Circuit Breaker Assisted Congestion Control
draft-ietf-mboned-cbacc-04
| Document | Type | Active Internet-Draft (mboned WG) | |
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| Author | Jake Holland | ||
| Last updated | 2022-03-07 | ||
| Replaces | draft-jholland-mboned-cbacc | ||
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draft-ietf-mboned-cbacc-04
Mboned J. Holland
Internet-Draft Akamai Technologies, Inc.
Intended status: Standards Track 7 March 2022
Expires: 8 September 2022
Circuit Breaker Assisted Congestion Control
draft-ietf-mboned-cbacc-04
Abstract
This document specifies Circuit Breaker Assisted Congestion Control
(CBACC). CBACC enables fast-trip Circuit Breakers by publishing rate
metadata about multicast channels from senders to intermediate
network nodes or receivers. The circuit breaker behavior is defined
as a supplement to receiver driven congestion control systems, to
preserve network health if misbehaving or malicious receiver
applications subscribe to a volume of traffic that exceeds capacity
policies or capability for a network or receiving device.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Background and Terminology . . . . . . . . . . . . . . . 4
1.2. Venues for Contribution and Discussion . . . . . . . . . 4
1.3. Non-obvious doc choices . . . . . . . . . . . . . . . . . 4
2. Circuit Breaker Behavior . . . . . . . . . . . . . . . . . . 5
2.1. Functional Components . . . . . . . . . . . . . . . . . . 5
2.1.1. Bitrate Advertisement . . . . . . . . . . . . . . . . 5
2.1.2. Circuit Breaker Node . . . . . . . . . . . . . . . . 6
2.1.3. Communication Method . . . . . . . . . . . . . . . . 7
2.1.4. Measurement Function . . . . . . . . . . . . . . . . 7
2.1.5. Trigger Function . . . . . . . . . . . . . . . . . . 8
2.1.6. Reaction . . . . . . . . . . . . . . . . . . . . . . 9
2.1.7. Feedback Control Mechanism . . . . . . . . . . . . . 10
2.2. States . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.1. Interface State . . . . . . . . . . . . . . . . . . . 10
2.2.2. Flow State . . . . . . . . . . . . . . . . . . . . . 11
2.3. Implementation Design Considerations . . . . . . . . . . 11
2.3.1. Oversubscription Thresholds . . . . . . . . . . . . . 12
2.3.2. Fairness Functions . . . . . . . . . . . . . . . . . 12
3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
3.2. Module . . . . . . . . . . . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
4.1. YANG Module Names Registry . . . . . . . . . . . . . . . 14
4.2. The XML Registry . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
5.1. Metadata Security . . . . . . . . . . . . . . . . . . . . 15
5.2. Denial of Service . . . . . . . . . . . . . . . . . . . . 15
5.2.1. State Overload . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Overjoining . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
This document defines Circuit Breaker Assisted Congestion Control
(CBACC). CBACC defines a Network Transport Circuit Breaker (CB), as
described by [RFC8084].
The CB behavior defined in this document uses bit-rate metadata about
multicast data streams coupled with policy, capacity, and load
information at a network location to prune multicast channels so that
the network's aggregate capacity at that location is not exceeded by
the subscribed channels.
To communicate the required metadata, this document defines a YANG
[RFC7950] module that augments the DORMS
[I-D.draft-ietf-mboned-dorms] YANG module. DORMS provides a
mechanism for senders to publish metadata about the multicast streams
they're sending through a RESTCONF service, so that receivers or
forwarding nodes can discover and consume the metadata with a set of
standard methods. The CBACC metadata MAY be communicated to
receivers or forwarding nodes by some other method, but the
definition of any alternative methods is out of scope for this
document.
The CB behavior defined in this document matches the description
provided in Section 3.2.3 of [RFC8084] of a unidirectional CB over a
controlled path. The control messages from that description are
composed of the messages containing the metadata required for
operation of the CB.
CBACC is designed to supplement protocols that use multicast IP and
rely on well-behaved receivers to achieve congestion control.
Examples of congestion control systems fitting this description
include [PLM], [RLM], [RLC], [FLID-DL], [SMCC], and WEBRC [RFC3738].
