Internet DRAFT - draft-ali-spring-sr-pm
draft-ali-spring-sr-pm
SPRING Working Group Z. Ali
Internet Draft C. Filsfils
Intended status: Standards Track R. Gandhi
Expires: June 22, 2018 N. Kumar
F. Iqbal
C. Pignataro
Cisco Systems, Inc.
D. Steinberg
Steinberg Consulting
S. Salsano
Universita di Roma "Tor Vergata"
G. Naik
Drexel University
December 23, 2017
Performance Measurement in Segment Routing Networks
draft-ali-spring-sr-pm-00.txt
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Abstract
RFC 6374 specifies protocol mechanisms to enable the efficient and accurate
measurement of packet loss, one-way and two-way delay, as well as related metrics
such as delay variation and channel throughput in MPLS networks. This document
describes how these mechanisms can be used for performance measurements in Segment
Routing with MPLS data plane (SR-MPLS) networks. The document also specifies how
similar mechanisms can be used for performance measurement in Segment Routing with
IPv6 data plane (SRv6) networks.
Table of Contents
1. Introduction...................................................2
2. Performance Measurement in SR-MPLS Networks....................3
2.1. Delay Measurement in SR-MPLS Networks.....................3
2.1.1. Delay Measurement Message Format.....................3
2.1.2. One Way Delay Measurement............................3
2.1.2.1. One-Way Delay Measurement using Synthetic Probes3
2.1.3. Two Way Delay Measurement............................3
3. Performance Measurement in SRv6 Networks.......................4
3.1. Terminology and Reference Topology........................4
3.2. Delay Measurement in SRv6 Networks........................5
3.2.1. One Way Delay Measurement............................5
3.2.2. Two Way Delay Measurement............................6
3.2.3. Delay Measurement Message Format.....................6
3.2.4. One-Way Delay Measurement using Synthetic Probes.....8
3.2.4.1. Example Procedure...............................8
3.2.5. In-situ One-Way Segment-by-Segment Delay Measurement.9
3.2.5.1. Example Procedure...............................9
4. Security Considerations.......................................10
5. IANA Considerations...........................................10
6. Contributors..................................................10
7. References....................................................10
7.1. Normative References.....................................10
7.2. Informative References...................................11
8. Acknowledgments...............................................11
1. Introduction
Service provider's ability to satisfy Service level agreements (SLAs) depend on
the ability to measure and monitor performance metrics for packet loss and one-way
and two-way delay, as well as related metrics such as delay variation and channel
throughput. The ability to monitor these performance metrics also provides
operators with greater visibility into the performance characteristics of their
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networks, thereby facilitating planning, troubleshooting, and network performance
evaluation. [RFC6374] specifies protocol mechanisms to enable the efficient and
accurate measurement of these performance metrics in MPLS networks. This document
describes how these mechanisms can be used for performance measurements in Segment
Routing with the MPLS data plane (SR-MPLS) networks. The document also specifies
how similar mechanisms can be used for performance measurement in Segment Routing
with the IPv6 data plane (SRv6) networks.
2. Performance Measurement in SR-MPLS Networks
SR-MPLS relies on MPLS data plane without any changes. Hence, the protocol
mechanisms for MPLS networks defined in [RFC6374] are equally applicable to SR-
MPLS networks. This version of the document focuses on delay measurement.
Measurements for loss and other performance metrics are to be added in the future
version of this document.
2.1. Delay Measurement in SR-MPLS Networks
2.1.1. Delay Measurement Message Format
As described in [RFC6374], Section 2.9.1, MPLS DM probe messages flow over the
MPLS Generic Associated Channel (G-ACh). Thus, a probe packet for a DM message
contains SR-MPLS label stack, with the G-ACh Label (GAL) at the bottom of the
stack. The GAL is followed by an Associated Channel Header (ACH) (value 0x000C
for delay measurement) [RFC6374], which identifies the message type, and the
message body following the ACH. The format of the DM message payload as defined
in [RFC6374] is used for SR-MPLS delay measurement.
2.1.2. One Way Delay Measurement
2.1.2.1. One-Way Delay Measurement using Synthetic Probes
The query and response mechanisms defined in [RFC6374] are followed for synthetic
delay measurement in SR-MPLS network.
For one-way delay measurement, the querier node SHOULD send the UDP Return Object
(URO) (Type=131) defined in [RFC7867]. The responder node SHOULD send the
response back to the querier node in an UDP message when the URO TLV is present in
the PM query message.
2.1.3. Two Way Delay Measurement
The two-way delay measurement for packet networks is defined in [RFC6374]. The
two-way delay measurement in SR-MPLS networks is to be added in the future version
of this document.
