Internet DRAFT - draft-ietf-tictoc-multi-path-synchronization
draft-ietf-tictoc-multi-path-synchronization
Network Working Group A. Shpiner
Internet Draft Technion - Israel Institute of Technology
Intended status: Experimental R. Tse
Expires: October 2016 C. Schelp
PMC-Sierra
T. Mizrahi
Marvell
April 18, 2016
Multi-Path Time Synchronization
draft-ietf-tictoc-multi-path-synchronization-04.txt
Abstract
Clock synchronization protocols are very widely used in IP-based
networks. The Network Time Protocol (NTP) has been commonly deployed
for many years, and the last few years have seen an increasingly
rapid deployment of the Precision Time Protocol (PTP). As time-
sensitive applications evolve, clock accuracy requirements are
becoming increasingly stringent, requiring the time synchronization
protocols to provide high accuracy. Slave Diversity is a recently
introduced approach, where the master and slave clocks (also known as
server and client) are connected through multiple network paths, and
the slave combines the information received through all paths to
obtain a higher clock accuracy compared to the conventional one-path
approach. This document describes a multi-path approach to PTP and
NTP over IP networks, allowing the protocols to run concurrently over
multiple communication paths between the master and slave clocks. The
multi-path approach can significantly contribute to clock accuracy,
security and fault tolerance. The Multi-Path Precision Time Protocol
(MPPTP) and Multi-Path Network Time Protocol (MPNTP) define an
additional layer that extends the existing PTP and NTP without the
need to modify these protocols. MPPTP and MPNTP also allow backward
compatibility with nodes that do not support the multi-path
extension.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Shpiner, et al. Expires October 18, 2016 [Page 1]
Internet-Draft Multi-Path Time Synchronization April 2016
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 18, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction...................................................3
2. Conventions Used in this Document..............................5
2.1. Abbreviations.............................................5
2.2. Terminology...............................................5
3. Multiple Paths in IP Networks..................................5
3.1. Load Balancing............................................5
3.2. Using Multiple Paths Concurrently.........................6
3.3. Two-Way Paths.............................................6
4. Solution Overview..............................................6
4.1. Path Configuration and Identification.....................6
4.2. Combining.................................................7
5. Multi-Path Time Synchronization Protocols over IP Networks.....7
5.1. Single-Ended Multi-Path Synchronization...................8
5.1.1. Single-Ended MPPTP Synchronization Message Exchange..8
5.1.2. Single-Ended MPNTP Synchronization Message Exchange..9
5.2. Dual-Ended Multi-Path Synchronization....................10
5.2.1. Dual-Ended MPPTP Synchronization Message Exchange...10
Shpiner, et al. Expires October 18, 2016 [Page 2]
Internet-Draft Multi-Path Time Synchronization April 2016
5.2.2. Dual-Ended MPNTP Synchronization Message Exchange...11
5.3. Using Traceroute for Path Discovery......................12
5.4. Using Unicast Discovery for MPPTP........................12
6. Combining Algorithm...........................................13
7. Security Considerations.......................................13
8. IANA Considerations...........................................13
9. Acknowledgments...............................................13
10. References...................................................13
10.1. Normative References....................................13
10.2. Informative References..................................14
1. Introduction
The two most common time synchronization protocols in IP networks are
the Network Time Protocol [NTP], and the Precision Time Protocol
(PTP), defined in the IEEE 1588 standard [IEEE1588].
The accuracy of the time synchronization protocols directly depends
on the stability and the symmetry of propagation delays on both
directions between the master and slave clocks. Depending on the
nature of the underlying network, time synchronization protocol
packets can be subject to variable network latency or path asymmetry
(e.g. [ASSYMETRY], [ASSYMETRY2]). As time sensitive applications
evolve, accuracy requirements are becoming increasingly stringent.
Using a single network path in a clock synchronization protocol
closely ties the slave clock accuracy to the behavior of the specific
path, which may suffer from temporal congestion, faults or malicious
attacks. Relying on multiple clock servers as in NTP solves these
problems, but requires active maintenance of multiple accurate
sources in the network, which is not always possible. The usage of
Transparent Clocks (TC) in PTP solves the congestion problem by
eliminating the queueing time from the delay calculations, but does
not address security or fault-tolerance aspects.
