Subject: RE: [rohc] Problems of implementating ROHC(RFC3095) on 802.11 WLAN

From: [email-masked]
Date: Tue, 18 Jun 2002 17:42:43 -0500

> o   The compressed packets' size may become less than 60 bytes.  60 bytes
>     is the minimun size of a ethernet frame.  So if the size of a compressed
>     packet is less than 60, it cannot be transefer in the ethernet.

Not sure you're talking about 802.11 or (wired) ethernet. If it is
ethernet and assuming you keep the ethernet frame header unchanged 
(see below), you have 46 bytes to carry the payload of ethernet frame. 
If ROHC packet is less than 46 bytes long, you can use ROHC padding as 
Carsten suggested. Or, you can add a length field (after the 14-byte 
ethernet frame header) which indicates the real ROHC packet size. 
For Linux, you can send ethernet frames < 60 bytes and the driver 
will do the padding for you.

6 bytes: dest ethernet address
6 bytes: src ethernet address
2 bytes: type

> In fact, the Wireless LAN is a broad band wireless environment.  
> We do not need to use ROHC. 

Then why implementing ROHC over WLAN where it is not needed?
Is it only for testing purpose? (I used ROHC over ethernet for
testing)

BR,
Zhigang

_______________________________________________
Rohc mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/rohc

---

From: Wang Hui <[email-masked]>
Date: Wed, 19 Jun 2002 09:36:48 +0800 (CST)

> will do the padding for you.

Yes, in my experiment, I found the Linux driver will do the padding.
But the padding is of random bytes.  The Linux driver just keeps the
minimun transport time and the 'padding data' is random which is not in
meaning.  At the receiver point we could not deduce the data length from
the layer 2 information.  So I guess 'using ROHC padding' as Carsten
suggested is a good choice. And adding a length field as you mentioned
will work  too.

> Is it only for testing purpose? (I used ROHC over ethernet for

Yes, we do it for the testing purpose.  We may move it to other platform
in future after its fully testing in WLAN or ethernet LAN.

BTW, you are do the testing work in ethernet?  I guess we have something
in common, we may keep in touch.

Best regards,
Wang

--
 Wang Hui
 Next Generation Internet Research Team,
 InfoNet Lab, USTC
 http://mail.ustc.edu.cn/~whui
 Tel: +86-551-3603634