Re: Interface reality check
Dear Paul,
> "Paul Bottorff" <pbottorf@nortelnetworks.com> writes:
> It doesn't look like 64/66 can be extended to ANSI T1X1 systems.
>
> So how is 64/66 going to extend the header mappings? The T1X1
> proposals relay on the <length><type><crc> to provide other frame and
> header types for extended environments. In particular the CRC check
> allows validation of the <type> field giving a broad range of format
> extensions. The header CRC in ANSI T1X1 formats become essential for
> the extended header fields used to address ring networks.
64/66 transparently supports all Ethernet packet signalling semantics.
Ethernet packets include a two-byte <length/type> field. The
<length/type> code is protected by CRC32 and is therefore quite
reliable.
The current mappings are:
L <= 1500 ; the frame is an LLC data frame
L = 34,824 ; the frame is a MAC control frame
L = 33,024 ; the frame is a VLAN-tagged frame
none of the above ; private use Type-frame
This leaves a very large number of type indicators currently undefined
by Ethernet. I expect that they can be used to create ANSI T1X1 packet
types if needed.
Best regards,
--
Rick Walker