CBACC addresses a problem with "overjoining" by untrusted receivers.
In an overjoining condition, receivers (either malicious,
misconfigured, or with implementation errors) subscribe to multicast
channels but do not respond appropriately to congestion. When
sufficient multicast traffic is available for subscription by such
receivers, this can overload any network.
The overjoining problem is relevant to misbehaving receivers for both
receiver-driven and feedback-driven congestion control strategies, as
described in Section 4.1 of [RFC8085].
Overjoining attacks and the challenges they present are discussed in
more detail in Appendix A.
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CBACC offers a solution for the recommendation in Section 4 of
[RFC8085] that circuit breaker solutions be used even where
congestion control is optional.
1.1. Background and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Venues for Contribution and Discussion
This document is in the Github repository at:
https://github.com/GrumpyOldTroll/ietf-dorms-cluster
Readers are welcome to open issues and send pull requests for this
document.
Please note that contributions may be merged and substantially
edited, and as a reminder, please carefully consider the Note Well
before contributing: https://datatracker.ietf.org/submit/note-well/
Substantial discussion of this document should take place on the
MBONED working group mailing list (mboned@ietf.org).
* Join: https://www.ietf.org/mailman/listinfo/mboned
* Search: https://mailarchive.ietf.org/arch/browse/mboned/
1.3. Non-obvious doc choices
* Since nothing is necessarily being actively measured by a network
component at the ingress, referring to the bitrate advertisement
as an "ingress meter" for this context was considered confusing by
reviewers, so the section was renamed with just a note pointing to
the link. Likewise the egress meter and "CB node".
* TBD: might need more and better examples explaining the point in
Section 2.1.5.1? Some reason to believe it's not sufficiently
clear...
* Another TBD: consider Dino's suggestion from 2020-04-09 to include
an operational considerations section that addresses some possible
optimizations for CB placement and configuration.
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* TBD: add a section walking through the requirements in
https://datatracker.ietf.org/doc/html/rfc8084#section-4
(https://datatracker.ietf.org/doc/html/rfc8084#section-4) and
explaining how this matches.
* I'm unclear on whether https://datatracker.ietf.org/doc/html/
rfc8407#section-3.8.2 (https://datatracker.ietf.org/doc/html/
rfc8407#section-3.8.2) applies here, such that providing an
augmentation inside the DORMS namespace causes an update to the
DORMS document.
2. Circuit Breaker Behavior
2.1. Functional Components
This section maps the functional components described in Section 3.1
of [RFC8084] to the operational components of the CBACC CB defined by
this document.
2.1.1. Bitrate Advertisement
The metadata provides an advertised maximum data bit-rate, namely the
"max-speed" field in the YANG model in Section 3. This is a self-
report by the sender about the maximum amount of traffic a sender
will send within any time interval given by the "data-rate-window"
field, which is the measurement interval for the CB. This value
refers to the total IP Payload data for all packets in the same
(S,G), and its units are in kilobits per second.
The sender MUST NOT send more data for a data stream than the amount
of data declared according to its advertised data rate within any
measurement window, and it's RECOMMENDED for the sender to provide
some margin to account for the possibility of burst forwarding after
traffic encounters a non-empty queue, e.g. as sometimes observed with
ACK compression (see [ZSC91] for a description of the phenomenon).
If a CB node observes a higher data rate transmitted within any
measurement window, it MAY circuit-break that flow immediately.
In the terminology of [RFC8084], the bitrate advertisement qualifies
as an ingress meter.
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2.1.2. Circuit Breaker Node
A circuit breaker node (CB node) is a location in a network where the
costraints of the network and the observations about active traffic
are compared to the bitrate advertisement in order to make the
decision loop about when and whether to perform the circuit breaking
behavior. In the terminology of [RFC8084], the CB node qualifies as
an egress meter.
The CB node has access to several pieces of information that can be
used as relevant egress metrics that may include:
1. Physical capacity limits on each interface.
2. Configured capacity limits for multicast traffic for each
interface.
3. The observed received data rates of subscribed multicast channels
with CBACC metadata.
4. The observed received data rates of subscribed multicast channels
without CBACC metadata.
