ippm R. Geib, Ed.
Internet-Draft Deutsche Telekom
Intended status: Standards Track December 23, 2020
Expires: June 26, 2021
A Connectivity Monitoring Metric for IPPM
draft-ietf-ippm-connectivity-monitoring-00
Abstract
Within a Segment Routing domain, segment routed measurement packets
can be sent along pre-determined paths. This enables new kinds of
measurements. Connectivity monitoring allows to supervise the state
and performance of a connection or a (sub)path from one or a few
central monitoring systems. This document specifies a suitable
type-P connectivity monitoring metric.
Status of This Memo
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This Internet-Draft will expire on June 26, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. A brief segment routing connectivity monitoring framework . . 4
3. Network topology requirements . . . . . . . . . . . . . . . . 9
4. Singleton Definition for Type-P-SR-Path-Connectivity-and-
Congestion . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 10
4.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Definition . . . . . . . . . . . . . . . . . . . . . . . 10
4.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . 11
4.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 11
4.7. Errors and Uncertainties . . . . . . . . . . . . . . . . 13
4.8. Reporting the Metric . . . . . . . . . . . . . . . . . . 13
5. Singleton Definition for Type-P-SR-Path-Round-Trip-Delay-
Estimate . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
Within a Segment Routing domain, measurement packets can be sent
along pre-determined segment routed paths [RFC8402]. A segment
routed path may consist of pre-determined sub paths, specific router-
interfaces or a combination of both. A measurement path may also
consist of sub paths spanning multiple routers, given that all
segments to address a desired path are available and known at the SR
domain edge interface.
A Path Monitoring System or PMS (see [RFC8403]) is a dedicated
central Segment Routing (SR) domain monitoring device (as compared to
a distributed monitoring approach based on router-data and -functions
only). Monitoring individual sub-paths or point-to-point connections
is executed for different purposes. IGP exchanges hello messages
between neighbors to keep alive routing and swiftly adapt routing to
topology changes. Network Operators may be interested in monitoring
connectivity and congestion of interfaces or sub-paths at a timescale
of seconds, minutes or hours. In both cases, the periodicity is
significantly smaller than commodity interface monitoring based on
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router counters, which may be collected on a minute timescale to keep
the processor- or monitoring data-load low.
The IPPM architecture was a first step to that direction [RFC2330].
Commodity IPPM solutions require dedicated measurement systems, a
large number of measurement agents and synchronised clocks.
Monitoring a domain from edge to edge by commodity IPPM solutions
increases scalability of the monitoring system. But localising the
site of a detected change in network behaviour may then require
network tomography methods.
The IPPM Metrics for Measuring Connectivity offer generic
connectivity metrics [RFC2678]. These metrics allow to measure
connectivity between end nodes without making any assumption on the
paths between them. The metric and the type-p packet specified by
this document follow a different approach: they are designed to
monitor connectivity and performance of a specific single link or a
path segment. The underlying definition of connectivity is partially
the same: a packet not reaching a destination indicates a loss of
connectivity. An IGP re-route may indicate a loss of a link, while
it might not cause loss of connectivity between end systems. The
metric specified here detects a link-loss, if the change in end-to-
end delay along a new route is differing from that of the original
path.
A Segment Routing PMS is part of an SR domain. The PMS is IGP
topology aware, covering the IP and (if present) the MPLS layer
topology [RFC8402]. This allows to steer PMS measurement packets
along arbitrary pre-determined concatenated sub-paths, identified by
suitable Segment IDs. Basically, the SR connectivity metric as
specified by this document requires set up of a number of
constrained, overlaid measurement loops (or measurement paths). The
delay of the packets sent along each of these measurement loops is
measured. A single congested interface or a single loss of
connectivity of a monitored sub-path cause a delay change on several
measurement paths. Any single evnet of that type on one of the
monitored sub-paths changes delays of a unique subset of measurement
loops. The number of measurement loops may be limited to one per
sub-path (or connection) to be monitored, if a hub-and-spoke like
sub-path topology as described below is monitored. In addition to
information revealed by a commodity ICMP ping measurement, the
metrics and methods specified here identify the location of a
congested interface. To do so, tomography assumptions and methods
are combined to first plan the overlaid SR measurement loop set up
and later on to evaluate the captured delay measurements.
