One document matched: draft-ietf-mpls-in-udp-08.xml
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<rfc category="std" docName="draft-ietf-mpls-in-udp-08" ipr="trust200902">
<front>
<title abbrev="Encapsulating MPLS in UDP">Encapsulating MPLS in
UDP</title>
<author fullname="Xiaohu Xu" initials="X.X." surname="Xu">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>No.156 Beiqing Rd</street>
<city>Beijing</city>
<region/>
<code>100095</code>
<country>CHINA</country>
</postal>
<phone>+86-10-60610041</phone>
<facsimile/>
<email>xuxiaohu@huawei.com</email>
<uri/>
</address>
</author>
<author fullname="Nischal Sheth" initials="N.S" surname="Sheth">
<organization>Juniper Networks</organization>
<address>
<postal>
<street>1194 N. Mathilda Ave</street>
<city>Sunnyvale</city>
<region>CA</region>
<code>94089</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>nsheth@juniper.net</email>
<uri/>
</address>
</author>
<author fullname="Lucy Yong" initials="L.Y" surname="Yong">
<organization>Huawei USA</organization>
<address>
<postal>
<street>5340 Legacy Dr</street>
<city>Plano</city>
<region>TX</region>
<code>75025</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>Lucy.yong@huawei.com</email>
<uri/>
</address>
</author>
<author fullname="Ross Callon" initials="R.C" surname="Callon">
<organization>Juniper Networks</organization>
<address>
<postal>
<street>10 Technology Park Drive</street>
<city>Westford</city>
<region>MA</region>
<code>01886</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>rcallon@juniper.net</email>
<uri/>
</address>
</author>
<author fullname="David Black" initials="D.B" surname="Black">
<organization>EMC Corporation</organization>
<address>
<postal>
<street>176 South Street</street>
<city>Hopkinton</city>
<region>MA</region>
<code>01748</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>david.black@emc.com</email>
<uri/>
</address>
</author>
<!--
-->
<date day="" month="" year="2014"/>
<abstract>
<t>This document specifies an IP-based encapsulation for MPLS, called
MPLS-in-UDP (User Datagram Protocol). The MPLS-in-UDP encapsulation
technology MUST only be deployed within a service provider network or
networks of an adjacent set of co-operating service providers where
congestion control is not a concern.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>This document specifies an IP-based encapsulation for MPLS, i.e.
MPLS-in-UDP (User Datagram Protocol), which is applicable in some
circumstances where IP-based encapsulation for MPLS is required and
further fine-grained load balancing of MPLS packets over IP networks
over Equal Cost Multi-Path (ECMP) and/or Link Aggregation Groups (LAG)
is required as well. There are already IP-based encapsulations for MPLS
that allow for fine-grained load balancing by using some special field
in the encapsulation header as an entropy field. However, MPLS-in-UDP
can be advantageous since some networks have used the UDP port number
fields as a basis for load-balancing solutions for some time. This is
similar to why LISP <xref target="RFC6830"/> uses UDP encapsulation.</t>
<t>Like other IP-based encapsulation methods for MPLS, this
encapsulation allows for two Label Switching Routers (LSR) to be
adjacent on a Label Switched Path (LSP), while separated by an IP
network. In order to support this encapsulation, each LSR needs to know
the capability to decapsulate MPLS-in-UDP by the remote LSRs. This
specification defines only the data plane encapsulation and does not
concern itself with how the knowledge to use this encapsulation is
conveyed. Specifically, this capability can be either manually
configured on each LSR or be dynamically advertised in manners that are
outside the scope of this document.</t>
<t>Similarly, the MPLS-in-UDP encapsulation format defined in this
document by itself cannot ensure the integrity and privacy of data
packets being transported through the MPLS-in-UDP tunnels and cannot
enable the tunnel decapsulators to authenticate the tunnel encapsulator.
