Internet DRAFT - draft-decraene-lsr-isis-flooding-speed
draft-decraene-lsr-isis-flooding-speed
Network Working Group B. Decraene
Internet-Draft Orange
Intended status: Standards Track C. Bowers
Expires: January 13, 2022 Jayesh. J
Juniper Networks, Inc.
T. Li
Arista Networks
G. Van de Velde
Nokia
G. Solignac
Orange
July 12, 2021
IS-IS Flooding Congestion Control
draft-decraene-lsr-isis-flooding-speed-07
Abstract
This document proposes a mechanism to adjust IS-IS flooding speed
between two adjacent routers by adjusting the sender flooding speed
to the capability of the receiver. This helps improving the flooding
throughput, reducing LSPs losses and retransmissions due to receiver
overload, and avoiding manual tuning of flooding parameters by the
network operator. This document defines a new TLV for Hello
messages. This TLV may carry a set of parameters indicating the
performance capacity to receive LSPs.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 13, 2022.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Flooding Parameters TLV . . . . . . . . . . . . . . . . . . . 5
3.1. InterfaceLSPReceiveWindow sub-TLV . . . . . . . . . . . . 5
3.2. minimumInterfaceLSPTransmissionInterval sub-TLV . . . . . 5
4. Flow control . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Operation on a point to point interface . . . . . . . . . 6
4.2. Faster acknowledgments of LSPs . . . . . . . . . . . . . 7
4.3. Operation on a LAN interface . . . . . . . . . . . . . . 8
5. Congestion control . . . . . . . . . . . . . . . . . . . . . 9
5.1. Slow start . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. Congestion avoidance . . . . . . . . . . . . . . . . . . 10
5.3. Remarks . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Interaction with other LSP rate limiting mechanisms . . . . . 11
7. Determining values to be advertised in the Flooding
Parameters TLV . . . . . . . . . . . . . . . . . . . . . . . 12
8. Operation considerations . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
12.1. Normative References . . . . . . . . . . . . . . . . . . 15
12.2. Informative References . . . . . . . . . . . . . . . . . 15
Appendix A. Changes / Author Notes . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
IGP flooding is paramount for Link State IGP as routing computations
assume that the Link State DataBases (LSDBs) are always in sync
across all nodes in the flooding domain.
Slow flooding directly translates to delayed network reaction to
failure and LSDB inconsistencies across nodes. The former increases
packet loss. The latter translates to routing inconsistencies and
possibly micro-loops leading to packet loss, link overload, and
jitter for all classes of service. Note that across the network,
multiple links may be affected by these forwarding issues, even in
the case of a single link failure.
In addition, one single event in the network can require the flooding
of multiple LSPs. The typical case is a node failure which requires
the flooding of at least one LSP per neighbor of the failed node.
Hence, if a node has N IGP neighbors, the failure of this node
requires the advertisement and flooding of at least N LSPs. The
network won't be able to converge to the new topology until all N
LSPs are received by all nodes. Hence there is a need to be able to
quickly exchange N LSPs. This document addresses this requirement by
allowing the fast flooding of a number of consecutive LSPs.
IGP flooding is hard. One would want fast flooding when the network
is stable and slow enough flooding to not overload the neighbor(s)
when the network is less stable. Since flooding is performed hop by
hop, not overloading the adjacent receiver is sufficient.
Improving the communication speed and efficiency between IS-IS
neighbors improves IS-IS scaling. These extensions do not compete
with proposed extensions to reduce LSP flooding traffic by reducing
the flooding topology such as [I-D.ietf-lsr-dynamic-flooding] . On
the contrary, this extension complements those proposals. Indeed
reducing the flooding topology does not reduce the size of the LSDB
or the total number of LSPs to exchange between two nodes. So
increasing the overall flooding speed can be beneficial for nodes
implementing dynamic flooding. The reverse is also true: as dynamic
flooding reduces the number of neighbors with flooding enabled, this
allows nodes implementing the flooding parameter extensions to focus
their flooding resources on those neighbors by sending better
parameters to the selected flooding nodes and worse parameters to
non-selected flooding nodes.