Shpiner, et al. Expires October 18, 2016 [Page 3]
Internet-Draft Multi-Path Time Synchronization April 2016
____
______/ \_____
___/ \____
____/ \
____ / path 1 / ___
/ \ / ________________________ \ / \
/Master\____\___/ \____\________/Slave\
\Clock / / \________ _______________/ \ \Clock/
\____/ \ / \__ /
\____ path 2 __/
\_______ ______/
\_________/
Figure 1 Multi-Path Connection
Since master and slave clocks are often connected through more than
one path in the network, as shown in Figure 1, [SLAVEDIV] suggested
that a time synchronization protocol can be run over multiple paths,
providing several advantages. First, it can significantly increase
the clock accuracy as shown in [SLAVEDIV]. Second, this approach
provides additional security, allowing to mitigate man-in-the-middle
attacks against the time synchronization protocol [DELAY-ATT]. Third,
using multiple paths concurrently provides an inherent failure
protection mechanism.
This document introduces Multi-Path PTP (MPPTP) and Multi-Path NTP
(MPNTP), respectively. These extensions are defined at the network
layer and do not require any changes in the PTP or in the NTP
protocols.
MPPTP and MPNTP are defined over IP networks. As IP networks
typically combine ECMP routing, this property is leveraged for the
multiple paths used in MPPTP and MPNTP. The key property of the
multi-path extension is that clocks in the network can use more than
one IP address. Each {master IP, slave IP} address pair defines a
path. Depending on the network topology and configuration, the IP
combination pairs can form multiple diverse paths used by the multi-
path synchronization protocols. It has been shown [MULTI] that using
multiple IP addresses over the wide Internet indeed allows two end-
points to attain multiple diverse paths.
This document introduces two variants for each of the two multi-path
protocols; a variant that requires both master and slave nodes to
support the multi-path protocol, referred to as the dual-ended
Shpiner, et al. Expires October 18, 2016 [Page 4]
Internet-Draft Multi-Path Time Synchronization April 2016
variant, and a backward compatible variant that allows a multi-path
clock to connect to a conventional single-path clock, referred to as
the single-ended variant.
2. Conventions Used in this Document
2.1. Abbreviations
BMC Best Master Clock [IEEE1588]
ECMP Equal Cost Multiple Path
LAN Local Area Network
MPNTP Multi-Path Network Time Protocol
MPPTP Multi-Path Precision Time Protocol
NTP Network Time Protocol [NTP]
PTP Precision Time Protocol [IEEE1588]
2.2. Terminology
In the NTP terminology, a time synchronization protocol is run
between a client and a server, while PTP uses the terms master and
slave. Throughout this document, the sections that refer to both PTP
and NTP generically use the terms master and slave.
3. Multiple Paths in IP Networks
3.1. Load Balancing
Traffic sent across IP networks is often load balanced across
multiple paths. The load balancing decisions are typically based on
packet header fields: source and destination addresses, Layer 4
ports, the Flow Label field in IPv6, etc.
Three common load balancing criteria are per-destination, per-flow
and per-packet. The per-destination load balancers take a load
balancing decision based on the destination IP address. Per-flow load
balancers use various fields in the packet header, e.g., IP addresses
and Layer 4 ports, for the load balancing decision. Per-packet load
balancers use flow-blind techniques such as round-robin without
basing the choice on the packet content.
Shpiner, et al. Expires October 18, 2016 [Page 5]
Internet-Draft Multi-Path Time Synchronization April 2016
3.2. Using Multiple Paths Concurrently
To utilize the diverse paths that traverse per-destination load-
balancers or per-flow load-balancers, the packet transmitter can vary
the IP addresses in the packet header. The analysis in [PARIS2] shows
that a significant majority of the flows on the internet traverse
per-destination or per-flow load-balancing. It presents statistics
that 72% of the flows traverse per-destination load balancing and 39%
of the flows traverse per-flow load-balancing, while only a
negligible part of the flows traverse per-packet load balancing.
These statistics show that the vast majority of the traffic on the
internet is load balanced based on packet header fields.
The approaches in this draft are based on varying the source and
destination IP addresses in the packet header. Possible extensions
have been considered that also vary the UDP ports. However some of
the existing implementations of PTP and NTP use fixed UDP port values
in both the source and destination UDP port fields, and thus do not
allow this approach.
