Pablo,
In L3VPN, all of these are combined into a single 20-bit MPLS label. Why can
SRv6 not do likewise?
Ron
Juniper Business Use Only
From: spring <spring-boun...@ietf.org> On Behalf Of Pablo Camarillo (pcamaril)
Sent: Thursday, December 19, 2019 6:47 AM
To: Wang, Weibin (NSB - CN/Shanghai) <weibin.w...@nokia-sbell.com>; Gyan Mishra
<hayabusa...@gmail.com>
Cc: spring@ietf.org; Voyer, Daniel <daniel.vo...@bell.ca>
Subject: [spring] End.DT/End.DX SIDs (was Re: USD/USP question in
draft-ietf-spring-srv6-network-programming-06.txt)
Gyan,
The End.DX4/End.DX6 can be seen as an equivalent to the MPLS per-CE VPN label.
The End.DT4/End.DT6 can be seen as an equivalent to the MPLS per-VRF VPN label.
I believe that they cannot be combined.
Cheers,
Pablo.
From: Gyan Mishra <hayabusa...@gmail.com<mailto:hayabusa...@gmail.com>>
Date: Sunday, 15 December 2019 at 08:29
To: "Wang, Weibin (NSB - CN/Shanghai)"
<weibin.w...@nokia-sbell.com<mailto:weibin.w...@nokia-sbell.com>>
Cc: "Pablo Camarillo (pcamaril)"
<pcama...@cisco.com<mailto:pcama...@cisco.com>>, "Voyer, Daniel"
<daniel.vo...@bell.ca<mailto:daniel.vo...@bell.ca>>,
"spring@ietf.org<mailto:spring@ietf.org>"
<spring@ietf.org<mailto:spring@ietf.org>>
Subject: Re: [spring] USD/USP question in
draft-ietf-spring-srv6-network-programming-06.txt
Hi Wang & Pablo & Spring Authors,
Had another question?
These 4 sections. Trying to understand the difference between end.dx4 end.dx6
and end.dt4 and end.dt6. They both seem very similar. One says xconnect but
other has v4 v6 lookup but for both you have to signal L3 vpn services sid.
Not sure why both SIDs dx dt Sid function why they cannot be combined.
I noticed this difference below that the dx4 dt4 account for the global table
scenario where the PE-CE is native IPv4 or IPv6. In the MPLS world that use
case is very different in that there is not any L3 vpn label and do the label
stack only had a single topmost label. Also in the MPLS scenario with IPv6
global table PE-CE with a IPv4 core you require BGP -LU labeled unicast "send
label" to label all the IPv6 prefixed tunneled over IPv4. Since that scenario
is very different with global table does it make sense to have a separate End.x
variant for global table for both IPv4 and IPv6.
Note that an End.DT6 may be defined for the main IPv6 table in which
case and End.DT6 supports the equivalent of an IPv6inIPv6
decapsulation (without VPN/tenant implication).
4.4<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.4__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JAaJnI7_$>.
End.DX6: Decapsulation and IPv6 cross-connect . . . . . .
12<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*page-12__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JH8Abwf7$>
4.5<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.5__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JEh8sRB2$>.
End.DX4: Decapsulation and IPv4 cross-connect . . . . . .
13<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*page-13__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JHAg09NC$>
4.6<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.6__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JHVgWtPg$>.
End.DT6: Decapsulation and specific IPv6 table lookup . .
14<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*page-14__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JA89XfKV$>
4.7<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.7__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JF59SaCO$>.
End.DT4: Decapsulation and specific IPv4 table lookup . .
15<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*page-15__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JICjeckL$>
Also I was trying to understand end.dt46.
So if the PE-CE edge is dual stacked anhas both v4 and v6 you have a VRF tenant
v4 and v6 separate peers signaled via L3 vpn services TLV. So why do you need
this end.dt46 sid
4.8<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.8__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JMbbI6-v$>.
End.DT46: Decapsulation and specific IP table lookup . .
16<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*page-16__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JMihsn8k$>
Kind Regards,
Gyan
On Sun, Dec 15, 2019 at 2:06 AM Gyan Mishra
<hayabusa...@gmail.com<mailto:hayabusa...@gmail.com>> wrote:
Hi Wang
I have a question regarding the PSP, USP and USD sections I pasted below.
I just sent an email to Spring WG related to PSP and technically why that is
necessary as that is a legacy concept that has parity to MPLS but is not used
today due to QOS issues. Please see that email related to that topic.
In the PSP section can If we have to keep PSP can we add verbiage that states
that PSP removal of the SRH header occurs on the Penultimate egress P node.
In the USP section can we also add that all remaining SRH present in the packet
are popped on the egress PE ultimate node.