Therefore, in the case where any of the above security issues is
concerned, the MPLS-in-UDP SHOULD be secured with IPsec <xref
target="RFC4301"/> or DTLS <xref target="RFC6347"/>. For more details,
please see Section 6 of Security Considerations.</t>
<section title="Existing Encapsulations">
<t>Currently, there are several IP-based encapsulations for MPLS such
as MPLS-in-IP, MPLS-in-GRE (Generic Routing Encapsulation) <xref
target="RFC4023"/>, and MPLS-in-L2TPv3 (Layer Two Tunneling Protocol -
Version 3) <xref target="RFC4817"/>. In all these methods, the IP
addresses can be varied to achieve load-balancing.</t>
<t>All these IP-based encapsulations for MPLS are specified for both
IPv4 and IPv6. In the case of IPv6-based encapsulations, the IPv6 Flow
Label can be used for ECMP and LAGs <xref target="RFC6438"/>. However,
there is no such entropy field in the IPv4 header.</t>
<t>For MPLS-in-GRE as well as MPLS-in-L2TPv3, protocol fields (the GRE
Key and the L2TPv3 Session ID respectively) can be used as the
load-balancing key as described in <xref target="RFC5640"/>. For this,
intermediate routers need to understand these fields in the context of
being used as load-balancing keys.</t>
</section>
<section title="Motivations for MPLS-in-UDP Encapsulation">
<t>Most existing routers in IP networks are already capable of
distributing IP traffic "microflows" <xref target="RFC2474"/> over
ECMPs and/or LAG based on the hash of the five-tuple of User Datagram
Protocol (UDP) <xref target="RFC0768"/> and Transmission Control
Protocol (TCP) packets (i.e., source IP address, destination IP
address, source port, destination port, and protocol). By
encapsulating the MPLS packets into an UDP tunnel and using the source
port of the UDP header as an entropy field, the existing
load-balancing capability as mentioned above can be leveraged to
provide fine-grained load-balancing of MPLS traffic over IP
networks.</t>
</section>
<section title="Application Statements">
<t>The MPLS-in-UDP encapsulation technology MUST only be deployed
within a Service Provider (SP) network or networks of an adjacent set
of co-operating SPs where congestion control is not a concern, rather
than over the Internet where congestion control is required.
Furthermore, packet filters SHOULD be added to prevent MPLS-in-UDP
packets from escaping from the service provider networks due to
misconfiguation or packet errors.</t>
</section>
</section>
<section anchor="Teminology" title="Terminology">
<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">RFC 2119</xref>.</t>
</section>
<section title="Encapsulation in UDP">
<t>MPLS-in-UDP encapsulation format is shown as follows:</t>
<t><figure>
<artwork align="center"><![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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = Entropy | Dest Port = MPLS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ MPLS Label Stack ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
~ Message Body ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="empty">
<t>Source Port of UDP<list style="empty">
<t>This field contains a 16-bit entropy value that is generated
by the encapsulator to uniquely identify a flow. What
constitutes a flow is locally determined by the encapsulator and
therefore is outside the scope of this document. What algorithm
is actually used by the encapsulator to generate an entropy
value is outside the scope of this document.</t>
<t>In case the tunnel does not need entropy, this field of all
packets belonging to a given flow SHOULD be set to a randomly
selected constant value so as to avoid packet reordering.</t>
<t>To ensure that the source port number is always in the range
49152 to 65535 (Note that those ports less than 49152 are
reserved by IANA to identify specific applications/protocols)
which may be required in some cases, instead of calculating a
16-bit hash, the encapsulator SHOULD calculate a 14-bit hash and
use those 14 bits as the least significant bits of the source
port field while the most significant two bits SHOULD be set to
binary 11. That still conveys 14 bits of entropy information
which would be enough as well in practice.</t>
</list></t>
<t>Destination Port of UDP<list style="empty">
<t>This field is set to a value (TBD1) allocated by IANA to
indicate that the UDP tunnel payload is an MPLS packet.</t>
</list></t>
<t>UDP Length<list style="empty">
<t>The usage of this field is in accordance with the current UDP
specification <xref target="RFC0768"/>.</t>
</list></t>
<t>UDP Checksum<list style="empty">
<t>For IPv4 UDP encapsulation, this field is RECOMMENDED to be
set to zero because the IPv4 header includes a checksum and use
