On 11/20/13 12:07 AM, Pankaj Garg wrote:
Wouldn't the decision to do L2 or L3 service be based on the inner frame fields
i.e. destination MAC/IP in the inner frame? Similar to how switches/routers
process packets i.e. based on frame's destination MAC and destination IP
address (if present)?
IMHO, Thomas's original text (pasted below) describes this quite well and
concisely.
<t>
A virtual network can also provide a combined L2 and L3
service to tenants. In such cases, a tenant sends and
receives both L2 and L3 packets. An NVE recieving packets
from a TS determines the type of service to be applied to
the packet on a per-packet basis as indicated by the
packet's destination MAC address as provided by the TS. If
the MAC address corresponds to that of an L3 router (as
determined by the NVE), traffic is given L3
semantics. Otherwise, the packet is given L2 service
semantics. A combined L2/L3 service presents no special
considerations for NVO3, other than packets received from a
tenant must be classified as to what type of service they
are to be given before they can be processed.
</t>
What is missing for me is a higher-level statement whether or not we see
an NVE providing combined L2 and L3 service as being architecturally
different that the non-overlay case of a bridge+router that provides
combined service L2 and L3 today.
If we think it is just the same architecturally, then it would make
sense to state that. If we think it is different, then I think we need
more details that Thomas' text above.
FWIW the existing bridge+routers handle multicast conceptually as
bridge-route-bridge. A received multicast packet might need to be
bridged out other L2 ports in the same bridge domain. Then one copy of
packet is passed to the L3 function, which does L3 multicast routing
(check iIF, decrement ttl, determine oIFs). Finally, a given L3 oIF
might correspond to a bridge domain i.e., multiple packets might need to
be sent out different L2 ports for each oIF.
While that is a bit complex, it is a lot better if the NVO3 architecture
is the same as existing combined bridge+router boxes.
And note that an existing combined bridge+router is architecturally
consistent with separate bridges and a router where the bridges only do
L2 and the router only does L3.
Erik
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