< draft-ietf-6man-ipv6-alt-mark-08.txt   draft-ietf-6man-ipv6-alt-mark-09.txt >
6MAN Working Group G. Fioccola 6MAN Working Group G. Fioccola
Internet-Draft T. Zhou Internet-Draft T. Zhou
Intended status: Standards Track Huawei Intended status: Standards Track Huawei
Expires: January 27, 2022 M. Cociglio Expires: February 28, 2022 M. Cociglio
Telecom Italia Telecom Italia
F. Qin F. Qin
China Mobile China Mobile
R. Pang R. Pang
China Unicom China Unicom
July 26, 2021 August 27, 2021
IPv6 Application of the Alternate Marking Method IPv6 Application of the Alternate Marking Method
draft-ietf-6man-ipv6-alt-mark-08 draft-ietf-6man-ipv6-alt-mark-09
Abstract Abstract
This document describes how the Alternate Marking Method can be used This document describes how the Alternate Marking Method can be used
as a passive performance measurement tool in an IPv6 domain. It as a passive performance measurement tool in an IPv6 domain. It
defines a new Extension Header Option to encode Alternate Marking defines a new Extension Header Option to encode Alternate Marking
information in both the Hop-by-Hop Options Header and Destination information in both the Hop-by-Hop Options Header and Destination
Options Header. Options Header.
Status of This Memo Status of This Memo
skipping to change at page 1, line 40 skipping to change at page 1, line 40
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 27, 2022. This Internet-Draft will expire on February 28, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Alternate Marking application to IPv6 . . . . . . . . . . . . 3 2. Alternate Marking application to IPv6 . . . . . . . . . . . . 3
2.1. Controlled Domain . . . . . . . . . . . . . . . . . . . . 5 2.1. Controlled Domain . . . . . . . . . . . . . . . . . . . . 5
3. Definition of the AltMark Option . . . . . . . . . . . . . . 6 2.1.1. Alternate Marking Measurement Domain . . . . . . . . 6
3.1. Data Fields Format . . . . . . . . . . . . . . . . . . . 6 3. Definition of the AltMark Option . . . . . . . . . . . . . . 7
4. Use of the AltMark Option . . . . . . . . . . . . . . . . . . 7 3.1. Data Fields Format . . . . . . . . . . . . . . . . . . . 7
5. Alternate Marking Method Operation . . . . . . . . . . . . . 9 4. Use of the AltMark Option . . . . . . . . . . . . . . . . . . 8
5.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 9 5. Alternate Marking Method Operation . . . . . . . . . . . . . 10
5.2. Packet Delay Measurement . . . . . . . . . . . . . . . . 11 5.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 10
5.3. Flow Monitoring Identification . . . . . . . . . . . . . 12 5.2. Packet Delay Measurement . . . . . . . . . . . . . . . . 12
5.3.1. Uniqueness of FlowMonID . . . . . . . . . . . . . . . 13 5.3. Flow Monitoring Identification . . . . . . . . . . . . . 13
5.4. Multipoint and Clustered Alternate Marking . . . . . . . 14 5.3.1. Uniqueness of FlowMonID . . . . . . . . . . . . . . . 14
5.5. Data Collection and Calculation . . . . . . . . . . . . . 14 5.4. Multipoint and Clustered Alternate Marking . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5.5. Data Collection and Calculation . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . 18 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . 18 9.1. Normative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 9.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
[RFC8321] and [RFC8889] describe a passive performance measurement [RFC8321] and [RFC8889] describe a passive performance measurement
method, which can be used to measure packet loss, latency and jitter method, which can be used to measure packet loss, latency and jitter
on live traffic. Since this method is based on marking consecutive on live traffic. Since this method is based on marking consecutive
batches of packets, the method is often referred to as the Alternate batches of packets, the method is often referred to as the Alternate
Marking Method. Marking Method.
This document defines how the Alternate Marking Method can be used to This document defines how the Alternate Marking Method can be used to
measure performance metrics in IPv6. The rationale is to apply the measure performance metrics in IPv6. The rationale is to apply the
Alternate Marking methodology to IPv6 and therefore allow detailed Alternate Marking methodology to IPv6 and therefore allow detailed
packet loss, delay and delay variation measurements both hop-by-hop packet loss, delay and delay variation measurements both hop-by-hop
and end-to-end to exactly locate the issues in an IPv6 network. and end-to-end to exactly locate the issues in an IPv6 network.
The Alternate Marking is an on-path telemetry technique and consists The Alternate Marking is an on-path telemetry technique and consists
in synchronizing the measurements in different points of a network by of synchronizing the measurements in different points of a network by
switching the value of a marking bit and therefore divide the packet switching the value of a marking bit and therefore dividing the
flow into batches. Each batch represents a measurable entity packet flow into batches. Each batch represents a measurable entity
unambiguously recognizable by all network nodes along the path. By recognizable by all network nodes along the path. By counting the
counting the number of packets in each batch and comparing the values number of packets in each batch and comparing the values measured by
measured by different nodes, it is possible to precisely measure the different nodes, it is possible to precisely measure the packet loss.
packet loss. In a similar way the alternation of the values of the Similarly, the alternation of the values of the marking bits can be
marking bits can be used as a time reference to calculate the delay used as a time reference to calculate the delay and delay variation.
and delay variation. The Alternate Marking operation is further The Alternate Marking operation is further described in Section 5.
described in Section 5.
The format of IPv6 addresses is defined in [RFC4291] while [RFC8200] The format of IPv6 addresses is defined in [RFC4291] while [RFC8200]
defines the IPv6 Header, including a 20-bit Flow Label and the IPv6 defines the IPv6 Header, including a 20-bit Flow Label and the IPv6
Extension Headers. Extension Headers.
[I-D.fioccola-v6ops-ipv6-alt-mark] summarizes the possible This document introduces a new TLV (type-length-value) that can be
implementation options for the application of the Alternate Marking encoded in the Options Headers (Hop-by-Hop or Destination) for the
Method in an IPv6 domain. This document, starting from the outcome purpose of the Alternate Marking Method application in an IPv6
of [I-D.fioccola-v6ops-ipv6-alt-mark], introduces a new TLV (type- domain.
length-value) that can be encoded in the Options Headers (Hop-by-Hop
or Destination) for the purpose of the Alternate Marking Method
application in an IPv6 domain. While the case of Segment Routing
Header (SRH), defined in [RFC8754], is also discussed, it is valid
for all the types of Routing Header (RH).
The threat model for the application of the Alternate Marking Method The threat model for the application of the Alternate Marking Method
in an IPv6 domain is reported in Section 6. As for all the on-path in an IPv6 domain is reported in Section 6. As with all on-path
telemetry technique, the only definitive solution is that this telemetry techniques, the only definitive solution is that this
methodology MUST be applied in a controlled domain and therefore the methodology MUST be applied in a controlled domain.
application to untrusted domain is NOT RECOMMENDED.
1.1. Terminology 1.1. Terminology
This document uses the terms related to the Alternate Marking Method This document uses the terms related to the Alternate Marking Method
as defined in [RFC8321] and [RFC8889]. as defined in [RFC8321] and [RFC8889].
1.2. Requirements Language 1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Alternate Marking application to IPv6 2. Alternate Marking application to IPv6
The Alternate Marking Method requires a marking field. As mentioned, The Alternate Marking Method requires a marking field. Several
several alternatives have been analysed in alternatives could be considered such as IPv6 Extension Headers, IPv6
Address and Flow Label. But, it is necessary to analyze the
[I-D.fioccola-v6ops-ipv6-alt-mark] such as IPv6 Extension Headers, drawbacks for all the available possibilities, more specifically:
IPv6 Address and Flow Label.
[I-D.fioccola-v6ops-ipv6-alt-mark] analyzed and discussed all the
available possibilities and the drawbacks:
Reusing existing Extension Header for Alternate Marking leads to a Reusing existing Extension Header for Alternate Marking leads to a
non-optimized implementation; non-optimized implementation;
Using the IPv6 destination address to encode the Alternate Marking Using the IPv6 destination address to encode the Alternate Marking
processing is very expensive; processing is very expensive;
Using the IPv6 Flow Label for Alternate Marking conflicts with the Using the IPv6 Flow Label for Alternate Marking conflicts with the
utilization of the Flow Label for load distribution purpose utilization of the Flow Label for load distribution purpose
([RFC6438]). ([RFC6438]).
