Internet DRAFT - draft-ietf-mpls-proxy-lsp-ping
draft-ietf-mpls-proxy-lsp-ping
Network Working Group G. Swallow
Internet-Draft V. Lim
Intended status: Standards Track Cisco Systems
Expires: September 26, 2015 S. Aldrin
Huawei Technologies
March 25, 2015
Proxy MPLS Echo Request
draft-ietf-mpls-proxy-lsp-ping-05
Abstract
This document defines a means of remotely initiating Multiprotocol
Label Switched Protocol Pings on Label Switched Paths. An MPLS Proxy
Ping Request is sent to any Label Switching Router along a Label
Switched Path. The primary motivations for this facility are first to
limit the number of messages and related processing when using LSP
Ping in large Point-to-Multipoint LSPs, and second to enable leaf to
leaf/root tracing.
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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This Internet-Draft will expire on September 26, 2015.
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Copyright Notice
Copyright (c) 2015 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Proxy Ping Overview . . . . . . . . . . . . . . . . . . . . . 5
2.1. Initiating Proxy Ping . . . . . . . . . . . . . . . . . . 6
2.2. Handling at Proxy LSR . . . . . . . . . . . . . . . . . . 6
2.2.1. Backward Compatibility . . . . . . . . . . . . . . . . 6
3. Proxy MPLS Echo Request / Reply Procedures . . . . . . . . . . 7
3.1. Procedures for the initiator . . . . . . . . . . . . . . . 7
3.2. Procedures for the Proxy LSR . . . . . . . . . . . . . . . 8
3.2.1. Proxy LSR Handling when it is egress for FEC . . . . . 10
3.2.2. Downstream Detailed/Downstream Maps in Proxy Reply . . 11
3.2.3. Sending an MPLS Proxy Ping Reply . . . . . . . . . . . 12
3.2.4. Sending the MPLS Echo Requests . . . . . . . . . . . . 12
3.2.4.1. Forming the base MPLS Echo Request . . . . . . . . 12
3.2.4.2. Per interface sending procedures . . . . . . . . . 14
4. Proxy Ping Request / Reply Messages . . . . . . . . . . . . . 14
4.1. Proxy Ping Request / Reply Message formats . . . . . . . . 14
4.2. Proxy Ping Request Message contents . . . . . . . . . . . 15
4.3. Proxy Ping Reply Message Contents . . . . . . . . . . . . 15
5. TLV formats . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. Proxy Echo Parameters TLV . . . . . . . . . . . . . . . . 16
5.1.1. Next Hop sub-TLV . . . . . . . . . . . . . . . . . . . 19
5.2. Reply-to Address TLV . . . . . . . . . . . . . . . . . . . 20
5.3. Upstream Neighbor Address TLV . . . . . . . . . . . . . . 20
5.4. Downstream Neighbor Address TLV . . . . . . . . . . . . . 21
6. Security Considerations . . . . . . . . . . . . . . . . . . . 22
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
8.1. Proxy Echo Parameters Sub-TLVs . . . . . . . . . . . . . . 23
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8.2. Downstream Address Mapping Registry [pending IANA
assignment] . . . . . . . . . . . . . . . . . . . . . . . 24
8.3. Next Hop Sub-TLV Address Type Registry . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
This document is motivated by two broad issues in connection with
diagnosing Point-to-Multipoint (P2MP) Label Switched Paths (LSPs).
The first is scalability due to the automatic replication of
Multiprotocol Label Switching (MPLS) Echo Request Messages as they
proceed down the tree. The second, which is primarily motivated by
Label Distribution Protocol based Point-to-Multipoint (P2MP) and
Multipoint-to-Multipoint (MP2MP) Label Switched Paths [RFC6388], is
the ability to trace a sub-LSP from leaf node to root node.
When tracing from a source to a particular leaf in a P2MP or MP2MP
tree, nodes not along that path will need to process MPLS Echo
Request messages that are received. The number of MPLS Echo Replies
sent in response to an MPLS Echo Request quickly multiplies, as the
Label Switching Routers (LSRs), which are part of the tree but not
along the path of the trace could be responding to the received MPLS
Echo Request as well. This could also overwhelm the source to process
all the MPLS Echo Reply messages it receives. It is anticipated that
many of the applications for P2MP/MP2MP tunnels will require OAM that
is both rigorous and scalable.
Suppose one wishes to trace a P2MP LSP to localize a fault which is
affecting one egress or a set of egresses. Suppose one follows the
normal procedure for tracing - namely repeatedly pinging from the
root, incrementing the Time to Live (TTL) by one after each three or
so pings. Such a procedure has the potential for producing a large
amount of processing at the P2MP-LSP midpoints and egresses. It also
could produce an unwieldy number of replies back to the root.
One alternative would be to begin sending pings from points at or
near the affected egress(es) and then working backwards toward the
root. The TTL could be held constant, say two, limiting the number of
responses to the number of next-next-hops of the point where a ping
is initiated.
In the case of Resource Reservation Protocol-Traffic Engineering
(RSVP-TE), all setup is initiated from the root of the tree. Thus,
the root of the tree has knowledge of both all the leaf nodes and
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usually the topology of the entire tree. Thus the above alternative
can easily be initiated by the root node.