5. The observed received data rates of competing non-multicast
traffic.
6. The loss rate for subscribed multicast channels, when available.
The loss rate is only sometimes observable at a CB node; for
example, when using AMBI [I-D.draft-ietf-mboned-ambi], or when
the data stream carries a protocol that is known to the CB node
by some out of band means, and whose traffic can be monitored for
loss. When available, the loss rates may be used.
Note that any on-path router can behave as a CB node, even though
there may be other CB nodes downstream or upstream covering the same
data streams. When viewing CB nodes as egress meters in the context
of [RFC8084], it's important to recall there's not a single egress
meter in the network, but rather an egress meter per CB node,
representing potentially multiple overlaid circuit breakers that may
redundantly cover parts of the same path, with potentially different
constraints based on the network location where the egress meter
operates. All of the CB nodes anywhere on a path constitute separate
circuit breakers that may trip independently of other circuit
breakers.
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Also note that other kinds of components besides on-path routers
forwarding the traffic can act as CB nodes, for example the operating
system or browser on a device receiving the traffic, or the receiving
application itself.
2.1.3. Communication Method
CBACC generally operates at a CB node, where metrics such as those
described in Section 2.1.2 are available through system calls, or by
communication with various locally deployable system monitoring
applications. However, the CBACC processing can equivalently occur
on a separate device that can monitor statistics gathered at a CB
node, as long as the necessary control functions to trigger the CB
can be invoked.
The communication path defined in this document for the CB node to
obtain the bitrate advertisement in Section 2.1.1 is the use of DORMS
[I-D.draft-ietf-mboned-dorms]. Other methods MAY be used as well or
instead, but are out of scope for this document.
2.1.4. Measurement Function
The measurement function maintains a few values for each interface,
computed from the metrics described in Section 2.1.2 and
Section 2.1.1:
1. The aggregate advertised maximum bit-rate capacity consumed by
CBACC data streams. This is the sum of the max-speed values in
the CBACC metadata for all data streams subscribed through an
interface
2. An oversubscription threshold for each interface. The
oversubscription threshold will be determined differently for CB
nodes in different contexts. In some network devices, it might
be as simple as an administratively configured absolute value or
proportion of an interface's capacity. For other situations,
like a CB node operating in a context with loss visibility, it
could be a dynamically changing value that grows when data
streams are successfully subscribed and receiving data without
loss, and shrinks as loss is observed across subscribed data
streams. The oversubscription threshold calculation could also
incorporate other information like out-of-band path capacity
measurements with bandwidth detection techniques such as
[PathChirp] or [CapProbe].
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This document covers some non-normative examples of valid
oversubscription threshold functions in Section 2.3.1. In
general, the oversubscription threshold is the primary parameter
that different CBs in different contexts can tune to provide the
safety guarantees necessary for their context.
2.1.5. Trigger Function
The trigger function fires when the aggregate advertised maximum bit-
rate exceeds the oversubscription threshold for any interface.
When oversubscribed, the trigger function changes the states of
subscribed channels to "blocked" until the aggregate subscribed bit-
rate is below the oversubscription threshold again.
2.1.5.1. Fairness and Inter-flow Ordering
The trigger function orders the monitored flows according to a
fairness function and a within-sender priority ordering (chosen by
the sender as part of the CBACC metadata). When flows are blocked,
they're blocked in order until the aggregate bitrate of the permitted
flows do not exceed the oversubscription thresholds monitored by the
CB node.
Flows from a single sender MUST be ordered according to their
priority field from the CBACC metadata when compared with each other.
This takes precedence over the fairness function ordering, since
certain flows from the same sender may need strict priority over
others.
For example, consider a sender using File Delivery over
Unidirectional Transport (FLUTE, defined in [RFC6726]) that sends
File Delivery Table (FDT) Instances (see section 3.2 of [RFC6726]) in
one (S,G) and data for the various referenced files in other (S,G)s.
In this case the data for the files will not be consumable without
the (S,G) containing the FDT. Other transport protocols may
similarly send control information (often with a lower bitrate) on
one channel, and data information on another. In these cases, the
sender may need to ensure that data channels are only available when
the control channels are also available.
