Re: [bess] Query about Ethernet Tag Id for TYpe-5 routes (RFC 9136)

["Joshi, Vinayak" <[e-mail]>]

Hi Jorge & Yubao,

In the most common use cases an IP prefix route has to be unique with an VRF.
The VPN Label/L3VNI brings in this separation of IP prefixes even for VLAN-aware bundling.
(With all L2 routes the Ethernet Tag has to be non-zero for VLAN-aware BD for sure to distinguish BDs).

In case of VLAN aware BD implementations that do NOT need BD level distinction of IP prefixes, would it be considered RFC violation if -

1)      EVPN speaker sends out a zero Ethernet tag in its RT-5.

2)      Ignores the non-zero Ethernet tag in the incoming RT-5 routes.

Regards,
Vinayak

From: [e-mail] [mailto:[e-mail]]
Sent: Saturday, December 4, 2021 9:56 AM
To: [e-mail]
Cc: [e-mail]; Joshi, Vinayak <[e-mail]>; [e-mail]
Subject: Re: [bess] Query about Ethernet Tag Id for TYpe-5 routes (RFC 9136)




Hi Jorge and Vinayak,



I don't understand this use case of RFC9136 very well either,

because when a BD of VLAN-aware bundle EVI is used in Bump-in-the-wire use case,

I don't sure how the IP prefixes routes are recursively rosolved.

I hope to share my understandings to help to make this use case more clear.



When  an IP Prefix route is advertised in the context of a VLAN-aware BD, and the IP Prefix route would be using a non-zero Ethernet Tag ID,

The overlay index of the IP prefix route should be considered to be the <ESI, Ethernet Tag ID> or just the ESI?

In section 3 of RFC9136, I see that only the ESI is considered to be the overlay index.



Thanks,

Yubao





On Fri, 3 Dec 2021 17:03:48 +0000

"Rabadan, Jorge (Nokia - US/Mountain View)" <[e-mail]<mailto:[e-mail]>> wrote:



> Hi again,

>

> John pointed to me that there are some cases where a non-zero Ethernet Tag ID on the IP Prefix route may be used in RFC9136.

>

> In the RFC9136 IP-VRF-to-IP-VRF use cases, the Ethernet Tag ID is always zero, since the IP Prefix route is advertised in the context of the IP-VRF. However it is true that RFC9136 also discusses some use-cases where the IP Prefix route is advertised in the context of a BD, in which case, if the BD belongs to a VLAN-aware bundle EVI, the IP Prefix routes would be using a non-zero Ethernet Tag ID.

>

> I overlooked that when I replied first.

> Thanks John.

>

> Jorge

>

> From: Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]<mailto:[e-mail]>>

> Date: Thursday, December 2, 2021 at 6:00 PM

> To: Joshi, Vinayak <[e-mail]<mailto:[e-mail]>>, [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>

> Subject: Re: Query about Ethernet Tag Id for TYpe-5 routes (RFC 9136)

> Hi Vinayak,

>

> RFC9136 does not have any use case for the use of a non-zero ethernet tag id. The IP Prefix route includes the ethernet tag id as part of the key for consistency with the rest of the EVPN service routes, for future use.

>

> Thanks.

> Jorge

>

> From: BESS <[e-mail]<mailto:[e-mail]>> on behalf of Joshi, Vinayak <[e-mail]<mailto:[e-mail]>>

> Date: Thursday, December 2, 2021 at 7:33 AM

> To: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>

> Subject: [bess] Query about Ethernet Tag Id for TYpe-5 routes (RFC 9136)

> Hi all,

>

> RFC 9136 says the following (Section 3.1)

>

>

> “   The RD, Ethernet Tag ID, IP prefix length, and IP prefix are part of

>    the route key used by BGP to compare routes.  The rest of the fields

>    are not part of the route key.

>

> With VLAN Aware Bundling the Eth Tag ID acts as a distinguisher for the routes while importing into L2-VRF.

> But for L3 prefix routes what is the use case for setting the Ether Tag ID to any non-zero value?

>

> Thanks in advance,

> Vinayak