In the end, [I-D.fioccola-v6ops-ipv6-alt-mark] demonstrated that a In the end, a new Hop-by-Hop or a new Destination Option is the best
new Hop-by-Hop or a new Destination Option was the best approach. choice.
The approach for the Alternate Marking application to IPv6 specified The approach for the Alternate Marking application to IPv6 specified
in this memo is compliant with [RFC8200]. It involves the following in this memo is compliant with [RFC8200]. It involves the following
operations: operations:
o The source node is the only one that writes the Option Header to o The source node is the only one that writes the Option Header to
mark alternately the flow (for both Hop-by-Hop and Destination mark alternately the flow (for both Hop-by-Hop and Destination
Option). The intermediate nodes and destination node MUST only Option). The intermediate nodes and destination node MUST only
read the marking values of the option without modifying the Option read the marking values of the option without modifying the Option
Header. Header.
o In case of Hop-by-Hop Option Header carrying Alternate Marking o In case of Hop-by-Hop Option Header carrying Alternate Marking
bits, it is not inserted or deleted, but can be read by any node bits, it is not inserted or deleted, but can be read by any node
along the path. The intermediate nodes may be configured to along the path. The intermediate nodes may be configured to
support this Option or not and the measurement can be done only support this Option or not and the measurement can be done only
for the nodes configured to read the Option. As further discussed for the nodes configured to read the Option. As further discussed
in Section 4, the presence of the hop-by-hop option should not in Section 4, the presence of the hop-by-hop option should not
affect the traffic throughput both on nodes that do not recognize affect the traffic throughput both on nodes that do not recognize
this option and on the nodes that support it. However it is this option and on the nodes that support it. However, it is
important to mention that there is a difference between the theory worth mentioning that there is a difference between theory and
and the implementation and it can happen that packets with hop-by- practice. Indeed, in a real implementation it can happen that
hop option could also be skipped or processed in the slow path. packets with hop-by-hop option could also be skipped or processed
While some proposals are trying to address this problem in the slow path. While some proposals are trying to address this
problem and make Hop-by-Hop Options more practical
([I-D.peng-v6ops-hbh], [I-D.hinden-6man-hbh-processing]), these ([I-D.peng-v6ops-hbh], [I-D.hinden-6man-hbh-processing]), these
aspects are out of the scope for this document. aspects are out of the scope for this document.
o In case of Destination Option Header carrying Alternate Marking o In case of Destination Option Header carrying Alternate Marking
bits, it is not processed, inserted, or deleted by any node along bits, it is not processed, inserted, or deleted by any node along
the path until the packet reaches the destination node. Note the path until the packet reaches the destination node. Note
that, if there is also a Routing Header (RH), any visited that, if there is also a Routing Header (RH), any visited
destination in the route list can process the Option Header. destination in the route list can process the Option Header.
Hop-by-Hop Option Header is also useful to signal to routers on the Hop-by-Hop Option Header is also useful to signal to routers on the
path to process the Alternate Marking. However, as said, routers path to process the Alternate Marking. However, as said, routers
will examine this option if properly configured. will only examine this option if properly configured.
The optimization of both implementation and scaling of the Alternate The optimization of both implementation and scaling of the Alternate
Marking Method is also considered and a way to identify flows is Marking Method is also considered and a way to identify flows is
required. The Flow Monitoring Identification field (FlowMonID), as required. The Flow Monitoring Identification field (FlowMonID), as
introduced in Section 5.3, goes in this direction and it is used to introduced in Section 5.3, goes in this direction and it is used to
identify a monitored flow. identify a monitored flow.
The FlowMonID is different from the Flow Label field of the IPv6 The FlowMonID is different from the Flow Label field of the IPv6
Header ([RFC6437]). The Flow Label field in the IPv6 header is used Header ([RFC6437]). The Flow Label field in the IPv6 header is used
by a source to label sequences of packets to be treated in the by a source to label sequences of packets to be treated in the
network as a single flow and, as reported in [RFC6438], it can be network as a single flow and, as reported in [RFC6438], it can be
used for load-balancing/equal cost multi-path (LB/ECMP). The reuse used for load-balancing/equal cost multi-path (LB/ECMP). The reuse
of Flow Label field for identifying monitored flows is not considered of Flow Label field for identifying monitored flows is not considered
since it may change the application intent and forwarding behaviour. because it may change the application intent and forwarding behavior.
Furthermore the Flow Label may be changed en route and this may also Also, the Flow Label may be changed en route and this may also
violate the measurement task. Also, since the Flow Label is pseudo- invalidate the integrity of the measurement. Furthermore, since the
random, there is always a finite probability of collision. Those Flow Label is pseudo-random, there is always a finite probability of
reasons make the definition of the FlowMonID necessary for IPv6. collision. Those reasons make the definition of the FlowMonID
Indeed, the FlowMonID is designed and only used to identify the necessary for IPv6. Indeed, the FlowMonID is designed and only used
monitored flow. Flow Label and FlowMonID within the same packet are to identify the monitored flow. Flow Label and FlowMonID within the
totally disjoint, have different scope, identify different flows, and same packet are totally disjoint, have different scope, are used to
are intended for different use cases. identify flows based on different criteria, and are intended for
different use cases.
The rationale for the FlowMonID is further discussed in Section 5.3. The rationale for the FlowMonID is further discussed in Section 5.3.
This 20 bit field allows easy and flexible identification of the This 20 bit field allows easy and flexible identification of the
monitored flow and enables a finer granularity and improved monitored flow and enables improved measurement correlation and finer
measurement correlation. An important point that will be discussed granularity since it can be used in combination with the traditional
in Section 5.3.1 is the uniqueness of the FlowMonID and how to allow 5-tuple to identify a flow. An important point that will be
disambiguation of the FlowMonID in case of collision. discussed in Section 5.3.1 is the uniqueness of the FlowMonID and how
to allow disambiguation of the FlowMonID in case of collision.
The following section highlights an important requirement for the The following section highlights an important requirement for the
application of the Alternate Marking to IPv6. The concept of the application of the Alternate Marking to IPv6. The concept of the
controlled domain is explained and it is considered an essential controlled domain is explained and it is considered an essential
precondition, as also highlighted in Section 6. precondition, as also highlighted in Section 6.
2.1. Controlled Domain 2.1. Controlled Domain
[RFC8799] introduces the concept of specific limited domain solutions [RFC8799] introduces the concept of specific limited domain solutions
and, in this regard, it is reported the IPv6 Application of the and, in this regard, it is reported the IPv6 Application of the
Alternate Marking Method as an example. Alternate Marking Method as an example.
IPv6 has much more flexibility than IPv4 and innovative applications IPv6 has much more flexibility than IPv4 and innovative applications
have been proposed, but for a number of reasons, such as the have been proposed, but for a number of reasons, such as the
policies, options supported, the style of network management and policies, options supported, the style of network management and
security requirements, it is suggested to limit some of these security requirements, it is suggested to limit some of these
applications to a controlled domain. This is also the case of the applications to a controlled domain. This is also the case of the
Alternate Marking application to IPv6 as assumed hereinafter. Alternate Marking application to IPv6 as assumed hereinafter.
Therefore, the IPv6 application of the Alternate Marking Method MUST Therefore, the IPv6 application of the Alternate Marking Method MUST
NOT be deployed outside a controlled domain. It is RECOMMENDED that be deployed in a controlled domain. It is RECOMMENDED that an
an implementation can be able to reject packets that carry Alternate implementation rejects packets that carry Alternate Marking data and
Marking data and are entering or leaving the controlled domains. are entering or leaving the controlled domains.