of the UDP checksum is optional with IPv4, unless checksum
protection of VPN labels is important (See Section 6). For IPv6
UDP encapsulation, the IPv6 header does not include a checksum,
so this field MUST contain a UDP checksum that MUST be used as
specified in <xref target="RFC0768"/> and <xref
target="RFC2460"/> unless one of the exceptions that allows use
of UDP zero-checksum mode (as specified in <xref
target="RFC6935"/>) applies. See Section 3.1 for specification
of these exceptions and additional requirements that apply when
UDP zero-checksum mode is used for MPLS-in-UDP traffic over
IPv6.</t>
</list></t>
<t>MPLS Label Stack<list style="empty">
<t>This field contains an MPLS Label Stack as defined in <xref
target="RFC3032"/>.</t>
</list></t>
<t>Message Body<list style="empty">
<t>This field contains one MPLS message body.</t>
</list></t>
</list></t>
<section title="UDP Checksum Usage with IPv6">
<t>When UDP is used over IPv6, the UDP checksum is relied upon to
protect the IPv6 header from corruption, and MUST be used unless the
requirements in <xref target="RFC6935"/> and <xref target="RFC6936"/>
for use of UDP zero-checksum mode with a tunnel protocol are
satisfied. MPLS-in-UDP is a tunnel protocol, and there is significant
successful deployment of MPLS-in-IPv6 without UDP (i.e., without a
checksum that covers the IPv6 header or the MPLS label stack), as
described in Section 3.1 of <xref target="RFC6936"/>:<list
style="empty">
<t>"There is extensive experience with deployments using tunnel
protocols in well-managed networks (e.g., corporate networks and
service provider core networks). This has shown the robustness of
methods such as Pseudowire Emulation Edge-to-Edge (PWE3) and MPLS
that do not employ a transport protocol checksum and that have not
specified mechanisms to protect from corruption of the unprotected
headers(such as the VPN Identifier in MPLS)".</t>
</list>This draft focuses on service provider core networks. The
requirements in Section 5 for use of MPLS-in-UDP to carry traffic that
is not necessarily congestion controlled involve significant service
provider traffic management and engineering - this is a hallmark of
the well-managed networks that the above <xref target="RFC6936"/> text
refers to. Therefore, the UDP checksum MUST be implemented and MUST be
used in accordance with <xref target="RFC0768"/> and <xref
target="RFC2460"/> for MPLS-in-UDP traffic over IPv6 unless one of the
following exceptions applies and the additional requirements stated
below are complied with. There are two exceptions that allow use of
UDP zero-checksum mode for IPv6 with MPLS-in-UDP, subject to the
additional requirements stated below in this section. The two
exceptions are:<list style="letters">
<t>Use of MPLS-in-UDP within a single service provider that
utilizes careful provisioning (e.g., rate limiting at the entries
of the network while over-provisioning network capacity) to ensure
against congestion and that actively monitors MPLS traffic for
errors; or</t>
<t>Use of MPLS-in-UDP within a limited number of service providers
who closely cooperate in order to jointly provide this same
careful provisioning and monitoring.</t>
</list> Even when one of the above exceptions applies, use of UDP
checksums may be appropriate when VPN services are provided over
MPLS-in-UDP, see Section 6. As such, for IPv6, the UDP checksum for
MPLS-in-UDP MUST be used as specified in <xref target="RFC0768"/> and
<xref target="RFC2460"/> over the general Internet, and over
non-cooperating SPs, even if each non-cooperating SP independently
satisfies the first exception for UDP zero-checksum mode usage with
MPLS-in-UDP over IPv6 within the SP's own network. Measures SHOULD be
taken to prevent UDP zero checksum mode MPLS-in-UDP over IPv6 traffic
from "escaping" to the general Internet; see Section 5 for examples of
such measures.</t>
<t>The following additional requirements apply to implementation and
use of UDP zero-checksum mode for MPLS-in-UDP over IPv6:<list
style="letters">
<t>Use of the UDP checksum with IPv6 MUST be the default
configuration of all MPLS-in-UDP implementations.</t>
<t>An MPLS-in-UDP implementation MUST comply with all requirements
specified in Section 4 of <xref target="RFC6936"/> and with
requirement 1 specified in Section 5 of <xref
target="RFC6936"/>.</t>
<t>An MPLS-in-UDP receiver MUST check that the source and
destination IPv6 addresses are valid for the MPLS-in-UDP tunnel
and discard any packet for which this check fails.</t>
<t>An MPLS-in-UDP sender SHOULD use different IPv6 addresses for
each MPLS-in-UDP tunnel that uses UDP zero-checksum mode in order
to strengthen the receiver's check of the IPv6 source address.
