[Idr] Destination-IP-Origin-AS Filter for BGP Flow Specification

Robert Raszuk <robert@raszuk.net> Mon, 04 November 2019 17:50 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Mon, 4 Nov 2019 18:50:29 +0100
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To: rainsword.wang@huawei.com, wangaj3@chinatelecom.cn, Zhuangshunwan <zhuangshunwan@huawei.com>
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Subject: [Idr] Destination-IP-Origin-AS Filter for BGP Flow Specification
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Dear Authors of draft-wang-idr-flowspec-dip-origin-as-filter

After reading this document with interest I am scared !

*You have constructed a fantastic tool to hijack traffic to any AS or for
that matter balckhole it completely with surgical precision. *

Yet the draft does not say a word about validation of such filters. In fact
it describes use cases where validation would not be done as no destination
IP address would be present at all. Section 4 just illustrates DST ASN +
SRC IP.

Technically you highlight the value of the proposal by stating that R1
needs to install only one rule in the data plane:

 Using the method defining in this draft, the ISP AS64597 needs to
   setup only *one "Destination Origin AS + Source Prefix" rule in Router
   R1 as following:
*
     +--------------+--------------+-------------------------+
     | Destination  | Source Prefix| Redirect to IP Nexthop  |
     | IP Origin AS |              |                         |
     +--------------+--------------+-------------------------+
     |  64598       | IP Prefix 61 |       R3                |
     +--------------+--------------+-------------------------+

     Figure 3: Steering the Traffic Using Origin AS and Source Prefix


Well packets do not carry ASNs so that may be a bit tricky for the data
plane.

I assume you mean that router will explode given Dst ASN into all atomic
BGP destination announcements either by BGP AS_PATH match or by RIR/RPKI
lookup. So effectively one such control plane rule may result in 100s of
not 1000s of data plane match rules.

And at the end you state:




*5.  Security Considerations   No new security issues are introduced to the
BGP protocol by this   specification.*

IMHO this proposal both on security and technical grounds should not
proceed any further.

Many Thx,
Robert.