In [RFC6388] the situation is quite different. Leaf nodes initiate
connectivity to the tree, which is granted by the first node toward
the root that is part of the tree. The root node may only be aware of
the immediately adjacent (downstream) nodes of the tree. Initially
the leaf node only has knowledge of the (upstream) node to which it
is immediately adjacent. However this is sufficient information to
initiate a trace. First the above procedure is applied by asking that
node to ping across the final link. That is, a message is sent from
the leaf to the upstream node requesting it to send an MPLS Echo
Request for the Forward Equivalence Class (FEC) of the tree in
question on said link. The leaf node also requests the identity of
the upstream neighbor's upstream neighbor for that FEC. With this
information, the procedure can iteratively be applied until the fault
is localized or the root node is reached. In all cases, the TTL for
the request need only be at most 2. Thus the processing load of each
request is small, since only a limited number of nodes will receive
the request.
This document defines protocol extensions to MPLS ping [RFC4379] to
allow a third party to remotely cause an MPLS Echo Request message to
be sent down an LSP or part of an LSP. The procedure described in the
paragraphs above does require that the initiator know the previous-
hop node to the one which was pinged on the prior iteration. This
information is readily available in [RFC4875]. This document also
provides a means for obtaining this information for [RFC6388].
While the motivation for this document came from multicast scaling
concerns, it's applicability may be wider. The procedures presented
in this document are applicable to all LSP ping FEC types where the
MPLS Echo Request/Reply are IP encapsulated and the MPLS Echo Reply
can sent out of band of the LSP over IP. Remote pinging of LSPs that
involve the use of in-band control channels is beyond the scope of
this document.
Other uses of this facility are beyond the scope of this document. In
particular, the procedures defined in this document only allow
testing of a FEC stack consisting of a single FEC. The procedures
also do not allow the initiator to specify the label assigned to that
FEC, nor does it allow the initiator to cause any additional labels
to be added to the label stack of the actual MPLS Echo Request
message.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The term "Must Be Zero" (MBZ) is used in TLV descriptions for
reserved fields. These fields MUST be set to zero when sent and
ignored on receipt.
Based on context the terms leaf and egress are used interchangeably.
Egress is used where consistency with[RFC4379] was deemed
appropriate. Receiver is used in the context of receiving protocol
messages.
1.2. Terminology
Term Definition
----- -------------------------------------------
LSP Label Switched Path
LSR Label Switching Router
mLDP Multipoint LDP
MP2MP Multipoint to Multipoint
MTU Maximum Transmission Unit
P2MP Point to Multipoint
TTL Time to Live
2. Proxy Ping Overview
This document defines a protocol interaction between a first LSR, an
LSR which is part of an LSP, to allow the first LSR to request that
the second LSR initiate an LSP ping for the LSP on the first LSR's
behalf. Since the second LSR sends the LSP Ping on behalf of the
first LSR, it does not maintain state to be able to handle the
corresponding LSP Ping response. Instead the responder to the LSP
ping sends the LSP Ping response to either the first LSR or another
LSR configured to handle it. Two new LSP Ping messages are defined
for remote pinging: the MPLS Proxy Ping Request and the MPLS Proxy
Ping Reply.
A remote ping operation on a P2MP LSP generally involves at least
three LSRs; in some scenarios none of these are the ingress (root) or
an egress (leaf) of the LSP.
We refer to these LSRs with the following terms:
Initiator - the LSR which initiates the ping operation by sending
an MPLS Proxy Ping Request message
Proxy LSR - the LSR which is the destination of the MPLS Proxy
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Ping Request message and potential initiator of the MPLS Echo
Request
Receiver(s) - the LSR(s) which receive the MPLS Echo Request
message
Responder - A receiver that responds to an MPLS Proxy Ping Request
or an MPLS Echo Request
We note that in some scenarios, the initiator could also be the
responder, in which case the response would be internal to the LSR.
2.1. Initiating Proxy Ping
The initiator formats an MPLS Proxy Ping Request message and sends it
to the Proxy LSR, an LSR it believes to be on the path of the LSP.
This message instructs the Proxy LSR to either Reply with Proxy
information or to send an MPLS Echo Request inband of the LSP. The
initiator requests Proxy information so that it can learn additional
information it needs to use to form a subsequent MPLS Proxy Ping
Request. For example, during LSP traceroute an initiator needs the
downstream map information to form an MPLS Echo Request. An initiator
may also want to learn a Proxy LSR's FEC neighbor information so that
it can form Proxy Ping Requests to various LSRs along the LSP.
2.2. Handling at Proxy LSR
The Proxy LSR either replies with the requested Proxy information or
it validates that it has a label mapping for the specified FEC and
that it is authorized to send the specified MPLS Echo Request on
behalf of the initiator.
If the Proxy LSR has a label mapping for the FEC and all
authorization checks have passed, the Proxy LSR formats an MPLS Echo
Request. If the source address of the MPLS Echo Request is not to be
set to the Proxy Request source address, the initiator MUST include a
Reply-to Address TLV containing the source address to use in the MPLS
Echo Request. It then sends it inband of the LSP.
The receivers process the MPLS Echo Request as normal, sending their
MPLS Echo Replies back to the initiator.
If the Proxy LSR failed to send an MPLS Echo Request as normal
because it encountered an issue while attempting to send, an MPLS
Proxy Ping Reply message is sent back with a Return Code indicating
that the MPLS Echo Request could not be sent.
