Subject: Re: some questions about MTU, template

From: James Kempf <[email-masked]>
Date: Fri, 24 Dec 1999 08:16:36 -0800 (PST)

>Concern 1. Path MTU
>What is the definition of MTU? I think this definition is not clear.
>I think MTU concerns only between Datalink layer and Network layer. 
>The fragmentation is processed in Network layer, and when we make a udp
>appilication, we don't have to care about MTU. Why does MTU concern UDP?
>

I believe you are talking about the net.slp.MTU configuration parameter
specified in RFC 2614 for the API. This parameter is needed because
the API library needs to know when to set the overflow flag for
a UDP-based return. If the reply to a SrvRqst (for example) overflows
a UDP packet, the replying agent (DA or SA) sets the overflow flag and the
UA can try the request again via TCP. The net.slp.MTU parameter tells
the API library what the packet size is, including IP, UDP, and
SLP headers. 

>Concern 2. Template implementation
>When the device(i.e printer) that behaves as SA has a template, can I add
>any private attributes to the template? And when UA issued any type of 
>requst with the template(i.e. service:printer:lpr), can SA issue AttrRqst
>with added one?
>
>

An SA can add any parameters it wants to the template, and the UA
can issue a request for added parameters. RFC 2608 specifies a
convention that additional attributes should begin with "x-" and
I believe Erik recently issued an Internet Draft 
(draft-guttman-svrloc-vendor-ext-00.txt) which describes additional
conventions for safe vendor extension.

		jak

---

From: Yasuji Takeuchi <[email-masked]>
Date: Wed, 29 Dec 1999 12:05:42 +0900

James,

Please see my comments below,

On Fri, 24 Dec 1999 08:16:36 -0800 (PST)

>the API library what the packet size is, including IP, UDP, and

Yes, I know MTU is used for OVERFLOW flag in the message headers.
What I'd like to know is why we have to care about the overflow.
MTU size varies with Datalink layer. Please stop me if I'm wrong. 
Even if the overflow happened, the sending data is fragmented in Network
layer. And the received fragmented data can be defragmented, so the
application don't have to care about whether this message is overflowed
or not.
Of course, we have to concern the reliability for data transmission.

regards,
Yasuji Takeuchi