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8:
9: <A HREF="mpd.html"><EM>Mpd 5.6 User Manual</EM></A>
10: <b>:</b> <A HREF="mpd17.html"><EM>Configuring Mpd</EM></A>
11: <b>:</b> <EM>Mpd Layers</EM><BR>
12: <b>Previous:</b> <A HREF="mpd18.html"><EM>General mpd commands</EM></A><BR>
13: <b>Next:</b> <A HREF="mpd20.html"><EM>Link layer</EM></A>
14:
15:
16: <HR NOSHADE>
17: <H2><A NAME="19"></A>4.2. Mpd Layers<A NAME="layers"></A></H2>
18: <p>Mpd consists of several <b>layers</b>, corresponding
19: to the layered nature of the PPP protocol. There are two
20: types of layers hierarchy connected with two different
21: operation modes as "ppp terminator" and "ppp repeater".
22: Operation mode is getting chosen dynamically depending on link
23: configuration and user auth name (see 'set link action ...' command).</p>
24: <p>In "ppp terminator" mode such hierarchy used:
25: <b>
26: <A HREF="mpd28.html#interface">interface</A></b> ->
27: <b>
28: <A HREF="mpd26.html#ipcp">ipcp</A></b> ->
29: <b>
30: <A HREF="mpd24.html#compression">compression</A></b> ->
31: <b>
32: <A HREF="mpd23.html#encryption">encryption</A></b> ->
33: <b>
34: <A HREF="mpd22.html#bundle">bundle</A></b> ->
35: <b>
36: <A HREF="mpd20.html#links">links</A></b></p>
37: <p>In "ppp repeater" mode different hierarchy used:
38: <b>
39: <A HREF="mpd20.html#links">links</A></b> ->
40: <b>Repeater</b> ->
41: <b>
42: <A HREF="mpd20.html#links">links</A></b></p>
43: <p>A <b>
44: <A HREF="mpd20.html#links">links</A></b> is a single point-to-point
45: connection between the local machine and a remote peer machine,
46: implemented by some kind of physical device,
47: such as a serial modem connection or a virtual PPTP connection.</p>
48: <p>Link parameters include whether authentication is enabled in
49: either direction, the authentication type (PAP or CHAP)
50: used, keep-alive packets, multilink negotiation options
51: and various other link specific parameters.</p>
52: <p>Lower half of the link layer is the physical devices layer.
53: Configuration of device type specific parameters happens at this layer.
54: Each device has a specific <em>type</em>
55: corresponding to one of the supported device types in mpd.
56: The type dictates how the device dependent part
57: is configured and what it's capabilities are.</p>
58: <p>A <b>
59: <A HREF="mpd22.html#bundle">bundle</A></b> is a collection
60: of one or more links, all connecting
61: to the same remote peer, that together form a single
62: multi-link PPP connection whose effective bandwidth is
63: the sum of the bandwidths of the individual links.</p>
64: <p>The bundle layer in effect lies just above the link layer.
65: The bundle layer handles the task of making multiple
66: physical links appear as a single virtual link.</p>
67: <p>At the bundle layer you configure multi-link
68: PPP settings and the link management policy. The link management
69: policy determines whether mpd tries to keep all the links
70: connected all the time, or whether it adds and subtracts
71: links depending on demand, and if so, according to what parameters.</p>
72: <p>With each bundle is a corresponding
73: <b>
74: <A HREF="mpd28.html#interface">interface</A></b> layer,
75: which corresponds directly to a system network interface
76: accessible via <code>ifconfig(8)</code>, such as <code>ng0</code>.
77: The interface layer handles configuring the interface,
78: bringing it up or down as appropriate, assigning
79: IP addresses, setting up static routes and configuring proxy-ARP.
80: The interface layer is also responsible for implementing
81: Dial-on-Demand and idle timeout functionality.</p>
82: <p>Each bundle has several corresponding NCP layers as
83: <b>
84: <A HREF="mpd26.html#ipcp">ipcp</A></b> and
85: <b>
86: <A HREF="mpd27.html#ipv6cp">ipv6cp</A></b>,
87: which manages the protocol specific configuration of the interface.
88: This layers handle the negotiation of local and remote addresses
89: and TCP header compression, as well as other optional
90: IP related information such as DNS servers and NBNS servers.</p>
91: <p>Each bundle also has corresponding
92: <b>
93: <A HREF="mpd24.html#compression">compression</A></b> and
94: <b>
95: <A HREF="mpd23.html#encryption">encryption</A></b> layers, which
96: allow you to enable and configure compression and encryption
97: for data sent and received over the bundle.</p>
98: <p>A <b>repeater</b> is a collection of two physical devices
99: (links). It is getting created when there is need to forward
100: connection coming from one physical device to another without
101: modification. This technology is also known as LAC
102: (L2TP Access Concentrator) and PAC (PPTP Access Concentrator).</p>
103: <p>While the combination of all the various layers presents
104: a large number of configuration options, mpd tries to
105: have reasonable defaults for everything.</p>
106:
107:
108:
109: <HR NOSHADE>
110: <A HREF="mpd.html"><EM>Mpd 5.6 User Manual</EM></A>
111: <b>:</b> <A HREF="mpd17.html"><EM>Configuring Mpd</EM></A>
112: <b>:</b> <EM>Mpd Layers</EM><BR>
113: <b>Previous:</b> <A HREF="mpd18.html"><EM>General mpd commands</EM></A><BR>
114: <b>Next:</b> <A HREF="mpd20.html"><EM>Link layer</EM></A>
115:
116:
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