3.3. Two-Way Paths
A key property of IP networks is that packets forwarded from A to B
do not necessarily traverse the same path as packets from B to A.
Thus, we define a two-way path for a master-slave connection as a
pair of one-way paths: the first from master to slave and the second
from slave to master.
If possible, a traffic engineering approach can be used to verify
that time synchronization traffic is always forwarded through
bidirectional two-way paths, i.e., that each two-way path uses the
same route on the forward and reverse directions, thus allowing
propagation time symmetry. However, in the general case two-way paths
do not necessarily use the same path for the forward and reverse
directions.
4. Solution Overview
The multi-path time synchronization protocols we present are
comprised of two building blocks; one is the path configuration and
identification, and the other is the algorithm used by the slave to
combine the information received from the various paths.
4.1. Path Configuration and Identification
The master and slave clocks must be able to determine the path of
transmitted protocol packets, and to identify the path of incoming
Shpiner, et al. Expires October 18, 2016 [Page 6]
Internet-Draft Multi-Path Time Synchronization April 2016
protocol packets. A path is determined by a {master IP, slave IP}
address pair. The synchronization protocol message exchange is run
independently through each path.
Each IP address pair defines a two-way path, and thus allows the
clocks to bind a transmitted packet to a specific path, or to
identify the path of an incoming packet.
If possible, the routing tables across the network should be
configured with multiple traffic engineered paths between the pair of
clocks. By carefully configuring the routers in such networks it is
possible to create diverse paths for each of the IP address pairs
between two clocks in the network. However, in public and provider
networks the load balancing behavior is hidden from the end users. In
this case the actual number of paths may be less than the number of
IP address pairs, since some of the address pairs may share common
paths.
4.2. Combining
Various methods can be used for combining the time information
received from the different paths. The output of the combining
algorithm is the accurate time offset. Combining methods are further
discussed in Section 6.
5. Multi-Path Time Synchronization Protocols over IP Networks
This section presents two variants of MPPTP and MPNTP; single-ended
multi-path time synchronization and dual-ended multi-path time
synchronization. In the first variant, the multi-path protocol is run
only by the slave and the master is not aware of its usage. In the
second variant, all clocks must support the multi-path protocol.
The dual-ended protocol provides higher path diversity by using
multiple IP addresses at both ends, the master and slave, while the
single-ended protocol only uses multiple addresses at the slave. On
the other hand, the dual-ended protocol can only be deployed when
both the master and the slave support this protocol. Dual-ended and
single-ended protocols can co-exist in the same network. Each slave
selects the connection(s) it wants to make with the available
masters. A dual-ended slave could switch to single-ended mode if it
does not see any dual-ended masters available. A single-ended slave
could connect to a single IP address of a dual-ended master.
Multi-path time synchronization, in both variants, requires clocks to
use multiple IP addresses. If possible, the set of IP addresses for
each clock should be chosen in a way that enables the establishment
Shpiner, et al. Expires October 18, 2016 [Page 7]
Internet-Draft Multi-Path Time Synchronization April 2016
of paths that are the most different. It is applicable if the load
balancing rules in the network are known. Using multiple IP addresses
introduces a tradeoff. A large number of IP addresses allows a large
number of diverse paths, providing the advantages of slave diversity
discussed in Section 1. On the other hand, a large number of IP
addresses is more costly, requires the network topology to be more
redundant, and exacts extra management overhead.
The descriptions in this section refer to the end-to-end scheme of
PTP, but are similarly applicable to the peer-to-peer scheme. The
MPNTP protocol described in this document refers to the NTP client-
server mode, although the concepts described here can be extended to
include the symmetric variant as well.
Multi-path synchronization protocols by nature require protocol
messages to be sent as unicast. Specifically in PTP, the following
messages must be sent as unicast in MPPTP: Sync, Delay_Req,
Delay_Resp, PDelay_Req, PDelay_Resp, Follow_Up, and
PDelay_Resp_Follow_Up. Note that [IEEE1588] allows these messages to
be sent either as multicast or as unicast.
