Subject: [TICTOC] sync over IP

From: Mikael Abrahamsson <[email-masked]>
Date: Wed, 14 Jul 2010 07:45:08 +0200 (CEST)

Hello. I'm a router guy.

I work for a mobile phone operator, we've been in the mobile phone and IP 
business for ~20 years. We're running GSM, UMTS and now deploying LTE. Our 
network also carries a lot of IP traffic for commerical and residential 
customers, mostly Internet traffic but we're also using MPLS L3 VPNs to 
provide L2/L3 services to our customers, mostly L3 VPNs.

We're going all-IP for all the mobile services, meaning we want to carry 
everything over IP, including sync and circuit switched calls.

This has made me a bit interested in sync over IP (since I've also been 
using NTP for 15+ years). I read the charter and it seems to indicate that 
this WG is trying to standardize sync over IP.

When I look at the last years communication on this list I see a lot of 
reference to 1588v2 and SyncE. When I look at these I keep seeing 
references to "ethernet switch" in the diagrams, not IP routers. I also 
see lots of references to new "compliant hardware" being announced. This 
worries me.

As an IP operator, we prefer to do routing as far out in the network as 
possible, as we've had bad experience with large L2 switching domains. We 
also prefer to keep our equipment for as long as possible, so any new 
service we deploy should work over existing infrastructure with devices 
that might be 10 years old. Deploying new IP/MPLS core/distribution 
hardware to support the new services is something we do not want to do.

I've been trying to understand the network requirements of 1588v2 but come 
up short. There is no 1588v2 article on wikipedia at all.

So I guess my question is if someone could please point me in the right 
direction, where can I find a primer for "sync over IP for a router guy" 
to make me better understand what's happening here?

-- 
Mikael Abrahamsson    email: [email-masked]

---

From: "Leonid Goldin (lgoldin)" <[email-masked]>
Date: Wed, 14 Jul 2010 09:41:23 -0500

Hi Mikael,

There is quite a bit of work was done in the area of your interest in
ITU-T Study Group 15 question 13. 
You may want to start from there.

Leon

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Mikael Abrahamsson
Sent: Wednesday, July 14, 2010 1:45 AM
To: [email-masked]
Subject: [TICTOC] sync over IP

Hello. I'm a router guy.

I work for a mobile phone operator, we've been in the mobile phone and
IP 
business for ~20 years. We're running GSM, UMTS and now deploying LTE.
Our 
network also carries a lot of IP traffic for commerical and residential 
customers, mostly Internet traffic but we're also using MPLS L3 VPNs to 
provide L2/L3 services to our customers, mostly L3 VPNs.

This has made me a bit interested in sync over IP (since I've also been 
using NTP for 15+ years). I read the charter and it seems to indicate
that 
this WG is trying to standardize sync over IP.

worries me.

possible, as we've had bad experience with large L2 switching domains.
We 

I've been trying to understand the network requirements of 1588v2 but
come 
up short. There is no 1588v2 article on wikipedia at all.

-- 
Mikael Abrahamsson    email: [email-masked]
_______________________________________________
TICTOC mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/tictoc

---

From: Mikael Abrahamsson <[email-masked]>
Date: Wed, 14 Jul 2010 21:04:24 +0200 (CEST)

> You may want to start from there.

I don't know anything about ITU-T at all. Googling for <"ITU-T Study Group 
15 question 13"> yields 10 hits or so, nothing of which I find very 
enlightning.

Any additional links is greatly appreciated.

---

From: "Matthews, Peter" <[email-masked]>
Date: Wed, 14 Jul 2010 15:17:52 -0400

Hi Mikael,

I have been trying to learn a lot of this from scratch. Not sure that
you want to start at as basic a level as I have, but I have found the
following links useful:

http://www.telecom-sync.com/index.php Papers presented 2008 earlier are
available, lots of stuff on ITU and other bodies, e.g.
http://www.telecom-sync.com/pdf/2008/Day1/Standards_Update_ITU_(Jean-Lou
p_Ferrant,_Alcatel-Lucent).pdf

http://tf.nist.gov/seminars/WSTS/WSTS.html Presentations don't seem to
be available but the agenda is, and I would guess that if you ask nicely
you might be able to get an author to send you a copy?

Peter Matthews

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Mikael Abrahamsson
Sent: Wednesday, July 14, 2010 3:04 PM
To: Leonid Goldin (lgoldin)
Cc: [email-masked]
Subject: Re: [TICTOC] sync over IP

> You may want to start from there.

