Re: [secdir] Secdir last call review of draft-ietf-ospf-ospfv3-segment-routing-extensions-16

Peter Psenak <> Mon, 05 November 2018 08:12 UTC

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Date: Mon, 05 Nov 2018 09:12:34 +0100
From: Peter Psenak <>
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Subject: Re: [secdir] Secdir last call review of draft-ietf-ospf-ospfv3-segment-routing-extensions-16
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Hi Yaron,

thanks for your comments, please see inline:

On 04/11/18 16:38 , Yaron Sheffer wrote:
> Reviewer: Yaron Sheffer
> Review result: Has Nits
> Summary: document has non-security related nits.
> Details
> * The definition of "segment" is different here from the one used in the
> architecture RFC. The RFC is more abstract, quoting: A node steers a packet
> through an ordered list of instructions, called "segments". Whereas here a
> segment is simply a sub-path. This is confusing to a non-expert, and perhaps
> indicates a change in the group's thinking.

the definition in this draft relates to segment as used by IGPs, in 
which case a segment represents the sub-path. There are other segments 
outside of IGPs which can represent other things, but they are not 
covered by this draft.

> * SID/Label Sub-TLV: is it Mandatory? If so, please point it out.

SID/Label Sub-TLV is not advertised on its own. It is advertised as a 
sub-TLV of the:

3.2.  SID/Label Range TLV
3.3.  SR Local Block TLV

Both of these section specify that SID/Label Sub-TLV MUST be included.

> * "The SR-Algorithm TLV is optional" - I find this sentence confusing. Maybe
> replace by "The SR-Algorithm TLV is mandatory for routers that implement
> segment routing"?

the text says:

    "If the SR-Algorithm TLV
    is not advertised by the node, such node is considered as not being
    segment routing capable."

Isn't that sufficient?

> * The reference under "IGP Algorithm Type" registry should be to the IANA
> registry itself, not to the I-D that defines it. (In particular since the IANA
> registry has already been established,

I got another comment from Opsdir last call review to include the I-D 
that defined it. I Added them both, hopefully that satisfy everybody.

> * OSPFv3 Extended Prefix Range TLV Flags octet: add the usual incantation about
> reserved bits.


> * In general I agree with the reasoning in the Security Considerations. I would
> like to raise the question if, in addition to mis-routing, this adds a threat
> of massive denial-of-service on MPLS endpoints, e.g. by allowing an attacker
> who has OSPF access to introduce routing loops. (This may be completely bogus,
> I am far from expert with either of these protocols).

above is addressed by usage of the usage of the OSPF authentication as 
described in the security section.


> .