Subject: [nvo3] NVO3 Arch: draft text on combined L2/L3 Service

From: Thomas Narten <[email-masked]>
Date: Mon, 27 Jan 2014 15:00:30 -0500

Hi.

Here is some draft text that the design team has been discussing on
the topic of combined L2/L3 service. This would go into architecture
document in 3.1. "VN Service (L2 and L3) "

Does this capture things appropriately? Comments?

      <t>
        NVO3 can also provide a combined L2 and L3 service to
        tenants. A combined service provides L2 service for intra-VN
        communication, but also provides L3 service for L3 traffic
        entering or leaving the VN.  Architecturally, the handling of
        a combined L2/L3 service in NVO3 is intended to match what is
        commonly done today in non-overlay environments by devices
        providing a combined bridge/router service. With combined
        service, the virtual network itself retains the semantics of
        L2 service and all traffic is processed according to its L2
        semantics. In addition, however, traffic requiring IP
        processing is also processed at the IP level.
      </t>
      
      <t>
	The IP processing for a combined service can be implemented on
        a standalone device attached to the virtual network (e.g., an
        IP router) or implemented locally on the NVE (see Section 5.4
        on Distributed Gateways).  For unicast traffic, NVE
        implementation of a combined service may result in a packet
        being delivered to another TS attached to the same NVE (on
        either the same or a different VN) or tunneled to a remote
        NVE, or even forwarded outside the NVO3 domain.  For multicast
        or broadcast packets, the combination of NVE L2 and L3
        processing may result in copies of the packet receiving both
        L2 and L3 treatments to realize delivery to all of the
        destinations involved.  This optimized NVE implementation of
        IP routing results in the same network delivery behavior as if
        the L2 processing of the packet included delivery of the
        packet to an IP router attached to the L2 VN as a TS, with the
        router having additional network attachments to other
        networks, either virtual or not.
      </t>