There's another difference as compared with commodity ping: the
measurement loop packets remain in the data plane of passed routers.
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These need to forward the measurement packets without additional
processing apart from that.
It is recommended to consider automated measurement loop set-ups.
The methods proposed here are error-prone if the topology and
measurement loop design isn't followed properly. While details of an
automated set-up are not within scope of this document, some formal
defintions of constraints to respected are given.
This document specifies a type-p metric determining properties of an
SR path which allows to monitor connectivity and congestion of
interfaces and further allows to locate the path or interface which
caused a change in the reported type-p metric. This document is
limited on the MPLS layer, but the methodology may be applied within
SR domains or MPLS domains in general.
1.1. 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 RFC 2119 [RFC2119].
2. A brief segment routing connectivity monitoring framework
The Segment Routing IGP topology information consists of the IP and
(if present) the MPLS layer topology. The minimum SR topology
information consists of Node-Segment-Identifiers (Node-SID),
identifying an SR router. The IGP exchange of Adjacency-SIDs
[RFC8667], which identify local interfaces to adjacent nodes, is
optional. It is RECOMMENDED to distribute Adj-SIDs in a domain
operating a PMS to monitor connectivity as specified below. If Adj-
SIDs aren't availbale, [RFC8029] provides methods how to steer
packets along desired paths by the proper choice of an MPLS Echo-
request IP-destination address. A detailed description of [RFC8029]
methods as a replacement of Adj-SIDs is out of scope of this
document.
An active round trip measurement between two adjacent nodes is a
simple method to monitor connectivity of a connecting link. If
multiple links are operational between two adjacent nodes and only a
single one fails, a single plain round trip measurement may fail to
notice that or identify which link has failed. A round trip
measurement also fails to identify which interface is congested, even
if only a single link connects two adjacent nodes.
Segment Routing enables the set-up of extended measurement loops.
Several different measurement loops can be set up to form a partial
overlay. If done properly, any network change impacts more than a
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single measurement loop's round trip delay (or causes drops of
packets of more than one loop). Randomly chosen measurement loop
paths including the interfaces or paths to be monitored may fail to
produce the desired unique result patterns, hence commodity network
tomography methods aren't applicable here [CommodityTomography]. The
approach pursued here uses a pre-specified measurement loop overlay
design.
A centralised monitoring approach doesn't require report collection
and result correlation from two (or more) receivers (the measured
delays of different measurement loops still need to be correlated).
An additional property of the measurement path set-up specified below
is that it allows to estimate the packet round trip and the one way
delay of a monitored sub-path. The delay along a single link is not
perfectly symmetric. Packet processing causes small delay
differences per interface and direction. These cause an error, which
can't be quantified or removed by the specified method. Quantifying
this error requires a different measurement set-up. As this will
introduce additional measurements loops, packets and evaluations, the
cost in terms of reduced scalability is not felt to be worth the
benefit in measurement accuracy. IPPM metrics prefer precision to
accuracy and the mentioned processing differences are relatively
stable, resulting in relatively precise delay estimates for each
monitored sub-path.
An example hub and spoke network, operated as SR domain, is shown
below. The included PMS shown is supposed to monitor the
connectivity of all 6 links (a very generic kind of sub-path)
attaching the spoke-nodes L050, L060 and L070 to the hub-nodes L100
and L200.
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+---+ +----+ +----+
|PMS| |L100|-----|L050|
+---+ +----+\ /+----+
| / \ \_/_____
| / \ / \+----+
+----+/ \/_ +----|L060|
|L300| / |/ +----+
+----+\ / /\_
\ / / \
\+----+ / +----+
|L200|-----|L070|
+----+ +----+
Hub and spoke connectivity verification with a PMS
Figure 1
The SID values are picked for convenient reading only. Node-SID: 100
identifies L100, Node-SID: 300 identifies L300 and so on. Adj-SID
10050: Adjacency L100 to L050, Adj-SID 10060: Adjacency L100 to L060,
Adj-SID 60200: Adjacency L60 to L200 and so on (note that the Adj-SID
are locally assigned per node interface, meaning two per link).