2.2.1. Backward Compatibility
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As described in sec 4.4 of [RFC4379], if the packet is not well-
formed, LSR X SHOULD send an MPLS Echo Reply with the Return Code set
to "Malformed echo request received" and the Subcode to zero. If
there are any TLVs not marked as "Ignore" that Proxy LSR does not
understand, Proxy LSR SHOULD send an MPLS "TLV not understood" (as
appropriate), and the Subcode set to zero.
In the case where the targeted Proxy LSR does not understand the LSP
ping Echo Request at all, like any other LSR which does not
understand the messages, it MUST drop them and MUST NOT send any
message back to the initiator.
3. Proxy MPLS Echo Request / Reply Procedures
3.1. Procedures for the initiator
The initiator creates an MPLS Proxy Ping request message.
The message MUST contain a Target FEC Stack that describes the FEC
being tested. The topmost FEC in the target FEC stack is used at the
Proxy LSR to lookup the MPLS label stack that will be used to
encapsulate the MPLS Echo Request packet.
The MPLS Proxy Ping Request message MUST contain a Proxy Echo
Parameters TLV. In that TLV, the address type is set to either IPv4
or IPv6. The Destination IP Address is set to the value to be used by
the Proxy LSR to build the MPLS Echo Request packet. The MPLS Echo
Request IP header destination address as specified in [RFC4379], if
the Address Type is IPv4, MUST be an address is from the range 127/8;
If the Address Type is IPv6, MUST be an address from the range
::FFFF:7F00:0/104.
The Reply mode and Global Flags of the Proxy Echo Parameters TLV are
set to the values to be used in the MPLS Echo Request message header.
The Source UDP Port is set to the value to be used in the MPLS Echo
Request (the source port is supplied by the Proxy Ping initiator
because it or an LSR known to it handles the LSP ping responses). The
TTL is set to the value to be used in the outgoing MPLS label stack.
See Section 5.1 for further details.
If the FEC's Upstream/Downstream Neighbor address information is
required, the initiator sets the "Request for FEC neighbor
information" Proxy Flags in the Proxy Echo Parameters TLV.
If a Downstream Detailed or Downstream Mapping TLV is required in an
MPLS Proxy Ping Reply, the initiator sets the "Request for Downstream
Detailed Mapping" or "Request for Downstream Mapping" Proxy Flags in
the Proxy Echo Parameters TLV. Only one of the two flags can be set.
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The Proxy Request reply mode is set with one of the reply modes
defined in [RFC4379] as appropriate.
A list of Next Hop IP Addresses MAY be included to limit the next
hops towards which the MPLS Echo Request message will be sent. These
are encoded as Next Hop sub-TLVs and included in the Proxy Echo
Parameters TLV.
Although not explicitly spelled out in [RFC4379], LSP Ping packets
can be formed to a desired size using a Pad TLV and then used to test
the Maximum Transmission Unit (MTU) of an LSP. When testing an LSPs
MTU, if the message is transported as an IP datagram, the IP header
DF bit MUST be set to prevent IP fragmentation by the IP forwarding
layer. The Proxy Echo Parameter TLV MPLS payload size field is
defined for this purpose and may be set to request that the MPLS Echo
Request (including any IP and UDP header) be zero padded to the
specified size. When a non zero MPLS payload size is specified, the
Proxy LSR introduces a Pad TLV to build the MPLS Echo Request packet,
so in this case, the Proxy Ping Request MUST NOT include a Pad TLV.
Any of following TLVs MAY be included; these TLVs are used to form
the MPLS Echo Request messages by the Proxy LSR:
Pad
Vendor Enterprise Number
Reply TOS Byte
P2MP Responder Identifier [RFC6425]
Echo Jitter TLV [RFC6425]
Vendor Private TLVs
Downstream Detailed Mapping (DDMAP) or Downstream Mapping (DSMAP)
TLVs MAY be included. These TLVs will be matched to the next hop
address for inclusion in those particular MPLS Echo Request messages.
The message is then encapsulated in a UDP packet. The source User
Datagram Protocol (UDP) port for the MPLS Proxy Ping Request message
is chosen by the initiator; the destination UDP port is set to 3503.
The IP header is set as follows: the source IP address is a routable
address of the initiator; the destination IP address is a routable
address to the Proxy LSR. The packet is then sent with the IP TTL set
to 255.
3.2. Procedures for the Proxy LSR
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A Proxy LSR that receives an MPLS Proxy Ping Request message, parses
the packet to ensure that it is a well-formed packet. It checks that
the TLVs that are not marked "Ignore" are understood. If any part of
the message is malformed, it sets the Return Code to "Malformed echo
request received". If all the TLVs are well formed and any TLVs are
not understood, the Return Code is set to "TLV not understood". The
Subcode is set to zero for both cases.
If the Reply Mode of the message header is not 1(Do not reply), an
MPLS Proxy Ping Reply message SHOULD be sent as described below.
If the Return Code is "TLV not understood", no more processing of the
MPLS Proxy Ping Request message is required. The Proxy LSR sends an
MPLS Proxy Ping Reply message with an Errored TLVs TLV containing all
the not understood TLVs (only).
