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.

My biggest issue with this document is that it is hard to read.  For example, the Introduction expands tLDP to "targeted LDP", and the Introduction begins with "LDP uses extended discovery...", but LDP itself is only expanded to "label distribution protocol" in the IANA considerations section.  Similarly, the much-overloaded term "application" is never explained except that some applications are "targeted" and that "FEC 128 pseudowire" is an example of an application.  I am sure this makes sense to participants of the MPLS working group, but to others this is much harder. There needs to be at least a reference to RFC 5036 where these terms are better explained (RFC 5036 is referenced but only as the document where tLDP adjacency is described).

Nits:
The Security Considerations section begins with "The Capability procedure described in this document will apply and does not introduce any change to LDP Security Considerations".  The procedure will apply what?  Or will apply to what?  I think the words "will apply and" are superfluous. 

The second paragraph seems to be repeating part of the (rather extensive) security considerations of RFC 5036, but it does not say why (or even whether) that particular anti-DoS measure applies in particular to the mechanism described in this document. IOW why is this measure singled out from among the three pages of security considerations from RFC 5036?

The third paragraph is not clear to me. It talks about two nodes not establishing a tLDP session if they don't support the same application. I don't know why that belongs in the security considerations section. The SHOULD NOT (establish a session) mandate definitely does not belong there.