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3. Performance Measurement in SRv6 Networks
This version of the document focuses on delay measurement. Loss and
other performance metric measurements are to be added in the future
version of this document.
3.1. Terminology and Reference Topology
Throughout the document, the following simple topology is used for illustration.
+--------------------------| N100 |------------------------+
| |
====== link1====== link3------ link5====== link9------
||N1||======||N2||======| N3 |======||N4||======| N5 |
|| ||------|| ||------| |------|| ||------| |
====== link2====== link4------ link6======link10------
| |
| ------ |
+--------| N6 |--------+
link7 | | link8
------
Reference Topology
In the reference topology:
Nodes N1, N2, and N4 are SRv6 capable nodes.
Nodes N3, N5 and N6 are classic IPv6 nodes.
Node 100 is a controller.
Node Nk has a classic IPv6 loopback address Bk::/128
Node Nk has Ak::/48 for its local SID space from which Local SIDs are explicitly
allocated.
The IPv6 address of the nth Link between node X and Y at the X side is represented
as 99:X:Y::Xn. e.g., the IPv6 address of link6 (the 2nd link) between N3 and N4 at
N3 in Figure 1 is 99:3:4:32. Similarly, the IPv6 address of link5 (the 1st link
between N3 and N4) at node 3 is 99:3:4::31.
Ak::0 is explicitly allocated as the END function at Node k.
Ak::Cij is explicitly allocated as the END.X function at node k towards neighbor
node i via jth Link between node i and node j. e.g., A2::C31 represents END.X at
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N2 towards N3 via link3 (the 1st link between N2 and N3). Similarly, A4::C52
represents the END.X at N4 towards N5 via link10.
SRH is the abbreviation for the Segment Routing Header.
SL is the abbreviation for the Segment Left.
SID is the abbreviation for the Segment ID.
<S1, S2, S3> represents a SID list where S1 is the first SID and S3 is the last
SID. (S3, S2, S1; SL) represents the same SID list but encoded in the SRH format
where the rightmost SID (S1) in the SRH is the first SID and the leftmost SID (S3)
in the SRH is the last SID.
ECMP is the abbreviation for the Equal Cost Multi-Path.
UCMP is the abbreviation for the Unequal Cost Multi-Path.
3.2. Delay Measurement in SRv6 Networks
3.2.1. One Way Delay Measurement
The one-way delay measurement for packet networks is defined in [RFC2679]. It is
further exemplified using the following Figure.
------
|N100|
| |
------
^
| Response Option2
T1 T2 |
+-------+/ Query \+-------+
| | - - - - - - - - - ->| |
| N1 |=====================| N4 |
| |<- - - - - - - - - - | |
+-------+\ Response Option1 /+-------+
T4 T3
Delay Measurement Reference Model
Nodes N1 and N4 may not be directly connected, as shown in the reference topology
in Figure 1. When N1 and N4 are not directly connected, the one-way delay
measurement reflects the delay observed by the packet over an arbitrary SRv6
segment-list/ policy. In other words, the one-way delay is associated with the
forward (N1 to N4) direction of the SRv6 segment-list/ policy.
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The delay measurement can be performed using Active (using synthetic probe) mode
and Passive (using data stream aka in-situ) mode. In both modes, T1 refers to the
time the packet is transmitted from N1. Timestamping is done as late as possible
at the egress pipeline (in hardware) at node N1. T2 refers to the time the packet
is received at N2. Timestamping at the receiver (N2) is done as soon as possible
at the ingress pipeline (in hardware).
The one-way delay metric can be defined as follow [RFC2679], [RFC6374],
One-way delay = T2 - T1.
Clock synchronization using methods detailed in [RFC6374] is assumed here.
Please note that for the one-way delay computation, the receiver (node N4 in
Figure 2) is not required to send a response. The response can be sent to a
controller (node N100 in Figure 2). The controller may also request the querier
(node N1 in Figure 2) to initiate a measurement (this messaging is not shown in
Figure 2 and is beyond the scope of this document).
3.2.2. Two Way Delay Measurement
The two-way delay measurement for packet networks is defined in [RFC6374]. The
two-way delay measurement in SRv6 networks is to be added in the future version of
this document.
3.2.3. Delay Measurement Message Format
[I-D.draft-ietf-6man-segment-routing-header] defines Segment Routing Header (SRH)
for SRv6. SRH can contain TLVs, as specified in [I-D.draft-ietf-6man-segment-
routing-header]. This document specifies Delay Measurement (DM) TLV of SRH. The
DM TLV adapts a message format similar to the message format specified in
[RFC6374]. The DM TLV format in SRv6 network is defined as following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QTF | RTF | RPTF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session Identifier | TC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp 1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
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. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp 4 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ SUB-TLV Block ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The meanings of the fields are summarized in the following table.