5.1. Single-Ended Multi-Path Synchronization
In the single-ended approach, only the slave is aware of the fact
that multiple paths are used, while the master is agnostic to the
usage of multiple paths. This approach allows a hybrid network, where
some of the clocks are multi-path clocks, and others are conventional
one-path clocks. A single-ended multi-path clock presents itself to
the network as N independent clocks, using N IP addresses, as well as
N clock identity values (in PTP). Thus, the usage of multiple slave
identities by a slave clock is transparent from the master's point of
view, such that it treats each of the identities as a separate slave
clock.
5.1.1. Single-Ended MPPTP Synchronization Message Exchange
The single-ended MPPTP message exchange procedure is as follows.
o Each single-ended MPPTP clock has a fixed set of N IP addresses
and N corresponding clockIdentities. Each clock arbitrarily
defines one of its IP addresses and clockIdentity values as the
clock primary identity.
o A single-ended MPPTP port sends Announce messages only from its
primary identity, according to the BMC algorithm.
Shpiner, et al. Expires October 18, 2016 [Page 8]
Internet-Draft Multi-Path Time Synchronization April 2016
o The BMC algorithm at each clock determines the master, based on
the received Announce messages.
o A single-ended MPPTP port that is in the 'slave' state uses
unicast negotiation to request the master to transmit unicast
messages to each of the N slave clock identities. The slave port
periodically sends N Signaling messages to the master, using each
of its N identities. The Signaling message includes the
REQUEST_UNICAST_TRANSMISSION_TLV.
o The master periodically sends unicast Sync messages from its
primary identity, identified by the sourcePortIdentity and IP
address, to each of the slave identities.
o The slave, upon receiving a Sync message, identifies its path
according to the destination IP address. The slave sends a
Delay_Req unicast message to the primary identity of the master.
The Delay_Req is sent using the slave identity corresponding to
the path the Sync was received through. Note that the rate of
Delay_Req messages may be lower than the Sync message rate, and
thus a Sync message is not necessarily followed by a Delay_Req.
o The master, in response to a Delay_Req message from the slave,
responds with a Delay_Resp message using the IP address and
sourcePortIdentity from the Delay_Req message.
o Upon receiving the Delay_Resp message, the slave identifies the
path using the destination IP address and the
requestingPortIdentity. The slave can then compute the
corresponding path delay and the offset from the master.
o The slave combines the information from all negotiated paths.
5.1.2. Single-Ended MPNTP Synchronization Message Exchange
The single-ended MPNTP message exchange procedure is as follows.
o A single-ended MPNTP client has N separate identities, i.e., N IP
addresses. The assumption is that the server information,
including its IP address is known to the NTP clients.
o A single-ended MPNTP client initiates the NTP protocol with an NTP
server N times, using each of its N identities.
o The NTP protocol is maintained between the server and each of the
N client identities.
Shpiner, et al. Expires October 18, 2016 [Page 9]
Internet-Draft Multi-Path Time Synchronization April 2016
o The client sends NTP messages to the master using each of its N
identities.
o The server responds to the client's NTP messages using the IP
address from the received NTP packet.
o The client, upon receiving an NTP packet, uses the IP destination
address to identify the path it came through, and uses the time
information accordingly.
o The client combines the information from all paths.
5.2. Dual-Ended Multi-Path Synchronization
In dual-ended multi-path synchronization each clock has N IP
addresses. Time synchronization messages are exchanged between some
of the combinations of {master IP, slave IP} addresses, allowing
multiple paths between the master and slave. Note that the actual
number of paths between the master and slave may be less than the
number of chosen {master, slave} IP address pairs.
Once the multiple two-way connections are established, a separate
synchronization protocol exchange instance is run through each of
them.
5.2.1. Dual-Ended MPPTP Synchronization Message Exchange
The dual-ended MPPTP message exchange procedure is as follows.
o Every clock has N IP addresses, but uses a single clockIdentity.
o The BMC algorithm at each clock determines the master. The master
is identified by its clockIdentity, allowing other clocks to know
the multiple IP addresses it uses.
o When a clock sends an Announce message, it sends it from each of
its IP addresses with its clockIdentity.
o A dual-ended MPPTP port that is in the 'slave' state uses unicast
negotiation to request the master to transmit unicast messages to
some or all of its N_s IP addresses. This negotiation is done
individually between a slave IP address and the corresponding
master IP address that the slave desires a connection with. The
slave port periodically sends Signaling messages to the master,
using some or all of its N_s IP addresses as source, to the
corresponding master's N_m IP addresses. The Signaling message
includes the REQUEST_UNICAST_TRANSMISSION_TLV.
