification works well when the
distribution of flows is evenly spread over the ECMP set and there are
a large number of flows that have low bandwidth relative to the paths.
A random allocation of a flow to a path provides a good approximation
to an even spread provided polarization effects are avoided. The
method proposed in this document has the same statistical properties
as an IP PSN.</t>
<t>ECMP is a load-sharing mechanism that is based on sharing the load
over a number of layer 3 paths through the PSN. Often however multiple
links exist between a pair of LSRs that are considered by the IGP to
be a single link. These are known as link bundles. The mechanism
described in this document can also be used to distribute the flows
within a pseudowire over the members of the link bundle by using the
flow label value to identify candidate flows. How that mapping takes
place is outside the scope of this specification. Similar
considerations apply to link aggregation groups.</t>
<t>In the ECMP case and the link bundling case the NSP may attempt to
take bandwidth into consideration when allocating groups of flows to a
common path. That is permitted, but it must be borne in mind that the
semantics of a label stack entry (LSE) as defined by <xref
target="RFC3032"></xref> cannot be modified, the value of the flow
label cannot be modified at any point on the LSP, and the
interpretation of bit patterns in or values of the flow label by an
LSR are undefined.</t>
<t>A different type of load balancing is the desire to carry a
pseudowire over a set of PSN links in which the bandwidth of members
of the link set is less than the bandwidth of the pseudowire. This
problem is addressed in <xref
target="I-D.stein-pwe3-pwbonding"></xref>. Such a mechanism can be
considered complementary to this mechanism.</t>
</section>
<section title="Link Aggregation Groups">
<t>Link Aggregation (LAG) is used to bond together several physical
circuits between two adjacent nodes so they appear to higher-layer
protocols as a single, higher bandwidth "virtual" pipe. These may
co-exist in various parts of a given network. An advantage of LAGs is
that they reduce the number of routing and signaling protocol
adjacencies between devices, reducing control plane processing
overhead. As with ECMP key problem related to LAG is, due to
inefficiencies in LAG load-distribution algorithms, a particular
component- link may experience congestion, and the mechanism proposed
here may be able to assist in producing a more uniform flow
distribution.</t>
<t>The same considerations requiring a flow to go over a single member
of an ECMP path set apply to a member of a LAG.</t>
</section>
<section title="The Single Large Flow Case">
<t>Clearly the operator should make sure that the service offered
using PW technology and the method described in this document does not
exceed the maximum planned link capacity unless it can be guaranteed
that it conforms to the Internet traffic profile of a very large
number of small flows.</t>
<t>If the payload on a PW is made of a single inner flow (i.e. an
encrypted connection between two routers), or the flow identifiers are
too deeply buried in the packet then the functionality described in
this document does not give any benefits, though neither does it cause
harm relative to the existing situation. The most common case where a
single flow dominated the traffic on a PW is when it is used to
transport enterprise traffic. Enterprise traffic may well consist of a
large single TCP flows , or encrypted flows that cannot be handled by
the methods described in this document.</t>
<t>An operator has six options under these circumstances:</t>
<t><list style="numbers">
<t>The operator can do nothing and the system will work as it does
without the flow label.</t>
<t>The operator can make the customer aware that the service
offering has a restriction on flow bandwidth and police flows to
that restriction. This would allow customers offering multiple
flows to use a larger fraction their access bandwidth, whilst
preventing an single flow from consuming a fraction of internal
link bandwidth that the operator considered excessive.</t>
<t>The operator could configure the ingress PE to assign a
constant flow label to all high bandwidth flows so that only one
path was affected by these flows,</t>
<t>The operator could configure the ingress PE to assign a random
flow label to all high bandwidth flows so as to minimise the
disruption to the network as a cost of out of order traffic to the
user.</t>
<t>The operator could configure the ingress to assign a label of
special significance to all high bandwidth flows so that some
other action (not specified in this document) could be taken on
