Ethernet frame encapsulation - multiple

Question

is it possible to encapsulate two Ethernet frame packets into one ether packet?

My search seems to indicate that there is not a way to do this, unless one was using something like VPN packets, be even then there doesnt appear to be a clear path to this answer. The thought of Jumbo packets came to mind but not sure that is an avenue either since we are talking about frames. I suppose that using fragmentation would help solve the issue but still not answering the question.

Thought I would reach out to see what people thought about the question. Is it possible? How would it be done?

Answer 1

The IEEE standardized Provider-Backbone Bridging (PBB), also known as MAC-in-MAC encapsulation, as 802.1ah, which has been integrated into the 802.1Q standard.

PBB is, aside from 32 bits service encapsulation, basically plain Ethernet frames as a payload of other Ethernet frames.

A typical PBB frame looks like this:

0                   1          
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  <-- Backbone Component
|                               |
+                               +
|              B-DA             |
+                               +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+                               +
|              B-SA             |
+                               +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       EtherType (0x88A8)      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             B-TAG             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  <-- Service encapsulation
|       EtherType (0x88E7)      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Flags     |               |
+-+-+-+-+-+-+-+-+               +
|             I-SID             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  <-- Customer frame
|                               |
+                               +
|              C-DA             |
+                               +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+                               +
|              C-SA             |
+                               +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       EtherType (0x8100)      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             C-TAG             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       EtherType Payload       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+                               +
|            Payload            |
+                               +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The customer frame can be slightly different than shown above of course. It may have no VLAN tag at all or it could also be double-tagged (802.1ad/QinQ).

An important application of the 802.1ah frame format is Shortest Path Bridging MAC-in-MAC encapsulation (SPBM) standardized in 802.1aq.

Answer 2

L2 VPN encapsulates Ethernet frames by a transport-layer protocol in order to cross an arbitrary network path.

Encapsulating one (or more) Ethernet frame(s) into yet another frame could only tunnel over one L2 network/segment. That wouldn't accomplish much. Also, there's no fragmentation mechanism for Ethernet (or for the data link layer generally).

So, is double L2 encapsulation possible? Yes, if size permits (note that jumbo frames are common, yet non-standard). Reasonable? Not very. The only application that comes to mind is remote port mirroring, but double encapsulation wouldn't be very efficient.