The MPLS Proxy Ping Request is expected to be transported to the
Proxy LSR via IP forwarding mechanisms instead of using the same
techniques that are employed to inject an MPLS Echo Request packet
into an LSP and use IP TTL, MPLS TTL and or loopback addresses (IPv4
127.x.x.x/IPv6::FFF:127/104) in the IP header destination address
field to trigger the packet to be handled via an LSR's forwarding
exception processing path. To gaurd against this, the Proxy LSR
checks that the MPLS Proxy Ping Request message did not arrive via
one of its exception processing paths. Packets arriving via IP TTL
expiry, IP destination address set to a loopback address or label ttl
expiry MUST be treated as "Unauthorized" packets. An MPLS Proxy Ping
Reply message MAY be sent with a Return Code of <TBA-7>, "Proxy Ping
not authorized".
The header fields Sender's Handle and Sequence Number are not
examined, but they are included in the MPLS Proxy Ping Reply or MPLS
Echo Request message, if either is sent as a direct result of the
received message.
The Proxy LSR validates that it has a label mapping for the specified
FEC, it then determines if it is an ingress, egress, transit or bud
node and sets the Return Code as appropriate. A new Return Code of
<TBA-10>, "Replying router has FEC mapping for topmost FEC" has been
defined for the case where the Proxy LSR is an ingress (for example
head of the TE tunnel or a transit router) because the existing
RFC4379 Return Codes don't match the situation. For example, when a
Proxy LSR is a transit router, it's not appropriate for the Return
Code to describe how the packet would transit because the MPLS Proxy
Ping Request doesn't contain information about what input interface
the MPLS Echo Request would be switched from at the Proxy LSR.
The Proxy LSR then determines if it is authorized to send the
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specified MPLS Echo Request on behalf of the initiator. A Proxy LSR
MUST be capable of filtering addresses to validate initiators. Other
filters on FECs or MPLS Echo Request contents MAY be applied. If a
configured filter has been invoked and an address does not pass the
filter, then an MPLS Echo Request message MUST NOT be sent, and the
event SHOULD be logged. An MPLS Proxy Ping Reply message MAY be sent
with a Return Code of <TBA-7>, "Proxy Ping not authorized".
The destination address specified in the Proxy Echo Parameters TLV is
checked to ensure that it conforms to the address allowed IPv4 or
IPv6 address range. If not, the Return Code set to "Malformed echo
request received" and the Subcode set to zero. If the Reply Mode of
the message header is not 1, an MPLS Proxy Ping Reply message SHOULD
be sent as described below.
If the "Request for FEC Neighbor Address info" flag is set, the
Upstream Neighbor Address and Downstream Neighbor Address TLVs are
formatted for inclusion in the MPLS Proxy Ping reply. If the Upstream
or Downstream address is unknown, the corresponding TLV is omitted.
If there are Next Hop sub-TLVs in the Proxy Echo Parameters TLV, each
address is examined to determine if it is a valid next hop for this
FEC. If any are not, Proxy Echo Parameters TLV SHOULD be updated
removing unrecognized Next Hop sub-TLVs. The updated Proxy Echo
Parameters TLV MUST be included in the MPLS Proxy Ping Reply.
If the "Request for Downstream Detailed Mapping" or "Request for
Downstream Mapping" flag is set, the Proxy LSR formats (for inclusion
in the MPLS Proxy Ping Reply) a Downstream Detailed/Downstream
Mapping (DD/DSMAP) TLV for each interface over which the MPLS Echo
Request will be sent.
If the Proxy LSR is the egress for the FEC, the behavior of the Proxy
LSR varies depending on whether the LSR is an egress of a P2P LSP, a
P2MP LSP or MP2MP LSP. Additional details can be found in the section
describing "Handling when Proxy LSR it is egress for FEC".
If the Reply Mode of the MPLS Proxy Ping Request message header is "1
- do not reply", no MPLS Proxy Ping Reply is sent. Otherwise an MPLS
Proxy Ping Reply message or MPLS Echo Request SHOULD be sent as
described below.
3.2.1. Proxy LSR Handling when it is egress for FEC
This section describes the different behaviors for the Proxy LSR when
it's the egress for the FEC. In the P2MP bud node and MP2MP bud node
and egress cases, different behavior is required.
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In the case where an MLSP Echo Request is originated by an LSR which
is a bud or egress node of a P2MP/MP2MP, MPLS Echo Replies are
returned from downstream/upstream LSRs and will not include an MPLS
Echo Reply from the LSR that originated the MPLS Echo Request. This
section describes the behavior required at a bud or egress node to
return or not return information from MPLS Echo Replies in the Proxy
Echo Reply so that no changes are required in [RFC4379] compliant
implementations. The Proxy Initiator should receive the same MPLS
Echo Replies as in the case where of the originator of the LSP ping,
any additional information such as the Proxy LSR being a bud or
egress node is returned in the MPLS Proxy Ping Reply.
When the Proxy LSR is the egress of a P2P FEC, an MPLS Proxy Ping
Reply SHOULD be sent to the initiator with the Return Code set to 3,
"Reply router is egress for FEC", with Return Subcode set to 0.
When the Proxy LSR is the egress of a P2MP FEC, it can be either a
bud node or just an egress. If the Proxy LSR is a bud node, a MPLS
Proxy Ping Reply SHOULD be sent to the initiator with the return code
set to 3 (Reply router is Egress for FEC) with return Subcode set to
0. DS/DDMAPs are included only if the Proxy initiator requested
information to be returned in a MPLS Proxy Ping Reply. If the Proxy
LSR is a bud node but not requested to return an MPLS Proxy Ping
Reply, the Proxy LSR SHOULD send MPLS Echo Request packet(s) to the
downstream neighbors (no MPLS Echo Reply is sent to the Proxy
Initiator to indicate that the Proxy LSR is an egress). If the Proxy
LSR is just an egress, an MPLS Proxy Ping Reply SHOULD be sent to the
initiator with the Return Code set to 3, "Reply router is egress for
FEC", and Return Subcode set to 0.