Monitoring the 6 links between hub nodes Ln00 (where n=1,2) and spoke
nodes L0m0 (where m=5,6,7) requires 6 measurement loops, which have
the following properties:
o Each measurement loop follows a single round trip from one hub
Ln00 to one spoke L0m0 (e.g., between L100 and L050).
o Each measurement loop passes two more links: one between the same
hub Ln00 and another spoke L0m0 and from there to the alternate
hub Ln00 (e.g., between L100 and L060 and then from L060 to L200)
o Every monitored link is passed by a single round trip measurement
loop only once and further only once unidirectional by two other
loops. These unidirectional mearurement loop sections forward
packets in opposing direction along the monitored link. In the
end, three measurement loops pass each single monitored link (sub-
path). In figure 1, e.g., one measurement loop having a round
trip L100 to L050 and back (M1, see below), a second loop passing
L100 to L050 only (M3) and a third loop passing L050 to L100 only
(M6).
Note that any 6 links connecting two to five nodes can be monitored
that way too. Further note that the measurement loop overlay chosen
is optimised for 6 links and a hub and spoke topology of two to five
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nodes. The 'one measurement loop per measured sub-path' paradigm
only works under these conditions.
The above overlay scheme results in 6 measurement loops for the given
example. The start and end of each measurement loop is PMS to L300
to L100 or L200 and a similar sub-path on the return leg. These
parts of the measurement loops are omitted here for brevity (some
discussion may befound below). The following delays are measured
along the SR paths of each measurement loop:
1. M1 is the delay along L100 -> L050 -> L100 -> L060 -> L200
2. M2 is the delay along L100 -> L060 -> L100 -> L070 -> L200
3. M3 is the delay along L100 -> L070 -> L100 -> L050 -> L200
4. M4 is the delay along L200 -> L050 -> L200 -> L060 -> L100
5. M5 is the delay along L200 -> L060 -> L200 -> L070 -> L100
6. M6 is the delay along L200 -> L070 -> L200 -> L050 -> L100
An example for a stack of a loop consisting of Node-SID segments
allowing to caprture M1 is (top to bottom): 100 | 050 | 100 | 060 |
200 | PMS.
An example for a stack of Adj-SID segments the loop resulting in M1
is (top to bottom): 100 | 10050 | 50100 | 10060 | 60200 | PMS. As
can be seen, the Node-SIDs 100 and PMS are present at top and bottom
of the segment stack. Their purpose is to transport the packet from
the PMS to the start of the measurement loop at L100 and return it to
the PMS from its end.
The Evaluation of the measurement loop Round Trip Delays M1 - M6
allow to detect the follwing state-changes of the monitored sub-
paths:
o If the loops are set up using Node-SIDs only, any single complete
loss of connectivity caused by a failing single link between any
Ln00 and any L0m0 node briefly disturbs (and changes the measured
delay) of three loops. The traffic to the Node-SIDs is rerouted
(in the case of a single links loss, no node is completely
disconnected in the example network).
o If the loops are set up using Adj-SIDs only, any single complete
loss of connectivity caused by a failing single link between any
Ln00 and any L0m0 node terminates the traffic along three
measurement loops. The packets of all three loops will be
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dropped, until the link gets back into service. Traffic to Adj-
SIDs is not rerouted. Note that Node-SIDs may be used to foward
the measurement packets from the PMS to the hub node, where the
first sub-path to be monitored begins and from the hub node,
receiving the measurement from the last monitored sub path, to the
PMS.
o Any congested single interface between any Ln00 and any L0m0 node
only impacts the measured delay of two measurement loops.
o As an example, the formula for a single link (sub-path) Round Trip
Delay (RTD) is shown here 4 * RTD_L100-L050-L100 = 3 * M1 + M3 +
M6 - M2 - M4 - M5. This formula is reproducible for all other
links: sum up 3*RTD measured along the loop passing the monitored
link of interest in round trip fashion, and add the RTDs of the
two measurement loops passing the link of interest only in a
single direction. From this sum subtract the RTD measured on all
loops not passing the monitored link of interest to get four times
the RTD of the monitored link of interest.
