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RE: Comments on draft-salam-l2vpn-evpn-oam-req-frmwk and draft-vgovindan-l2vpn-evpn-bfd

"Vengada Prasad Govindan (venggovi)" <venggovi@cisco.com> Fri, 13 December 2013 11:01 UTC

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From: "Vengada Prasad Govindan (venggovi)" <venggovi@cisco.com>
To: Gregory Mirsky <gregory.mirsky@ericsson.com>, "Samer Salam (ssalam)" <ssalam@cisco.com>, "Ali Sajassi (sajassi)" <sajassi@cisco.com>, "Sam Aldrin (aldrin.ietf@gmail.com)" <aldrin.ietf@gmail.com>, "John E Drake (jdrake@juniper.net)" <jdrake@juniper.net>, "l2vpn@ietf.org" <l2vpn@ietf.org>
Subject: RE: Comments on draft-salam-l2vpn-evpn-oam-req-frmwk and draft-vgovindan-l2vpn-evpn-bfd
Thread-Topic: Comments on draft-salam-l2vpn-evpn-oam-req-frmwk and draft-vgovindan-l2vpn-evpn-bfd
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Date: Fri, 13 Dec 2013 11:01:43 +0000
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References: <7347100B5761DC41A166AC17F22DF1121B71E5A9@eusaamb103.ericsson.se> <CEB27671.165BF%ssalam@cisco.com> <315041E4211CB84E86EF7C25A2AB583D33843129@xmb-rcd-x15.cisco.com> <7347100B5761DC41A166AC17F22DF1121B732DBB@eusaamb103.ericsson.se>
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Hello Greg,
    Sincere thanks for your email. Agreed, the BFD sessions could be slowed down to tolerable (large) timer values instead of tearing down and (re)establishing BFD sessions. I will incorporate this change in the next revision of this draft.
Thanks
Prasad

From: Gregory Mirsky [mailto:gregory.mirsky@ericsson.com]
Sent: Thursday, December 12, 2013 4:42 AM
To: Vengada Prasad Govindan (venggovi); Samer Salam (ssalam); Ali Sajassi (sajassi); Sam Aldrin (aldrin.ietf@gmail.com); John E Drake (jdrake@juniper.net); l2vpn@ietf.org
Subject: RE: Comments on draft-salam-l2vpn-evpn-oam-req-frmwk and draft-vgovindan-l2vpn-evpn-bfd

Hi Prasad,
thank you for you careful consideration of my notes. Proposed text tagged with GIM>>.

                Regards,
                                Greg
[snip]

*         Section 4
o   Not clear which BFD modes can be used and in what manner as on-demand OAM to troubleshoot and localize fault. AFAIK, BFD-based OAM used primarily as proactive continuity check and LSP Ping as on-demand troubleshooting tool.
 GVP1> The intent of this Section is to highlight the possible scalability issues that could arise. The term demand-driven manner was used to imply that BFD could be turned ON and OFF as desired, instead of an ALWAYS-ON mode. Do you have any suggestions to improve the text here? Please let us know.

GIM>> Bringing BFD session up has its tax of triple handshake to exchange Discriminator values. Alternative to turning ON and OFF could be dynamically changing Rx and Tx intervals  to a very large value, i.e. minutes if not hours. As I understand, "demand-driven", also referred as "on-demand", OAM tools primarily used for fault localization. LSP traceroute is one of widely used in MPLS networks, ETH-LT (linktrace) - in Ethernet domain. Proactive tools like BFD or CFM primarily used for fault detection. I don't think that BFD needs to be enhanced to match diagnostic capabilities available in LSP Ping/traceroute.

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