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1.1. Requirements Language
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 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
2. Overview
Ensuring the goodput between two entities is a layer 4 responsibility
as per the OSI model and a typical example is the TCP protocol
defined in RFC 793 [RFC0793] . It typically relies on the following
sub-functions: flow control, congestion control and reliability.
Flow control is about creating a control loop between a single
transmitter and single receiver. TCP provides a mean for the
receiver to govern the amount of data sent by the sender. This is
achieved by advertising a "receive window", in units of octets, with
every ACK. This document proposes to use the same mechanism by
advertising a receive window, in units of LSP packets, in IS-IS
Hello. The window indicates an allowed number of LSPs that the
sender may transmit before receiving acknowledgment of those LSPs.
There is an assumption that this is related to the currently
available data buffer space available for this adjacency. Indicating
a large window encourages transmissions.
Congestion control is about creating multiple interacting control
loops between multiple transmitters and multiple receivers. Whereas
flow control prevents the sender from overwhelming the receiver,
congestion control prevents senders from overwhelming the network.
For an IS-IS adjacency, the network between two IS-IS neighbors is
relatively limited in scope and consist in a link which is typically
over-sized compared to the capability of the IS-IS speakers, but also
includes components inside both routers such as a fabric switch, line
card CPU and forwarding plane buffers which may experience
congestion. This document proposes to use the AIMD (Additive
Increase Multiplicative Decrease) algorithm to react to packet loss.
Note that TCP Reno relies on the same algorithm.
Reliability relies on loss detection and recovery. IS-IS already has
mechanisms to ensure the reliable transmission of LSPs. This is not
changed by this document.
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3. Flooding Parameters TLV
This document defines a new TLV called "Flooding Parameters TLV" that
may be included in IIH PDUs. It allows the LSP receiver to advertise
receiver related parameters and capabilities which allows the LSP
sender to better adapt to the receiver.
Type: TBD1.
Length: variable, the size in octet of the Value field.
Value: a list of sub-TLVs.
Two sub-TLVs are defined in this document.
3.1. InterfaceLSPReceiveWindow sub-TLV
The sub-TLV InterfaceLSPReceiveWindow advertises the maximum number
of un-acknowledged LSPs that the node can receive/process with no
separation interval between LSPs.
Type: 1.
Length: 4 octets.
Value: number of un-acknowledged LSPs which can be sent back to back.
Note that if an LSP has not been acknowledged and is sent again, it
does not count twice. The reason is that this LSP is assumed to be
lost and hence not in a buffer at the receiver.
3.2. minimumInterfaceLSPTransmissionInterval sub-TLV
The sub-TLV minimumInterfaceLSPTransmissionInterval advertises the
minimum interval, in micro-seconds, between LSPs arrivals which can
be processed/received on this interface, after the maximum number of
un-acknowledged LSPs has been sent.
Type: 2.
Length: 4 octets.
Value: minimum interval, in micro-seconds, between two consecutive
LSPs sent after the receive window has been used.
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4. Flow control
Flow control is about creating a control loop between a single
transmitter and single receiver. This document proposes to use a
mechanism similar to the TCP receive window to allow the receiver to
govern the amount of data sent by the sender. This receive window
indicates an allowed number of LSPs that the sender may transmit
before receiving acknowledgment of those LSPs. This receive window,
in units of LSPs, is advertised in the sub-TLV
InterfaceLSPReceiveWindow.
4.1. Operation on a point to point interface
By sending the InterfaceLSPReceiveWindow sub-TLV with a value N, the
node advertises to its IS-IS neighbor, its ability to receive a
maximum of N un-acknowledged LSPs from this neighbor, with no
separation interval. This is akin to a reception window or sliding
window in flow control. This value typically reflects the socket
buffer size. Special care must be taken to let space for Hello and
SNP PDUs if they share the same socket. In this case, this document
suggests to advertise a Receive Window corresponding to half the size
of the socket buffer.
