Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

[Curtis Villamizar <[e-mail]>]

In message <[e-mail]>
[e-mail] writes:
 
> the text is not satisfactory. never recommend setting to zero,
> as that poses a risk to your and to other traffic. Suggested text:
> ***
> The UDP checksum SHOULD be used to protect the payload and
> ensure correct demultiplexing and delivery to the tunnel, and not to
> other UDP destinations, by protecting the UDP pseudoheader.
> Use of a zero UDP checksum is NOT RECOMMENDED, even when
> desired for performance or necessitated by implementation
> reasons, for the reasons outlined in [RFC6936] section 3.

I agree that UDP checksums SHOULD be used (ie: SHOULD NOT be set to
zero).  There are cases where it is impossible so it can't be MUST.

> UDP-Lite [RFC3828] can provide a demultiplexing check and MPLS
> stack integrity check while avoiding the overhead of computing an
> integrity check over a tunnelled frame that has its own integrity check.

UDP-List doesn't solve the ECMP problems because most of the older LSR
that are forcing the use of MPLS over UDP to get ECMP don't look at
the port numbers if the protocol is not 6 or 17.  But this has only
been said three or four times so maybe you missed it.

> ***
>  
> Lloyd Wood
> http://about.me/lloydwood
> ________________________________________
> From: Xuxiaohu [[e-mail]]
> Sent: 23 January 2014 12:35
> To: Wood L  Dr (Electronic Eng); [e-mail]; [e-mail]
> Cc: [e-mail]; [e-mail]
> Subject: re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard
>  
> > -----ÓʼþÔ­¼þ-----
> > ·¢¼þÈË: [e-mail] [mailto:[e-mail]]
> > ·¢ËÍʱ¼ä: 2014Äê1ÔÂ23ÈÕ 12:44
> > ÊÕ¼þÈË: Xuxiaohu; [e-mail]; [e-mail]
> > ³­ËÍ: [e-mail]; [e-mail]
> > Ö÷Ìâ: RE: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS
> > in UDP) to Proposed Standard
> >
> > Sasha
> >
> > > - UDP checksums (or lack thereof) is a non-issue because native MPLS
> > > does not have anything like that. And yes, there are cases where
> > > packets are corrupted within the routers)
> >
> > So you admit that packets can be corrupted within the routers - a check that can
> > only be caught by an end-to-end check, a corruption that can lead to the
> > problems detailed in RFC 6936 section 3 - and then you say it's a non-issue
> > because this doesn't affect native MPLS. But we're not doing native MPLS here.
> > We're doing MPLS over UDP.
> >
> > draft-ietf-mpls-in-udp-04.txt is about tunnelling MPLS in UDP. It's an issue.
> > Please read the other 150 messages that you refer to.
>  
> Hi Lloyd,
>  
> The draft doesn't require the IPv6 UDP checksum to be set to zero regardless. See the following text quoted from that draft:
>  
> UDP Checksum
>  
> The usage of this field is in accordance with the current UDP specification [RFC768]. To simplify the operation on the decapsulator, this field is RECOMMENDED to be set to zero in IPv4 UDP encapsulation case. In the IPv6 UDP encapsulation case, if appropriate according to the requirements defined in [RFC6935] [RFC6936], this field is also RECOMMENDED to be set to zero. Specifically, if the MPLS payload is Internet Protocol (IPv4 or IPv6) packets, it is RECOMMENDED to be set to zero when the inner packet integrity checks is available. In addition, if the MPLS payload is non-IP packet which is specifically designed for transmission over a lower layer that does not provide a packet integrity guarantee, it is RECOMMENDED to be set to zero as well. Otherwise, using zero checksum is NOT RECOMMENDED. Note that other IP encapsulations for MPLS do not have a checksum in the tunnel header.
>  
> If you still believe the above text is not satisfactory, please provide your text.
>  
> Best regards,
> Xiaohu
>  
> > Lloyd Wood
> > http://about.me/lloydwood
> > ________________________________________
> > From: mpls [[e-mail]] On Behalf Of Xuxiaohu
> > [[e-mail]]
> > Sent: 23 January 2014 03:16
> > To: Alexander Vainshtein; Eggert, Lars