the flow.</t>
</list></t>
<t>The issues described above are mitigated by the following two
factors:</t>
<t><list style="symbols">
<t>Firstly, the customer of a high-bandwidth PW service has an
incentive to get the best transport service because an inefficient
use of the PSN leads to jitter and eventually to loss to the
PW’s payload.</t>
<t>Secondly, the customer is usually able to tailor their
applications to generate many flows in the PSN. A well-known
example is massive data transport between servers which use many
parallel TCP sessions. This same technique can be used by any
transport protocol: multiple UDP ports, multiple L2TPv3 Session
ID’s, multiple GRE keys may be used to decompose a large
flow into smaller components. This approach may be applied to
IPsec where multiple SPI’s may be allocated to the same
security association.</t>
</list></t>
</section>
</section>
<section title="Applicability to MPLS">
<t>A further application of this technique would be to create a basis
for hash diversity without having to peek below the label stack for IP
traffic carried over LDP LSPs. Work on the generalization of this to
MPLS has been described in draft-kompella-mpls-entropy-label. This is
can be regarded as a complementary but distinct approach since although
similar consideration may apply to the identification of flows and the
allocation of flow label values, the flow labels are imposed by
different network components and the associated signalling mechanisms
are different.</t>
</section>
<section title="Security Considerations">
<t>The pseudowire generic security considerations described in <xref
target="RFC3985"></xref> and the security considerations applicable to a
specific pseudowire type (for example, in the case of an Ethernet
pseudowire <xref target="RFC4448"></xref> apply.</t>
<t>The ingress PE SHOULD take steps to ensure that the load-balance
label is not used as a covert channel.</t>
<t>It is useful to give consideration to the choice of TTL value in the
flow label LSE. Since the flow label is the bottom of stack and even
when PHP is employed will on arrival at the egress PE be prepended by
the PW label, the flow label TTL MAY be set to a value of 1. This will
prevent the packet being inadvertently forwarded based on the value of
the flow label. Note that this may be a departure from considerations
that apply to the general MPLS case.</t>
</section>
<section title="IANA Considerations">
<t>IANA is requested to allocate the next available values from the IETF
Consensus range in the Pseudowire Interface Parameters Sub-TLV type
Registry as a Flow Label indicator.</t>
<figure>
<artwork><![CDATA[
Parameter Length Description
TBD 4 Load Balancing Label
]]></artwork>
<postamble></postamble>
</figure>
</section>
<section title="Congestion Considerations">
<t>The congestion considerations applicable to pseudowires as described
in <xref target="RFC3985"></xref> and any additional congestion
considerations developed at the time of publication apply to this
design.</t>
<t>The ability to explicitly configure a PW to leverage the availability
of multiple ECMP paths is beneficial to capacity planning as, all other
parameters being constant, the statistical multiplexing of a larger
number of smaller flows is more efficient than with a smaller number of
larger flows.</t>
<t>Note that if the classification into flows is only performed on IP
packets the behaviour of those flows in the face of congestion will be
as already defined by the IETF for packets of that type and no
additional congestion processing is required.</t>
<t>Where flows that are not IP are classified pseudowire congestion
avoidance must be applied to each non-IP load balance group.</t>
</section>
<section title="Acknowledgements">
<t>The authors wish to thank Joerg Kuechemann, Wilfried Maas, Luca
Martini, Mark Townsley, Kireeti Kompella and Lucy Yong for valuable
comments on this document.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.RFC.2119'?>
<?rfc include='reference.RFC.4447'?>
<?rfc include='reference.RFC.4448'?>
<?rfc include='reference.RFC.4928'?>
<?rfc include='reference.RFC.4553'?>
<?rfc include='reference.RFC.4385'?>
<?rfc include='reference.RFC.4378'?>
<?rfc include='reference.RFC.4379'?>
<?rfc include='reference.RFC.3032'?>
<?rfc include='reference.RFC.5085'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.3985'?>
<?rfc include='reference.I-D.ietf-mpls-lsr-self-test'?>
<?rfc include='reference.I-D.kompella-mpls-entropy-label'?>
<?rfc include='reference.I-D.ietf-rtgwg-ipfrr-spec-base'?>
<?rfc include='reference.I-D.stein-pwe3-pwbonding'?>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 05:40:18 |