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Cell Relay Retreat>List Archive>month:1996-Dec> msg00246



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Re: Ethertype in ATM Driver

  • From: alagu@mailman.apple.com (Alagu Periyannan)
  • Date: 23 Dec 1996 19:38:57 GMT

In article <59fg9m$ekg@nntp1.apple.com>
alagu@mailman.apple.com (Alagu Periyannan) writes:

> Since RFC1577 uses LLC/SNAP encapsulation, if you receive a packet
> over the network with 0x0806 in its length field it is most certainly
> an IP (or some other packet) of length 0x0806.
> 
> All packets will start with 0xAAAA03 followed by the 5-byte SNAP.
> This 5-byte SNAP is 0x0000000800 for IP and 0x0000000806 for ARP.
> So you can always distiguish between IP and ARP.

A correction to the above statements:

Actually an RFC1577 packet will always start with 0xAAAA03
followed by the 5-byte SNAP. There will be no length field
as indicated above. The length is determined by the AAL5
packet length.

Thanks to Rajeev (Trillium) for point this out.


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Alagu Periyannan                              Internet: alagu@apple.com
Communications Products & Technology
Apple Computer, Inc.