By sending the minimumInterfaceLSPTransmissionInterval sub-TLV with a
value T, the node advertises to its IS-IS neighbor, its ability to
receive, after the receive window is full, LSPs separated by at least
T micro-seconds from this neighbor.
The IS transmitter MUST NOT exceed these parameters. After having
sent N un-acknowledged LSPs, it MUST send the following LSPs with an
interval of at least T micro-seconds between each LSP.
Note however that if either the LSP transmitter or receiver does not
adhere to these parameters, for example because of transient
conditions, this causes no fatal condition to the operation of IS-IS.
The worst case, the loss of LSP on the IS receiver, is already
accounted for in [ISO10589] . As per [ISO10589] , after a few
seconds, respectively 2 and 10 by default in [ISO10589] , neighbors
will exchange PSNP (for point to point interface) or CSNP (for
broadcast interface) and recover from the lost LSPs. This worst case
(overrunning the receiver) should however be avoided as those
additional seconds are impacting the network and the traffic as the
LSDB is not fully synchronized. Hence it is better to err on the
conservative side and to under-run the receiver rather than over-run
it.
For a given IS-IS adjacency, the Flooding Parameters TLV does not
need to be advertised in each IIH. The IS transmitter uses the
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latest received value for each parameter (sub-TLV) until a new value
is advertised by the IS receiver. Note however that IIH are not
reliably exchanged, hence may never be received. For a parameter
which has never been advertised, the IS transmitter use its local
default value. That value SHOULD be configurable on a per node basis
and MAY be configurable on a per interface basis.
4.2. Faster acknowledgments of LSPs
As per [ISO10589] , on point to point interfaces, the LSP receiver
dynamically acknowledges the received LSPs by sending PSNP messages.
By acknowledging the LSPs before the InterfaceLSPReceiveWindow is
exhausted, the receiver can achieve dynamic flow control and increase
the flooding throughput without risking overloading any IS-IS router.
If the InterfaceLSPReceiveWindow is large enough, the downstream
flooding node can acknowledge a set of multiple LSPs up to the
maximum size of a PSNP (90 LSPs) which allows dynamic flow control
with limited or even no increase in the number of sent PSNPs.
In order to avoid reducing the throughput, the receiver should avoid
letting the receive window exhaust. Therefore, the receiver SHOULD
acknowledge the LSP more quickly than the default specified in
[ISO10589] . This is beneficial both to the LSP sender which receives
faster feedback and to the LSP receiver which has more time to
acknowledge many LSPs before the sender times out and resend the LSP.
Receiver SHOULD reduce partialSNPInterval. The choice of this lower
value is a local choice. It may depend on the (available) processing
power of the node, the number of adjacencies, the requirement to
synchronize the LSDB more quickly. 200 ms seems a reasonable value.
In addition to the timer based partialSNPInterval, the receiver
SHOULD keep track of the number of unacknowledged LSPs per circuit
and level. When this number exceeds a preset threshold LSP per PSNP
(LPP), the receiver SHOULD immediately send a PSNP without waiting
for the PSNP timer to expire. In case of a burst of LSPs, this
allows for more frequent PSNPs, hence a faster feedback loop to the
sender. In the absence of burst, the usual time-based PSNP approach
comes into effect. This number SHOULD be lower than the advertised
receive window InterfaceLSPReceiveWindow, e.g.,
InterfaceLSPReceiveWindow/2. This number SHOULD also be lower or
equal to 90 as this is the maximum number of LSPs that can be
acknowledged in a PSNP, hence waiting longer would not reduce the
number of PSNPs sent but would delay the acknowledgements. Best
performance is achieved when this number is an integer fraction of
InterfaceLSPReceiveWindow. Based on experimental evidence, 15
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unacknowledged LSPs is a right value assuming that
InterfaceLSPReceiveWindow is at least twice bigger (>30).
By deploying both the time-based and the threshold-based PSNP
approaches, the receiver can be adaptive to both LSP bursts and
infrequent LSP updates.