Some scenarios may imply that the Alternate Marking Method is applied
outside a controlled domain, either intentionally or unintentionally, A controlled domain is a managed network where it is required to
but in these cases, IPsec authentication and encryption MUST be used. select, monitor and control the access to the network by enforcing
policies at the domain boundaries in order to discard undesired
external packets entering the domain and check the internal packets
leaving the domain. It does not necessarily mean that a controlled
domain is a single administrative domain or a single organization. A
controlled domain can correspond to a single administrative domain or
can be composed by multiple administrative domains under a defined
network management. Indeed, some scenarios may imply that the
Alternate Marking Method involves more than one domain, but in these
cases, it is RECOMMENDED that the multiple domains create a whole
controlled domain while traversing the external domain by employing
IPsec [RFC4301] authentication and encryption or other VPN technology
that provides full packet confidentiality and integrity protection.
In a few words, it must be possible to control the domain boundaries
and eventually use specific precautions if the traffic traverse the
Internet.
The security considerations reported in Section 6 also highlight this The security considerations reported in Section 6 also highlight this
requirement. requirement.
2.1.1. Alternate Marking Measurement Domain
The Alternate Marking measurement domain can overlap with the
controlled domain or may be a subset of the controlled domain. The
typical scenarios for the application of the Alternate Marking Method
depend on the controlled domain boundaries, in particular:
the user equipment can be the starting or ending node, only in
case it is fully managed and if it belongs to the controlled
domain. In this case the user generated IPv6 packets contain the
Alternate Marking data. But, in practice, this is not common due
to the fact that the user equipment cannot be totally secured in
the majority of cases.
the CPE (Customer Premises Equipment) is most likely to be the
starting or ending node since it connects the user's premises with
the service provider's network and therefore belongs to the
operator's controlled domain. Typically the CPE encapsulates a
received packet in an outer IPv6 header which contains the
Alternate Marking data. The CPE can also be able to filter and
drop packets from outside of the domain with inconsistent fields
to make effective the relevant security rules at the domain
boundaries, for example a simple security check can be to insert
the Alternate Marking data if and only if the destination is
within the controlled domain.
3. Definition of the AltMark Option 3. Definition of the AltMark Option
The definition of a new TLV for the Options Extension Headers, The definition of a new TLV for the Options Extension Headers,
carrying the data fields dedicated to the Alternate Marking method, carrying the data fields dedicated to the Alternate Marking method,
is reported below. is reported below.
3.1. Data Fields Format 3.1. Data Fields Format
The following figure shows the data fields format for enhanced The following figure shows the data fields format for enhanced
Alternate Marking TLV. This AltMark data can be encapsulated in the Alternate Marking TLV (AltMark). This AltMark data can be
IPv6 Options Headers (Hop-by-Hop or Destination Option). encapsulated in the IPv6 Options Headers (Hop-by-Hop or Destination
Option).
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | | Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowMonID |L|D| Reserved | | FlowMonID |L|D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
o Option Type: 8 bit identifier of the type of Option that needs to o Option Type: 8-bit identifier of the type of Option that needs to
be allocated. Unrecognized Types MUST be ignored on receipt. For be allocated. Unrecognized Types MUST be ignored on processing.
Hop-by-Hop Options Header or Destination Options Header, [RFC8200] For Hop-by-Hop Options Header or Destination Options Header,
defines how to encode the three high-order bits of the Option Type [RFC8200] defines how to encode the three high-order bits of the
field. The two high-order bits specify the action that must be Option Type field. The two high-order bits specify the action
taken if the processing IPv6 node does not recognize the Option that must be taken if the processing IPv6 node does not recognize
Type; for AltMark these two bits MUST be set to 00 (skip over this the Option Type; for AltMark these two bits MUST be set to 00
Option and continue processing the header). The third-highest- (skip over this Option and continue processing the header). The
order bit specifies whether or not the Option Data can change en third-highest-order bit specifies whether the Option Data can
route to the packet's final destination; for AltMark the value of change en route to the packet's final destination; for AltMark the
this bit MUST be set to 0 (Option Data does not change en route). value of this bit MUST be set to 0 (Option Data does not change en
In this way, since the three high-order bits of the AltMark Option route). In this way, since the three high-order bits of the
are set to 000, it means that nodes can simply skip this Option if AltMark Option are set to 000, it means that nodes can simply skip
they do not recognize and that the data of this Option do not this Option if they do not recognize and that the data of this
change en route, indeed the source is the only one that can write Option do not change en route, indeed the source is the only one
it. that can write it.
o Opt Data Len: 4. It is the length of the Option Data Fields of o Opt Data Len: 4. It is the length of the Option Data Fields of
this Option in bytes. this Option in bytes.
o FlowMonID: 20 bits unsigned integer. The FlowMon identifier is o FlowMonID: 20-bit unsigned integer. The FlowMon identifier is
described in Section 5.3. As further discussed below, it has been described in Section 5.3. As further discussed below, it has been
picked 20 bit since it is a reasonable value and a good compromise picked as 20 bits since it is a reasonable value and a good
in relation to the chance of collision if it is set pseudo compromise in relation to the chance of collision if it is set
randomly by the source node or set by a centralized controller. pseudo randomly by the source node or set by a centralized
controller.
o L: Loss flag for Packet Loss Measurement as described in o L: Loss flag for Packet Loss Measurement as described in
Section 5.1; Section 5.1;
o D: Delay flag for Single Packet Delay Measurement as described in o D: Delay flag for Single Packet Delay Measurement as described in
Section 5.2; Section 5.2;
o Reserved: is reserved for future use. These bits MUST be set to o Reserved: is reserved for future use. These bits MUST be set to
zero on transmission and ignored on receipt. zero on transmission and ignored on receipt.
skipping to change at page 7, line 46 skipping to change at page 8, line 36
processed only by the source and destination nodes: the source node processed only by the source and destination nodes: the source node
inserts and the destination node removes it. While, in case of Hop- inserts and the destination node removes it. While, in case of Hop-
by-Hop Option, it may be examined by any node along the path, if by-Hop Option, it may be examined by any node along the path, if
explicitly configured to do so. explicitly configured to do so.
It is important to highlight that the Option Layout can be used both It is important to highlight that the Option Layout can be used both
as Destination Option and as Hop-by-Hop Option depending on the Use as Destination Option and as Hop-by-Hop Option depending on the Use
Cases and it is based on the chosen type of performance measurement. Cases and it is based on the chosen type of performance measurement.
In general, it is needed to perform both end to end and hop by hop In general, it is needed to perform both end to end and hop by hop
measurements, and the Alternate Marking methodology allows, by measurements, and the Alternate Marking methodology allows, by
definition, both performance measurements. But, in many cases the definition, both performance measurements. In many cases the end-to-
end-to-end measurement is not enough and it is required also the hop- end measurement is not enough and it is required the hop-by-hop
by-hop measurement, so the most complete choice is the Hop-by-Hop measurement, so the most complete choice can be the Hop-by-Hop
Options Header. Options Header.
IPv6, as specified in [RFC8200], allows nodes to optionally process IPv6, as specified in [RFC8200], allows nodes to optionally process
Hop-by-Hop headers. Specifically the Hop-by-Hop Options header is Hop-by-Hop headers. Specifically the Hop-by-Hop Options header is
not inserted or deleted, but may be examined or processed by any node not inserted or deleted, but may be examined or processed by any node
along a packet's delivery path, until the packet reaches the node (or along a packet's delivery path, until the packet reaches the node (or
each of the set of nodes, in the case of multicast) identified in the each of the set of nodes, in the case of multicast) identified in the
Destination Address field of the IPv6 header. Also, it is expected Destination Address field of the IPv6 header. Also, it is expected
that nodes along a packet's delivery path only examine and process that nodes along a packet's delivery path only examine and process
the Hop-by-Hop Options header if explicitly configured to do so. the Hop-by-Hop Options header if explicitly configured to do so.