When this is not possible, it is RECOMMENDED to use each source
IPv6 address for as few UDP zero-checksum mode MPLS-in-UDP tunnels
as is feasible.</t>
<t>An MPLS-in-UDP receiver MUST check that the top label of the
MPLS label stack is valid for the tunnel. This check will often be
part of the MPLS LSR forwarding logic, but MUST be scoped to the
specific tunnel.</t>
<t>An MPLS-in-UDP receiver node SHOULD only enable the use of UDP
zero-checksum mode on a single UDP port and SHOULD NOT support any
other use UDP zero-checksum mode on any other UDP port.</t>
<t>Any middlebox support for MPLS-in-UDP with UDP zero-checksum
mode for IPv6 MUST comply with requirements 1 and 8-10 in Section
5 of <xref target="RFC6936"/>.</t>
</list>The above requirements do not change the requirements
specified in <xref target="RFC2460"/> as modified by <xref
target="RFC6935"/> and the requirements specified in <xref
target="RFC6936"/>.</t>
<t>The requirements to check the source IPv6 address and top label of
the MPLS stack (in addition to the destination IPv6 address), plus the
strong recommendation against reuse of source IPv6 addresses among
MPLS-in-UDP tunnels collectively provide some offset for the absence
of UDP checksum coverage of the IPv6 header. The expected result for
IPv6 UDP zero-checksum mode for MPLS-in-UDP is that corruption of the
destination IPv6 address will usually cause packet discard, as
offsetting corruptions to the source IPv6 and/or MPLS top label are
unlikely. Additional assurance is provided by the restrictions in the
above exceptions that limit usage of IPv6 UDP zero-checksum mode to
specific types of well-managed networks for which MPLS packet
corruption has not been a problem in practice.</t>
<t>Hence MPLS-in-UDP is suitable for transmission over lower layers in
the well-managed networks that are allowed by the two exceptions
stated above and is not expected to increase the rate of corruption of
the inner IP packet on such networks by comparison to MPLS traffic
that is not encapsulated in UDP. For these reasons, MPLS-in-UDP does
not provide an additional integrity check when UDP zero-checksum mode
is used with IPv6, and this design is in accordance with requirements
2, 3 and 5 specified in Section 5 of <xref target="RFC6936"/>.</t>
<t>MPLS does not accumulate incorrect state as a consequence of label
stack corruption. A corrupt MPLS label results in either packet
discard or forwarding (and forgetting) of the packet without
accumulation of MPLS protocol state. Active monitoring of MPLS-in-UDP
traffic for errors is REQUIRED as occurrence of errors will result in
some accumulation of error information outside the MPLS protocol for
operational and management purposes. This design is in accordance with
requirement 4 specified in Section 5 of <xref target="RFC6936"/>.</t>
<t>The remaining requirements specified in Section 5 of <xref
target="RFC6936"/> are inapplicable to MPLS-in-UDP. Requirements 6 and
7 do not apply because MPLS does not have an MPLS-generic control
feedback mechanism. Requirements 8-10 are middlebox requirements that
do not apply to MPLS-in-UDP tunnel endpoints, but see Section 3.2 for
further middlebox discussion.</t>
<t>In summary, UDP zero-checksum mode for IPv6 is allowed to be used
with MPLS-in-UDP when one of the two exceptions specified above
applies, provided that the additional requirements specified above are
complied with. Otherwise the UDP checksum MUST be used for IPv6 as
specified in <xref target="RFC0768"/> and <xref
target="RFC2460"/>.</t>
<t>This entire section and its requirements apply only to use of UDP
zero-checksum mode for IPv6; they can be avoided by using the UDP
checksum as specified in <xref target="RFC0768"/> and <xref
target="RFC2460"/>.</t>
</section>
<section title="Middlebox Considerations for IPv6 UDP Zero Checksums">
<t>IPv6 datagrams with a zero UDP checksum will not be passed by any
middlebox that validates the checksum based on <xref
target="RFC2460"/> or that updates the UDP checksum field, such as
NATs or firewalls. Changing this behavior would require such
middleboxes to be updated to correctly handle datagrams with zero UDP
checksums. The MPLS-in-UDP encapsulation does not provide a mechanism
to safely fall back to using a checksum when a path change occurs
redirecting a tunnel over a path that includes a middlebox that
discards IPv6 datagrams with a zero UDP checksum. In this case the
MPLS-in-UDP tunnel will be black-holed by that middlebox. Recommended
changes to allow firewalls, NATs and other middleboxes to support use
of an IPv6 zero UDP checksum are described in Section 5 of <xref