In looking at these 3 SID functions the PSP and USP pop the EH and the USP
removes the 6in6 encapsulation so that the other end.x dt4 dt6 etc can pop the
services L3vpn headers.
Why can't the USD 6in6 encapsulation removal be done on with the USP SID?
Why does the USP and USD SID have to be separate?
4.16.1<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.16.1__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JNXuPqZh$>.
PSP: Penultimate Segment Pop of the SRH
The SRH processing of the End, End.X and End.T behaviors are
modified: after the instruction "S14. Update IPv6 DA with Segment
List[Segments Left]" is executed, the following instructions must be
executed as well:
S14.1. If (updated SL == 0) {
S14.2. Pop the SRH
S14.3. }
4.16.2<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.16.2__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JLGcpaqu$>.
USP: Ultimate Segment Pop of the SRH
The SRH processing of the End, End.X and End.T behaviors are
modified: the instructions S02-S04 are substituted by the following
ones:
S02. If (Segments Left == 0) {
S03. Pop the SRH
S04. }
4.16.3<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05*section-4.16.3__;Iw!!NEt6yMaO-gk!QzHlcRglDrowIq4p7kbUU8tNwsbwrneoRiLDYAClyLIXp1ZLWOSxDhU6JKFZ-dKZ$>.
USD: Ultimate Segment Decapsulation
The SRH processing of the End, End.X and End.T behaviors are
modified: the instructions S02-S04 are substituted by the following
ones:
S02. If (Segments Left == 0) {
S03. Skip the SRH processing and proceed to the next header
S04. }
Further on, the Upper-layer header processing of the End, End.X and
End.T behaviors are modified as follows:
Kind regards,
Gyan
On Sat, Dec 14, 2019 at 9:08 PM Wang, Weibin (NSB - CN/Shanghai)
<weibin.w...@nokia-sbell.com<mailto:weibin.w...@nokia-sbell.com>> wrote:
Hi Pablo:
After the 2 context assumption in previous version of this draft, "we assume
that there is no other extension header than the SRH." and "We assume
that the SRH may be present multiple times inside each packet", are removed
in this last draft, I feel a bit confusion on USD SID, as well as combination
of USD & USP.
First, within the content of this last draft, the word "Further on" marked red
in the following pseudocode in section "4.16.3" is hard to understand if the
packet being processed has other EH embed between SRH and Upper-layer header,
such as AH or other EH, then the processing control of this packet will be
passed to normal IPv6 module from current SRH processing module in SR-Node, so
my question is : Can its control after completing AH processing (for example)
be back to SRH module (or call it pseudocode module) to proceed the next header
like "upper-lay header type ==41 or 4".
Or, if not, Did you created a new EH processing protocol stack instance in
parallel to normal IPv6 module within the scope of SRH processing in SR-node.
4.16.3. USD: Ultimate Segment Decapsulation
S02. If (Segments Left == 0) {
S03. Skip the SRH processing and proceed to the next header
S04. }
Further on, the Upper-layer header processing of the End, End.X and
End.T behaviors are modified as follows:
End:
S01. If (Upper-layer Header type == 41 || 4) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Submit the packet to the egress IP FIB lookup and
transmission to the new destination
S04. } Else {
S05. Send an ICMP Parameter Problem message to the Source Address
Code 4 (SR Upper-layer Header Error),
Pointer set to the offset of the upper-layer header.
Interrupt packet processing and discard the packet.
S06. }
>From my understanding, the all processing action about specific SID must be
>completed successively. That is to say, upon USD, the upper-layer header (type
>41 or 4) must be followed the SRH header being processed currently, or second
>SRH following the same rule (of course, the draft not considering 2 or more
>successive SRHs).
Second, the mixed SIDs function with combination of USD and USP (even
PSP&USD&USP), I think, it is easy to understand when the two assumption above
exist, but now I think it isn't clear if you only provide the following
sentence in this draft, i.e. "if ... else..." statement:
"An implementation that supports the USD flavor in conjunction with
the USP flavor MAY optimize the packet processing by first looking
whether the conditions for the USD flavor are met, in which case it
can proceed with USD processing else do USP processing."
This confusion is also described in my another mail. Of course, if the first
question is addressed then this confusion does not exist.
By the way, is it really no different in text description before and after the
two context assumption above removed?
Cheers !
WANG Weibin
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IT Network Engineering & Technology
Verizon Communications Inc. (VZ)
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Gyan S. Mishra
IT Network Engineering & Technology
Verizon Communications Inc. (VZ)
13101 Columbia Pike FDC1 3rd Floor
Silver Spring, MD 20904
United States
Phone: 301 502-1347
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