The AppleTalk Protocol
523
Datagram Delivery Protocol
DDP
provides unique addressing of all
nodes on the AppleTalk internetwork, and is responsible for connectionless
delivery of datagrams between nodes.
Name Binding Protocol
NBP
provides name-to-address resolution that
is similar to DNS in TCP/IP; it also handles additional functions.
Routing Table Maintenance Protocol
AppleTalk's default routing
protocol is
RTMP
. Updates are sent every 10 seconds, and routes are
aged out of the table after 20 seconds. This can result in route flapping
on congested segments as the RTMP updates are dropped.
Zone Information Protocol
Zones are logical divisions of AppleTalk
resources.
ZIP
maps zone names to network addresses. Although nodes
belong to one zone, zones can span multiple physical networks.
AppleTalk Addressing
An AppleTalk address contains network and node information in the format
network.node
. This is similar to the IPX protocol--there is no subnet as with IP.
The administrator defines the network portion of the address by defining a cable
range. This range varies in size, depending on the phase (version) of AppleTalk
and the needs of the network. The network portion of the address is composed
of a 16-bit number, whereas the node is defined with eight bits.
AppleTalk Cable Range
AppleTalk networks define their network numbers by assigning a cable
range. This range, in the more common AppleTalk
phase two
, can be very
large in scope--accommodating a virtually unlimited number of nodes.
AppleTalk
phase one
is capable only of addressing one cable number, and it
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