When the Proxy LSR is the egress of a MP2MP FEC, it can be either a
bud node or just an egress. LSP pings sent from a leaf of a MP2MP
have different behavior in this case. MPLS Echo Requests are sent to
all upstream/downstream neighbors. The Proxy LSRs need to be
consistent with this variation in behavior. If the Proxy LSR is a bud
node or just an egress, an MPLS Proxy Ping Reply SHOULD be sent to
the Proxy Initiator with the return code set to 3, "Reply router is
Egress for FEC", with Return Subcode set to 0 and DS/DDMAPs included
only if the Proxy initiator requested information to be returned in a
MPLS Proxy Ping Reply. If the Proxy LSR is not requested to return
information in an MPLS Proxy Ping Reply, the Proxy LSR SHOULD send
MPLS Echo Request packets to all upstream/downstream neighbors as
would be done when sourcing an LSP ping from a MP2MP leaf (no MPLS
Echo Reply is sent to the Proxy initiator indicating that the Proxy
LSR is an egress).
3.2.2. Downstream Detailed/Downstream Maps in Proxy Reply
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When the Proxy LSR is a transit or bud node, downstream maps
corresponding to how the packet is transited cannot be supplied
unless an ingress interface for the MPLS Echo Request is specified.
Since this information is not available and all valid output paths
are of interest, the Proxy LSR SHOULD include DS/DDMAP(s) to describe
the entire set of paths that the packet can be replicated. This is
similar to the case in which an LSP ping is initiated at the Proxy
LSR. For mLDP, there is a DSMAP/DDMAP per upstream/downstream
neighbor for MP2MP LSPs, or per downstream neighbor in the P2MP LSP
case.
When the Proxy LSR is a bud node or egress in an MP2MP LSP or a bud
node in a P2MP LSP, an LSP ping initiated from the Proxy LSR would
source packets only to the neighbors but not itself, despite the fact
that the Proxy LSR is itself an egress for the FEC. In order to match
the behavior as seen from LSP Ping initiated at the Proxy LSR, the
Proxy Reply SHOULD contain DSMAP/DDMAPs for only the paths to the
upstream/downstream neighbors, but no DSMAP/DDMAP describing its own
egress paths. The proxy LSR identifies that it's an egress for the
FEC using a different Proxy Reply Return Code. The Proxy reply Return
Code is either set to "Reply router has a mapping for the topmost
FEC" or "Reply router is egress for the FEC".
3.2.3. Sending an MPLS Proxy Ping Reply
The Reply mode, Sender's Handle and Sequence Number fields are copied
from the Proxy Ping Request message. The TLVs specified above are
included. The message is encapsulated in a UDP packet. The source IP
address is a routable address of the Proxy LSR; the source port is
the well-known UDP port for LSP ping. The destination IP address and
UDP port are copied from the source IP address and UDP port of the
MPLS Proxy Ping Request. The IP TTL is set to 255.
3.2.4. Sending the MPLS Echo Requests
An MPLS Echo Request is formed as described in the next section. The
section below that describes how the MPLS Echo Request is sent on
each interface.
3.2.4.1. Forming the base MPLS Echo Request
If Next Hop sub-TLVs were included in the received Proxy Echo
Parameters TLV, the Next_Hop_List is created from the addresses in
those sub-TLVs adjusted as described in Section 3.2. Otherwise, the
list is set to all the next hops to which the FEC would be forwarded.
The Proxy LSR then formats an MPLS Echo Request message. The Global
Flags and Reply Mode are copied from the Proxy Echo Parameters TLV.
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The Return Code and Return Subcode are set to zero.
The Sender's Handle and Sequence Number are copied from the remote
echo request message.
The TimeStamp Sent is set to the time-of-day (in seconds and
microseconds) that the MPLS Echo Request is sent. The TimeStamp
Received is set to zero.
If the reply-to address TLV is present, it is used to set the echo
request source address; otherwise the echo request source address is
set to the Proxy Request source address.
The following TLVs are copied from the MPLS Proxy Ping Request
message. Note that of these, only the Target FEC Stack is REQUIRED to
appear in the MPLS Proxy Ping Request message. The Pad TLV is not
copied if the Proxy Echo Parameter TLV MPLS payload size is set to a
non zero value.
Target FEC Stack
Pad
Vendor Enterprise Number
Reply TOS Byte
P2MP Responder Identifier [RFC6425]
Echo Jitter TLV [RFC6425]
Vendor Private TLVs
If the Proxy Echo Parameter TLV MPLS payload size is non zero, the
Proxy LSR introduces a Pad TLV such that size of the MPLS Echo
Request (including any IP and UDP header) is zero padded to the
specified MPLS payload size. The First Octet in Value part of the
Pad TLV is set to 1, "Drop Pad TLV from Reply", the remaining Octets
of the Value part of the Pad TLV is filled with zeros. If IP header
is use to encapsulate in the MPLS Echo Request the DF bit MUST be set
to one.
The message is then encapsulated in a UDP packet. The source UDP port
is copied from the Proxy Echo Parameters TLV. The destination port is
copied from the MPLS Proxy Ping Request message.