A closer look reveals that each single event of interest for the
proposed metric, which are a loss of connectivity or a case of
congestion, uniquely only impacts a single set of measurement loops
which can be determined a-priori. If, e.g., connectivity is lost
between L200 and L050, measurement loops (3), (4) and (6) indicate a
change in the measured delay.
As a second example: if the interface L070 to L100 is congested,
measurement loops (3) and (5) indicate a change in the measured
delay. Without listing all events, all cases of single losses of
connectivity or single events of congestion influence only delay
measurements of a unique set of measurement loops.
Assume that the measurement loops are set up while there's no
congestion. In that case, the congestion free RTDs of all monitored
links can be calculated as shown above. A single congestion event
adds queuing delay to the RTD measured by two specific measurement
loops. The two measurement loops impacted allow to distinct the
congested interface and calculation of the queue-depth in terms of
seconds. As an example, assume a queue of an average depth of 20 ms
to build up at interface L200 to L070 after the uncongested
measurement interval T0. The measurement loops M5 and M6 are the
only ones passing the interface in that direction. Both indicate a
congestion M5 and M6 of + 20 ms during measurement interval T1, while
M1-4 indicate no change. The location of the congested interface is
determined by the combination of the two (and only two) measurement
loops M5 and M6 showing an increased delay. The average queue depth
= ( M5[T1] - M5[T0] + M5[T1] - M5[T0] )/2.
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As mentioned there's a constant delay added for each measurement
loop, which is the delay of the path transversed from PMS -> L100 +
L200 -> PMS. Please note, that this added delay is appearing twice
in the formula resulting in the monitored link delay estimate of the
example network. Then it is the RTD PMS -> L100 + RTD L200 -> PMS.
Both RTDs can be directly measured by two additional measurements
Cor1 = RTD ( PMS -> L100 -> PMS) and Cor2 = RTD (PMS -> L200 -> PMS).
The monitored link RTD formula was linkRTDuncor = 3*Mx + My + Mz - Ms
- Mt - Mu. The correct 4*linkRTDx = 4*linkRTDxuncor - Cor1 - Cor2.
If the interface between PMS and L100/L200 is congested, all
measurements loops M1-M6 as well as Cor1 and Cor2 will see a change.
A congested interface of a monitored link doesn't impact the RTDs
captured by Cor1 and Cor2.
The measurement loops may also be set up between hub nodes L100 and
L200, if that's preferred and supported by the nodes. In that case,
the above formulas apply without correction.
3. Network topology requirements
The metric and methods specified below can be applied in networks
with a hub and spoke topology. A single network change of type loss
of connectivity or congestion can be detected. The nodes don't have
to be hubs or spokes, this is just a topology requirement. In
detail, the topology MUST meet the following constraints:
o The SR domain sub-paths to be monitored create a hub and spoke
topology with a PMS connected to all hub nodes. The PMS may
reside in a hub.
o Exactly 6 (six) sub-paths are monitored.
o The monitored sub-paths connect at least two and no more than 5
nodes.
o Every spoke node MUST have at least one path to every hub node.
o Every spoke node MUST at least be connected to one (or more) hub
node(s) by two monitored sub-paths.
o Sub-paths between spokes can't be monitored and therefore are out
of scope (the overlay measurement loops can't be set up as
desired).
Shared resources, like a Shared Risk Link Group (e.g., a single fiber
bundle) or a shared queue passed by several logical links need to be
considered during set up. Shared resources may either be desired or
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to be avoided. As an example, if a set of logical links share one
parental scheduler queue, it is sufficient to monitor a single
logical connection to monitor the state of that parental scheduler.
