Re: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?

[Renwei Li <renweili at huawei.com>]

Hi Dave,

I understand that the crafted IP options may be exploited by malicious users
to launch attacks, but some software vendors also develop their software
tools based on the options. The Class 2 options can't be simply ignored.

If an LER makes an IP packet un-routable because LSR doesn't install BGP
routes, the particular LER has an implementation problem. 

As I said before, if an IP packet has options inside, there has to be some
reasons for the options. Sometimes, if LER doesn't look at the options, the
packet can't be correctly forwarded. For example, if the packet wants to be
selectively broadcast to multiple destinations, the options must be
examined.

Moreover, IP options are also used for research and experiment. In such
cases, such experimental options are sometimes expected to be processed at
each hop.

As suggested before, it could be a CLI knob to turn on/off the feature.

If you try to standardize the forwarding path in LER, you have to consider
all the possible IP options. 

Regards,

Renwei



> -----Original Message-----
> From: David Smith (djsmith) [mailto:djsmith at cisco.com]
> Sent: Friday, October 24, 2008 8:50 AM
> To: renweili at huawei.com; Loa Andersson; mpls at ietf.org
> Cc: Ross Callon; David Ward
> Subject: RE: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?
> 
> 
> Hi Renwei,
> 
> Rather than a local LER implementation issue, I'd say this is really a
> LER "forwarding issue". And the MPLS WG has defined many standards on
> "forwarding issues". Consider RFC3443 (TTL Processing in MPLS Networks)
> and RFC3270 (MPLS Support of DiffServ). Our draft complements RFC3443
> and RFC3270.
> 
> >Moreover, when an IP packet has an option, it usually has a
> >reason for having such an option, and thus expects to be
> >processed along the forwarding path in the network.
> 
> Keep in mind one reason (used by an attacker) may simply be "DoS LSRs".
> While the attacker hopes the packet is processed along the forwarding
> path, the MPLS network operator expects it to be tunnelled via an LSP.
> 
> >In this case, an ingress LER is essentially just one hop
> >away from the exit LER. The processing of such options on
> >LER should be no different from on other routers
> 
> This is not true for IP option packets. For packets w/o IP options this
> is true because they are LSP tunnelled from ingress LER to egress LER.
> However, for packets "with" IP options this MAY not be true (depending
> upon the ingress LER implementation) because such option packets are IP
> routed downstream and NOT LSP tunneled.
> 
> I'll argue this is a LER & LSR inter-op issue because the LSRs may not
> be carrying BGP routes and, if so, cannot route (unlabelled) transit
> packets that were not MPLS encapsulated by the ingress LER.
> 
> For these reasons, I think the MPLS WG needs a well-defined (ingress)
> LER forwarding rule to mitigate the risk of IP option packets on MPLS
> networks (ie, LSRs).
> 
> Regards,
> 
> /dave
> 
> 
> -----Original Message-----
> From: Renwei Li [mailto:renweili at huawei.com]
> Sent: Thursday, October 23, 2008 10:10 PM
> To: David Smith (djsmith); 'Loa Andersson'; mpls at ietf.org
> Cc: 'Ross Callon'; 'David Ward'
> Subject: RE: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?
> 
> Hi Dave,
> 
> I do see your point. But it is really a local implementation issue. With
> or without it, LER would still work. It could at most serve as a CLI
> knob which can be turned on or off according to whatever someone wants,
> but it doesn't look like a requirement for LER.
> 
> > If so, should we not promote a consistent implementation among vendor
> > LERs via
> 
> It depends on what you mean by "consistent implementation"? If it has an
> effect on inter-op for LERs from different vendors, no doubt we should
> promote it and I will fully support it. But if it doesn't have anything
> to do with inter-op, I am afraid we should not promote it. There are so
> many different LERs that have different local implementations inside,
> but they are just fine provided they inter-op.
> 
> Moreover, when an IP packet has an option, it usually has a reason for
> having such an option, and thus expects to be processed along the
> forwarding path in the network. In this case, an ingress LER is
> essentially just one hop away from the exit LER. The processing of such
> options on LER should be no different from on other routers.
> 
> Regards,
> 
> Renwei
> 
> 
> > -----Original Message-----
> > From: David Smith (djsmith) [mailto:djsmith at cisco.com]
> > Sent: Thursday, October 23, 2008 7:17 AM
> > To: renweili at huawei.com; Loa Andersson; mpls at ietf.org
> > Cc: Ross Callon; David Ward
> > Subject: RE: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?
> >
> >
> > Hi Renwei,
> >
> > Yes, it's a local LER decision.....but the LER implementation has
> > consequences on downstream LSRs.
> >
> > Do you agree that failing to MPLS encapsulate a IPv4 packet simply
> > because it has an IP option header may be a problem for the downstream
> 
> > network?
> >
> > If so, should we not promote a consistent implementation among vendor
> > LERs via an MPLS WG standard such that when an LER decides "whether to
> 
> > push an MPLS label stack onto an IP packet, the determination is made
> > without considering any IP options that may be carried in the IP
> > packet header"??
> >
> > Regards,
> >
> > /dave
> >
> >
> > -----Original Message-----
> > From: mpls-bounces at ietf.org [mailto:mpls-bounces at ietf.org] On Behalf
> > Of Renwei Li
> > Sent: Thursday, October 23, 2008 1:38 AM
> > To: 'Loa Andersson'; mpls at ietf.org
> > Cc: 'Ross Callon'; 'David Ward'
> > Subject: Re: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?
> >
> > Opposed.
> >
> > This draft imposes a new requirement on LER. But the new requirement
> > has nothing to do with inter-op. Moreover, the new requirement is
> > really a matter of local implementation, and doesn't look really like
> a "MUST"
> > requirement.
> >
> > Regards,
> >
> > Renwei
> >
> >
> > > -----Original Message-----
> > > From: mpls-bounces at ietf.org [mailto:mpls-bounces at ietf.org] On Behalf
> 
> > > Of Loa Andersson
> > > Sent: Tuesday, October 21, 2008 1:14 PM
> > > To: mpls at ietf.org
> > > Cc: Ross Callon; David Ward
> > > Subject: [mpls] draft-dasmith-mpls-ip-options-01.txt as a WG doc?
> > >
> > > Working Group,
> > >
> > > we have been asked to adopt draft-dasmith-mpls-ip-options-01.txt
> > > as a WG doc.
> > >
> > > This is to start a two week poll. Please send your comments on
> > > whether
> >
> > > you think this is ready to become a wg document.
> > >
> > > George and Loa
> > >
> > > --
> > > Loa Andersson
> > >
> > > Principal Networking Architect
> > > Acreo AB                           phone:  +46 8 632 77 14
> > > Isafjordsgatan 22                  mobile: +46 739 81 21 64
> > > Kista, Sweden                      email:  loa.andersson at acreo.se
> > >                                            loa at pi.nu
> > > _______________________________________________
> > > mpls mailing list
> > > mpls at ietf.org
> > > https://www.ietf.org/mailman/listinfo/mpls
> >
> >
> > _______________________________________________
> > mpls mailing list
> > mpls at ietf.org
> > https://www.ietf.org/mailman/listinfo/mpls
> 



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