The source IP address is set to a routable address specified in the
reply-to-address TLV or the source address of the received Proxy
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Request. Per usual the TTL of the IP packet is set to 1.
If the Explicit Differentiated Services Code Point (DSCP) flag is
set, the Requested DSCP byte is examined. If the setting is permitted
then the DSCP byte of the IP header of the MPLS Echo Request message
is set to that value. If the Proxy LSR does not permit explicit
control for the DSCP byte, the MPLS Proxy Echo Parameters with the
Explicit DSCP flag cleared MUST be included in any MPLS Proxy Ping
Reply message to indicate why an MPLS Echo Request was not sent. The
Return Code MUST be set to <TBA-8>, "Proxy Ping parameters need to be
modified". If the Explicit DSCP flag is not set, the Proxy LSR SHOULD
set the MPLS Echo Request DSCP settings to the value normally used to
source LSP ping packets..
3.2.4.2. Per interface sending procedures
The Proxy LSR now iterates through the Next_Hop_List modifying the
base MPLS Echo Request to form the MPLS Echo Request packet which is
then sent on that particular interface.
The outgoing label stack is determined for each next hop address. The
TTL for the label corresponding to the FEC specified in the FEC stack
is set such that the TTL on the wire will be other TTL specified in
the Proxy Echo Parameters. If any additional labels are pushed onto
the stack, their TTLs are set to 255. This will ensure that the
requestor will not have control over tunnels not relevant to the FEC
being tested.
If the MPLS Proxy Ping Request message contained Downstream Mapping/
Downstream Detailed Mapping TLVs, they are examined. If the
Downstream IP Address matches the next hop address, that Downstream
Mapping TLV is included in the MPLS Echo Request.
The packet is then transmitted on this interface.
4. Proxy Ping Request / Reply Messages
This document defines two new LSP Ping messages, the MPLS Proxy Ping
Request and the MPLS Proxy Ping Reply.
4.1. Proxy Ping Request / Reply Message formats
The packet format is as defined in [RFC4379]. Two new message types,
Proxy Ping Request and Reply, are being added.
Message Type
Type Message
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---- -------
TBA-1 MPLS Proxy Ping Request
(Pending IANA assignment)
TBA-2 MPLS Proxy Ping Reply
(Pending IANA assignment)
4.2. Proxy Ping Request Message contents
The MPLS Proxy Ping Request message MAY contain the following
TLVs:
Type TLV
---- -----------
1 Target FEC Stack
2 Downstream Mapping
3 Pad
5 Vendor Enterprise Number
10 Reply TOS Byte
11 P2MP Responder Identifier [RFC6425]
12 Echo Jitter TLV [RFC6425]
20 Downstream Detailed Mapping
21 Reply Path [RFC7110]
22 Reply TC [RFC7110]
TBA-3 Proxy Echo Parameters (Pending IANA assignment)
TBA-4 Reply-to-Address TLV
* Vendor Private TLVs
* TLVs types in the Vendor Private TLV Space MUST be
ignored if not understood
4.3. Proxy Ping Reply Message Contents
The MPLS Proxy Ping Reply message MAY contain the following TLVs:
Type TLV
---- -----------
1 Target FEC Stack
2 Downstream Mapping
5 Vendor Enterprise Number
9 Errored TLVs
20 Downstream Detailed Mapping
TBA-3 Proxy Echo Parameters (Pending IANA assignment)
TBA-5 Upstream Neighbor Address (Pending IANA assignment)
TBA-6 Downstream Neighbor Address (0 or more)
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(Pending IANA assignment)
* Vendor Private TLVs
* TLVs types in the Vendor Private TLV Space MUST be
ignored if not understood
5. TLV formats
5.1. Proxy Echo Parameters TLV
The Proxy Echo Parameters TLV is a TLV that MUST be included in an
MPLS Proxy Ping Request message. The length of the TLV is 12 + K + S,
where K is the length of the Destination IP Address field and S is
the total length of the sub-TLVs. The Proxy Echo Parameters TLV can
be used either to 1) control attributes used in composing and sending
an MPLS Echo Request or 2) query the Proxy LSR for information about
the topmost FEC in the target FEC stack, but not both. In the case
where the Proxy LSR is being queried (i.e., information needs to be
returned in an MPLS Proxy Ping Reply), no MPLS Echo Request will be
sent from the Proxy LSR. The MPLS Proxy Ping Request echo header's
Reply Mode SHOULD be set to "Reply with Proxy Info".
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | Reply mode | Proxy Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTL | Rqst'd DSCP | Source UDP Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global Flags | MPLS Payload size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Destination IP Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: :
: Sub-TLVs :
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
The type and length of the address found in the in the Destination
IP Address and Next Hop IP Addresses fields. The values are shared
with the Downstream Mapping Address Type Registry.
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The type codes applicable in this case appear in the table below:
Address Family Type Length
IPv4 1 4
IPv6 3 16
Reply mode
The reply mode to be sent in the MPLS Echo Request message; the
values are as specified in [RFC4379].
Proxy Flags
The Proxy Request Initiator sets zero, one or more of these flags
to request actions at the Proxy LSR.