Field Meaning
--------------------- -----------------------------------------------
Type SRH TLV type (Value TBA)
Length Total length of the TLV in bytes
Version Protocol version
Flags Message control flags
Control Code Code identifying the query or response type
QTF Querier timestamp format
RTF Responder timestamp format
RPTF Responder's preferred timestamp format
Reserved Reserved for future specification
Session Identifier Set arbitrarily by the querier
Traffic Traffic Class being measured
Class (TC) Field
Timestamp 1-4 64-bit timestamp values (as shown in Figure 2)
TLV Block Optional block of Type-Length-Value fields
Reserved fields MUST be set to 0 and ignored upon receipt. The
possible values for the remaining fields are as follows.
Version: Currently set to 1 (to identify definition of TC field in [RFC6374])
Flags: As specified in [RFC6374]. The T flag in a DM message is set to 1.
Control Code: As specified in [RFC6374].
Message Length: Set to the total length of this message in bytes, including the
Version, Flags, Control Code, and Message Length fields as well as the TLV Block,
if any.
Querier Timestamp Format: The format of the timestamp values written by the
querier, as specified in Section 3.4 of [RFC6374].
Responder Timestamp Format: The format of the timestamp values written by the
responder, as specified in Section 3.4 of [RFC6374].
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Responder's Preferred Timestamp Format: The timestamp format preferred by the
responder, as specified in Section 3.4 of [RFC6374].
Session Identifier: Set arbitrarily in a query and copied in the response, if any.
This field uniquely identifies a measurement operation (also called a session)
that consists of a sequence of messages. All messages in the sequence have the
same Session Identifier [RFC6374].
TC: Traffic Class being measured.
Timestamp 1-4 (T1-T4): Referring to Figure 2.
The mapping of timestamps to the Timestamp 1-4 fields is designed to ensure that
transmit timestamps are always written at the same fixed offset in the packet, and
likewise for receive timestamps. This property is important for hardware
processing.
TLV Block: Zero or more TLV fields. This document assumes the use of the DM
message TLV defined in [RFC6374].
3.2.4. One-Way Delay Measurement using Synthetic Probes
For delay measurement using synthetic probes, a DM TLV in the SRH to record the
timestamps and END.OTP SID as described in the pseudocode in [I-D.draft-filsfils-
spring-srv6-network-programming] to punt the packet are used.
3.2.4.1. Example Procedure
To measure one-way delay from node N1 over an SR Policy that goes through a
segment-list (A2::C31, A4::C52) to node N4, following procedure is followed:
O Node N1 constructs a DM probe packet with (B1::0, A2::C31)(A4::C52, A2::C31,
SL=1; NH=NONE, DM TLV). To punt the DM probe packet at node N4, node N1 inserts
the END.OTP SID [I-D.draft-filsfils-spring-srv6-network-programming] just before
the target SID A4::C52 in the SRH. Thus, the packet as it leaves node N1 looks
like (B1::0, A2::C31)(A4::C52, A4::OTP, A2::C31; SL=2; NH=NONE, DM TLV (with T1
from N1)). The PM synthetic probe query message does not contain any payload
data.
O When node N4 receives the packet (B1::0, A4::OTP)(A4::C52, A4::OTP, A2::C31;
SL=1; NH=NONE, DM TLV), it processes the END.OTP SID, as described in the
pseudocode in [I-D.draft-filsfils-spring-srv6-network-programming]. In doing so,
it punts the timestamped packet (with T2 from N4) to the Performance Measurement
(PM) process for processing.
The PM process on node N4 responds to the DM probe message as following:
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O The Source Address object (Type=130) and Destination Address object (Type=129)
TLVs [RFC6374] indicate the addresses of the sender and the intended recipient of
the PM message, respectively. The Source Address of a query message SHOULD be
used as the destination unless an out-of-band response mechanism has been
configured such as return controller's address is locally configured.
O When a Return Address TLV object (Type=1) [RFC6374] is present in which case
the Return Address specifies the target address for the response message.
O If the querier node N1 requires the response to be sent to the controller
(N100), it adds the target controller's IP address in the Return Address TLV
object of the DM message.
O For one-way delay measurement, the querier node can send the UDP Return Object
(URO) (Type=131) defined in [RFC7867]. From the responder node, the response is
sent back to the PM querier node using the UDP Return Object (URO) TLV (Type=131)
defined in [RFC7867] when the URO TLV is present in the PM query message. The PM
process copies the content of the DM TLV into the payload of the PM reply message.
