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<H2><A NAME="s4">4. Compatibility</A></H2>



<H2><A NAME="ss4.1">4.1 Can PPP talk to a SLIP interface?</A></H2>

<P>No. SLIP works with SLIP. PPP works with PPP.</P>
<P>Some vendors may offer products which work both as
SLIP and PPP. However, they must be configured to run in one mode
or the other. There is no present method to determine, based upon
the protocol passed at the time of a connection, which combination
of SLIP protocols or PPP is being requested.</P>


<H2><A NAME="ss4.2">4.2 Which is better? PPP or SLIP?</A></H2>

<P><B>IT DEPENDS UPON MANY FACTORS</B>.</P>
<P>The people who post this type of question have usually not read
the <EM>Net-2-HOWTO</EM> document.</P>
<P>A good technical discussion is available at Morning
Star\s www server, <EM>www.morningstar.com</EM>.</P>


<H2><A NAME="ss4.3">4.3 Is CHAP or PAP better for authentication?</A></H2>

<P>If you have the choice, use CHAP. Failing that, PAP is better than nothing.</P>


<H2><A NAME="ss4.4">4.4 What about CHAP which Microsoft uses with Windows NT?</A></H2>

<P>CHAP is a Cryptographic Handshake Authentication Protocol.
It means that it takes some form of a key and will encrypt the
response using a one-way encryption algorithm. The algorithm is
negotiated at the time that the CHAP protocol is requested. The
most common is called MD5. It has an encryption code of 05 in
the CHAP request.</P>
<P>Microsoft uses a DES algorithm which, until
recently, was incompatible with the pppd process. If you wish
to connect to a Windows NT server, there are a set of patches
which are included with the pppd source code to support the DES
style used by Microsoft.</P>
<P><EM>Contrary to what some un-informed people believe
at Stanford University believe, Microsoft did not just go against
the recommendations of the IETF working group. The code values
were properly requested and the implementation has been fully
documented.</EM></P>


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