Internet DRAFT - draft-ietf-mpls-rfc6374-udp-return-path
draft-ietf-mpls-rfc6374-udp-return-path
MPLS S. Bryant
Internet-Draft Independent
Intended status: Standards Track S. Sivabalan
Expires: October 9, 2016 S. Soni
Cisco Systems
April 7, 2016
RFC6374 UDP Return Path
draft-ietf-mpls-rfc6374-udp-return-path-05
Abstract
RFC6374 defines a protocol for Packet Loss and Delay Measurement for
MPLS networks (MPLS-PLDM). This document specifies the procedures to
be used when sending and processing out-of-band MPLS performance
management responses over an IP/UDP return path.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 9, 2016.
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
(http://trustee.ietf.org/license-info) in effect on the date of
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
This document describes how Packet Loss and Delay Measurement for
MPLS Networks protocol (MPLS-PLDM) [RFC6374] out-of-band responses
can be delivered to the querier using UDP/IP.
The use of UDP may be required to support data path management such
as passage through firewalls, or to provide the necessary
multiplexing needed in bistatic operation where the querier and the
collector are not co-located and the collector is gathering the
response information for a number of responders. In a highly scaled
system some MPLS-PLDM sessions may be off-loaded to a specific node
within the distributed system that comprises the Label Switching
Router (LSR) as a whole. In such systems the response may arrive via
any interface in the LSR and need to be forwarded internally to the
processor tasked with handling the particular MPLS-PLDM measurement.
Currently the MPLS-PLDM protocol does not have any mechanism to
deliver the PLDM Response message to a particular node within a
multi-CPU LSR.
The procedure described in this specification describes how the
querier requests delivery of the MPLS-PLDM response over IP to a
dynamic UDP port. It makes no other changes to the protocol and thus
does not affect the case where the response is delivered over a MPLS
Associated Channel [RFC5586].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Solution Overview
This document specifies that, unless configured otherwise, if a UDP
Return Object (URO) is present in a MPLS-PLDM Query, the responder
SHOULD use the IP address and UDP port in the URO to reply back to
the querier. The querier MAY include multiple UROs in a MPLS-PLDM
Query indicating to the responder that an identical responses SHOULD
be sent to each address-port pair. A responder MAY be designed or
configured to only transmit a single response, in which case the
response MUST be sent using the parameters specified in the first URO
in the query packet that it is able to use (see Section 4.3).
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The procedures defined in this document may be applied to both
unidirectional and bidirectional LSPs. In this document, the term
bidirectional LSP includes the co-routed bidirectional LSP defined in
[RFC3945] and the associated bidirectional LSP that is constructed
from a pair of unidirectional LSPs (one for each direction) that are
associated with one another at the LSP's ingress/egress points
[RFC5654]. The mechanisms defined in this document can apply to both
IP/MPLS and to the MPLS Transport Profile (MPLS-TP)[RFC5654],
[RFC5921]
3.1. UDP Return Object
NOTE TO RFC Editor please delete the following paragraph before
publication.
START DELETE
Note to reviewers - We considered a number of approaches to the
design. The first was to use the existing address object and a
separate UDP object, but concern was expressed in the WG that there
may be more than one collector that required this information, and
the combined size of the two objects was large. The next approach
considered by the authors was to create a new object by appending a
UDP port to the existing generalized address object. However, noting
that UDP is only likely to be sent over IP and that it will be a long
time before we design a third major version of IP we can compress the
object either by having separate IPv4 and IPv6 objects, or using the
address length as the discriminator. The object design below uses
the latter approach. The resultant combined UDP port + address
object is thus the same size as the original address object.
END DELETE
The format of the UDP Return Object (URO) is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| URO TLV Type | Length={6,18} | UDP-Destination-Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Type and Length fields are each 8 bits long. The Length field
indicates the size in bytes of the remainder of the object (i.e. is
the size of the address in bytes plus 2). When the address is IPv4
the length field is thus 6 and when the address is IPv6 the length
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field is thus 18. The length field therefore acts as both the TLV
parsing parameter and the address family type indicator.
The UDP Return Object Type (URO TLV Type) has a value of 131.
The UDP Destination Port is a UDP Destination port as specified in
[RFC0768].