4.3. Operation on a LAN interface
On a LAN interface, an IS receiver will generally receive LSPs from
multiple IS transmitters. Also the LSPs sent by a given IS
transmitter is received by all of the IS receivers on that LAN. In
this section, we clarify how the flooding parameters should be
interpreted in the context of a LAN.
An IS receiver on a LAN will communicate its desired flooding
parameters using a single Flooding Parameters TLV, copies of which
will be received by all N transmitters. The flooding parameters sent
by the IS receiver MUST be understood as instructions from the
receiver to each transmitter about the desired maximum transmit
characteristics of each transmitter. The receiver is aware that
there are N transmitters that can send LSPs to the receiver LAN
interface. The receiver might want to take that into account by
advertising a higher value of InterfaceLSPTransmissionInterval on
this LAN interface than what it would advertise on a point to point
interface. When the transmitters receive the
InterfaceLSPTransmissionInterval value advertised by the DIS
receiver, the transmitters should rate limit LSPs according to the
advertised flooding parameters. They should not apply any further
interpretation to the flooding parameters advertised by the receiver.
A given IS transmitter will receive flooding parameter advertisements
from N different Flooding Parameters TLVs, which may carry different
flooding parameter values. A given transmitter SHOULD use the most
convervative value on a per Flooding parameter basis. For example,
if the transmitter receivers InterfaceLSPReceiveWindow from N IS-Is
nodes on the LAN, it should use the smallest value.
In order for the InterfaceLSPReceiveWindow to be a useful parameter,
an IS transmitter needs to be able to keep track of the number of un-
acknowledged LSPs it has sent to a given IS receiver. On a LAN there
is no explicit acknowledgment of the receipt of LSPs between a given
IS transmitter and a given IS receiver. However, an IS transmitter
on a LAN can infer whether any IS receiver on the LAN has requested
retransmission of LSPs from the DIS, by monitoring PSNPs generated on
the LAN. If no PSNPs have been generated on the LAN for a suitable
period of time, then an IS transmitter can safely set the number of
un-acknowledged LSPs to zero. Since this suitable period of time is
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much higher than the fast acknowledgment of LSP defined in
Section 4.2 , the substainable sending rate of LSP will be much
slower on a LAN interface compared to a point to point interface.
However, InterfaceLSPReceiveWindow is still very useful for the first
LSPs sent and hence usefull for the faster flooding in case of a
single node failure which requires to flood a relatively small number
of LSPs.
A compliant implementation may choose to not support this operation
on a LAN interface.
5. Congestion control
Whereas flow control prevents the sender from overwhelming the
receiver, congestion control prevents senders from overwhelming the
network. For an IS-IS adjacency, the network between two IS-IS
neighbors is relatively limited in scope and includes a single link
which is typically over-sized compared to the capability of the IS-IS
speakers. It also includes components inside both routers such as a
fabric switch, line cards CPU and forwarding plane buffers which may
experience congestion. This document proposes one optional
congestion control algorithm but implementations may choose a
different one or none.
The congestion control algorithm defined in this document is largely
inspired by the TCP congestion control algorithm RFC 5681 [RFC5681].
A congestion control algorithm is comprised of three elements : a
slow start phase, a congestion avoidance phase, and a transition
between the two.
The proposed algorithm uses a variable Congestion window 'cwin'. It
plays the same role as Receive Window described before. The main
difference is that CWin is dynamically changed according to the
feedback obtained by the PSNPs.
5.1. Slow start
The goal of the slow start phase is to grow fast and try to estimate
the effective link capacity.
The algorithm is circuit scoped. At the beginning of the slow start,
the sender starts with:
o a congestion window (cwin) set to one. cwin := 1;
o a number of acked LSPs. acked_lsps := 0;
o a max seen bandwidth. max_bw := 0;
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o a current rtt estimate. cur_rtt := NA;
Upon LSP sending, a sender records for said LSP the current time in
time_sent and acked_lsps in acked_lsps_sent. This data is tied to
each LSP.