target="RFC6936"/>.</t>
</section>
</section>
<section title="Processing Procedures">
<t>This MPLS-in-UDP encapsulation causes MPLS packets to be forwarded
through "UDP tunnels". When performing MPLS-in-UDP encapsulation by the
encapsulator, the entropy value would be generated by the encapsulator
and then be filled in the Source Port field of the UDP header. The
Destination Port field is set to a value (TBD1) allocated by IANA to
indicate that the UDP tunnel payload is an MPLS packet. As for whether
the top label in the MPLS label stack is downstream-assigned or
upstream-assigned, it SHOULD be determined based on the tunnel
destination IP address. That is to say, if the destination IP address is
a multicast address, the top label SHOULD be upstream-assigned,
otherwise if the destination IP address is a unicast address, it SHOULD
be downstream-assigned. Intermediate routers, upon receiving these UDP
encapsulated packets, could balance these packets based on the hash of
the five-tuple of UDP packets. Upon receiving these UDP encapsulated
packets, the decapsulator would decapsulate them by removing the UDP
headers and then process them accordingly. For other common processing
procedures associated with tunneling encapsulation technologies
including but not limited to Maximum Transmission Unit (MTU) and
preventing fragmentation and reassembly, Time to Live (TTL) and
differentiated services, the corresponding "Common Procedures" defined
in <xref target="RFC4023"/> which are applicable for MPLS-in-IP and
MPLS-in-GRE encapsulation formats SHOULD be followed.</t>
</section>
<section title="Congestion Considerations">
<t>Section 3.1.3 of <xref target="RFC5405"/> discussed the congestion
implications of UDP tunnels. As discussed in <xref target="RFC5405"/>,
because other flows can share the path with one or more UDP tunnels,
congestion control <xref target="RFC2914"/> needs to be considered.</t>
<t>A major motivation for encapsulating MPLS in UDP is to improve the
use of multipath (such as ECMP) in cases where traffic is to traverse
routers which are able to hash on UDP Port and IP address. As such, in
many cases this may reduce the occurrence of congestion and improve
usage of available network capacity. However, it is also necessary to
ensure that the network, including applications that use the network,
responds appropriately in more difficult cases, such as when link or
equipment failures have reduced the available capacity.</t>
<t>The impact of congestion must be considered both in terms of the
effect on the rest of the network of a UDP tunnel that is consuming
excessive capacity, and in terms of the effect on the flows using the
UDP tunnels. The potential impact of congestion from a UDP tunnel
depends upon what sort of traffic is carried over the tunnel, as well as
the path of the tunnel.</t>
<t>MPLS is widely used to carry a wide range of traffic. In many cases
MPLS is used to carry IP traffic. IP traffic is generally assumed to be
congestion controlled, and thus a tunnel carrying general IP traffic (as
might be expected to be carried across the Internet) generally does not
need additional congestion control mechanisms. As specified in <xref
target="RFC5405"/>: <list style="empty">
<t>"IP-based traffic is generally assumed to be
congestion-controlled, i.e., it is assumed that the transport
protocols generating IP-based traffic at the sender already employ
mechanisms that are sufficient to address congestion on the path.
Consequently, a tunnel carrying IP-based traffic should already
interact appropriately with other traffic sharing the path, and
specific congestion control mechanisms for the tunnel are not
necessary".</t>
</list></t>
<t>For this reason, where MPLS-in-UDP tunneling is used to carry IP
traffic that is known to be congestion controlled, the UDP tunnels MAY
be used across any combination of a single service provider, multiple
cooperating service providers, or across the general Internet. Internet
IP traffic is generally assumed to be congestion-controlled. Similarly,
in general Layer 3 VPNs are carrying IP traffic that is similarly
assumed to be congestion controlled.</t>
<t>Whether or not Layer 2 VPN traffic is congestion controlled may
depend upon the specific services being offered and what use is being
made of the layer 2 services.</t>
<t>However, MPLS is also used in many cases to carry traffic that is not
necessarily congestion controlled. For example, MPLS may be used to
carry pseudowire or VPN traffic where specific bandwidth guarantees are
provided to each pseudowire, or to each VPN.</t>
