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

["David Smith (djsmith)" <djsmith at cisco.com>]

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
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