I don't know anything about ITU-T at all. Googling for <"ITU-T Study
Group 
15 question 13"> yields 10 hits or so, nothing of which I find very 
enlightning.

---

From: Yaakov Stein <[email-masked]>
Date: Thu, 15 Jul 2010 16:58:22 +0300

Mikael

As you have not been completely happy with the answers so far, 
let me try to help.

1588v2 can (and usually does) run over UDP/IP (although it has other transport options,
including a pure Ethernet one with Ethertype 88F7).

So why do we need 1588 instead of NTP which has been around for a long time ?
1588 has an advantage when there is support from the network elements it traverses,
and this happens in Ethernet switches. To date, there aren't routers that provide
on-path 1588 support (your "new compliant hardware"), 
and so there is little reason to prefer 1588.

In fact, there are multiple reasons to prefer NTP in such cases
(security, scalability, bandwidth consumption, ...).

The 1588-2008 standard is available from the IEEE.
The Q13/15 work in the ITU has produced the G.826x series of Recommendations,
that are available from the ITU-T web site.
Contributions to Q13 are only visible to those with a TIES password.

There IS a 1588 wikipedia entry - http://en.wikipedia.org/wiki/Precision_Time_Protocol
and much more material available on-line (e.g., John Eidson's tutorial).

Y(J)S

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Mikael Abrahamsson
Sent: Wednesday, July 14, 2010 08:45
To: [email-masked]
Subject: [TICTOC] sync over IP

Hello. I'm a router guy.

---

From: Danny Mayer <[email-masked]>
Date: Sun, 18 Jul 2010 15:23:38 -0400

On 7/15/2010 9:58 AM, Yaakov Stein wrote:
> and this happens in Ethernet switches.

And NTP already has some support for 1588 where it is available. PTP in
contrast which is strictly hierarchical and basically only uses
1588-enabled Ethernet.

> To date, there aren't routers that provide

The reality is that there is something like a 10-15 year rollout of any
scheme in new hardware that will be able to deploy such PTP/1588 types
of networks unless there is a clear and pressing reason to do so. In
that case the protocol *must* be right or the whole thing will die under
its own weight.

What I haven't seen anywhere is any analysis of how all of the
processing that is necessary for example in the MPLS proposal, will
affect things like latency, jitter, precision, etc. of the resultant
packets to the recipient client system. If it cannot deliver better
results than what is currently available then there's no point to the
whole exercise.

Danny

---

From: Yaakov Stein <[email-masked]>
Date: Mon, 19 Jul 2010 12:12:01 +0300

Danny

> The reality is that there is something like a 10-15 year rollout of any scheme in new hardware that will be able to deploy such PTP/1588 types of networks unless there is a clear and pressing reason to do so. In that case the protocol *must* be right or the whole thing will die under its own weight.

That depends on what kind of network you are talking about.
I have seen greenfield SP networks built up in less than a year.

> What I haven't seen anywhere is any analysis of how all of the processing that is necessary for example in the MPLS proposal, will affect things like latency, jitter, precision, etc. of the resultant packets to the recipient client system. If it cannot deliver better results than what is currently available then there's no point to the whole exercise.

If the requirement is to deliver highly accurate frequency and/or ToD to network
elements of the service provider, e.g., cellular base stations, 
the results can be dramatically better. 
I agree if this is delivered to an uncontrolled client network then the exercise
might not be worthwhile.

Y(J)S

---

From: Danny Mayer <[email-masked]>
Date: Mon, 19 Jul 2010 09:36:33 -0400

On 7/19/2010 5:12 AM, Yaakov Stein wrote:
> Danny
> 
>> The reality is that there is something like a 10-15 year rollout
>> of any scheme in new hardware that will be able to deploy such PTP/1588
types of networks unless there is a clear and pressing reason to do so.
In that case the protocol *must* be right or the whole thing will die
under its own weight.
> I have seen greenfield SP networks built up in less than a year.

I don't disagree with this but in general networks live a long time on
existing hardware on the basis of what works does not need to be
replaced. Only compelling reasons (think Money) will get network gear
replaced.

> the results can be dramatically better.

That's the hope for all of this, but someone needs to look at the
overhead involved and make sure that this continues to be true with the
proposed implementations over MPLS for example.

> I agree if this is delivered to an uncontrolled client network then the exercise

Rubber hits road.

Danny