Subject: [GROW] Secdir last call review of draft-ietf-grow-bgp-session-culling-04

From: Paul Wouters <[email-masked]>
Date: Mon, 25 Sep 2017 08:45:49 -0700

Reviewer: Paul Wouters
Review result: Ready

I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the IESG.
These comments were written primarily for the benefit of the  security
area directors.  Document editors and WG chairs should treat  these
comments just like any other last call comments.

The summary of the review is Ready.

(note I am a tourist in the BGP area)

This document basically states that people doing network maintenance so often
make mistakes that leak into the global BGP table, that it would be a good idea
to just firewall all the BGP traffic going out of your network edge as a
preventive measure. It's a sad state of software/firmware that an external
firewalling process is deemed necessary to properly (re)configure BGP.

This document has an empty Security Considerations section. As this BCP
document is basically a "cut yourself off the internet while doing maintenance"
I agree that there is basically nothing worse that could happen other then not
doing this RFC BCP and then leaking faulty BGP information onto the public
internet. One could add something like "don't forget to delete the firewall
rules afterwards" or "be sure to use ipv4 and ipv6 rules to prevent BGP leaks",
but then again this whole band aid RFC is meant for people who apparently have
shown an inability of properly executing RFC's anyway, and this document just
tries to convince them to only cut themselves, and not everyone else.

---

From: "Will Hargrave" <[email-masked]>
Date: Mon, 25 Sep 2017 17:29:24 +0100

> firewalling process is deemed necessary to properly (re)configure BGP.

Hi Paul,

I am afraid you have got the wrong end of the stick here. This technique 
is intended for IXP and other L2 operators, not those who operate BGP 
speakers / IP networks. It is a workaround to unwanted blackholing of 
traffic as a result of the dataplane being broken whilst waiting for BGP 
holdtimers to expire - nothing to do with actual BGP route policy.

I gave a presentation earlier this year at the UK Network Operators 
Forum which attempts to explain this 
https://indico.uknof.org.uk/event/39/contribution/8

Regards,

Will

---

From: Job Snijders <[email-masked]>
Date: Mon, 25 Sep 2017 18:36:11 +0200

On Mon, Sep 25, 2017 at 04:29:24PM +0000, Will Hargrave wrote:
> > This document basically states that people doing network maintenance
> > so often make mistakes that leak into the global BGP table, that it
> > would be a good idea to just firewall all the BGP traffic going out
> > of your network edge as a preventive measure. It's a sad state of
> > software/firmware that an external firewalling process is deemed
> > necessary to properly (re)configure BGP.
> 
> Hi Paul,
> 
> I am afraid you have got the wrong end of the stick here. This
> technique is intended for IXP and other L2 operators, not those who
> operate BGP speakers / IP networks.

Small nit pick: section 3.1 applies to those who operate BGP speakers /
IP networks. But yes, it appears that the review is based on a
misunderstanding about the layering of the ISO model and how the IP
filters trigger rerouting as (desired) second order effect.

> It is a workaround to unwanted blackholing of traffic as a result of
> the dataplane being broken whilst waiting for BGP holdtimers to expire
> - nothing to do with actual BGP route policy.
> 

I'd also like to note that the techniques described in the culling
document have nothing to do with 'leaking' of any sort, nor is the BCP
attempting or purposed to describe firewalling best practises from a
general perspective.

Kind regards,

Job