Upon PSNP reception, a sender does the following:
cwin := min(cwin + nb_of_lsp_entries, rwin)
acked_lsps += nb_of_lsp_entries
max_diff := 0
max_bw := 0
for every LSP entry:
time_to_ack := time_now - time_sent
nb_acked := acked_lsps - acked_lsps_sent
bw_est := nb_acked/time_to_ack
max_bw := max(max_bw, bw_est)
max_diff := max(max_diff, time_to_ack)
if cur_rtt == NA then cur_rtt = max_diff
else cur_rtt := 7/8 * cur_rtt + 1/8 * max_diff
Figure 1
Starting with the first PSNP, max_bw is checked every cur_rtt. Once
it has stalled for 3 consecutive times, the congestion control
algorithm transitions from slow start to congestion avoidance. There
is bandwidth stalling when the bandwidth has not increased by at
least 25% compared the last RTT. Note that this is similar to
Google's BBR ([I-D.cardwell-iccrg-bbr-congestion-control] ) slow
start phase.
5.2. Congestion avoidance
The goal of the congestion avoidance phase is to try to stay close to
the effective capacity of the link. For this, the algorithm
estimates the maximum time taken by the receiver to acknowledge a
LSP. If an LSP arrives slower than this delay, congestion is
inferred and cwin is decreased.
Upon PSNP reception, a sender does the following:
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cwin = min(cwin + N/congestion window, rwin)
rtt_est := 0
for every LSP entry:
time_to_ack = time_now - time_sent
rtt_est = max(rtt_est, time_to_ack)
if rtt_var == NA then rtt_var = rtt_est / 2
else rtt_var = 3/4 * rtt_var + 1/4 * abs(cur_rtt - rtt_est)
cur_rtt = 7/8 * cur_rtt + 1/8 * rtt_est
Figure 2
Every LSP is checked to be acked within cur_rtt + rtt_var. If an LSP
arrives late, cwin is divided by two. This behaviour is similar to
TCP retransmission timer defined in RFC 6298 [RFC6298]
Note: there is no need for a timer per LSP. A timer per RTT is
enough. During an RTT, sent LSPs are recorded in a list list_1.
Once the RTT is over, list_1 is kept and another list list_2 is used
to store the next LSPs. LSPs are removed from the lists when acked.
At the end of the second RTT, every LSP in list_1 should have been
acked, so list_1 is checked to be empty. List_1 can then be reused
for the next RTT.
If there is no transmitted LSP for a fixed period of time, e.g. 2
seconds, the sender switches back to the slow start phase.
5.3. Remarks
This algorithm's performance is dependent on the LPP value. Indeed,
the smaller LPP is, the more information is available for the
congestion control algorithm to perform well. However, it also
increases the resources spent on sending PSNPs, so a tradeoff must be
made. This document recommends to use an LPP of 15 or less.
Note that this congestion control algorithm benefits from the
extensions proposed in this document. The advertisement of a receive
window from the receiver ( Section 4 ) avoids the use of an arbitrary
maximum value by the sender. The faster acknowledgment of LSP (
Section 4.2 ) allows for a faster control loop and hence a faster
increase of the congestion window in the absence of congestion.
6. Interaction with other LSP rate limiting mechanisms
[ISO10589] describes a mechanism that limits the rate at which LSPs
from the same source system are sent out on interfaces. (See the
description of the parameter
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minimumBroadcastLSPTranLSPTransmissionInterval in section 7.3.15.6 of
[ISO10589] ). In practice, however, router vendors have implemented
mechanisms that limit the rate of LSPs sent on a given interface.
This is often configurable on a per-interface basis using 'lsp-
interval' or 'lsp-pacing-interval' CLI configuration). The mechanism
described in the current document extends the practice of limiting
the rate of LSPs sent on a given interface, by using parameters
advertised by the LSP receiver. When the mechanism described in the
current document is used, the mechanism described in section 7.3.15.6
of [ISO10589] is not used.