0x01 Request for FEC Neighbor Address info
When set, this requests that the Proxy LSR supply the
Upstream and Downstream neighbor address information in the
MPLS Proxy Ping Reply message. This flag is only applicable
for the topmost FEC in the FEC stack if the FEC type
corresponds with a P2MP or MP2MP LSP. The Proxy LSR MUST
respond as applicable with Upstream Neighbor Address and
Downstream Neighbor Address TLV(s) in the MPLS Proxy Ping
Reply message. The Upstream Neighbor Address TLV needs be
included only if there is an upstream neighbor. Similarly,
one Downstream Neighbor Address TLV needs to be included for
each Downstream Neighbor from which the LSR learned
bindings.
Setting this flag will cause the Proxy LSR to cancel sending
any MPLS Echo Request. The initiator may use information
learned from the MPLS Proxy Ping Reply that is sent instead
to generate subsequent proxy requests.
0x02 Request for Downstream Mapping
When set, this requests that the Proxy LSR supply a
Downstream Mapping TLV see [RFC4379] in the MPLS Proxy Ping
Reply message. Either this flag may be set or the Request
for Downstream Detailed Mapping flag may be set, but not
both.
Setting this flag will cause the Proxy LSR to cancel sending
an Echo request. Information learned with such Proxy Reply
may be used by the Proxy initiator to generate subsequent
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Proxy Requests.
0x04 Request for Downstream Detailed Mapping
When set, this requests that the Proxy LSR supply a
Downstream Detailed Mapping TLV see [RFC6424] in the MPLS
Proxy Ping Reply message. It's not valid to have Request for
Downstream Mapping flag set when this flag is set. Setting
this flag will cause the Proxy LSR to cancel sending an Echo
request. The initiator may use information learned from the
MPLS Proxy Ping Reply that is sent instead to generate
subsequent proxy requests.
0x08 Explicit DSCP Request
When set, this requests that the Proxy LSR use the supplied
"Rqst'd DSCP" byte in the Echo Request message
TTL
The TTL to be used in the label stack entry corresponding to
the topmost FEC in the in the MPLS Echo Request packet. Valid
values are in the range [1,255]. A setting of 0 SHOULD be
ignored by the Proxy LSR.
Requested DSCP
This field is valid only if the Explicit DSCP flag is set. If
not set, the field MUST be zero on transmission and ignored on
receipt. When the flag is set, this field contains the DSCP
value to be used in the MPLS Echo Request packet IP header.
Source UDP Port
The source UDP port to be sent in the MPLS Echo Request packet
Global Flags
The Global Flags to be sent in the MPLS Echo Request message
MPLS Payload Size
Used to request that the MPLS payload (IP header + UDP header +
MPLS Echo Request) be padded using a zero filled Pad TLV so
that the IP header, UDP header and MPLS Echo Request total the
specified size. Field set to zero means no size request is
being made. If the requested size is less than the minimum size
required to form the MPLS Echo Request, the request will be
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treated as a best effort request with the Proxy LSR building
the smallest possible packet (i.e. not using a Pad TLV). The IP
header DF bit MUST be set when this field is non zero.
Destination IP Address
If the Address Type is IPv4, an address from the range 127/8;
If the Address Type is IPv6, an address from the range
::FFFF:7F00:0/104
Sub-TLVs
List of TLV-encoded sub-TLVs. Currently one is defined.
Sub-TLV Type Length Value Field
------------ ------ -----------
<TBA-13> 8+ Next Hop
5.1.1. Next Hop sub-TLV
This sub-TLV is used to describe a particular next hop towards which
the Echo Request packet should be sent. If the topmost FEC in the
FEC-stack is a multipoint LSP, this sub-TLV may appear multiple
times.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Type | MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop Interface (0, 4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
Type Type of Next Hop Addr Length IF Length
1 IPv4 Numbered 4 4
2 IPv4 Unnumbered 4 4
3 IPv6 Numbered 16 16
4 IPv6 Unnumbered 16 4
5 Reserved
TBA-11 IPv4 Protocol Adj 4 0
TBA-12 IPv6 Protocol Adj 16 0
Note: Types 1-4 correspond to the types in the DS Mapping TLV.
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They are expected to populated with information obtained
through a previously returned DS Mapping TLV. Types
<TBA-11> and <TBA-12> are intended to be populated
from the local address information obtained from a
previously returned Downstream Neighbor Address
TLV(s)/Upstream Neighbor Address TLV.
Next Hop IP Address
A next hop address that the echo request message is to
be sent towards
Next Hop Interface
Identifier of the interface through which the echo request
message is to be sent. For Addr Type 5, and 6, the Next Hop
interface field isn't used and MUST be of an associated byte
length of "0" octets.
5.2. Reply-to Address TLV
Used to specify the MPLS Echo Request IP source address. This address
MUST be IP reachable via the Proxy LSR; otherwise it will be
rejected.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Reply-to Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
A type code as specified in the table below:
Type Type of Address
1 IPv4
3 IPv6
5.3. Upstream Neighbor Address TLV
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
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Upst Addr Type |Local Addr Type| MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Upstream Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Local Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Upst Addr Type; Local Addr Type
These two fields determine the type and length of the
respective addresses. The codes are specified in the table
below:
Type Type of Address Length
0 No Address Supplied 0
1 IPv4 4
3 IPv6 16
Upstream Address
The address of the immediate upstream neighbor for the topmost
FEC in the FEC stack. If protocol adjacency exists by which the
label for this FEC was exchanged, this address MUST be the
address used in that protocol exchange.
Local Address
The local address used in the protocol adjacency exists by
which the label for this FEC was exchanged.