The Address is either an IPv4 or an IPv6 address.
The URO MUST NOT appear in a response and MUST be ignored if it is
found to be present.
To prevent any ambiguity as to which address the responder needs to
reply to, an MPLS-PLDM Query message containing a URO MUST NOT
include an RFC6374 Return Address TLV (TLV 1). Additionally, the
method of constructing the return address from the Source Address TLV
(TLV 130) described in Section 3.5.2 of RFC6374 MUST NOT be used to
construct a Response to a Query message that contains a URO.
4. Theory of Operation
This document defines the UDP Return Object to enable the MPLS-PLDM
querier to specify the return path for the MPLS-PLDM reply using UDP/
IP encapsulation.
When the MPLS-PLDM Response is requested out-of-band by setting the
Control Code of the MPLS-PLDM query to "Out-of-band Response
Requested", and the URO is present, the responder SHOULD send the
response back to querier on the specified destination UDP port at the
specified destination IP address contained in the URO.
If the URO is expected but is not present in a query message and an
MPLS-PLDM Response is requested out-of-band, the query message MUST
NOT be processed further, and if possible an "Error - Invalid
Message" ([RFC6374] Section 3.1) SHOULD be send to the querier and
the operator notified via the management system (see Section 4.2 for
further details.
4.1. Sending an MPLS-PLDM Query
When sending an MPLS-PLDM query message, in addition to the rules and
procedures defined in [RFC6374]; the Control Code of the MPLS-PLDM
query MUST be set to "Out-of-band Response Requested", and a URO MUST
be carried in the MPLS-PLDM query message.
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If the querier uses the UDP port to de-multiplex the response for
different measurement type, there MUST be a different UDP port for
each measurement type (Delay, loss and delay-loss combined).
An implementation MAY use multiple UDP ports for same measurement
type to direct the response to the correct management process in the
LSR.
4.2. Receiving an MPLS PLDM Query Request
The processing of MPLS-PLDM query messages as defined in [RFC6374]
applies in this document. In addition, when an MPLS-PLDM query
message is received, with the control code of the MPLS-PLDM query set
to "Out-of-band Response Requested" with a URO present, then the
responder SHOULD use that IP address and UDP port to send MPLS-PLDM
response back to querier.
If an Out-of-band response is requested and the URO is missing, the
query SHOULD be dropped in the case of a unidirectional LSP. If the
TLV is missing on a bidirectional LSP, the control code of the
Response message SHOULD set to 0x1C indicating "Error - Invalid
Message" ([RFC6374] Section 3.1) and the response SHOULD be sent over
the reverse LSP. The receipt of such a mal-formed request SHOULD be
notified to the operator through the management system, taking the
normal precautions with respect to the prevention of overload of the
error reporting system.
4.3. Sending an MPLS-PLDM Response
As specified in [RFC6374] the MPLS-PLDM Response can be sent over
either the reverse MPLS LSP for a bidirectional LSP or over an IP
path. It MUST NOT be sent other than in response to an MPLS-PLDM
query message.
When the requested return path is an IP forwarding path and this
method is in use, the destination IP address and UDP port is copied
from the URO. The source IP address and the source UDP Port of the
Response packet is left to discretion of the responder subject to the
normal management and security considerations. If the querier has
included URO(s) for only one IP address family and a return path of
that type is not available, then the query message MUST be discarded,
and the operator SHOULD be informed of the error through the
management system using the normal rate limited approach. If the
responder is configured to only respond with a single response, and a
path using the IP address family in the first URO is not available,
the responder MAY search the UROs for the first URO specifying a
return address family for which it does have a path and use the
parameters in that URO to respond. If the responder is designed or
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configured not to search for a URO that it can respond to, then the
operator SHOULD be informed of the error through the management
system using the normal rate limited approach.
The packet format for the MPLS-PLDM response after the UDP header is
as specified in [RFC6374]. As shown in Figure 1 the Associate
Channel Header (ACH) [RFC5586] is not included. The information
provided by the ACH is not needed since the correct binding between
the query and response messages is achieved though the UDP Port and
the session indentifier contained in the RFC6374 message.