When comparing flows between senders, (S,G)s from the same sender
with different priorities should be treated as aggregated (S,G)s with
regard to their declared bitrate consumption, to ensure that if any
flows from the same sender need to be pruned by the circuit-breaker,
the least preferred priority flows from that sender are pruned first.
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Between-sender flows and flows from the same sender with the same
priority are ordered according to the fairness function. TBD: need
to work thru detsils, this does not work as written. Sample fairness
function would reward senders for splitting a flow in 2 (more total
subscribers). Maybe should count offload instead? This has trouble
from favoring padding in your flow, but is (i think?) dominated by
subscriber count where that's known. The fairness function can be
different for CBs in different contexts.
A CBACC CB implementation SHOULD provide mechanisms for
administrative controls to configure explicit biases, as this may be
necessary to support Service Level Agreements for specific events or
providers, or to block or de-prioritize channels with historically
known misbehavior.
Subject to the above constraints, where possible the default fairness
behavior SHOULD favor streams with many receivers over streams with
few receivers, and streams with a low bit-rate over streams with a
high bit-rate. See Section 2.3.2 for further considerations and
examples.
2.1.6. Reaction
When the trigger function fires and a subscribed channel becomes
blocked, the reaction depends on whether it's an upstream interface
or a downstream interface.
If a channel is blocked on one or more downstream interfaces, it may
still be unblocked on other downstream interfaces. When this is the
case, traffic is simply not forwarded along blocked interfaces, even
though clients might still be joined downstream of those interfaces.
When a channel is blocked on all downstream interfaces or when the
upstream interface is oversubscribed, the channel is pruned so that
data no longer arrives from the network on the upstream interface.
The prune would be performed with a PIM prune (Section 3.5 of
[RFC7761]), or a "leave" operation to be communicated via IGMP, MLD,
or another multicast group signaling mechanism, according to the
expected signaling within the network.
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Once initially pruned, a flow SHOULD remain pruned for a minimum
amount of time. The minimum hold-down duration SHOULD be no less
than 2.5 minutes by default, even if available bitrate space clears
up, to ensure downstream subscriptions will notice and respond. The
hold-down duration SHOULD be extended from the minimum by a randomly
chosen number of seconds uniformly distributed over a configurable
desynchronization period, to avoid synchronized recovery of different
circuit breakers along the path. The default length of the
desynchronization period should be at least 30 seconds.
2.5 minutes is chosen to exceed the default maximum lifetime of 2
minutes that can occur if an IGMP responder suddenly stops operation,
and ceases responding to IGMP queries with membership reports, and 30
seconds is chosen to allow for some flexibility in lost packets. The
values MAY be administratively tuned as needed by network operators
to meet performance goals specific to their networks or to the
traffic they're forwarding.
When enough capacity is available for a circuit-broken stream to be
unblocked and the circuit-breaker hold-down time is expired, flows
SHOULD be unblocked according to the priority order until no more
flows can be unblocked without exceeding the circuit breaker limits.
2.1.7. Feedback Control Mechanism
The bitrate advertisement metadata from Section 2.1.1 should be
refreshed as needed to maintain up to date values. When using DORMS
and RESTCONF, the Subscription to YANG Notifications for Datastore
Updates [RFC8641] is the preferred method to receive changes if
available.
If datastore subscriptions are not supported by the client or server,
the HTTP Cache Control headers provide valid refresh time properties
from the server, and SHOULD be used if present. If No-Cache is used,
the default refresh timing SHOULD be 30 seconds. A uniformly
distributed random value between 0 and 10 seconds SHOULD be added to
the Cache Control or the default refresh timing to avoid
synchronization across multiple clients.
2.2. States
2.2.1. Interface State
A CB holds the following state for each interface, for both the
inbound and outbound directions on that interface:
* aggregate bandwidth: The sum of the bandwidths of all non-circuit-
broken CBACC flows that transit this interface in this direction.
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* bandwidth limit: The maximum aggregate CBACC advertised bandwidth
allowed, not including circuit-broken flows.
When reducing the bandwidth limit due to congestion, the circuit
breaker SHOULD NOT reduce the limit by more than half its value in
10 seconds, and SHOULD use a smoothing function to reduce the
limit gradually over time.
