Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question
I will take a swing at what I have in mind, run it up the flagpole in 6man, and see what happens there. Thanks - Fred > -Original Message- > From: Tom Herbert > Sent: Monday, November 27, 2023 1:01 PM > To: Templin (US), Fred L > Cc: int-area > Subject: Re: [EXTERNAL] Re: "Identification Extension for the Internet > Protocol" question > > EXT email: be mindful of links/attachments. > > > > On Mon, Nov 27, 2023 at 12:42 PM Templin (US), Fred L > wrote: > > > > Tom, > > > > > > I think the best way forward would be to simply define a HBH option > > > > that includes an Identification extension to the standard Fragment > > > > Header, as per my draft -05: > > > > > > > Hi Frad, > > > > > > The problem with that is that the correct processing of the Fragment > > > Header would depend on a HBH option, so that HBH can't be ignored by > > > the receiving host lest the fragment header is incorrectly processed. > > > So the HBH option high order bits can't be 00 (skip when unknown). > > > > If the source has some sort of operational assurance that the destination > > will > > recognize the HBH option, then it should be OK to include the option even if > > the high order bits are 00. And, that is plenty good enough for me. > > Fred, > > Unfortunately, that probably wouldn't be good enough for IETF. IP is > an inherently stateless protocol and receiver processing must be > correctly done just based on a packet's contents; we can never assume > that there is external context needed to correctly process IP packets. > Introducing statefulness into IP makes it a best effort protocol (this > is the first time someone's suggested this) that might work almost all > the time-- like maybe 99.999%. But, 99.999% isn't 100% and that is > enough to say the protocol isn't robust. In practice, at full Internet > scale, someone, somewhere will inevitably see that some operation > assurance fails-- when that happens it cannot lead to detrimental > behaviors. If you can account for all possible behaviors and show that > there are no detrimental behaviors in the edge condition, then the > protocol might be considered robust. > > Tom > > > > > Thanks - Fred > > > > > -Original Message- > > > From: Tom Herbert > > > Sent: Monday, November 27, 2023 11:31 AM > > > To: Templin (US), Fred L > > > Cc: int-area > > > Subject: [EXTERNAL] Re: "Identification Extension for the Internet > > > Protocol" question > > > > > > EXT email: be mindful of links/attachments. > > > > > > > > > > > > On Mon, Nov 27, 2023 at 9:24 AM Templin (US), Fred L > > > wrote: > > > > > > > > Hi Tom, > > > > > > > > > -Original Message- > > > > > From: Tom Herbert > > > > > Sent: Monday, November 27, 2023 9:00 AM > > > > > To: Templin (US), Fred L > > > > > Cc: int-area > > > > > Subject: Re: "Identification Extension for the Internet Protocol" > > > > > question > > > > > > > > > > On Mon, Nov 27, 2023 at 8:01 AM Templin (US), Fred L > > > > > wrote: > > > > > > > > > > > > Hi Tom, > > > > > > > > > > > > > -Original Message- > > > > > > > From: Tom Herbert > > > > > > > Sent: Friday, November 24, 2023 11:33 AM > > > > > > > To: Templin (US), Fred L > > > > > > > Cc: int-area > > > > > > > Subject: Re: "Identification Extension for the Internet Protocol" > > > > > > > question > > > > > > > > > > > > > > On Wed, Nov 22, 2023 at 10:57 AM Templin (US), Fred L > > > > > > > wrote: > > > > > > > > > > > > > > > > Tom, please have another look at the draft – it gets the job > > > > > > > > done without requiring any new kinds of IPv6 extension headers, > HBH > > > > > options, > > > > > > > etc,: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://datatracker.ietf.org/doc/draft-templin-intarea-ipid-ext/ > > > > > > > > > > > > > > Hi Fred, > > > > > > >
Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question