<t>In such cases service providers may avoid congestion by careful
provisioning of their networks, by rate limiting of user data traffic,
and/or by using MPLS Traffic Engineering (MPLS-TE) to assign specific
bandwidth guarantees to each LSP. Where MPLS is carried over UDP over
IP, the identity of each individual MPLS flow is in general lost and
MPLS-TE cannot be used to guarantee bandwidth to specific flows (since
many LSPs may be multiplexed over a single UDP tunnel, and many UDP
tunnels may be mixed in an IP network).</t>
<t>For this reason, where the MPLS traffic is not congestion controlled,
MPLS-in-UDP tunnels MUST only be used within a single service provider
that utilizes careful provisioning (e.g., rate limiting at the entries
of the network while over-provisioning network capacity) to ensure
against congestion, or within a limited number of service providers who
closely cooperate in order to jointly provide this same careful
provisioning.</t>
<t>As such, MPLS-in-UDP MUST NOT be used over the general Internet, or
over non-cooperating SPs, to carry traffic that is not
congestion-controlled.</t>
<t>Measures SHOULD be taken to prevent non-congestion-controlled
MPLS-in-UDP traffic from "escaping" to the general Internet, e.g.: <list
style="letters">
<t>Physical or logical isolation of the links carrying MPLS-over-UDP
from the general Internet.</t>
<t>Deployment of packet filters that block the UDP ports assigned
for MPLS-over-UDP.</t>
<t>Imposition of restrictions on MPLS-in-UDP traffic by software
tools used to set up MPLS-in-UDP tunnels between specific end
systems (as might be used within a single data center).</t>
<t>Use of a "Managed Circuit Breaker" for the MPLS traffic as
described in <xref
target="I-D.fairhurst-tsvwg-circuit-breaker"/>.</t>
</list></t>
<t/>
</section>
<section anchor="Security" title="Security Considerations">
<t>The security problems faced with the MPLS-in-UDP tunnel are exactly
the same as those faced with MPLS-in-IP and MPLS-in-GRE tunnels <xref
target="RFC4023"/>. In other words, the MPLS-in-UDP tunnel as defined in
this document by itself cannot ensure the integrity and privacy of data
packets being transported through the MPLS-in-UDP tunnel and cannot
enable the tunnel decapsulator to authenticate the tunnel encapsulator.
In the case where any of the above security issues is concerned, the
MPLS-in-UDP tunnel SHOULD be secured with IPsec or DTLS. IPsec was
designed as a network security mechanism and therefore it resides at the
network layer. As such, if the tunnel is secured with IPsec, the UDP
header would not be visible to intermediate routers anymore in either
IPsec tunnel or transport mode. As a result, the meaning of adopting the
MPLS-in-UDP tunnel as an alternative to the MPLS-in-GRE or MPLS-in-IP
tunnel is lost. By comparison, DTLS is better suited for application
security and can better preserve network and transport layer protocol
information. Specifically, if DTLS is used, the destination port of the
UDP header will be filled with a value (TBD2) indicating MPLS with DTLS
and the source port can still be used as an entropy field for
load-sharing purposes.</t>
<t>If the tunnel is not secured with IPsec or DTLS, some other method
should be used to ensure that packets are decapsulated and forwarded by
the tunnel tail only if those packets were encapsulated by the tunnel
head. If the tunnel lies entirely within a single administrative domain,
address filtering at the boundaries can be used to ensure that no packet
with the IP source address of a tunnel endpoint or with the IP
destination address of a tunnel endpoint can enter the domain from
outside. However, when the tunnel head and the tunnel tail are not in
the same administrative domain, this may become difficult, and filtering
based on the destination address can even become impossible if the
packets must traverse the public Internet. Sometimes only source address
filtering (but not destination address filtering) is done at the
boundaries of an administrative domain. If this is the case, the
filtering does not provide effective protection at all unless the
decapsulator of an MPLS-in-UDP validates the IP source address of the
packet.</t>
<t>This document does not require that the decapsulator validate the IP
source address of the tunneled packets (with the exception that the IPv6
source address MUST be validated when UDP zero-checksum mode is used
with IPv6), but it should be understood that failure to do so
presupposes that there is effective destination-based (or a combination
of source-based and destination-based) filtering at the boundaries.