3.2.5. In-situ One-Way Segment-by-Segment Delay Measurement
For delay measurement for in-situ with data traffic, a DM TLV in the SRH to record
timestamps and O-bit as described in [I-D.draft-filsfils-spring-srv6-network-
programming] to punt the packet on every SRv6 nodes are used.
3.2.5.1. Example Procedure
Consider the case where the user wants to measure one-way delay from node N1 over
an SR Policy that goes through a segment-list (A2::C31, A4::C52). However, the
user desired to get the delay measurement done in-situ with data traffic on a
segment-by-segment basis.
O To force a punt of the time-stamped copy of the data packet at node N2 and node
N4, node N1 sets the O-bit in SRH at locally configured periodic measurement
interval. The packet, as it leaves node 1, looks like (B1::0, A2::C31)(A4::C52,
A2::C31; SL=1, Flags.O=1, DM TLV (with T1 from N1), NH=data payload type)(data
payload). Here, the data payload refers to the actual data traffic going over the
policy whose performance is being measured. Node N1 may optionally punt a time-
stamped copy of the packet with T1 to the local PM process.
O When node N2 receives the packet (B1::0, A2::C31)(A4::C52, A2::C31; SL=1,
Flags.O=1, DM TLV, NH=data payload type)(data payload) packet, it processes the O-
bit in SRH, as described in the pseudocode in [I-D.draft-filsfils-spring-srv6-
network-programming]. A time-stamped copy of the packet gets punted to the PM
process for processing. Node N2 continues to apply the A2::C31 SID function on
the original packet and forwards it, accordingly. As SRH.Flags.O=1, Node N2 also
disables the PSP flavour, i.e., does not remove the SRH.
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O The PM process at node N2 sends the copy of the time-stamped packet (with DM
TLV containing T1 from N1 and T2 from N2) to a locally configured controller or to
the querier. Please note that, as mentioned in [I-D.draft-filsfils-spring-srv6-
network-programming], if node N2 does not support the O-bit, it simply ignores it
and processes the local SID, A2::C31. In this case, the controller will not get
the performance data from the segments with the nodes that do not support the O-
bit.
O When node N4 receives the packet (B1::0, A4::C52)(A4::C52, A2::C31; SL=0,
Flags.O=1, DM TLV (containing T1 from N1); NH=data payload type)(data payload), it
processes the O-bit in SRH, as described in the pseudocode in [I-D.draft-filsfils-
spring-srv6-network-programming]. A time-stamped copy of the packet gets punted
to the PM process for processing.
O The PM process at node N2 sends the copy of the time-stamped packet (with DM
TLV containing T1 from N1 and T2 from N4) to a locally configured controller.
The Controller processes the time-stamped packet from each segment and computes
the segment-by-segment one-way delay. Support for O-bit is part of node
capability advertisement. That enables node N1 and the controller know which
segment nodes are capable of sending time-stamped copy of the packet.
4. Security Considerations
TBA.
5. IANA Considerations
IANA is requested to allocate a value for the new SRH TLV Type for Delay
Measurement.
6. Contributors
Faisal Iqbal
Cisco Systems, Inc.
Email: faiqbal@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
Email: cpignata@cisco.com
7. References
7.1. Normative References
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS
Networks", DOI 10.17487/RFC6374, RFC 6374, September 2011.
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[RFC7876] Bryant, S., Sivabalan, S., and Soni, S., "UDP Return Path for Packet
Loss and Delay Measurement for MPLS Networks", RFC 7876, July 2016.
[I.D-filsfils-spring-srv6-network-programming] SRv6 Network Programming, draft-
filsfils-spring-srv6-network-programming, C. Fisfils, work in
progress.
7.2. Informative References
[I-D.brockners-inband-oam-data] Data Formats for In-situ OAM. F.
Brockners, work in progress.
[I-D.brockners-inband-oam-transport] Encapsulations for In-situ OAM Data,
F.Brockners, work in progress.
[I-D.brockners-inband-oam-requirements] Requirements for In-situ OAM,
F.Brockners, work in progress.
8. Acknowledgments
To be added.
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Authors' Addresses
Clarence Filsfils
Cisco Systems, Inc.
Email: cfilsfil@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Rakesh Gandhi
Cisco Systems, Inc.
Email: rgandhi@cisco.com
Nagendra Kumar
Cisco Systems, Inc.
Email: naikumar@cisco.com
Dirk Steinberg
Steinberg Consulting
Germany
Email: dws@dirksteinberg.de
Stefano Salsano
Universita di Roma "Tor Vergata"
Italy
Email: stefano.salsano@uniroma2.it
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