On Mon, Nov 27, 2023 at 12:42 PM Templin (US), Fred L wrote: > > Tom, > > > > I think the best way forward would be to simply define a HBH option > > > that includes an Identification extension to the standard Fragment > > > Header, as per my draft -05: > > > > > Hi Frad, > > > > The problem with that is that the correct processing of the Fragment > > Header would depend on a HBH option, so that HBH can't be ignored by > > the receiving host lest the fragment header is incorrectly processed. > > So the HBH option high order bits can't be 00 (skip when unknown). > > If the source has some sort of operational assurance that the destination will > recognize the HBH option, then it should be OK to include the option even if > the high order bits are 00. And, that is plenty good enough for me. Fred, Unfortunately, that probably wouldn't be good enough for IETF. IP is an inherently stateless protocol and receiver processing must be correctly done just based on a packet's contents; we can never assume that there is external context needed to correctly process IP packets. Introducing statefulness into IP makes it a best effort protocol (this is the first time someone's suggested this) that might work almost all the time-- like maybe 99.999%. But, 99.999% isn't 100% and that is enough to say the protocol isn't robust. In practice, at full Internet scale, someone, somewhere will inevitably see that some operation assurance fails-- when that happens it cannot lead to detrimental behaviors. If you can account for all possible behaviors and show that there are no detrimental behaviors in the edge condition, then the protocol might be considered robust. Tom > > Thanks - Fred > > > -Original Message- > > From: Tom Herbert > > Sent: Monday, November 27, 2023 11:31 AM > > To: Templin (US), Fred L > > Cc: int-area > > Subject: [EXTERNAL] Re: "Identification Extension for the Internet > > Protocol" question > > > > EXT email: be mindful of links/attachments. > > > > > > > > On Mon, Nov 27, 2023 at 9:24 AM Templin (US), Fred L > > wrote: > > > > > > Hi Tom, > > > > > > > -Original Message- > > > > From: Tom Herbert > > > > Sent: Monday, November 27, 2023 9:00 AM > > > > To: Templin (US), Fred L > > > > Cc: int-area > > > > Subject: Re: "Identification Extension for the Internet Protocol" > > > > question > > > > > > > > On Mon, Nov 27, 2023 at 8:01 AM Templin (US), Fred L > > > > wrote: > > > > > > > > > > Hi Tom, > > > > > > > > > > > -Original Message- > > > > > > From: Tom Herbert > > > > > > Sent: Friday, November 24, 2023 11:33 AM > > > > > > To: Templin (US), Fred L > > > > > > Cc: int-area > > > > > > Subject: Re: "Identification Extension for the Internet Protocol" > > > > > > question > > > > > > > > > > > > On Wed, Nov 22, 2023 at 10:57 AM Templin (US), Fred L > > > > > > wrote: > > > > > > > > > > > > > > Tom, please have another look at the draft – it gets the job done > > > > > > > without requiring any new kinds of IPv6 extension headers, HBH > > > > options, > > > > > > etc,: > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://datatracker.ietf.org/doc/draft-templin-intarea-ipid-ext/ > > > > > > > > > > > > Hi Fred, > > > > > > > > > > > > From the draft: "For an advanced Identification, this specification > > > > > > permits the source to include a second Fragment Header immediately > > > > > > following the first such that the two are bonded together to create > > > > > > a > > > > > > conceptual IPv6"-- How would this be processed for a legacy receiver > > > > > > that doesn't understand these headers are to be bonded? > > > > > > > > > > > > From the draft: "For the second Fragment Header, only the Next > > > > > > Header > > > > > > field is interpreted as a control field that MUST encode the value N > > > > > > corresponding to the next header to follow while the remaining 7 > > > > > > octets are interpreted
Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question
Tom, > > I think the best way forward would be to simply define a HBH option > > that includes an Identification extension to the standard Fragment > > Header, as per my draft -05: > > > Hi Frad, > > The problem with that is that the correct processing of the Fragment > Header would depend on a HBH option, so that HBH can't be ignored by > the receiving host lest the fragment header is incorrectly processed. > So the HBH option high order bits can't be 00 (skip when unknown). If the source has some sort of operational assurance that the destination will recognize the HBH option, then it should be OK to include the option even if the high order bits are 00. And, that is plenty good enough for me. Thanks - Fred > -Original Message- > From: Tom Herbert > Sent: Monday, November 27, 2023 11:31 AM > To: Templin (US), Fred L > Cc: int-area > Subject: [EXTERNAL] Re: "Identification Extension for the Internet Protocol" > question > > EXT email: be mindful of links/attachments. > > > > On Mon, Nov 27, 2023 at 9:24 AM Templin (US), Fred L > wrote: > > > > Hi Tom, > > > > > -Original Message- > > > From: Tom Herbert > > > Sent: Monday, November 27, 2023 9:00 AM > > > To: Templin (US), Fred L > > > Cc: int-area > > > Subject: Re: "Identification Extension for the Internet Protocol" question > > > > > > On Mon, Nov 27, 2023 at 8:01 AM Templin (US), Fred L > > > wrote: > > > > > > > > Hi Tom, > > > > > > > > > -Original Message- > > > > > From: Tom Herbert > > > > > Sent: Friday, November 24, 2023 11:33 AM > > > > > To: Templin (US), Fred L > > > > > Cc: int-area > > > > > Subject: Re: "Identification Extension for the Internet Protocol" > > > > > question > > > > > > > > > > On Wed, Nov 22, 2023 at 10:57 AM Templin (US), Fred L > > > > > wrote: > > > > > > > > > > > > Tom, please have another look at the draft – it gets the job done > > > > > > without requiring any new kinds of IPv6 extension headers, HBH > > > options, > > > > > etc,: > > > > > > > > > > > > > > > > > > > > > > > > https://datatracker.ietf.org/doc/draft-templin-intarea-ipid-ext/ > > > > > > > > > > Hi Fred, > > > > > > > > > > From the draft: "For an advanced Identification, this specification > > > > > permits the source to include a second Fragment Header immediately > > > > > following the first such that the two are bonded together to create a > > > > > conceptual IPv6"-- How would this be processed for a legacy receiver > > > > > that doesn't understand these headers are to be bonded? > > > > > > > > > > From the draft: "For the second Fragment Header, only the Next Header > > > > > field is interpreted as a control field that MUST encode the value N > > > > > corresponding to the next header to follow while the remaining 7 > > > > > octets are interpreted as an Identification Extension."-- This is > > > > > repurposing fields in a standard protocol header. Even if it > > > > > functionally works, this can break diagnostics and debugging tools in > > > > > deployment. > > > > > > > > How would it be if instead of repurposing the fragmentation control > > > > fields > > > > in the second Fragment Header we instead make them to be identical > > > > copies > > > > of the same fields that occurred in the first Fragment Header? Then, the > > > > Identification field in the first FH would contain the low-order 4 > > > > octets > > > > while the Identification field in the second FH would contain the > > > > high-order 4 octets of an 8-octet (64-bit) extended Identification, > > > > while the fragmentation control fields are identical? I would ideally > > > > like to be able to support Identification extension all the way out to > > > > 128bits, but I would be happy with 64bits for now. > > > > > > Hi Fred, > > > > > > I think the question to be asked is what happens if we send two > > > Fragment Headers to a host that is conformant with RFC8200 but unaware > > > of the proposed semantics. I
Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question
Tom, >The bar for creating any new EH is high. If the data needs to be read or >modified by routers then Hop-by-Hop Options is appropriate, if it's only read >at the end host or intermediate nodes then Destination Options should be used. The Identification needs to be included in the Per-Fragment headers, so I guess that means it needs to be “Hop-by-Hop Option”, right? Thanks - Fred From: Tom Herbert Sent: Tuesday, November 21, 2023 4:22 PM To: Templin (US), Fred L Cc: Templin (US), Fred L ; int-area Subject: [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question EXT email: be mindful of links/attachments. On Tue, Nov 21, 2023, 2:45 PM Templin (US), Fred L mailto:40boeing@dmarc.ietf.org>> wrote: Tom, I am going to circle back again to where this all started many draft versions ago. Based on my read of RFC6564 and how that was then taken up in RFC8200, it looks like the barrier would be very high to specify any new extension header that does not begin with the two 1-octet fields “Next Header” and “Hdr Ext Len”. The reason for that specification is to ensure backwards compatibility for widely-deployed hardware in the rare event that a new extension header would be defined. So, going back to what I said in earlier draft versions, wouldn’t it be better if we just put the Identification extension in a Hop-by-Hop option instead of defining a new Fragment Header type? Fred, The bar for creating any new EH is high. If the data needs to be read or modified by routers then Hop-by-Hop Options is appropriate, if it's only read at the end host or intermediate nodes then Destination Options should be used. Tom Fred From: Int-area mailto:int-area-boun...@ietf.org>> On Behalf Of Templin (US), Fred L Sent: Tuesday, November 21, 2023 1:30 PM To: Tom Herbert mailto:40herbertland@dmarc.ietf.org>> Cc: int-area mailto:int-area@ietf.org>> Subject: Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question Tom, 4 bytes per packet worth of wasted transmission is a pain point experienced by all nodes on the local (shared) transmission media as well as along the networked path – not just for the original source and final destination. Conversely, an odd-sized roadblock in the middle of a path of otherwise 8-octet-aligned stepping stones is a processing anomaly experienced only by the forwarding nodes and end systems on the path. And, how bad would that be, really? There is currently no hardware logic that recognizes the IPv6 Extended Fragment Header (since it does not yet exist) and software logic can easily be made to step around an 8-octet alignment anomaly until ASICs begin to emerge that can do it more efficiently. So, I say we bend the rules and make the IPv6 Extended Fragment Header as the sole exception IPv6 extension header that does not support 8-octet alignment. All it would take is an update to RFC8200, but we already have to do that in order to define a new extension header type. Fred From: Tom Herbert mailto:tom=40herbertland@dmarc.ietf.org>> Sent: Tuesday, November 21, 2023 1:11 PM To: Templin (US), Fred L mailto:fred.l.temp...@boeing.com>> Cc: int-area mailto:int-area@ietf.org>> Subject: [EXTERNAL] Re: [Int-area] "Identification Extension for the Internet Protocol" question EXT email: be mindful of links/attachments. On Tue, Nov 21, 2023, 12:15 PM Templin (US), Fred L mailto:40boeing@dmarc.ietf.org>> wrote: Tom, >The text you quoted says why we can't do that. If a frag header length is not >a multiple of eight bytes then the alignment requirements for all subsequent >extension headers and the payload are not met. >This potentially breaks a >receiving implementation that relies on alignment. I both do and don’t understand why this limitation applies here. Currently, no IP protocol number exists for the IPv6 Extended Fragment Header, so currently no receiving implementations recognize it. So, why can’t we define one special-case IPv6 extension header that bends the rules? As implementations are deployed to recognize it, they will naturally accommodate the discontinuity in 8-octet aligned extension headers. Fred, The problem isn't with the new header, it's the effects on existing extension headers that might follow it. With modern architectures, I would think that saving the network transmission overhead of 4 wasted octets per message would outweigh the processing drawbacks in having a discontinuity in 8-octet alignment. Especially since no implementations currently exist. 4 bytes is 0.3% of minimum 1280 bytes MTU. I don't believe that is significant enough savings to diverge from the long established requirements of the standard. Tom Fred From: Tom Herbert mailto:40herbertland@dmarc.ietf.org>> Sent: Tuesday, November 21, 2023 12:04 PM To: Templin (US
Re: [Int-area] [EXTERNAL] Re: "Identification Extension for the Internet Protocol" question