Shpiner, et al. Expires October 18, 2016 [Page 10]
Internet-Draft Multi-Path Time Synchronization April 2016
o The master periodically sends unicast Sync messages from each of
its IP addresses to the corresponding slave IP addresses for which
a unicast connection was negotiated.
o The slave, upon receiving a Sync message, identifies its path
according to the {source, destination} IP addresses. The slave
sends a Delay_Req unicast message, swapping the source and
destination IP addresses from the Sync message. Note that the rate
of Delay_Req messages may be lower than the Sync message rate, and
thus a Sync message is not necessarily followed by a Delay_Req.
o The master, in response to a Delay_Req message from the slave,
responds with a Delay_Resp message using the sourcePortIdentity
from the Delay_Req message, and swapping the IP addresses from the
Delay_Req.
o Upon receiving the Delay_Resp message, the slave identifies the
path using the {source, destination} IP address pair. The slave
can then compute the corresponding path delay and the offset from
the master.
o The slave combines the information from all negotiated paths.
5.2.2. Dual-Ended MPNTP Synchronization Message Exchange
The MPNTP message exchange procedure is as follows.
o Each NTP clock has a set of N IP addresses. The assumption is that
the server information, including its multiple IP addresses is
known to the NTP clients.
o The MPNTP client chooses N_svr of the N server IP addresses and
N_c of the N client IP addresses and initiates the N_svr*N_c
instances of the protocol, one for each {server IP, client IP}
pair, allowing the client to combine the information from the
N_s*N_c paths.
(N_svr and N_c indicate the number of IP addresses of the server
and client, respectively, which a client chooses to connect with)
o The client sends NTP messages to the master using each of the
source-destination address combinations.
o The server responds to the client's NTP messages using the IP
address combination from the received NTP packet.
Shpiner, et al. Expires October 18, 2016 [Page 11]
Internet-Draft Multi-Path Time Synchronization April 2016
o Using the {source, destination} IP address pair in the received
packets, the client identifies the path, and performs its
computations for each of the paths accordingly.
o The client combines the information from all paths.
5.3. Using Traceroute for Path Discovery
The protocols presented above use multiple IP addresses in a single
clock to create multiple paths. However, although each two-way path
is defined by a different {master, slave} address pair, some of the
IP address pairs may traverse exactly the same network path, making
them redundant. Traceroute-based path discovery can be used for
filtering only the IP addresses that obtain diverse paths. 'Paris
Traceroute' [PARIS] and 'TraceFlow' [TRACEFLOW] are examples of tools
that discover the paths between two points in the network.
The Traceroute-based filtering can be implemented by both master and
slave nodes, or it can be restricted to run only on slave nodes to
reduce the overhead on the master. For networks that guarantee the
path of the timing packets in the forward and reverse direction are
the same, path discovery should only be performed at the slave.
5.4. Using Unicast Discovery for MPPTP
As presented above, MPPTP uses Announce messages and the BMC
algorithm to discover the master. The unicast discovery option of PTP
can be used as an alternative.
When using unicast discovery the MPPTP slave ports maintain a list of
the IP addresses of the master. The slave port uses unicast
negotiation to request unicast service from the master, as follows:
o In single-ended MPPTP, the slave uses unicast negotiation from
each of its identities to the master's (only) identity.
o In dual-ended MPPTP, the slave uses unicast negotiation from its
IP addresses, each to a corresponding master IP address to request
unicast synchronization messages.
Afterwards, the message exchange continues as described in sections
5.1.1. and 5.2.1.
The unicast discovery option can be used in networks that do not
support multicast or in networks in which the master clocks are known
in advance. In particular, unicast discovery avoids multicasting
Announce messages.
Shpiner, et al. Expires October 18, 2016 [Page 12]
Internet-Draft Multi-Path Time Synchronization April 2016
6. Combining Algorithm
Previous sections discussed the methods of creating the multiple
paths and obtaining the time information required by the slave
algorithm. Once the time information is received through each of the
paths, the slave should use a combining algorithm, which consolidates
the information from the different paths into a single clock.