7. Determining values to be advertised in the Flooding Parameters TLV
The values that a receiving IS advertises do not need to be close to
perfection. It is OK to be too low and hence not to use the full
bandwidth or CPU resources. It is OK to be too high during some
situation and hence have the receiver drop some LSPs as the IS-IS
protocol has mechanisms to recover. What is not OK is to flood
multiple order of magnitudes slower than both nodes can achieve, or
to consistently overload the receiver.
The values may not need to be dynamic as a form of dynamic is
provided by the dynamic acknowledgment of LSPs in SNP messages.
Acknowledgments provides a feedback loop on how fast/slower the LSPs
are processed by the receiver. They also signal that the LSPs have
been processed by the receiver hence removed from receive window,
explicitly signaling to the sender that more LSPs may be sent. By
advertising relatively static parameters, we expect to produce
overall flooding behavior similar to what might be achieved by
manually configuring per-interface LSP rate limiting on all
interfaces in the network. The advertised values may be based, for
example, on an off line tests of the overall LSP processing speed for
a particular set of hardware and the number of interfaces configured
for IS-IS. With such a formula, the values advertised in the
Flooding Parameters TLV would only change when additional IS-IS
interfaces are configured.
The values may be updated dynamically, to reflect the relative change
of load of the receiver, by improving the values when the receiver
load is getting lower and degrading the values when the receiver load
is getting higher. For example, if LSPs are regularly dropped, or
the queue regularly comes close to being filled, then values may be
too high. On the other hand, if the queue is barely used (by IS-IS),
then values may be too low.
The values may also be absolute value reflecting relevant (averaged)
hardware resources that are been monitored, typically the amount of
buffer space used by incoming LSPs. In this case, care must be taken
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when choosing the parameters influencing the values, in order to
avoid undesirable or instable feedback loops. It would be
undesirable to use a formula that depends, for example, on an active
measurement of the instantaneous CPU load to modify the values
advertised in the Flooding Parameters TLV. This could introduce
feedback into the IGP flooding process that could produce unexpected
behavior.
8. Operation considerations
As discussed in Section 4.3 , the solution is more effective on point
to point adjacencies. Hence a broadcast interface (e.g. Ethernet)
only shared by two IS-IS neighbhors should be configured as point to
point in order to have a more effective flooding.
9. IANA Considerations
IANA is requested to allocate one TLV from the IS-IS TLV codepoint
registry.
Type Description IIH LSP SNP Purge
---- --------------------------- --- --- --- ---
TBD1 Flooding Parameters TLV y n n n
Figure 3
This document creates the following sub-TLV Registry:
Name: Sub-TLVs for TLV TBD1 (Flooding Parameters TLV).
Registration Procedure: Expert Review [RFC8126] .
+-------+-----------------------------------------+
| Type | Description |
+-------+-----------------------------------------+
| 0 | Reserved |
| 1 | InterfaceLSPReceiveWindow |
| 2 | minimumInterfaceLSPTransmissionInterval |
| 3-255 | Unassigned |
+-------+-----------------------------------------+
Table 1: Initial allocations
10. Security Considerations
Any new security issues raised by the procedures in this document
depend upon the ability of an attacker to inject a false but
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apparently valid SNP or IIH, the ease/difficulty of which has not
been altered.
As with others TLV advertisements, the use of a cryptographic
authentication as defined in [RFC5304] or [RFC5310] allows the
authentication of the peer and the integrity of the message. As this
document defines a TLV for SNP or IIH message, the relevant
cryptographic authentication is for SNP and IIH message.
In the absence of cryptographic authentication, as IS-IS does not run
over IP but directly over the link layer, it's considered difficult
to inject false SNP/IHH without having access to the link layer.
If a false SNP/IIH is sent with a Flooding Parameters TLV set to
conservative values, the attacker can reduce the flooding speed
between the two adjacent neighbors which can result in LSDB
inconsistencies and transient forwarding loops. However, it is not
significantly different than filtering or altering LSPDUs which would
also be possible with access to the link layer. In addition, if the
downstream flooding neighbor has multiple IGP neighbors, which is
typically the case for reliability or topological reasons, it would
receive LSPs at a regular speed from its other neighbors and hence
would maintain LSDB consistency.
