MPLS is not only for QoS it provides layer 2 type services in the layer 3
environment (QoS, CoS, Traffic engineered paths etc) . If using Ethernet or
PoS then a label is inserted between layer 2 and layer 3 protocols, if using
ATM then the label is inserted into the ATM header. The MPLS label is used
to forward the packet to the next hop. MPLS was not designed as a VPN
protocol, however it does support features that allow VPNs (stacks of
labels). The VPNs are primarily created by the ability for the PE (Provider
edge or Label Edge router (LER)) being able to run Virtual Routers. VR's
allow multiple independent routing tables to be held on a single device.
The security is gained by only being able to use a certain routing table.

As you stated vendor implementations are different and therefore have
different security strengths. I have attempted some simple penetration
tests on a Cisco router running VRs with no luck in breaking it (it was a
simple test though)

At a guess the place to look for weaknesses would probably be BGP as this is
used to carry VPN routes across the network. BGP uses some extra features
such as new address families and extended communities (see RFC 2547 & RFC
2283). A spoofed injection of BGP could lead to VPN routes being populated
into the wrong VRs.

Simon

-----Original Message-----
From: Penetration Testers [mailto:PEN-TESTSECURITYFOCUS.COM]On Behalf
Of Sheldon Dubrowin
Sent: 04 January 2001 18:27
To: PEN-TESTSECURITYFOCUS.COM
Subject: Re: [PEN-TEST] Vulnerabilities within MPLS ??

My understanding of QoS, I did QoS at BBN in a previous life, is that it
only
works within a provider's network. MPLS is a form of QoS (Quality of
Service). MPLS will give preference up to a certain point (configured in
the
network) to packets with a "better" tag. Once a packet reaches the edge it
is no longer gauranteed better performance. One of the issues in putting
QoS
into a large network is the fact that either you have to tag all the packets
at the edge or you may end up giving preferential treatment to someone who
isn't paying for it.

Adding a VPN is just having VPN traffic (all/some? probably depends on the
provider) being given preferential treat, or getting out of the routers more
quickly than "regular" traffic.

        Shel

On Wed, Jan 03, 2001 at 04:42:50PM -0500, Ruscher, Mike wrote:
> > I am searching for information on vulnerabilities in the Multi-protocol
> > Label Switching (MPLS) protocol. I have been unable to gather
information
> > by searching on the common search engines, as the majority of the hits
are
> > related to the RFC's.
> >
> > I have organized several questions to better understand the subject: Are
> > there any big holes that could lead to a security compromise? What is
the
> > difference between MPLS and MPLS VPN? I realize that plain MPLS does
not
> > provide confidentiality, integrity, and authentication by itself unless
it
> > is used along with IPSec. How is the route negotiated between the PE's
> > (provider edge routers)? Can the route negotiation be compromised in
any
> > manner? What happens with traffic if one of the PE routers goes
offline?
> >
> > I realize that these are difficult questions and the answers are likely
to
> > be lengthy. Any information will be greatly appreciated.
> >
> > Thanks
> >
> Mike Ruscher
> Communications Security Establishment
> mgruschercse-cst.gc.ca
> >
> >
> >
> >

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