Tom, 4 bytes per packet worth of wasted transmission is a pain point experienced by all nodes on the local (shared) transmission media as well as along the networked path – not just for the original source and final destination. Conversely, an odd-sized roadblock in the middle of a path of otherwise 8-octet-aligned stepping stones is a processing anomaly experienced only by the forwarding nodes and end systems on the path. And, how bad would that be, really? There is currently no hardware logic that recognizes the IPv6 Extended Fragment Header (since it does not yet exist) and software logic can easily be made to step around an 8-octet alignment anomaly until ASICs begin to emerge that can do it more efficiently. So, I say we bend the rules and make the IPv6 Extended Fragment Header as the sole exception IPv6 extension header that does not support 8-octet alignment. All it would take is an update to RFC8200, but we already have to do that in order to define a new extension header type. Fred From: Tom Herbert Sent: Tuesday, November 21, 2023 1:11 PM To: Templin (US), Fred L Cc: int-area Subject: [EXTERNAL] Re: [Int-area] "Identification Extension for the Internet Protocol" question EXT email: be mindful of links/attachments. On Tue, Nov 21, 2023, 12:15 PM Templin (US), Fred L mailto:40boeing@dmarc.ietf.org>> wrote: Tom, >The text you quoted says why we can't do that. If a frag header length is not >a multiple of eight bytes then the alignment requirements for all subsequent >extension headers and the payload are not met. >This potentially breaks a >receiving implementation that relies on alignment. I both do and don’t understand why this limitation applies here. Currently, no IP protocol number exists for the IPv6 Extended Fragment Header, so currently no receiving implementations recognize it. So, why can’t we define one special-case IPv6 extension header that bends the rules? As implementations are deployed to recognize it, they will naturally accommodate the discontinuity in 8-octet aligned extension headers. Fred, The problem isn't with the new header, it's the effects on existing extension headers that might follow it. With modern architectures, I would think that saving the network transmission overhead of 4 wasted octets per message would outweigh the processing drawbacks in having a discontinuity in 8-octet alignment. Especially since no implementations currently exist. 4 bytes is 0.3% of minimum 1280 bytes MTU. I don't believe that is significant enough savings to diverge from the long established requirements of the standard. Tom Fred From: Tom Herbert mailto:40herbertland@dmarc.ietf.org>> Sent: Tuesday, November 21, 2023 12:04 PM To: Templin (US), Fred L mailto:fred.l.temp...@boeing.com>> Cc: int-area mailto:int-area@ietf.org>> Subject: [EXTERNAL] Re: [Int-area] "Identification Extension for the Internet Protocol" question EXT email: be mindful of links/attachments. On Tue, Nov 21, 2023, 11:44 AM Templin (US), Fred L mailto:40boeing@dmarc.ietf.org>> wrote: Section 8 of "Identification Extension for the Internet Protocol" proposes a new IPv6 extension header called the "Extended Fragment Header" that includes a 96-bit (12 octet) Identification field making the total length of the extension header 128-bits (16 octets): https://datatracker.ietf.org/doc/draft-templin-intarea-ipid-ext/ However, the only reason for the 96-bit Identification field was to make the whole extension header be an integral multiple of 8 octets - what would be preferable would be to have only a 64-bit Identification field and limit the Extended Fragment Header as a whole to 96-bits (12 octets) which is not a multiple of 8 octets. The IPv6 Fragment Header is unique among IPv6 extension headers in that it does not include a "Hdr Ext Len" field that tells the length of the header in 8-octet units. This means that implementations must be able to determine its length (8 octets) solely based on the IP protocol number "44". The proposed IPv6 Extended Fragment Header would likewise not include a "Hdr Ext Len" field and would use a new IP protocol number to be assigned by IANA, with the IP protocol number determining the extension header length. RFC8200, Section 4 states: "Each extension header is an integer multiple of 8 octets long, in order to retain 8-octet alignment for subsequent headers." But, can an exception be made for the proposed IPv6 Extended Fragment Header with a 64-bit Identification field, making the total extension header length 12 octets which is not a integer multiple of 8? Hi Fred, The text you quoted says why we can't do that. If a frag header length is not a multiple of eight bytes then the alignment requirements for all subsequent extension headers and t
