Re: [Time] [OPSAWG] Strong Technology Dependency

Gregory Mirsky <gregory.mirsky@ericsson.com> Mon, 30 June 2014 22:51 UTC

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From: Gregory Mirsky <gregory.mirsky@ericsson.com>
To: Tom Taylor <tom.taylor.stds@gmail.com>, Qin Wu <bill.wu@huawei.com>, "time@ietf.org" <time@ietf.org>, "opsawg@ietf.org" <opsawg@ietf.org>
Thread-Topic: [OPSAWG] Strong Technology Dependency
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Date: Mon, 30 Jun 2014 22:51:26 +0000
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Subject: Re: [Time] [OPSAWG] Strong Technology Dependency
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Hi Tom,
I agree that agreeing on terminology is important, if not critical to in order to have productive discussion and to reach positive results.
I think that "reachability" is "continuity", i.e. availability of a path between two end-points.
"Connectivity" does include "continuity" but as well, IMO, it monitors for unwarranted OAM packets either sent by unexpected source of addressed to other destination. "Connectivity", IMO, requires presence of "connection" defined between two end-points.

	Regards,
		Greg

-----Original Message-----
From: Tom Taylor [mailto:tom.taylor.stds@gmail.com] 
Sent: Monday, June 30, 2014 6:05 AM
To: Qin Wu; time@ietf.org; opsawg@ietf.org
Cc: Gregory Mirsky
Subject: Re: [OPSAWG] Strong Technology Dependency

I think one problem here is over-use of the word "connectivity". Aren't you really testing for reachability?

Tom Taylor

On 30/06/2014 3:39 AM, Qin Wu wrote:
> Thanks for comments on the following proposed table or figure as follows:
> Greg>MPLS-TP uses LSP ping or, though more rarely, ICMP as-is. In fact, MPLS-TP largely re-used all IP/MPLS OAM though adding some functionality, i.e. RDI, CV, and PCS.
> Greg>Again, as in previous comment, MPLS-TP OAM does not present itself “different OAM technology”.
>
> [Qin]: You are right, I realized both LSP Ping and MPLS-OAM use MPLS technology while ICMP uses IP technology. I will fix this in the update.
>
> Greg>should add OWAMP and TWAMP for Performance Measurement in the 
> Greg>following table
>
> [Qin]: Agree.
>
> Greg>Echo(Ping) in fact belongs continuity check.
>
> [Qin]: Agree.
>
> Greg>Echo(Ping) does not provide CV as IP is connectionless and has no definition of Misconnection defect.
>
> [Qin]:Not sure about this. RFC7276 said LSP Ping is used for end-to-end
>    Connectivity Verification between two LERs.
> Therefore I think  IP Ping can also provide CV, what am I missing?
>
> Greg>Actually can be used for BW, Delay and Loss measurement, though very rough.
>
> [Qin]: Agree and will add this into the  following table.
>
> Greg>Not, BFD and BFD Echo do not provide CV for the same reason as for ICMP – do definition of Misconnection defect. Besides, BFD Echo doesn’t work for multi-hop case but only for single hop.
>
> [Qin]: Not sure about this. RFC7276 said SP Ping is used for end-to-end
>    Connectivity Verification between two LERs.
> Since BFD Echo is similar to LSP Ping, I think BFD Echo also can provide CV.
>
> Greg>LSP Ping provides Continuity Check too
>
> [Qin]: Agree.
>
> Greg>All MPLS-TP OAM applicable to IP/MPLS as well
>
> [Qin]: Agree.
> Greg>MPLS-TP provides CC through use of BFD MPLS-TP provides CV 
> Greg>through use of BFD and extension  to provide Source ID.
>
> [Qin]: Besides using BFD, is there any other way to provide CC or CV?
>
>
> 发件人: OPSAWG [mailto:opsawg-bounces@ietf.org] 代表 Qin Wu
> 发送时间: 2014年6月25日 16:06
> 收件人: time@ietf.org; opsawg@ietf.org
> 抄送: mohamed.boucadair@orange.com
> 主题: [OPSAWG] Strong Technology Dependency
>
> Hi, Mohamed:
> Thanks for details review to problem statement draft
> http://tools.ietf.org/html/draft-ww-opsawg-multi-layer-oam-00
> and update I sent to you.
>
> Regarding strong technology dependency issue, Section 4.2 gives an 
> address scheme  example to explain why the existing OAM mechanism has 
> strong Technology as follows:
> “
>
> Addressing scheme is a good example for an issue
>
> that has a high price for being non-generic.  Ping of IPv4 and IPv6
>
> looks different in the addressing scheme as well in the ICMP
>
> indication field, but they have the same OAM functionalities.
> ”
> You asked to clarify the exact point of this paragraph.
> I think what this paragraph said is
> For IP ping, IPv4 Ping protocol [RFC792] and IPv6 ping protocol [RFC4443] use different IP technology but share the same OAM function.
>
> But I agree with you address scheme is not a typical example for strong technology dependency.
> I think the typical example is ICMP, LSP Ping and MPLS-TP OAM are 
> using different network technology but share the same OAM 
> functionality, i.e., Path Discovery.  Another example is ICMP,BFD,LSP Ping and MPLS-TP OAM are using different network technology but share the same functionality, i.e., continuity check.
>
> The following figure shows common OAM functionalities shared by various existing OAM protocols.
>     |--------+-----------+--------------+--------------+------------+
>     |        |Continuity |  Connectivity|    Path      | Performance|
>     |        |  Check    |  Verification|  Discovery   | Monitoring |
>     +--------+-----------+--------------+--------------+------------+
>     |        |           |              |              |            |
>     | ICMP   |           |   Echo(Ping) |  Traceroute  |            |
>     |        |           |              |              |            |
>     +--------+-----------+--------------+--------------+------------+
>     |        |           |              |              |            |
>     | BFD    |  BFD      |   BFD Echo   |              |            |
>     |        | Control   |              |              |            |
>     +--------+-----------+--------------+--------------+------------+
>     | LSP    |           |              |              | - Delay    |
>     | Ping   |           |   Ping       |  Traceroute  | - Packet   |
>     |        |           |              |              |    Loss    |
>     +--------+-----------+--------------+--------------+------------+
>     |        |           |              |              |            |
>     | IPPM   |           |              |              |            |
>     |        |           |              |              |            |
>     |--------+-----------+--------------+--------------+------------+
>     | MPLS-TP|           |              |              |            |
>     | OAM    |  CC       |   CV         |  Traceroute  | -Delay     |
>     |        |           |              |              | -Packet    |
>     |        |           |              |              |   Loss     |
>     +--------+-----------+--------------+--------------+------------+
>
> Hope this clarifies.
>
> Regards!
> -Qin
>
> 发件人: mohamed.boucadair@orange.com<mailto:mohamed.boucadair@orange.com> 
> [mailto:mohamed.boucadair@orange.com]
> 发送时间: 2014年6月24日 22:13
> 收件人: Qin Wu
> 主题: RE: Unified oam BOF proposal request in IETF 90
>
> Hi Qin,
>
> Please find attached a first set of comments.
>
> Cheers,
> Med
>
>
>
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