+----------------------------------------------------------+
| IP Header |
. Source Address = Responders IP Address |
. Destination Address = URO.Address |
. Protocol = UDP .
. .
+----------------------------------------------------------+
| UDP Header |
. Source Port = As chosen by Responder .
. Destination Port = URO.UDP-Destination-Port .
. .
+----------------------------------------------------------+
| Message as specified in RFC6374 |
. .
+----------------------------------------------------------+
Figure 1: Response packet Format
If the return path is an IP path, only one-way delay or one-way loss
measurement can be carried out. In this case timestamps 3 and 4 MUST
be zero as specified in [RFC6374].
4.4. Receiving an MPLS-PLDM Response
If the response was received over UDP/IP and an out-of-band response
was expected, the Response message SHOULD be directed to the
appropriate measurement process as determined by the destination UDP
Port, and processed using the corresponding measurement type
procedure specified in F [RFC6374].
If the Response was received over UDP/IP and an out-of-band response
was not requested, that response SHOULD be dropped and the event
SHOULD be notified to the operator through the management system,
taking the normal precautions with respect to the prevention of
overload of the error reporting system.
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5. Congestion Considerations
This protocol MUST be run in accordance the guidance provided in
[RFC5405]. As advised in section 3.2.1 of RFC5405, operators that
wish to run this protocol at rates in excess of one packet per three
seconds need to ensure that the MPLS path being monitored and any IP
path that may be used to carry the response are provisioned such that
there is a negligible chance of this protocol causing congestion.
Additionally, if a significant number of response packets are lost,
the querier MUST reduce the sending rate to a point where there is a
negligible chance that this protocol is contributing to network
congestion. The operator should also take precautions that response
packets do not leak out of the network domain being used and cause
congestion elsewhere. If a default IP address is configured by the
equipment vendor, this MUST be an address known to contain the
response packet within the responder, such as the IPv4 localhost
address [RFC6890] or the IPv6 loopback address [RFC4291]. A
responder receiving a query specifying this as a return address, and
not being configured to expect such a return address*, SHOULD notify
the operator in a suitably rate limited manner.
6. Manageability Considerations
The manageability considerations described in Section 7 of [RFC6374]
are applicable to this specification. Additional manageability
considerations are noted within the elements of procedure of this
document.
Nothing in this document precludes the use of a configured UDP/IP
return path in a deployment in which configuration is preferred to
signalling. In these circumstances the URO MAY be omitted from the
MPLS-PLDM messages.
7. Security Considerations
The MPLS-PLDM system is not intended to be deployed on the public
Internet. It is intended for deployment in well managed private and
service provider networks. The security considerations described in
Section 8 of [RFC6374] are applicable to this specification and the
reader's attention is drawn to the last two paragraphs.
Cryptographic measures may be enhanced by the correct configuration
of access control lists and firewalls.
To prevent the use of this protocol as a reflection attack vector,
the operator should ensure that the IP address in the URO addresses a
system that is expecting to act as a receiver of PLDM responses.
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There is no additional exposure of information to pervasive
monitoring systems observing LSPs that are being monitored.
8. IANA Considerations
IANA has made an early allocation of a new Optional TLV type from
MPLS Loss/Delay Measurement TLV Object Registry contained within the
Generic Associated Channel (G-ACh) Parameters registry set. IANA is
requested to modify the description text as shown below.
Code Description Reference
131 UDP Return [This]
9. Acknowledgements
We acknowledge the contribution of Joseph Chin and Rakesh Gandhi,
both with Cisco Systems. We thank Loa Andersson, Eric Osborne,
Mustapha Aissaoui, Jeffrey Zhang and Ross Callon for their review
comments.
We thank all who have reviewed this text and provided feedback.
10. References
10.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
<http://www.rfc-editor.org/info/rfc3945>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405,
DOI 10.17487/RFC5405, November 2008,
<http://www.rfc-editor.org/info/rfc5405>.
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[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>.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <http://www.rfc-editor.org/info/rfc5654>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<http://www.rfc-editor.org/info/rfc6890>.
10.2. Informative References
[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>.
Authors' Addresses
Stewart Bryant
Independent
Email: stewart.bryant@gmail.com
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Sagar Soni
Cisco Systems
Email: sagsoni@cisco.com
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