The Hop-by-Hop Option defined in this document is designed to take Another scenario that can be mentioned is the presence of a Routing
advantage of the property of how Hop-by-Hop options are processed. Header, in particular it is possible to consider SRv6. A new type of
Nodes that do not support this Option SHOULD ignore them. This can Routing Header, referred as Segment Routing Header (SRH), has been
mean that, in this case, the performance measurement does not account defined in [RFC8754] for SRv6. Like any other use case of IPv6, Hop-
for all links and nodes along a path. by-Hop and Destination Options are usable when SRv6 header is
present. Because SRv6 is implemented through a Segment Routing
Another application that can be mentioned is the presence of a Header (SRH), Destination Options before the Routing Header are
Routing Header, in particular it is possible to consider SRv6. A new processed by each destination in the route list, that means, in case
type of Routing Header, referred as SRH, has been defined for SRv6. of SRH, by every SR node that is identified by the SR path. More
Like any other use case of IPv6, Hop-by-Hop and Destination Options details about the SRv6 application are described in
are useable when SRv6 header is present. Because SRv6 is implemented [I-D.fz-spring-srv6-alt-mark].
through a Segment Routing Header (SRH), Destination Options before
the Routing Header are processed by each destination in the route
list, that means, in case of SRH, by every SR node that is identified
by the SR path. More details about the SRv6 application are
described in [I-D.fz-spring-srv6-alt-mark].
In summary, it is possible to list the alternative possibilities: In summary, it is possible to list the alternative possibilities:
o Destination Option not preceding a Routing Header => measurement o Destination Option not preceding a Routing Header => measurement
only by node in Destination Address. only by node in Destination Address.
o Hop-by-Hop Option => every router on the path with feature o Hop-by-Hop Option => every router on the path with feature
enabled. enabled.
o Destination Option preceding a Routing Header => every destination o Destination Option preceding a Routing Header => every destination
skipping to change at page 9, line 4 skipping to change at page 9, line 35
ways to implement Alternate Marking. ways to implement Alternate Marking.
It is worth mentioning that new Hop-by-Hop Options are not strongly It is worth mentioning that new Hop-by-Hop Options are not strongly
recommended in [RFC7045] and [RFC8200], unless there is a clear recommended in [RFC7045] and [RFC8200], unless there is a clear
justification to standardize it, because nodes may be configured to justification to standardize it, because nodes may be configured to
ignore the Options Header, drop or assign packets containing an ignore the Options Header, drop or assign packets containing an
Options Header to a slow processing path. In case of the AltMark Options Header to a slow processing path. In case of the AltMark
data fields described in this document, the motivation to standardize data fields described in this document, the motivation to standardize
a new Hop-by-Hop Option is that it is needed for OAM (Operations, a new Hop-by-Hop Option is that it is needed for OAM (Operations,
Administration, and Maintenance). An intermediate node can read it Administration, and Maintenance). An intermediate node can read it
or not but this does not affect the packet behavior. The source node or not, but this does not affect the packet behavior. The source
is the only one that writes the Hop-by-Hop Option to mark alternately node is the only one that writes the Hop-by-Hop Option to mark
the flow, so, the performance measurement can be done for those nodes alternately the flow, so, the performance measurement can be done for
configured to read this Option, while the others are simply not those nodes configured to read this Option, while the others are
considered for the metrics. simply not considered for the metrics.
It is important to highlight that the definition of the Hop-by-Hop The Hop-by-Hop Option defined in this document is designed to take
Options in this document is designed to minimize throughput impact advantage of the property of how Hop-by-Hop options are processed.
both on nodes that do not recognize the Option and on node that Nodes that do not support this Option SHOULD ignore them. This can
support it. Indeed, the three high-order bits of the Options Header mean that, in this case, the performance measurement does not account
defined in this draft are 000 and, in theory, as per [RFC8200] and for all links and nodes along a path. The definition of the Hop-by-
[I-D.hinden-6man-hbh-processing], this means "skip if do not Hop Options in this document is also designed to minimize throughput
impact both on nodes that do not recognize the Option and on node
that support it. Indeed, the three high-order bits of the Options
Header defined in this draft are 000 and, in theory, as per [RFC8200]
and [I-D.hinden-6man-hbh-processing], this means "skip if do not
recognize and data do not change en route". [RFC8200] also mentions recognize and data do not change en route". [RFC8200] also mentions
that the nodes only examine and process the Hop-by-Hop Options header that the nodes only examine and process the Hop-by-Hop Options header
if explicitly configured to do so. For these reasons, this HbH if explicitly configured to do so. For these reasons, this Hop-by-
Option should not affect the throughput. However, in practice, it is Hop Option should not affect the throughput. However, in practice,
important to be aware for the implementation that the things may be it is important to be aware that the things may be different in the
different and it can happen that packets with Hop-by-Hop are forced implementation and it can happen that packets with Hop-by-Hop are
onto the slow path, but this is a general issue, as also explained in forced onto the slow path, but this is a general issue, as also
[I-D.hinden-6man-hbh-processing]. explained in [I-D.hinden-6man-hbh-processing]. It is also worth
mentioning that the application to a controlled domain should avoid
the risk of arbitrary nodes dropping packets with Hop-by-Hop Options.
5. Alternate Marking Method Operation 5. Alternate Marking Method Operation
This section describes how the method operates. [RFC8321] introduces This section describes how the method operates. [RFC8321] introduces
several alternatives but in this section the most applicable methods several applicable methods which are reported below, and a new field
are reported and a new field is introduced to facilitate the is introduced to facilitate the deployment and improve the
deployment and improve the scalability. scalability.
5.1. Packet Loss Measurement 5.1. Packet Loss Measurement
The measurement of the packet loss is really straightforward. The The measurement of the packet loss is really straightforward in
comparison to the existing mechanisms, as detailed in [RFC8321]. The
packets of the flow are grouped into batches, and all the packets packets of the flow are grouped into batches, and all the packets
within a batch are marked by setting the L bit (Loss flag) to a same within a batch are marked by setting the L bit (Loss flag) to a same
value. The source node can switch the value of the L bit between 0 value. The source node can switch the value of the L bit between 0
and 1 after a fixed number of packets or according to a fixed timer, and 1 after a fixed number of packets or according to a fixed timer,
and this depends on the implementation. The source node is the only and this depends on the implementation. The source node is the only
one that marks the packets to create the batches, while the one that marks the packets to create the batches, while the
intermediate nodes only read the marking values and identify the intermediate nodes only read the marking values and identify the
packet batches. By counting the number of packets in each batch and packet batches. By counting the number of packets in each batch and
comparing the values measured by different network nodes along the comparing the values measured by different network nodes along the
path, it is possible to measure the packet loss occurred in any path, it is possible to measure the packet loss occurred in any
single batch between any two nodes. Each batch represents a single batch between any two nodes. Each batch represents a
measurable entity unambiguously recognizable by all network nodes measurable entity recognizable by all network nodes along the path.
along the path.
Both fixed number of packets and fixed timer can be used by the Both fixed number of packets and fixed timer can be used by the
source node to create packet batches. But, as also explained in source node to create packet batches. But, as also explained in
[RFC8321], using a fixed timer for the switching offers better [RFC8321], the timer-based batches are preferable because they are
more deterministic than the counter-based batches. There is no
definitive rule for counter-based batches, differently from timer-
based batches. Using a fixed timer for the switching offers better
control over the method, indeed the length of the batches can be control over the method, indeed the length of the batches can be
chosen large enough to simplify the collection and the comparison of chosen large enough to simplify the collection and the comparison of
the measures taken by different network nodes. In the implementation the measures taken by different network nodes. In the implementation
the counters can be sent out by each node to the controller that is the counters can be sent out by each node to the controller that is
responsible for the calculation. It is also possible to exchange responsible for the calculation. It is also possible to exchange
this information by using other on-path techniques. But this is out this information by using other on-path techniques. But this is out
of scope for this document. of scope for this document.