It is RECOMMENDED that no more than half the capacity for a link
be allocated to CBACC flows if the link might be shared with
unicast traffic that is responsive to congestion.
2.2.2. Flow State
Data streams with CBACC metadata have a state for the upstream
interface through which the stream is joined:
* 'subscribed'
Indicates that the circuit breaker is subscribed upstream to the
flow and forwarding packets through zero or more egress
interfaces.
* 'pruned'
Indicates that the flow has been circuit-broken. A request to
unsubscribe from the flow has been sent upstream, e.g. a PIM prune
(Section 3.5 of [RFC7761]) or a "leave" operation communicated via
IGMP, MLD, or another group membership management mechanism.
Data streams also have a per-interface state for downstream
interfaces with subscribers, where the data is being forwarded. It's
one of:
* 'forwarding'
Indicates that the flow is a non-circuit-broken flow in steady
state, forwarding packets downstream.
* 'blocked'
Indicates that data packets for this flow are NOT forwarded
downstream via this interface.
2.3. Implementation Design Considerations
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2.3.1. Oversubscription Thresholds
TBD.
2.3.2. Fairness Functions
As an example fairness function that makes good sense for a general
case of unknown traffic:
Consider a network where the receiver count for multicast channels is
known, for example via the experimental PIM extension for population
count defined in [RFC6807].
A good fairness metric for a flow is max-bandwidth divided by
receiver-count, with lower values of the fairness metric favored over
higher values.
An overview of some other approaches to appropriate fairness metrics
is given in Section 2.3 of [RFC5166].
3. YANG Module
3.1. Tree Diagram
The tree diagram below follows the notation defined in [RFC8340].
module: ietf-cbacc
augment /dorms:dorms/dorms:metadata/dorms:sender/dorms:group:
+--rw cbacc!
+--rw max-speed uint32
+--rw max-packet-size? uint16
+--rw data-rate-window? uint32
+--rw priority? uint16
3.2. Module
<CODE BEGINS>
file ietf-cbacc@2022-03-07.yang
module ietf-cbacc {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-cbacc";
prefix "cbacc";
import ietf-dorms {
prefix "dorms";
reference "I-D.jholland-mboned-dorms";
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}
organization "IETF";
contact
"Author: Jake Holland
<mailto:jholland@akamai.com>
";
description
"Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of
draft-jholland-mboned-cbacc. See the internet draft for full
legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
This module contains the definition for bandwidth consumption
metadata for SSM channels, as an extension to DORMS
(draft-ietf-mboned-dorms).";
revision 2021-07-08 {
description "Draft version, post-early-review.";
reference
"draft-ietf-mboned-cbacc";
}
augment
"/dorms:dorms/dorms:metadata/dorms:sender/dorms:group" {
description "Definition of the manifest stream providing
integrity info for the data stream";
container cbacc {
presence "CBACC-enabled flow";
description
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"Information to enable fast-trip circuit breakers";
leaf max-speed {
type uint32;
units "kilobits/second";
mandatory true;
description "Maximum bitrate for this stream, in Kilobits
of IP packet data (including headers) of native
multicast traffic per second";
}
leaf max-packet-size {
type uint16;
default 1400;
description "Maximum IP payload size, in octets.";
}
leaf data-rate-window {
type uint32;
units "milliseconds";
default 2000;
description
"Time window over which data rate is guaranteed,
in milliseconds.";
/* TBD: range limits? */
}
leaf priority {
type uint16;
default 256;
description
"The relative preference level for keeping this flow
compared to other flows from this sender (higher
value is more preferred to keep)";
}
}
}
}
<CODE ENDS>
4. IANA Considerations
4.1. YANG Module Names Registry
This document adds one YANG module to the "YANG Module Names"
registry maintained at <https://www.iana.org/assignments/yang-
parameters>. The following registrations are made, per the format in
Section 14 of [RFC6020]:
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name: ietf-cbacc
namespace: urn:ietf:params:xml:ns:yang:ietf-cbacc
prefix: cbacc
reference: I-D.draft-ietf-mboned-cbacc
4.2. The XML Registry
This document adds the following registration to the "ns" subregistry
of the "IETF XML Registry" defined in [RFC3688], referencing this
document.