5.4. Downstream Neighbor Address TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Dnst Addr Type |Local Addr Type| MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Downstream Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
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: Local Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Dnst Addr Type; Local Addr Type
These two fields determine the type and length of the
respective addresses. The codes are specified in the table
below:
Type Type of Address Length
0 No Address Supplied 0
1 IPv4 4
3 IPv6 16
Downstream Address
The address of a immediate downstream neighbor for the topmost
FEC in the FEC stack. If protocol adjacency exists by which the
label for this FEC was exchanged, this address MUST be the
address used in that protocol exchange.
Local Address
The local address used in the protocol adjacency exists by
which the label for this FEC was exchanged.
6. Security Considerations
The mechanisms described in this document are intended to be used
within a Service Provider network and to be initiated only under the
authority of that administration.
If such a network also carries Internet traffic, or permits IP access
from other administrations, MPLS Proxy Ping message SHOULD be
discarded at the points that where the IP packet is received from the
other administrations. This can be accomplished by filtering on
source address or by filtering all MPLS ping messages on UDP port.
Any node which acts as a Proxy LSR SHOULD validate requests against a
set of valid source addresses. An implementation MUST provide such
filtering capabilities.
MPLS Proxy Ping Request messages are IP addressed directly to the
Proxy LSR. If a Proxy LSR receives an MPLS Proxy Ping message via
expiration of the IP or Label Stack Entry TTL, it MUST NOT be acted
upon.
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If an MPLS Proxy Ping Request IP source address is not IP reachable
by the Proxy LSR, the Proxy Request MUST NOT be acted upon.
MPLS Proxy Ping Requests are limited to making their request via the
specification of a FEC. This ensures that only valid MPLS Echo
Request messages can be created. No label spoofing attacks are
possible.
7. Acknowledgements
The authors would like to thank Nobo Akiya, Adrian Farrel, Tom Yu,
Tom Taylor and Warren Kumari for their detailed review and insightful
comments.
8. IANA Considerations
This document makes the following assignments (pending IANA action)
MPLS LSP Ping Message Types
Type Value Field
---- -----------
TBA-1 MPLS Proxy Ping Request
TBA-2 MPLS Proxy Ping Reply
TLVs
Type Value Field
---- -----------
TBA-3 Proxy Echo Parameters
TBA-4 Reply-to Address
TBA-5 Upstream Neighbor Address
TBA-6 Downstream Neighbor Address
Return Code [pending IANA assignment]
Value Meaning
----- -------
TBA-7 Proxy Ping not authorized.
TBA-8 Proxy Ping parameters need to be modified.
TBA-9 MPLS Echo Request Could not be sent.
TBA-10 Replying router has FEC mapping for topmost FEC.
8.1. Proxy Echo Parameters Sub-TLVs
The IANA will create and maintain this new registry for Proxy Echo
Parameters Sub-TLV's. Assignments will use the same rules spelled out
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in sec 7.2 of [RFC4379].
Sub-TLV Type Meaning
----------- -------
0 Reserved
TBA-13 Next Hop
8.2. Downstream Address Mapping Registry [pending IANA assignment]
This document makes the following assignments in the Downstream
Address Mapping Registry(pending IANA assignment). This document
updates the registry defined by [RFC6426], modifying the allocation
procedures.
The allocation procedures of Downstream Mapping Address Type Registry
is changed to read 'Standards action - each time a code point is
assigned from this registry, unless the same registration is made in
both registries, the corresponding Next Hop Address Type Registry
must be Marked "Reserved".
Value Meaning K Octets
----- ------- --------
TBA-11 Reserved N/A [this doc]
TBA-12 Reserved N/A [this doc]
8.3. Next Hop Sub-TLV Address Type Registry
IANA is requested to create a new registry called "Next Hop Address
Type Registry". The allocation policy for this registry is
"Standards action". Further, each time a code point is assigned from
this registry, unless the same registration is made in both
registries, the corresponding Downstream Address Mapping Registry
must be Marked "Reserved". The initial allocations are:
Type Type of Next Hop Addr Length IF Length Reference
1 IPv4 Numbered 4 4 [RFC4379]
2 IPv4 Unnumbered 4 4 [RFC4379]
3 IPv6 Numbered 16 16 [RFC4379]
4 IPv6 Unnumbered 16 4 [RFC4379]
5 Reserved [this doc]
TBA-11 IPv4 Protocol Adj 4 0 [this doc]
TBA-12 IPv6 Protocol Adj 16 0 [this doc]
x-255 Unassigned
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
Performing Label Switched Path Ping (LSP Ping) over MPLS
Tunnels", RFC 6424, November 2011.
[RFC6425] Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa,
S., and T. Nadeau, "Detecting Data-Plane Failures in
Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC
6425, November 2011.
[RFC6426] Gray, E., Bahadur, N., Boutros, S., and Aggarwal, R.,
"MPLS On-Demand Connectivity Verification and Route
Tracing", RFC 6426, November 2011.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and Delord, S.,
"Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, January 2014.
9.2. Informative References
[RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
Authors' Addresses
George Swallow
Cisco Systems
1414 Massachusetts Ave
Boxborough, MA 01719
USA
Email: swallow@cisco.com
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Vanson Lim
Cisco Systems
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: vlim@cisco.com
Sam Aldrin
Huawei Technologies
2330 Central Express Way
Santa Clara, CA 95951
USA
Email: aldrin.ietf@gmail.com
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