Subject: [L2VPN] Comments to draft-sajassi-l2vpn-evpn-inter-subnet-forwarding-04

From: Zhuangshunwan <[email-masked]>
Date: Fri, 11 Jul 2014 16:09:13 +0800

Dear Authors,

I have some comments to section 5 of
draft-sajassi-l2vpn-evpn-inter-subnet-forwarding-04, see inline with
[Vincent].

…

5 Operational Models for Symmetric Inter-Subnet Forwarding

   The following sections describe several main symmetric IRB forwarding

   scenarios.

5.1 IRB forwarding on NVEs without core-facing IRB Interface

…

5.1.1 Control Plane Operation for IRB forwarding without core-facing I/F

Sajassi et al.          Expires January 4, 2015                [Page 15]

INTERNET DRAFT   Integrated Routing & Bridging in EVPN February 13, 2014

   Each NVE advertises an RT-2 (MAC/IP Advertisement Route) for each of

   its TSes with the following field set:

   - RD and ESI per [EVPN]

   - Ethernet Tag = 0; assuming VLAN-based service

   - MAC Address Length = 48

   - MAC Address = Mi ; where i = 1,2,3,4, or 5 in the above example

[Vincent]: According to my understanding of the symmetric IRB Solution，no
need to advertise the MAC Addresses of the TSes? I understand aright?

   - IP Address Length = 32 or 128

   - IP Address = IPi ; where i = 1,2,3,4, or 5 in the above example

   - Label-1 = MPLS Label or VNID corresponding to EVI

[Vincent]: I have read section 5.1.2, but found that Label-1 is not been
used, I understand aright?

   - Label-2 = MPLS Label or VNID corresponding to IP-VRF

…

5.1.2 Data Plane Operation for IRB forwarding without core-facing I/F

…

   -  The packet is then encapsulated with the proper header based on

   the above info. The inner MAC SA and VTEP SA is set to NVE's MAC and

   IP addresses respectively. The packet is then forwarded to the egress

   NVE.

   - On the egress NVE, if the packet is VxLAN encapsulated, the VxLAN

   header is removed. Since the inner MAC DA is that of egress NVE, the

   NVE knows that it needs to perform an IP lookup. It uses VNID to

   identify the IP-VRF table and then performs an IP lookup which

   results in destination TS (TS3) MAC address and the access-facing IRB

   interface over which the packet needs to be sent. 

   - The IP packet is encapsulated with an Ethernet header with MAC SA

   set to that of NVE-2 MAC address(MACy) and MAC DA set to that of

   destination TS (TS3) MAC address. The packet is sent to the

   corresponding MAC-VRF and after a lookup of MAC DA, is forwarded to

   the destination TS (TS3) over the corresponding interface.  

[Vincent]: Missing the description of MPLS encapsulated case?

5.2 IRB forwarding on NVEs with core-facing IRB Interface

…

5.2.1 Control Plane Operation for IRB forwarding with core-facing I/F

   Each NVE advertises an RT-2 (MAC/IP Advertisement Route) for each of

   its TSes and it also advertises a single RT-2 for core-facing IRB

   interface (which is per tenant or per IP-VPN). 

   The fields of RT-2 for each TS are set as follow: 

   - RD and ESI per [EVPN]

   - Ethernet Tag = 0; assuming VLAN-based service

   - MAC Address Length = 48

   - MAC Address = Mi ; MAC address of TS

   - IP Address Length = 32 or 128

   - IP Address = IPi ; IP address of TS

   - Label-1 = MPLS Label or VNID corresponding to access-facing EVI

[Vincent]: I have read section 5.2.2, according to my understanding, the
label carrying in Label-1 field is not been used by “Data Plane Operation
for IRB forwarding with core-facing I/F”?

…

5.2.2 Data Plane Operation for IRB forwarding with core-facing I/F

…

   - On the egress NVE, if the packet is VxLAN encapsulated, the VxLAN

   header is removed and the resultant Ethernet frame is fed into the

   core-facing MAC-VRF associated with that tenant based on the VNID. 

   - The MAC DA lookup yields the core-facing IRB interface of the

   egress NVE over which the frame is sent. Next, the Ethernet header is

   removed and a lookup is performed based on IP DA in the associated

   IP-VRF for that tenant. The IP lookup yields the destination TS (TS3)

   MAC address and the access-facing IRB interface over which the packet

   needs to be sent. 

   - The IP packet is encapsulated with an Ethernet header with the MAC

   SA set to that of the access-facing IRB interface of the egress NVE

   (NVE2) and the MAC DA is set to that of destination TS (TS4) MAC

   address. The packet is sent to the corresponding MAC-VRF and after a

   lookup of MAC DA, is forwarded to the destination TS (TS3) over the

   corresponding interface.  

[Vincent]: Missing the descrition of MPLS encapsulated case?

6 BGP Encoding

…

Regards,

Vincent