Re: [tsvwg] Status of ECN encapsulation drafts (i.e., stuck)
"Rodney W. Grimes" <ietf@gndrsh.dnsmgr.net> Sun, 15 March 2020 17:30 UTC
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From: "Rodney W. Grimes" <ietf@gndrsh.dnsmgr.net>
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To: Bob Briscoe <ietf@bobbriscoe.net>
Date: Sun, 15 Mar 2020 10:30:28 -0700
CC: "Rodney W. Grimes" <ietf@gndrsh.dnsmgr.net>, Sebastian Moeller <moeller0@gmx.de>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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Subject: Re: [tsvwg] Status of ECN encapsulation drafts (i.e., stuck)
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> Rod, > > On 14/03/2020 22:18, Rodney W. Grimes wrote: > > Bob, > > Questions and comments in line. > > > > > >> Finding the best max packet size is an area where neither IPv4 nor IPv6 > >> has ever found a good solution. Getting a tunnel to fragment and > >> reassemble is indeed painfully sub-optimal, but all the other solutions > >> have their own problems. It is possible the sub-optimality is often > >> going on under-the-covers, just because it works. I do know that, for > >> IPv4, the Don't Fragment (DF) flag is often ignored by tunnels, as a > >> preferable alternative to just ditching the traffic. > > > > What do you base your "know" on? > > Can you please site an implementaiton? > > Here's a selection of implementations that allow you to configure > clearing the DF flag in order to allow fragmentation prior to encapsulation: Thank you for this Bob, that clears up things a fair bit. Describing "configurable clearing of DF" as "often ignored by tunnels..." is what lead to my questions. > > * Cisco IOS: > https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_dplane/configuration/15-mt/sec-ipsec-data-plane-15-mt-book/sec-df-bit-ovride.html > * Juniper JunOS: > https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/clear-dont-fragment-bit-edit-interfaces.html > * Huawei: > https://support.huawei.com/enterprise/en/doc/EDOC1100034238/a1bd518c/optional-configuring-the-df-flag-bit-for-gre-packets > * Ericsson Redback: > http://rbman.ito.expert/en_lzn7830011_1_r4a/3_19082-CRA1191170_1-V1Uen.G.html#CHAPTER1.59 > * Linux: iptables -t mangle -A PREROUTING -j DF --clear > > While searching, I also found clear-df by accident in a firewall manual > (not even doing any tunnelling) > > And I even discovered "clear-df" in an (expired) individual Internet > Draft from Ericsson for the Yang data model of an IPv4 tunnel: > draft-liu-intarea-ipipv4-tunnel-yang-02 > > Note, these are not to be confused with suppressing propagation of DF=1 > from the arriving IP header to the outer (so that a downstream router > within the tunnel is allowed to fragment). In Linux, that would be: > iptables -t mangle -A POSTROUTING -j DF --clear > > So yes, I know this is often done, but I don't know how often. Probably more often than desireable. BUT this is done intentionally by an Operator, so I do not view this as a severe a problem as if there actually was an implementation that just flat out ignored DF. > Bob > Bob Briscoe http://bobbriscoe.net/ -- Rod Grimes rgrimes@freebsd.org
- [tsvwg] Status of ECN encapsulation drafts (i.e.,… Black, David
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Black, David
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- [tsvwg] SCE / L4S and fragmentation (was: Status … Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Holland, Jake
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Holland, Jake
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Holland, Jake
- Re: [tsvwg] SCE / L4S and fragmentation (was: Sta… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Sebastian Moeller
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Rodney W. Grimes
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Sebastian Moeller
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] SCE / L4S and fragmentation Bob Briscoe
- Re: [tsvwg] SCE / L4S and fragmentation Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Rodney W. Grimes
- Re: [tsvwg] SCE / L4S and fragmentation Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] SCE / L4S and fragmentation Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Bob Briscoe
- Re: [tsvwg] SCE / L4S and fragmentation Bob Briscoe
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Sebastian Moeller
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Sebastian Moeller
- Re: [tsvwg] SCE / L4S and fragmentation Sebastian Moeller
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] SCE / L4S and fragmentation Wesley Eddy
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Rodney W. Grimes
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Jonathan Morton
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Rodney W. Grimes
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joseph Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Rodney W. Grimes
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Joe Touch
- Re: [tsvwg] Status of ECN encapsulation drafts (i… John Leslie
- Re: [tsvwg] Status of ECN encapsulation drafts (i… Holland, Jake
- Re: [tsvwg] SCE / L4S and fragmentation Black, David