Packets with different L values may get swapped at batch boundaries, Packets with different L values may get swapped at batch boundaries,
and in this case, it is required that each marked packet can be and in this case, it is required that each marked packet can be
skipping to change at page 10, line 27 skipping to change at page 11, line 20
network delay. These can create offsets between the batches and out- network delay. These can create offsets between the batches and out-
of-order of the packets. The mathematical formula on timing aspects, of-order of the packets. The mathematical formula on timing aspects,
explained in section 3.2 of [RFC8321], must be satisfied and it takes explained in section 3.2 of [RFC8321], must be satisfied and it takes
into considerations the different causes of reordering such as clock into considerations the different causes of reordering such as clock
error and network delay. The assumption is to define the available error and network delay. The assumption is to define the available
counting interval where to get stable counters and to avoid these counting interval where to get stable counters and to avoid these
issues. Specifically, if the effects of network delay are ignored, issues. Specifically, if the effects of network delay are ignored,
the condition to implement the methodology is that the clocks in the condition to implement the methodology is that the clocks in
different nodes MUST be synchronized to the same clock reference with different nodes MUST be synchronized to the same clock reference with
an accuracy of +/- B/2 time units, where B is the fixed time duration an accuracy of +/- B/2 time units, where B is the fixed time duration
of the block. In this way each marked packet can be assigned to the of the batch, which refers to the original marking interval at the
right batch by each node. Usually the counters can be taken in the source node considering that this interval could fluctuate along the
middle of the batch period to be sure to take still counters. In a path. In this way each marked packet can be assigned to the right
few words this implies that the length of the batches MUST be chosen batch by each node. Usually the counters can be taken in the middle
of the batch period to be sure to take still counters. In a few
words this implies that the length of the batches MUST be chosen
large enough so that the method is not affected by those factors. large enough so that the method is not affected by those factors.
The length of the batches can be determined based on the specific The length of the batches can be determined based on the specific
deployment scenario. deployment scenario.
L bit=1 ----------+ +-----------+ +---------- L bit=1 ----------+ +-----------+ +----------
| | | | | | | |
L bit=0 +-----------+ +-----------+ L bit=0 +-----------+ +-----------+
Batch n ... Batch 3 Batch 2 Batch 1 Batch n ... Batch 3 Batch 2 Batch 1
<---------> <---------> <---------> <---------> <---------> <---------> <---------> <---------> <---------> <--------->
Traffic Flow Traffic Flow
===========================================================> ===========================================================>
L bit ...1111111111 0000000000 11111111111 00000000000 111111111... L bit ...1111111111 0000000000 11111111111 00000000000 111111111...
===========================================================> ===========================================================>
Figure 1: Packet Loss Measurement and Single-Marking Methodology Figure 1: Packet Loss Measurement and Single-Marking Methodology
using L bit using L bit
It is worth mentioning that the length of the batches is considered It is worth mentioning that the duration of the batches is considered
stable over time in the previous figure. In theory, it is possible stable over time in the previous figure. In theory, it is possible
to change the length of batches over time and and among different to change the length of batches over time and among different flows
flows for more flexibility. But, in practice, it could complicate for more flexibility. But, in practice, it could complicate the
the correlation of the information. correlation of the information.
5.2. Packet Delay Measurement 5.2. Packet Delay Measurement
The same principle used to measure packet loss can be applied also to The same principle used to measure packet loss can be applied also to
one-way delay measurement. Delay metrics MAY be calculated using the one-way delay measurement. Delay metrics MAY be calculated using the
two possibilities: two possibilities:
1. Single-Marking Methodology: This approach uses only the L bit to 1. Single-Marking Methodology: This approach uses only the L bit to
calculate both packet loss and delay. In this case, the D flag calculate both packet loss and delay. In this case, the D flag
MUST be set to zero on transmit and ignored by the monitoring MUST be set to zero on transmit and ignored by the monitoring
skipping to change at page 11, line 33 skipping to change at page 12, line 27
timestamp of the first packet of the new batch, that timestamp timestamp of the first packet of the new batch, that timestamp
can be compared with the timestamp of the first packet of the can be compared with the timestamp of the first packet of the
same batch on a second node to compute packet delay. But this same batch on a second node to compute packet delay. But this
measurement is accurate only if no packet loss occurs and if measurement is accurate only if no packet loss occurs and if
there is no packet reordering at the edges of the batches. A there is no packet reordering at the edges of the batches. A
different approach can also be considered and it is based on the different approach can also be considered and it is based on the
concept of the mean delay. The mean delay for each batch is concept of the mean delay. The mean delay for each batch is
calculated by considering the average arrival time of the packets calculated by considering the average arrival time of the packets
for the relative batch. There are limitations also in this case for the relative batch. There are limitations also in this case
indeed, each node needs to collect all the timestamps and indeed, each node needs to collect all the timestamps and
calculate the average timestamp for each batch. In addition the calculate the average timestamp for each batch. In addition, the
information is limited to a mean value. information is limited to a mean value.
2. Double-Marking Methodology: This approach is more complete and 2. Double-Marking Methodology: This approach is more complete and
uses the L bit only to calculate packet loss and the D bit (Delay uses the L bit only to calculate packet loss and the D bit (Delay
flag) is fully dedicated to delay measurements. The idea is to flag) is fully dedicated to delay measurements. The idea is to
use the first marking with the L bit to create the alternate flow use the first marking with the L bit to create the alternate flow
and, within the batches identified by the L bit, a second marking and, within the batches identified by the L bit, a second marking
is used to select the packets for measuring delay. The D bit is used to select the packets for measuring delay. The D bit
creates a new set of marked packets that are fully identified creates a new set of marked packets that are fully identified
over the network, so that a network node can store the timestamps over the network, so that a network node can store the timestamps
skipping to change at page 12, line 13 skipping to change at page 13, line 8
marked packet can be chosen within the available counting marked packet can be chosen within the available counting
interval that is not affected by factors such as clock errors. interval that is not affected by factors such as clock errors.
If a double-marked packet is lost, the delay measurement for the If a double-marked packet is lost, the delay measurement for the
considered batch is simply discarded, but this is not a big considered batch is simply discarded, but this is not a big
problem because it is easy to recognize the problematic batch and problem because it is easy to recognize the problematic batch and
skip the measurement just for that one. So in order to have more skip the measurement just for that one. So in order to have more
information about the delay and to overcome out-of-order issues information about the delay and to overcome out-of-order issues
this method is preferred. this method is preferred.
In summary the approach with double marking is better than the In summary the approach with double marking is better than the
approach with single marking. Moreover the two approaches can also approach with single marking. Moreover, the two approaches provide
be combined to have even more information and statistics on delay. slightly different pieces of information and the data consumer can
combine them to have a more robust data set.
Similar to what said in Section 5.1 for the packet counters, in the Similar to what said in Section 5.1 for the packet counters, in the
implementation the timestamps can be sent out to the controller that implementation the timestamps can be sent out to the controller that
is responsible for the calculation or could also be exchanged using is responsible for the calculation or could also be exchanged using
other on-path techniques. But this is out of scope for this other on-path techniques. But this is out of scope for this
document. document.
L bit=1 ----------+ +-----------+ +---------- L bit=1 ----------+ +-----------+ +----------
| | | | | | | |
L bit=0 +-----------+ +-----------+ L bit=0 +-----------+ +-----------+
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===========================================================> ===========================================================>
Figure 2: Double-Marking Methodology using L bit and D bit Figure 2: Double-Marking Methodology using L bit and D bit
Likewise to packet delay measurement (both for Single Marking and Likewise to packet delay measurement (both for Single Marking and
Double Marking), the method can also be used to measure the inter- Double Marking), the method can also be used to measure the inter-
arrival jitter. arrival jitter.
5.3. Flow Monitoring Identification 5.3. Flow Monitoring Identification
The Flow Monitoring Identification (FlowMonID) is required for some The Flow Monitoring Identification (FlowMonID) identifies the flow to
general reasons: be measured and is required for some general reasons:
o First, it helps to reduce the per node configuration. Otherwise, o First, it helps to reduce the per node configuration. Otherwise,
each node needs to configure an access-control list (ACL) for each each node needs to configure an access-control list (ACL) for each
of the monitored flows. Moreover, using a flow identifier allows of the monitored flows. Moreover, using a flow identifier allows
a flexible granularity for the flow definition. a flexible granularity for the flow definition, indeed, it can be
used together with the 5-tuple.
o Second, it simplifies the counters handling. Hardware processing o Second, it simplifies the counters handling. Hardware processing
of flow tuples (and ACL matching) is challenging and often incurs of flow tuples (and ACL matching) is challenging and often incurs
into performance issues, especially in tunnel interfaces. into performance issues, especially in tunnel interfaces.
o Third, it eases the data export encapsulation and correlation for o Third, it eases the data export encapsulation and correlation for
the collectors. the collectors.