If a false SNP/IIH is sent with a Flooding Parameters TLV set to
aggressive values, the attacker can increase the flooding speed which
can either overload a node or more likely generate loss of LSPs.
However, it is not significantly different than sending many LSPs
which would also be possible with access to the link layer, even with
cryptographic authentication enabled. In addition, IS-IS has
procedures to detect the loss of LSPs and recover.
This TLV advertisement is not flooded across the network but only
sent between adjacent IS-IS neighbors. This would limit the
consequences in case of forged messages, and also limits the
dissemination of such information.
11. Acknowledgments
The authors would like to thank Henk Smit, Sarah Chen, Xuesong Geng,
Pierre Francois and Hannes Gredler for their reviews, comments and
suggestions.
The authors would like to thank David Jacquet, Sarah Chen, and
Qiangzhou Gao for the tests performed on commercial implementations
and their identification of some limiting factors.
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12. References
12.1. Normative References
[ISO10589]
International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473)", ISO/
IEC 10589:2002, Second Edition, Nov 2002.
[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>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC6298] Paxson, V., Allman, M., Chu, J., and M. Sargent,
"Computing TCP's Retransmission Timer", RFC 6298,
DOI 10.17487/RFC6298, June 2011,
<https://www.rfc-editor.org/info/rfc6298>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
12.2. Informative References
[I-D.cardwell-iccrg-bbr-congestion-control]
Cardwell, N., Cheng, Y., Yeganeh, S. H., and V. Jacobson,
"BBR Congestion Control", draft-cardwell-iccrg-bbr-
congestion-control-00 (work in progress), July 2017.
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[I-D.ietf-lsr-dynamic-flooding]
Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda,
T., Cooper, D., Jalil, L., Dontula, S., and G. S. Mishra,
"Dynamic Flooding on Dense Graphs", draft-ietf-lsr-
dynamic-flooding-08 (work in progress), December 2020.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>.
Appendix A. Changes / Author Notes
[RFC Editor: Please remove this section before publication]
00: Initial version.
01: Two notes added in section 3 "Operation".
02: Refresh, no technical change.
03:
o Flooding Parameters TLV: name changed, advertised in both Hello
and SNP rather than just Hello, contains sub-TLVs, parameters
encoded in 4 octets.
o Terminology: upstream/downstream terms removed, in favor of terms
from ISO specification (transmitter, receiver); burst-size rename
to receive-window.
o Significant editorials changes.
o New section on the faster acknowledgment of LSPs.
o New section on the faster retransmission of lost LSPs.
04:
o Adding general introduction on flow control, congestion control,
loss detection and recovery.
o Reorganizing sections as per the high level functions: flow
control, congestion control, loss detection and recovery.
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o Adding a section on congestion control.
05:
o Some editorials changes.
o Updating section "Faster acknowledgments of LSPs" following the
IS-IS flooding performance tests presented during IETF 108.
o Updated IANA section (new registry).
06: Refresh, no technical change.
07:
o Precision that if a LSP is lost and resent, it does not count
twice in the InterfaceLSPReceiveWindow.
o Title changed.
o Removed fast retransmissions of LSPs.
o Changed congestion control algorithm.
o Removed support of TLV in SNP.
Authors' Addresses
Bruno Decraene
Orange
Email: bruno.decraene@orange.com
Chris Bowers
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
USA
Email: cbowers@juniper.net
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Jayesh J
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
USA
Email: jayeshj@juniper.net
Tony Li
Arista Networks
5453 Great America Parkway
Santa Clara, California 95054
USA
Email: tony.li@tony.li
Gunter Van de Velde
Nokia
Copernicuslaan 50
Antwerp 2018
Belgium
Email: gunter.van_de_velde@nokia.com
Guillaume Solignac
Orange
Email: guillaume.solignac@orange.com
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