URI: urn:ietf:params:xml:ns:yang:ietf-cbacc
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
5. Security Considerations
TBD: Yang Doctor review from Reshad said this should "mention the
YANG data nodes". I think this means "do what
https://tools.ietf.org/html/rfc8407#section-3.7 says"?
5.1. Metadata Security
Be sure to authenticate the metadata. See DORMS security
considerations, and don't accept unauthenticated metadata if using an
alternative means.
5.2. Denial of Service
5.2.1. State Overload
Since CBACC flows require state, it may be possible for a set of
receivers and/or senders, possibly acting in concert, to generate
many flows in an attempt to overflow the circuit breakers' state
tables.
It is permissible for a network node to behave as a CBACC circuit
breaker for some CBACC flows while treating other CBACC flows as non-
CBACC, as part of a load balancing strategy for the network as a
whole, or simply as defense against this concern when the number of
monitored flows exceeds some threshold.
The same techniques described in Section 3.1 of [RFC4609] can be used
to help mitigate this attack, for much the same reasons. It is
RECOMMENDED that network operators implement measures to mitigate
such attacks.
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6. Acknowledgements
Many thanks to Devin Anderson, Ben Kaduk, Cheng Jin, Scott Brown,
Miroslav Ponec, Bob Briscoe, Lenny Giuliani, Christian Worm
Mortensen, Dino Farinacci, and Reshad Rahman for their thoughtful
comments and contributions.
7. References
7.1. Normative References
[I-D.draft-ietf-mboned-ambi]
Holland, J. and K. Rose, "Asymmetric Manifest Based
Integrity", Work in Progress, Internet-Draft, draft-ietf-
mboned-ambi-01, 31 October 2020,
<https://www.ietf.org/archive/id/draft-ietf-mboned-ambi-
01.txt>.
[I-D.draft-ietf-mboned-dorms]
Holland, J., "Discovery Of Restconf Metadata for Source-
specific multicast", Work in Progress, Internet-Draft,
draft-ietf-mboned-dorms-01, 31 October 2020,
<https://www.ietf.org/archive/id/draft-ietf-mboned-dorms-
01.txt>.
[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>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers",
BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017,
<https://www.rfc-editor.org/info/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
7.2. Informative References
[CapProbe] Kapoor, R., Chen, L., Lao, L., Gerla, M., and M.Y.
Sanadidi, "CapProbe: A Simple and Accurate Capacity
Estimation Technique", September 2004,
<https://dl.acm.org/doi/pdf/10.1145/1015467.1015476>.
[FLID-DL] Byers, J.W., Horn, G., Luby, M., Mitzenmacher, M., Shaver,
W., and IEEE, "FLID-DL: congestion control for layered
multicast", DOI 10.1109/JSAC.2002.803998, n.d.,
<https://ieeexplore.ieee.org/document/1038584>.
[PathChirp]
Ribeiro, V.J., Riedi, R.H., Baraniuk, R.G., Navratil, J.,
Cottrell, L., Department of Electrical and Computer
Engineering Rice University, and SLAC/SCS-Network
Monitoring, Stanford University, "pathChirp: Efficient
Available Bandwidth Estimation for Network Paths", 2003.
[PLM] Biersack, Institut EURECOM, A.Legout, E.W., "PLM: Fast
Convergence for Cumulative Layered Multicast Transmission
Schemes", 1999,
<http://www.eurecom.fr/en/publication/340/download/ce-
legoar-000601.pdf>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC3738] Luby, M. and V. Goyal, "Wave and Equation Based Rate
Control (WEBRC) Building Block", RFC 3738,
DOI 10.17487/RFC3738, April 2004,
<https://www.rfc-editor.org/info/rfc3738>.
[RFC4609] Savola, P., Lehtonen, R., and D. Meyer, "Protocol
Independent Multicast - Sparse Mode (PIM-SM) Multicast
Routing Security Issues and Enhancements", RFC 4609,
DOI 10.17487/RFC4609, October 2006,
<https://www.rfc-editor.org/info/rfc4609>.