MPLS-based VPN services rely on a VPN label in the MPLS label stack to
identify the VPN. Corruption of that label could leak traffic across VPN
boundaries. Such leakage is highly undesirable when inter-VPN isolation
is used for privacy or security reasons. When that is the case, UDP
checksums SHOULD be used for MPLS-in-UDP with both IPv4 and IPv6, and in
particular, UDP zero-checksum mode SHOULD NOT be used with IPv6. Each
UDP checksum covers the VPN label, thereby providing increased assurance
of isolation among VPNs.</t>
<!---->
</section>
<!---->
<section anchor="IANA" title="IANA Considerations">
<t>One UDP destination port number indicating MPLS needs to be allocated
by IANA:</t>
<t><list style="empty">
<t>Service Name: MPLS-in-UDP</t>
<t>Transport Protocol(s): UDP</t>
<t>Assignee: IESG <iesg@ietf.org></t>
<t>Contact: IETF Chair <chair@ietf.org>.</t>
<t>Description: Encapsulate MPLS packets in UDP tunnels.</t>
<t>Reference: This document -- draft-ietf-mpls-in-udp (MPLS WG
document).</t>
<t>Port Number: TBD1 -- To be assigned by IANA.</t>
</list></t>
<t>One UDP destination port number indicating MPLS with DTLS needs to be
allocated by IANA:</t>
<t><list style="empty">
<t>Service Name: MPLS-in-UDP-with-DTLS</t>
<t>Transport Protocol(s): UDP</t>
<t>Assignee: IESG <iesg@ietf.org></t>
<t>Contact: IETF Chair <chair@ietf.org>.</t>
<t>Description: Encapsulate MPLS packets in UDP tunnels with
DTLS.</t>
<t>Reference: This document -- draft-ietf-mpls-in-udp (MPLS WG
document).</t>
<t>Port Number: TBD2 -- To be assigned by IANA.</t>
</list></t>
<!---->
</section>
<section title="Contributors">
<t>Note that contributors are listed in alphabetical order according to
their last names. <list style="empty">
<t>Yongbing Fan</t>
<t>China Telecom</t>
<t>Email: fanyb@gsta.com</t>
<t/>
<t> Adrian Farrel</t>
<t>Juniper Networks</t>
<t>Email: adrian@olddog.co.uk </t>
<t/>
<t>Zhenbin Li</t>
<t>Huawei Technologies</t>
<t>Email: lizhenbin@huawei.com</t>
<t/>
<t>Carlos Pignataro</t>
<t>Cisco Systems</t>
<t>Email: cpignata@cisco.com</t>
<t/>
<t>Curtis Villamizar</t>
<t>Outer Cape Cod Network Consulting, LLC</t>
<t>Email: curtis@occnc.com</t>
</list></t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>Thanks to Shane Amante, Dino Farinacci, Keshava A K, Ivan Pepelnjak,
Eric Rosen, Andrew G. Malis, Kireeti Kompella, Marshall Eubanks, George
Swallow, Loa Andersson, Vivek Kumar, Stewart Bryant, Wen Zhang, Joel M.
Halpern, Noel Chiappa, Scott Brim, Alia Atlas, Alexander Vainshtein,
Joel Jaeggli, Edward Crabbe, Mark Tinka, Lars Eggert, Joe Touch, Lloyd
Wood, Gorry Fairhurst, Weiguo Hao, Mark Szczesniak, Zhenxiao Liu and
Xing Tong for their valuable comments and suggestions on this
document.</t>
<t>Special thanks to Alia Atlas for her insightful suggestion of adding
an applicability statement.</t>
<t>Thanks to Daniel King, Gregory Mirsky and Eric Osborne for their
valuable MPLS-RT reviews on this document. Thanks to Charlie Kaufman for
his SecDir review of this document. Thanks to Nevil Brownlee for the
OPSDir review of this document. Thanks to Roni Even for the Gen-ART
review of this document. Thanks to Pearl Liang for the IANA review of
this documents.</t>
<!---->
</section>
</middle>
<back>
<references title="Normative References">
&RFC2119;
<?rfc include="reference.RFC.0768"?>
<?rfc include="reference.RFC.2460"?>
<?rfc include="reference.RFC.3032"?>
<?rfc include="reference.RFC.4301"?>
<?rfc include="reference.RFC.5405"?>
<?rfc include="reference.RFC.6347"?>
<?rfc include="reference.RFC.6935"?>
<?rfc include="reference.RFC.6936"?>
<!---->
</references>
<references title="Informative References">
<!---->
<?rfc include="reference.RFC.4817"?>
<?rfc include="reference.RFC.5640"?>
<?rfc include="reference.RFC.2474"?>
<?rfc include="reference.RFC.2914"?>
<?rfc include="reference.RFC.4023"?>
<?rfc include="reference.RFC.6830"?>
<?rfc include="reference.RFC.6438"?>
<?rfc include="reference.I-D.fairhurst-tsvwg-circuit-breaker"?>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-22 17:41:37 |