The FlowMon identifier field is to uniquely identify a monitored flow The FlowMon identifier field is to uniquely identify a monitored flow
within the measurement domain. The field is set at the source node. within the measurement domain. The field is set at the source node.
The FlowMonID can be set in two ways: The FlowMonID can be set in two ways:
* It can be uniformly assigned by the central controller. Since * It can be assigned by the central controller. Since the
the controller knows the network topology, it can set the value controller knows the network topology, it can set the value
properly to avoid or minimize ambiguity and guarantee the properly to avoid or minimize ambiguity and guarantee the
uniqueness. uniqueness. In this regard, the controller can simply verify that
there is no ambiguity between different pseudo-randomly generated
FlowMonIDs on the same path.
* It can be algorithmically generated by the source node, that can * It can be algorithmically generated by the source node, that can
set it pseudo-randomly with some chance of collision. This set it pseudo-randomly with some chance of collision. This
approach cannot guarantee the uniqueness of FlowMonID but it may approach cannot guarantee the uniqueness of FlowMonID but it may
be preferred for local or private networks, where the conflict be preferred for local or private networks, where the conflict
probability is small due to the large FlowMonID space. probability is small due to the large FlowMonID space.
The value of 20 bits has been selected for the FlowMonID since it is The value of 20 bits has been selected for the FlowMonID since it is
a good compromise and implies a low rate of ambiguous FlowMonIDs that a good compromise and implies a low rate of ambiguous FlowMonIDs that
can be considered acceptable in most of the applications. Indeed can be considered acceptable in most of the applications. Indeed,
with 20 bits the number of combinations is 1048576. with 20 bits the number of combinations is 1048576.
if the FlowMonID is set by the source node, the intermediate nodes If the FlowMonID is set by the source node, the intermediate nodes
can read the FlowMonIDs from the packets in flight and act can read the FlowMonIDs from the packets in flight and act
accordingly. While, if the FlowMonID is set by the controller, both accordingly. While, if the FlowMonID is set by the controller, both
possibilities are feasible for the intermediate nodes which can learn possibilities are feasible for the intermediate nodes which can learn
by reading the packets or can be instructed by the controller. by reading the packets or can be instructed by the controller.
When all values in the FlowMonID space are consumed, the centralized When all values in the FlowMonID space are consumed, the centralized
controller can keep track and reassign the values that are not used controller can keep track and reassign the values that are not used
any more by old flows, while if the FlowMonID is pseudo randomly any more by old flows, while if the FlowMonID is pseudo randomly
generated by the source, conflicts and collisions are possible. generated by the source, conflicts and collisions are possible.
5.3.1. Uniqueness of FlowMonID 5.3.1. Uniqueness of FlowMonID
It is important to note that if the 20 bit FlowMonID is set It is important to note that if the 20 bit FlowMonID is set
independently and pseudo randomly there is a chance of collision. independently and pseudo randomly there is a chance of collision.
Indeed, by using the well-known birthday problem in probability Indeed, by using the well-known birthday problem in probability
theory, if the 20 bit FlowMonID is set independently and pseudo theory, if the 20 bit FlowMonID is set independently and pseudo
randomly without any additional input entropy, there is a 50% chance randomly without any additional input entropy, there is a 50% chance
of collision for 1206 flows. So, for more entropy, FlowMonID can of collision for 1206 flows. So, for more entropy, FlowMonID can
either be combined with other identifying flow information in a either be combined with other identifying flow information in a
packet (e.g. it is possible to consider the hashed 3-tuple Flow packet (e.g. it is possible to consider the hashed 3-tuple Flow
Label, Source and Destination addresses) or the FlowMonID size could Label, Source and Destination addresses).
be increased.
This issue is more visible when the FlowMonID is pseudo randomly This issue is more visible when the FlowMonID is pseudo randomly
generated by the source node and there needs to tag it with generated by the source node and there needs to tag it with
additional flow information to allow disambiguation. While, in case additional flow information to allow disambiguation. While, in case
of a centralized controller, the controller should set FlowMonID by of a centralized controller, the controller should consider these
considering these aspects and instruct the nodes properly in order to aspects and instruct the nodes properly in order to guarantee its
guarantee its uniqueness. uniqueness.
It is worth highlighting that in most of the applications a low rate It is worth highlighting that in most of the applications a low rate
of ambiguous FlowMonIDs can be acceptable, since this only affects of ambiguous FlowMonIDs can be acceptable, since this only affects
the measurement. For large scale measurements, where it is possible the measurement. For large scale measurements, where it is possible
to monitor a big number of flows, the disambiguation of the FlowMonID to monitor a big number of flows, the disambiguation of the FlowMonID
field is something to take into account. field is something to take into account.
5.4. Multipoint and Clustered Alternate Marking 5.4. Multipoint and Clustered Alternate Marking
The Alternate Marking method can also be extended to any kind of The Alternate Marking method can also be extended to any kind of
skipping to change at page 15, line 17 skipping to change at page 16, line 17
This document aims to apply a method to perform measurements that This document aims to apply a method to perform measurements that
does not directly affect Internet security nor applications that run does not directly affect Internet security nor applications that run
on the Internet. However, implementation of this method must be on the Internet. However, implementation of this method must be
mindful of security and privacy concerns. mindful of security and privacy concerns.
There are two types of security concerns: potential harm caused by There are two types of security concerns: potential harm caused by
the measurements and potential harm to the measurements. the measurements and potential harm to the measurements.
Harm caused by the measurement: Alternate Marking implies Harm caused by the measurement: Alternate Marking implies
modifications on the fly to an Option Header of IPv6 packets by the modifications on the fly to an Option Header of IPv6 packets by the
source node but this must be performed in a way that does not alter source node, but this must be performed in a way that does not alter
the quality of service experienced by the packets and that preserves the quality of service experienced by the packets and that preserves
stability and performance of routers doing the measurements. As stability and performance of routers doing the measurements. As
already discussed in Section 4, it is RECOMMENDED that the AltMark already discussed in Section 4, it is RECOMMENDED that the AltMark
Option does not affect the throughput and therefore the user Option does not affect the throughput and therefore the user
experience. experience.
Harm to the measurement: Alternate Marking measurements could be Harm to the measurement: Alternate Marking measurements could be
harmed by routers altering the fields of the AltMark Option (e.g. harmed by routers altering the fields of the AltMark Option (e.g.
marking of the packets, FlowMonID) or by a malicious attacker adding marking of the packets, FlowMonID) or by a malicious attacker adding
AltMark Option to the packets in order to consume the resources of AltMark Option to the packets in order to consume the resources of
network devices and entities involved. As described above, the network devices and entities involved. As described above, the
source node is the only one that writes the Option Header while the source node is the only one that writes the Option Header while the
intermediate nodes and destination node only read it without intermediate nodes and destination node only read it without
modifying the Option Header. But, for example, an on-path attacker modifying the Option Header. But, for example, an on-path attacker
can modify the flags, whether intentionally or accidentally, or can modify the flags, whether intentionally or accidentally, or
insert deliberately a new option to the packet flow or delete the deliberately insert a new option to the packet flow or delete the
option from the packet flow. The consequent effect could be to give option from the packet flow. The consequent effect could be to give
the appearance of loss or delay or invalidate the measurement by the appearance of loss or delay or invalidate the measurement by
modifying option identifiers, such as FlowMonID. The malicious modifying option identifiers, such as FlowMonID. The malicious
implication can be to cause actions from the network administrator implication can be to cause actions from the network administrator
where an intervention is not necessary or to hide real issues in the where an intervention is not necessary or to hide real issues in the
network. Since the measurement itself may be affected by network network. Since the measurement itself may be affected by network
nodes intentionally altering the bits of the AltMark Option or nodes intentionally altering the bits of the AltMark Option or
injecting Options headers as a means for Denial of Service (DoS), the injecting Options headers as a means for Denial of Service (DoS), the
Alternate Marking MUST be applied in the context of a controlled Alternate Marking MUST be applied in the context of a controlled
domain, where the network nodes are locally administered and this domain, where the network nodes are locally administered and this
type of attack can be avoided. type of attack can be avoided. For this reason, the implementation
of the method is not done on the end node if it is not fully managed
and does not belong to the controlled domain. Packets generated
outside the controlled domain may consume router resources by
maliciously using the HbH Option, but this can be mitigated by
filtering these packets at the controlled domain boundary. This can
be done because, if the end node does not belong to the controlled
domain, it is not supposed to add the AltMark HbH Option, and it can
be easily recognized.