[RFC5166] Floyd, S., Ed., "Metrics for the Evaluation of Congestion
Control Mechanisms", RFC 5166, DOI 10.17487/RFC5166, March
2008, <https://www.rfc-editor.org/info/rfc5166>.
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[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6726] Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen,
"FLUTE - File Delivery over Unidirectional Transport",
RFC 6726, DOI 10.17487/RFC6726, November 2012,
<https://www.rfc-editor.org/info/rfc6726>.
[RFC6807] Farinacci, D., Shepherd, G., Venaas, S., and Y. Cai,
"Population Count Extensions to Protocol Independent
Multicast (PIM)", RFC 6807, DOI 10.17487/RFC6807, December
2012, <https://www.rfc-editor.org/info/rfc6807>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/info/rfc8641>.
[RLC] Rizzo, L., Vicisano, L., and J. Crowcroft, "The RLC
multicast congestion control algorithm", 1999,
<http://www.iet.unipi.it/~a007834/rlc99.ps.gz>.
[RLM] McCanne, S., Jacobson, V., Vetterli, M., University of
California, Berkeley, and Lawrence Berkeley National
Laboratory, "Receiver-driven Layered Multicast", 1995,
<http://www1.cs.columbia.edu/~danr/courses/6761/Fall00/
week9/layering.pdf>.
[SMCC] Kwon, G., Byers, J.W., and Computer Science Department,
Boston University, "Smooth Multirate Multicast Congestion
Control", 2002,
<http://www.cs.bu.edu/techreports/pdf/2002-025-smcc.pdf>.
[ZSC91] Zhang, L., Shenker, S., and D.D. Clark, "Observations and
Dynamics of a Congestion Control Algorithm: The Effects of
Two-Way Traffic", Proc. ACM SIGCOMM, ACM Computer
Communications Review (CCR), Vol 21, No 4, pp.133-147. ,
1991.
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Appendix A. Overjoining
[RFC8085] describes several remedies for unicast congestion control
under UDP, even though UDP does not itself provide congestion
control. In general, any network node under congestion could in
theory collect evidence that a unicast flow's sending rate is not
responding to congestion, and would then be justified in circuit-
breaking it.
With multicast IP, the situation is different, especially in the
presence of malicious receivers. A well-behaved sender using a
receiver-controlled congestion scheme such as WEBRC does not reduce
its send rate in response to congestion, instead relying on receivers
to leave the appropriate multicast groups.
This leads to a situation where, when a network accepts inter-domain
multicast traffic, as long as there are senders somewhere in the
world with aggregate bandwidth that exceeds a network's capacity,
receivers in that network can join the flows and overflow the network
capacity. A receiver controlled by an attacker could do this at the
IGMP/MLD level without running the application layer protocol that
participates in the receiver-controlled congestion control.
A network might be able to detect and defend against the most naive
version of such an attack by blocking end users that try to join too
many flows at once. However, an attacker can achieve the same effect
by joining a few high-bandwidth flows, if those exist anywhere, and
an attacker that controls a few machines in a network can coordinate
the receivers so they join disjoint sets of non-responsive sending
flows.
This scenario will produce congestion in a middle node in the network
that can't be easily detected at the edge where the IGMP/MLD join is
accepted. Thus, an attacker with a small set of machines in a target
network can always trip a circuit breaker if present, or can induce
excessive congestion among the bandwidth allocated to multicast.
This problem gets worse as more multicast flows become available.
Although the same can apply to non-responsive unicast traffic,
network operators can assume that non-responsive sending flows are in
violation of congestion control best practices, and can therefore cut
off flows associated with the misbehaving senders. By contrast, non-
responsive multicast senders are likely to be well-behaved
participants in receiver-controlled congestion control schemes.
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However, receiver controlled congestion control schemes also show the
most promise for efficient massive scale content distribution via
multicast, provided network health can be ensured. Therefore,
mechanisms to mitigate overjoining attacks while still permitting
receiver-controlled congestion control are necessary.
Author's Address
Jake Holland
Akamai Technologies, Inc.
150 Broadway
Cambridge, MA 02144,
United States of America
Email: jakeholland.net@gmail.com
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