> > Cc: Joel Jaeggli; [e-mail]
> > Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating
> > MPLS in UDP) to Proposed Standard
> >
> > Hi
> >
> > > -----ÓʼþÔ­¼þ-----
> > > ·¢¼þÈË: Alexander Vainshtein [mailto:[e-mail]]
> > > ·¢ËÍʱ¼ä: 2014Äê1ÔÂ22ÈÕ 19:05
> > > ÊÕ¼þÈË: Eggert, Lars
> > > ³­ËÍ: Joel Jaeggli; [e-mail]; Xuxiaohu
> > > Ö÷Ìâ: RE: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt>
> > > (Encapsulating MPLS in UDP) to Proposed Standard
> > >
> > > Lars and all,
> > > Last time I've counted the IETF LC thread on this draft has more than
> > > 150 messages in it, and it seems that on some issues (congestion
> > > control and UDP
> > > checksums) we are going round the mulberry bush.
> > >
> > > IMHO and FWIW:
> > > - UDP checksums (or lack thereof) is a non-issue because native MPLS
> > > does not have anything like that. And yes, there are cases where
> > > packets are corrupted within the routers), but so far it did not
> > > prevent MPLS deployment. There is, e.g., RFC 4720 for FCS retention in
> > > PWs, but I doubt it is widely implemented and deployed (would be nice to
> > know).
> > > - E2E congestion control (regardless of its implications) simply
> > > cannot be added to this protocol without some major changes. A short
> > > applicability statement explaining that should suffice IMO.
> >
> > Hi Sasha,
> >
> > I fully agree with your points.
> >
> > Best regards,
> > Xiaohu
> >
> > > My 2c,
> > >        Sasha
> > > Email: [e-mail]
> > > Mobile: [phone]
> > >
> > > > -----Original Message-----
> > > > From: mpls [mailto:[e-mail]] On Behalf Of Eggert, Lars
> > > > Sent: Wednesday, January 22, 2014 12:23 PM
> > > > To: Xuxiaohu
> > > > Cc: Joel Jaeggli; [e-mail]
> > > > Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt>
> > > > (Encapsulating MPLS in UDP) to Proposed Standard
> > > >
> > > > Hi,
> > > >
> > > > On 2014-1-22, at 11:12, Xuxiaohu <[e-mail]> wrote:
> > > > > I wonder whether the following text is OK to you:
> > > > >
> > > > > Since the MPLS-in-UDP encapsulation causes MPLS packets to be
> > > > forwarded through "UDP tunnels", the congestion control guidelines
> > > > for UDP tunnels as defined in Section 3.1.3 of [RFC5405] SHOULD be
> > followed.
> > > > Specifically, MPLS can carry a number of different protocols as payloads.
> > > > When an UDP tunnel is used for MPLS payload traffic that is known at
> > > > configuration time to be IP-based and congestion-controlled, the UDP
> > > > tunnel SHOULD NOT employ its own congestion control mechanism,
> > > > because congestion losses of tunneled traffic will trigger an
> > > > congestion response at the original senders of the tunneled traffic.
> > > > When an UDP tunnel is used for MPLS payload traffic that is known at
> > > > configuration time not to be IP-based and congestion-controlled, the
> > > > UDP tunnel SHOULD employ an appropriate congestion control mechanism
> > > > as described in [RFC3985]. Note that it STRONGLY RECOMMENDED to
> > > > deploy such encapsulation technology only within a SP network or
> > > > networks of an adjacent set of co-operating SPs, rather than over the
> > Internet.
> > > > Furthermore, packet filters should be added to block traffic with
> > > > the UDP port number for MPLS over UDP to prevent MPLS over UDP
> > > > packets to escape from the service provider networks due to
> > > > misconfiguation or packet
> > > errors.
> > > >
> > > > I think it would be better to describe the OAM control loop in
> > > > (some) more detail, rather than pointing to RFC3985, which doesn't
> > > > have a whole lot of detail either. Also because the adding of
> > > > firewall rules requires an OAM hook.
> > > >
> > > > Since STRONGLY RECOMMENDED is not an RFC2119 term and
> > > RECOMMENDED is
> > > > too weak, I'd suggest to change this to MUST.
> > > >
> > > > Finally, the applicability statement should be prominently made in
> > > > the abstract, introduction, etc.
> > > >
> > > > Lars