The flow identifier (FlowMonID) composes the AltMark Option together The flow identifier (FlowMonID) composes the AltMark Option together
with the two marking bits (L and D). As explained in Section 5.3.1, with the two marking bits (L and D). As explained in Section 5.3.1,
there is a chance of collision if the FlowMonID is set pseudo there is a chance of collision if the FlowMonID is set pseudo
randomly and a solution exist. In general this may not be a problem randomly and a solution exists. In general this may not be a problem
and a low rate of ambiguous FlowMonIDs can be acceptable, since this and a low rate of ambiguous FlowMonIDs can be acceptable, since this
does not cause significant harm to the operators or their clients and does not cause significant harm to the operators or their clients and
this harm may not justify the complications of avoiding it. But, for this harm may not justify the complications of avoiding it. But, for
large scale measurements, a big number of flows could be monitored large scale measurements, a big number of flows could be monitored
and the probability of a collision is higher, thus the disambiguation and the probability of a collision is higher, thus the disambiguation
of the FlowMonID field can be considered. of the FlowMonID field can be considered.
The privacy concerns also need to be analyzed even if the method only The privacy concerns also need to be analyzed even if the method only
relies on information contained in the Option Header without any relies on information contained in the Option Header without any
release of user data. Indeed, from a confidentiality perspective, release of user data. Indeed, from a confidentiality perspective,
although AltMark Option does not contain user data, the metadata can although AltMark Option does not contain user data, the metadata can
be used for network reconnaissance to compromise the privacy of users be used for network reconnaissance to compromise the privacy of users
by allowing attackers to collect information about network by allowing attackers to collect information about network
performance and network paths. AltMark Option contains two kind of performance and network paths. AltMark Option contains two kinds of
metadata: the marking bits (L and D bits) and the flow identifier metadata: the marking bits (L and D bits) and the flow identifier
(FlowMonID). (FlowMonID).
The marking bits are the small information that is exchanged The marking bits are the small information that is exchanged
between the network nodes. Therefore, due to this intrinsic between the network nodes. Therefore, due to this intrinsic
characteristic, network reconnaissance through passive characteristic, network reconnaissance through passive
eavesdropping on data-plane traffic is difficult. Indeed an eavesdropping on data-plane traffic is difficult. Indeed, an
attacker cannot gain information about network performance from a attacker cannot gain information about network performance from a
single monitoring point. The only way for an attacker can be to single monitoring point. The only way for an attacker can be to
eavesdrop on multiple monitoring points at the same time, because eavesdrop on multiple monitoring points at the same time, because
they have to do the same kind of calculation and aggregation as they have to do the same kind of calculation and aggregation as
Alternate Marking requires, and, after that, it can finally gain Alternate Marking requires.
information about the network performance, but this is not
immediate.
The FlowMonID field is used in the AltMark Option as identifier of The FlowMonID field is used in the AltMark Option as the
the monitored flow. It represents a more sensitive information identifier of the monitored flow. It represents a more sensitive
for network reconnaissance and may allow a flow tracking type of information for network reconnaissance and may allow a flow
attack because an attacker could collect information about network tracking type of attack because an attacker could collect
paths. information about network paths.
Furthermore, in a pervasive surveillance attack, the information that Furthermore, in a pervasive surveillance attack, the information that
can be derived over time is more. But the application of the can be derived over time is more. But, as further described
Alternate Marking to a controlled domain helps to mitigate all the hereinafter, the application of the Alternate Marking to a controlled
above aspects of privacy concerns. domain helps to mitigate all the above aspects of privacy concerns.
At the management plane, attacks can be set up by misconfiguring or At the management plane, attacks can be set up by misconfiguring or
by maliciously configuring AltMark Option. Thus, AltMark Option by maliciously configuring AltMark Option. Thus, AltMark Option
configuration MUST be secured in a way that authenticates authorized configuration MUST be secured in a way that authenticates authorized
users and verifies the integrity of configuration procedures. users and verifies the integrity of configuration procedures.
Solutions to ensure the integrity of AltMark Option are outside the Solutions to ensure the integrity of AltMark Option are outside the
scope of this document. scope of this document. Also, attacks on the reporting of the
statistics between the monitoring points and the network management
system (e.g. centralized controller) can interfere with the proper
functioning of the system. Hence, the channels used to report back
flow statistics MUST be secured.
As stated above, the precondition for the application of the As stated above, the precondition for the application of the
Alternate Marking is that it MUST be applied in specific controlled Alternate Marking is that it MUST be applied in specific controlled
domains, thus confining the potential attack vectors within the domains, thus confining the potential attack vectors within the
network domain. [RFC8799] analyzes and discusses the trend towards network domain. [RFC8799] analyzes and discusses the trend towards
network behaviors that can be applied only within a limited domain. network behaviors that can be applied only within a limited domain.
This is due to the specific set of requirements especially related to This is due to the specific set of requirements especially related to
security, network management, policies and options supported which security, network management, policies and options supported which
may vary between such limited domains. A limited administrative may vary between such limited domains. A limited administrative
domain provides the network administrator with the means to select, domain provides the network administrator with the means to select,
monitor and control the access to the network, making it a trusted monitor and control the access to the network, making it a trusted
domain. In this regard it is expected to enforce policies at the domain. In this regard it is expected to enforce policies at the
domain boundaries to filter both external packets with AltMark Option domain boundaries to filter both external packets with AltMark Option
entering the domain and internal packets with AltMark Option leaving entering the domain and internal packets with AltMark Option leaving
the domain. Therefore the trusted domain is unlikely subject to the domain. Therefore, the trusted domain is unlikely subject to
hijacking of packets since packets with AltMark Option are processed hijacking of packets since packets with AltMark Option are processed
and used only within the controlled domain. and used only within the controlled domain.
Additionally, it is to be noted that the AltMark Option is carried by Additionally, it is to be noted that the AltMark Option is carried by
the Options Header and it may have some impact on the packet sizes the Options Header and it may have some impact on the packet sizes
for the monitored flow and on the path MTU, since some packets might for the monitored flow and on the path MTU, since some packets might
exceed the MTU. However the relative small size (48 bit in total) of exceed the MTU. However, the relative small size (48 bit in total)
these Option Headers and its application to a controlled domain help of these Option Headers and its application to a controlled domain
to mitigate the problem. help to mitigate the problem.
It is worth mentioning that the security concerns may change based on It is worth mentioning that the security concerns may change based on
the specific deployment scenario and related threat analysis, which the specific deployment scenario and related threat analysis, which
can lead to specific security solutions that are beyond the scope of can lead to specific security solutions that are beyond the scope of
this document. As an example, the AltMark Option can be used as Hop- this document. As an example, the AltMark Option can be used as Hop-
by-Hop or Destination Option and, in case of Destination Option, by-Hop or Destination Option and, in case of Destination Option,
multiple domains may be traversed by the AltMark Option that is not multiple administrative domains may be traversed by the AltMark
confined to a single domain. In this case, the user, aware of the Option that is not confined to a single administrative domain. In
kind of risks, may still want to use Alternate Marking for telemetry this case, the user, aware of the kind of risks, may still want to
and test purposes but the inter-domain links need to be secured use Alternate Marking for telemetry and test purposes but the
(e.g., by IPsec) in order to avoid external threats. For these controlled domain must be composed by more than one administrative
specific scenarios the application of the Alternate Marking Method domains. To this end, the inter-domain links need to be secured
outside a controlled domain is possible but IPsec through AH (e.g., by IPsec, VPNs) in order to avoid external threats and realize
(Authentication Header) or ESP (Encapsulating Security Payload) MUST the whole controlled domain.
be used.