Various methods have been suggested for combining information from
different paths or from different clocks, e.g., [NTP], [SLAVEDIV],
[HIGH-AVAI], [KALMAN]. The choice of the combining algorithm is local
to the slave, and does not affect the interoperability of the
protocol. Hence, this document does not define a specific method to
be used by the slave.
7. Security Considerations
The security aspects of time synchronization protocols are discussed
in detail in [TICTOCSEC]. The methods describe in this document
propose to run a time synchronization protocol through redundant
paths, and thus allow to detect and mitigate man-in-the-middle
attacks, as described in [DELAY-ATT].
8. IANA Considerations
There are no IANA actions required by this document.
RFC Editor: please delete this section before publication.
9. Acknowledgments
The authors gratefully acknowledge the useful comments provided by
Peter Meyer and Doug Arnold, as well as other comments received from
the TICTOC working group participants.
This document was prepared using 2-Word-v2.0.template.dot.
10. References
10.1. Normative References
[IEEE1588] IEEE Instrumentation and Measurement Society, "IEEE
Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control
Systems", IEEE Std 1588, 2008.
Shpiner, et al. Expires October 18, 2016 [Page 13]
Internet-Draft Multi-Path Time Synchronization April 2016
[NTP] D. Mills, J. Martin, J. Burbank, W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", IETF, RFC 5905, 2010.
10.2. Informative References
[ASSYMETRY] Yihua He and Michalis Faloutsos and Srikanth
Krishnamurthy and Bradley Huffaker, "On routing
asymmetry in the internet", IEEE Globecom, 2005.
[ASSYMETRY2] Abhinav Pathak, Himabindu Pucha, Ying Zhang, Y.
Charlie Hu, and Z. Morley Mao, "A measurement study of
internet delay asymmetry", PAM'08, 2008.
[DELAY-ATT] T. Mizrahi, "A Game Theoretic Analysis of Delay
Attacks against Time Synchronization Protocols",
ISPCS, 2012.
[HIGH-AVAI] P. Ferrari, A. Flammini, S. Rinaldi, G. Prytz, "High
availability IEEE 1588 nodes over IEEE 802.1 aq
Shortest Path Bridging networks" ISPCS, 2013.
[KALMAN] G. Giorgi, C. Narduzzi, "Kalman filtering for multi-
path network synchronization" ISPCS, 2014.
[MULTI] A. Shpiner, Y. Revah, T. Mizrahi, "Multi-path Time
Protocols" ISPCS, 2013.
[PARIS] Brice Augustin, Timur Friedman and Renata Teixeira,
"Measuring Load-balanced Paths in the Internet", IMC,
2007.
[PARIS2] B. Augustin, T. Friedman, and R. Teixeira, "Measuring
Multipath Routing in the Internet", IEEE/ACM
Transactions on Networking, 19(3), p. 830 - 840, June
2011.
[SLAVEDIV] T. Mizrahi, "Slave Diversity: Using Multiple Paths to
Improve the Accuracy of Clock Synchronization
Protocols", ISPCS, 2012.
[TICTOCSEC] T. Mizrahi, "Security Requirements of Time Protocols
in Packet Switched Networks", IETF, RFC 7384, 2014.
[TRACEFLOW] J. Narasimhan, B. V. Venkataswami, R. Groves and P.
Hoose, "Traceflow", IETF, draft-janapath-intarea-
traceflow, work in progress, 2012.
Shpiner, et al. Expires October 18, 2016 [Page 14]
Internet-Draft Multi-Path Time Synchronization April 2016
Authors' Addresses
Alex Shpiner
Department of Electrical Engineering
Technion - Israel Institute of Technology
Haifa, 32000 Israel
Email: shalex@tx.technion.ac.il
Richard Tse
PMC-Sierra
8555 Baxter Place
Burnaby, BC
Canada
V5A 4V7
Email: Richard.Tse@pmcs.com
Craig Schelp
PMC-Sierra
8555 Baxter Place
Burnaby, BC
Canada
V5A 4V7
Email: craig.schelp@pmcs.com
Tal Mizrahi
Marvell
6 Hamada St.
Yokneam, 20692 Israel
Email: talmi@marvell.com
Shpiner, et al. Expires October 18, 2016 [Page 15]