4. Singleton Definition for Type-P-SR-Path-Connectivity-and-Congestion
4.1. Metric Name
Type-P-SR-SubPath-Connectivity
4.2. Metric Parameters
o Src, the IP address of a source host
o Dst, the IP address of a destination host if IP routing is
applicable; in the case of MPLS routing, a diagnostic address as
specified by [RFC8029]
o T, a time
o L, a packet length in bits. The packets of a Type P packet stream
from which the sample Path-Connectivity-and-Congestion metric is
taken MUST all be of the same length.
o MLA, a stack of Segment IDs determining a Monitoring Loop. The
Segment-IDs MUST be chosen so that a singleton type-p packet
passes one single monitored sub-path_a bidirectional, one
monitored sub-path_b unidirectional and one monitored sub-path_c
unidirectional, where sub-path_a, -_b and -_c MUST NOT be
identical and MUST NOT share properties to be monitored.
o P, the specification of the packet type, over and above the source
and destination addresses
o DS, a constant time interval between two type-P packets in unit
seconds
4.3. Metric Units
A sequence of consecutive time values.
4.4. Definition
A moving average of AV time values per measurement path is compared
by a change point detection algorithm. The temporal packet spacing
value DS represents the smallest period within which a change in
connectivity or congestion may be detected.
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A single loss of connectivity of a sub-path between two nodes affects
three different measurement paths. Depending on the value chosen for
DS, packet loss might occur (note that the moving average evaluation
needs to span a longer period than convergence time; alternatively,
packet-loss visible along the three measurement paths may serve as an
evaluation criterium). After routing convergence the type-p packets
along the three measurement paths show a change in delay.
A congestion of a single interface of a sub-path connecting two nodes
affects two different measurement paths. The the type-p packets
along the two congested measurement paths show an additional change
in delay.
4.5. Discussion
Detection of a multiple losses of monitored sub-path connectivity or
congestion of a multiple monitored sub-paths may be possible. These
cases have not been investigated, but may occur in the case of Shared
Risk Link Groups. Monitoring Shared Risk LinkGroups and sub-paths
with multiple failures abd congestion is not within scope of this
document.
4.6. Methodologies
For the given type-p, the methodology is as follows:
o The set of measurement paths MUST be routed in a way that each
single loss of connectivity and each case of single interface
congestion of one of the sub-paths passed by a type-p packet
creates a unique pattern of type-p packets belonging to a subset
of all configured measurement paths indicate a change in the
measured delay. As a minimum, each sub-path to be monitored MUST
be passed
o
* by one measurement_path_1 and its type-p packet in
bidirectional direction
* by one measurement_path_2 and its type-p packet in "downlink"
direction
* by one measurement_path_3 and its type-p packet in "uplink"
direction
o "Uplink" and "Downlink" have no architectural relevance. The
terms are chosen to express, that the packets of
measurement_path_2 and measuremnt_path_3 pass the monitored sub-
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path unidirectional in opposing direction. Measuremnt_path_1,
measurement_path_2 and measurement_path_3 MUST NOT be identical.
o All measurement paths SHOULD terminate between identical sender
and receiver interfaces. It is recommended to connect the sender
and receiver as closely to the paths to be monitored as possible.
Each intermediate sub-path between sender and receiver one one
hand and sub-paths to be monitored is an additional source of
errors requiring separate monitoring.
o Segment Routed domains supporting Node- and Adj-SIDs should enable
the monitoring path set-up as specified. Other routing protocols
may be used as well, but the monitoring path set up might be
complex or impossible.
o Pre-compute how the two and three measurement path delay changes
correlate to sub-path connectivity and congestion patterns.
Absolute change valaues aren't required, a simultaneous change of
two or three particular measurement paths is.
o Ensure that the temporal resolution of the measurement clock
allows to reliably capture a unique delay value for each
configured measurement path while sub-path connectivity is
complete and no congestion is present.
o Synchronised clocks are not strictly required, as the metric is
evaluating differences in delay. Changes in clock synchronisation
SHOULD NOT be close to the time interval within which changes in
connectivity or congestion should be monitored.
o At the Src host, select Src and Dst IP addresses, and address
information to route the type-p packet along one of the configured
measurement path. Form a test packet of Type-P with these
addresses.
o Configure the Dst host access to receive the packet.
o At the Src host, place a timestamp, a sequence number and a unique
identifier of the measurement path in the prepared Type-P packet,
and send it towards Dst.
o Capture the one-way delay and determine packet-loss by the metrics
specified by [RFC7679] and [RFC7680] respectively and store the
result for the path.
o If two or three subpaths indicate a change in delay, report a
change in connectivity or congestion status as pre-computed above.