It might be theoretically possible to modulate the marking or the
other fields of the AltMark Option to serve as a covert channel to be
used by an on-path observer. This may affect both the data and
management plane, but, here too, the application to a controlled
domain helps to reduce the effects.
The Alternate Marking application described in this document relies The Alternate Marking application described in this document relies
on an time synchronization protocol. Thus, by attacking the time on a time synchronization protocol. Thus, by attacking the time
protocol, an attacker can potentially compromise the integrity of the protocol, an attacker can potentially compromise the integrity of the
measurement. A detailed discussion about the threats against time measurement. A detailed discussion about the threats against time
protocols and how to mitigate them is presented in [RFC7384]. Also, protocols and how to mitigate them is presented in [RFC7384].
the time, which is distributed to the network nodes through the time Network Time Security (NTS), described in [RFC8915], is a mechanism
protocol, is centrally taken from an external accurate time source, that can be employed. Also, the time, which is distributed to the
such as an atomic clock or a GPS clock, and by attacking the time network nodes through the time protocol, is centrally taken from an
source it can be possible to compromise the integrity of the external accurate time source, such as an atomic clock or a GPS
measurement as well. There are security measures that can be taken clock. By attacking the time source it can be possible to compromise
to mitigate the GPS spoofing attacks and a network administrator the integrity of the measurement as well. There are security
should certainly employ solutions to secure the network domain. measures that can be taken to mitigate the GPS spoofing attacks and a
network administrator should certainly employ solutions to secure the
network domain.
7. IANA Considerations 7. IANA Considerations
The Option Type should be assigned in IANA's "Destination Options and The Option Type should be assigned in IANA's "Destination Options and
Hop-by-Hop Options" registry. Hop-by-Hop Options" registry.
This draft requests the following IPv6 Option Type assignment from This draft requests the following IPv6 Option Type assignment from
the Destination Options and Hop-by-Hop Options sub-registry of the Destination Options and Hop-by-Hop Options sub-registry of
Internet Protocol Version 6 (IPv6) Parameters Internet Protocol Version 6 (IPv6) Parameters
(https://www.iana.org/assignments/ipv6-parameters/). (https://www.iana.org/assignments/ipv6-parameters/).
Hex Value Binary Value Description Reference Hex Value Binary Value Description Reference
act chg rest act chg rest
---------------------------------------------------------------- ----------------------------------------------------------------
TBD 00 0 tbd AltMark [This draft] TBD 00 0 tbd AltMark [This draft]
8. Acknowledgements 8. Acknowledgements
The authors would like to thank Bob Hinden, Ole Troan, Stewart The authors would like to thank Bob Hinden, Ole Troan, Martin Duke,
Bryant, Christopher Wood, Yoshifumi Nishida, Tom Herbert, Stefano Lars Eggert, Roman Danyliw, Alvaro Retana, Eric Vyncke, Warren
Previdi, Brian Carpenter, Eric Vyncke, Greg Mirsky, Ron Bonica for Kumari, Benjamin Kaduk, Stewart Bryant, Christopher Wood, Yoshifumi
the precious comments and suggestions. Nishida, Tom Herbert, Stefano Previdi, Brian Carpenter, Greg Mirsky,
Ron Bonica for the precious comments and suggestions.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 19, line 5 skipping to change at page 20, line 22
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References 9.2. Informative References
[I-D.chen-pce-pcep-ifit] [I-D.chen-pce-pcep-ifit]
Yuan, H., Zhou, T., Li, W., Fioccola, G., and Y. Wang, Yuan, H., Zhou, T., Li, W., Fioccola, G., and Y. Wang,
"Path Computation Element Communication Protocol (PCEP) "Path Computation Element Communication Protocol (PCEP)
Extensions to Enable IFIT", draft-chen-pce-pcep-ifit-04 Extensions to Enable IFIT", draft-chen-pce-pcep-ifit-04
(work in progress), July 2021. (work in progress), July 2021.
[I-D.fioccola-v6ops-ipv6-alt-mark]
Fioccola, G., Velde, G. V. D., Cociglio, M., and P. Muley,
"IPv6 Performance Measurement with Alternate Marking
Method", draft-fioccola-v6ops-ipv6-alt-mark-01 (work in
progress), June 2018.
[I-D.fz-spring-srv6-alt-mark] [I-D.fz-spring-srv6-alt-mark]
Fioccola, G., Zhou, T., and M. Cociglio, "Segment Routing Fioccola, G., Zhou, T., and M. Cociglio, "Segment Routing
Header encapsulation for Alternate Marking Method", draft- Header encapsulation for Alternate Marking Method", draft-
fz-spring-srv6-alt-mark-01 (work in progress), July 2021. fz-spring-srv6-alt-mark-01 (work in progress), July 2021.
[I-D.hinden-6man-hbh-processing] [I-D.hinden-6man-hbh-processing]
Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
Processing Procedures", draft-hinden-6man-hbh- Processing Procedures", draft-hinden-6man-hbh-
processing-01 (work in progress), June 2021. processing-01 (work in progress), June 2021.
[I-D.ietf-idr-sr-policy-ifit] [I-D.ietf-idr-sr-policy-ifit]
Qin, F., Yuan, H., Zhou, T., Fioccola, G., and Y. Wang, Qin, F., Yuan, H., Zhou, T., Fioccola, G., and Y. Wang,
"BGP SR Policy Extensions to Enable IFIT", draft-ietf-idr- "BGP SR Policy Extensions to Enable IFIT", draft-ietf-idr-
sr-policy-ifit-02 (work in progress), July 2021. sr-policy-ifit-02 (work in progress), July 2021.
[I-D.peng-v6ops-hbh] [I-D.peng-v6ops-hbh]
Peng, S., Li, Z., Xie, C., Qin, Z., and G. Mishra, Peng, S., Li, Z., Xie, C., Qin, Z., and G. Mishra,
"Processing of the Hop-by-Hop Options Header", draft-peng- "Processing of the Hop-by-Hop Options Header", draft-peng-
v6ops-hbh-04 (work in progress), June 2021. v6ops-hbh-06 (work in progress), August 2021.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, "IPv6 Flow Label Specification", RFC 6437,
DOI 10.17487/RFC6437, November 2011, DOI 10.17487/RFC6437, November 2011,
<https://www.rfc-editor.org/info/rfc6437>. <https://www.rfc-editor.org/info/rfc6437>.
[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label [RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
for Equal Cost Multipath Routing and Link Aggregation in for Equal Cost Multipath Routing and Link Aggregation in
Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011, Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
<https://www.rfc-editor.org/info/rfc6438>. <https://www.rfc-editor.org/info/rfc6438>.
skipping to change at page 20, line 26 skipping to change at page 21, line 45
[RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet [RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet
Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020, Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
<https://www.rfc-editor.org/info/rfc8799>. <https://www.rfc-editor.org/info/rfc8799>.
[RFC8889] Fioccola, G., Ed., Cociglio, M., Sapio, A., and R. Sisto, [RFC8889] Fioccola, G., Ed., Cociglio, M., Sapio, A., and R. Sisto,
"Multipoint Alternate-Marking Method for Passive and "Multipoint Alternate-Marking Method for Passive and
Hybrid Performance Monitoring", RFC 8889, Hybrid Performance Monitoring", RFC 8889,
DOI 10.17487/RFC8889, August 2020, DOI 10.17487/RFC8889, August 2020,
<https://www.rfc-editor.org/info/rfc8889>. <https://www.rfc-editor.org/info/rfc8889>.
[RFC8915] Franke, D., Sibold, D., Teichel, K., Dansarie, M., and R.
Sundblad, "Network Time Security for the Network Time
Protocol", RFC 8915, DOI 10.17487/RFC8915, September 2020,
<https://www.rfc-editor.org/info/rfc8915>.
Authors' Addresses Authors' Addresses
Giuseppe Fioccola Giuseppe Fioccola
Huawei Huawei
Riesstrasse, 25 Riesstrasse, 25
Munich 80992 Munich 80992
Germany Germany
Email: giuseppe.fioccola@huawei.com Email: giuseppe.fioccola@huawei.com
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