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- Path: sparky!uunet!charon.amdahl.com!pacbell.com!ames!data.nas.nasa.gov!taligent!apple!macwinders.support.apple.com!user
- From: winders@aux.support.apple.com (Scott Winders)
- Newsgroups: comp.protocols.appletalk
- Subject: Re: Need AppleTalk Frame/Header Formats
- Message-ID: <winders-061192172545@macwinders.support.apple.com>
- Date: 7 Nov 92 01:25:27 GMT
- References: <1992Nov5.212222.14389@eagle.lerc.nasa.gov>
- Sender: daemon@Apple.COM
- Followup-To: comp.protocols.appletalk
- Distribution: na
- Organization: Apple Computer, Inc.
- Lines: 63
-
- In article <1992Nov5.212222.14389@eagle.lerc.nasa.gov>,
- fsgreen@dredd.lerc.nasa.gov (Doug Greenwald) wrote:
- >
- > Howdy,
- >
- > I'm writing a small network analyzer to gather statistics. I have most of the
- > IP protocols done but am having problems finding information regarding
- > AppleTalk. I need the type field of the ethernet frame for general
- > statistics gathering and would like the higher layer protocol packet
- > formats for completeness.
- >
- > Any pointers to references or information you could shed would be appreciated.
- >
- > For those interested in the program, I'm writing it for Sun workstations. If
- > responses warrant (and the program doesn't turn into a load of crap), I'll
- > make it available.
-
-
-
- EtherTalk 2.x (802.3) Frame
-
- 802.3 Destination 6 bytes
- 802.3 Source 6 bytes
- 802.2 LLC Length 2 bytes
- 802.2 LLC Header
- 802.2 LLC DSAP 1 bytes (always $AA (SNAP SAP) for EtherTalk
- 2.x)
- 802.2 LLC SSAP 1 bytes (always $AA (SNAP SAP) for EtherTalk
- 2.x)
- 802.2 LLC Control 1 bytes (always $03)
- SNAP Header 5 bytes (always $080007809B for EtherTalk 2.x)
- DDP Header 13 bytes
- AppleTalk Data ?? bytes (586 bytes maximum)
- Padding (if needed) ?? bytes
- ---------------
- 60 to 621 bytes
-
- DSAP - Destination Service Access Point
- SSAP - Source Service Access Point
- The SNAP SAP is defined as $AA
-
- If the 802.3 packet is less than 60 bytes in size, padding is added to make
- the packet 60 bytes long.
-
- In 802.2, DSAP and SSAP are almost always the same except in frames that
- are
- establishing an initial SNA connection.
-
- 2. The SNAP (SubNetwork Address Protocol) unique identifier assigned to
- Apple by the IEEE is $0800070000. This first 3 bytes of the unique
- identifier is the vendor address. The last 2 bytes are the local
- administered (by Apple) identifiers. We (Apple) have defined $809B as
- EtherTalk. The unique identifier for EtherTalk 2.0 is $080007809B. This
- is considered to be a locally administered SNAP address.
-
- A global SNAP address has been defined by the IEEE for AARP packets.
- The SNAP number is $00000080F3.
-
-
- Scott Winders
- winders@aux.support.apple.com
-
- "My opinions are my own, not my employer's"
-