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o If two or three sub paths indicate a change in delay, report a
change in connectivity or congestion status as pre-computed above.
Note that monitoring 6 sub paths requires setting up 6 monitoring
paths as shown in the figure above.
4.7. Errors and Uncertainties
Sources of error are:
o Measurement paths whose delays don't indicate a change after sub-
path connectivity changed.
o A timestamps whose resolution is missing or inacurrate at the
delays measured for the different monitoring paths.
o Multiple occurrences of sub path connectivity and congestion.
o Loss of connectivity and congestion along sub-paths connecting the
measurement device(s) with the sub-paths to be monitored.
4.8. Reporting the Metric
The metric reports loss of connectivity of monitored sub-path or
congestion of an interface and identifies the sub-path and the
direction of traffic in the case of congestion.
The temporal resolution of the detected events depends on the spacing
interval of packets transmitted per measurement path. An identical
sending interval is chosen for every measurement path. As a rule of
thumb, an event is reliably detected if a sample consists of at least
5 probes indicating the same underlying change in behavior.
Depending on the underlying event either two or three measurement
paths are impacted. At least two consecutively received measurement
packets per measurement path should suffice to indicate a change.
The values chosen for an operational network will have to reflect
scalability constraints of a PMS measurement interface. As an
example, a PMS may work reliable if no more than one measurement
packet is transmitted per millisecond. Further, measurement is
configured so that the measurement packets return to the sender
interface. Assume always groups of 6 links to be monitored as
described above by 6 measurements paths. If one packet is sent per
measurement path within 500 ms, up to 498 links can be monitored with
a reliable temporal resolution of roughly one second per detected
event.
Note that per group measurement packet spacing, measurement loop
delay difference and latency caused by congestion impact the
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reporting interval. If each measurement path of a single 6 link
monitoring group is addressed in consecutive milliseconds (within the
500 ms interval) and the sum of maximum physical delay of the per
group measurement paths and latency possibly added by congestion is
below 490 ms, the one second reports reliably capture 4 packets of
two different measurement paths, if two measurement paths are
congested, or 6 packets of three different measurement paths, if a
link is lost.
A variety of reporting options exist, if scalability issues and
network properties are respected.
5. Singleton Definition for Type-P-SR-Path-Round-Trip-Delay-Estimate
This section will be added in a later version, if there's interest in
picking up this work.
6. IANA Considerations
If standardised, the metric will require an entry in the IPPM metric
registry.
7. Security Considerations
This draft specifies how to use methods specified or described within
[RFC8402] and [RFC8403]. It does not introduce new or additional SR
features. The security considerations of both references apply here
too.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
Connectivity", RFC 2678, DOI 10.17487/RFC2678, September
1999, <https://www.rfc-editor.org/info/rfc2678>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Delay Metric for IP Performance Metrics
(IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
2016, <https://www.rfc-editor.org/info/rfc7679>.
Geib Expires June 26, 2021 [Page 14]
Internet-Draft Abbreviated Title December 2020
[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Loss Metric for IP Performance Metrics
(IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
2016, <https://www.rfc-editor.org/info/rfc7680>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
8.2. Informative References
[CommodityTomography]
Lakhina, A., Papagiannaki, K., Crovella, M., Diot, C.,
Kolaczyk, ED., and N. Taft, "Structural analysis of
network traffic flows", 2004,
<https://www.cc.gatech.edu/classes/AY2007/cs7260_spring/
papers/odflows-sigm04.pdf>.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
DOI 10.17487/RFC2330, May 1998,
<https://www.rfc-editor.org/info/rfc2330>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.
Author's Address
Geib Expires June 26, 2021 [Page 15]
Internet-Draft Abbreviated Title December 2020
Ruediger Geib (editor)
Deutsche Telekom
Heinrich Hertz Str. 3-7
Darmstadt 64295
Germany
Phone: +49 6151 5812747
Email: Ruediger.Geib@telekom.de
