HP 3000 Manuals HP 3000 Manuals
Address Resolution
Address resolution in NS networks refers to the mapping of node names to
IP addresses and the mapping of IP addresses to lower level addresses
(such as an X.25 address or a station address). Several address
resolution methods are available for you to use individually or in
combination with each other. You can configure these methods according
to the needs of your network.
The available address resolution methods are:
* Domain name services.
* Network directory.
* Probe (and probe proxy) (LAN only).
* Address resolution protocol (ARP) (LAN, FDDI, and Token Ring
only).
Domain Name Services
The domain name services are a mechanism for resolving node names to IP
addresses. They conform to an open networking standard and will
facilitate communications between 900 Series HP 3000 systems as well as
with non-HP 3000 nodes.
To use the domain name services, you must assign a name, in ARPANET
standard format, to each system on the network or internetwork. You
configure this name on the NS Configuration screen (see configuration
chapters for details).
You will also need to create a set of ASCII files on each system which
contain the addressing information the system will need. Instructions
for creating these files are in chapter 12.
Once you have configured the domain name services, the network will be
able to access the node using its domain name and the domain name service
routines will resolve the domain name to the node's IP address.
NOTE Domain name services provide name to IP address resolution only.
If a lower level address is required for network communication (for
example, an X.25 address) you will need to configure the network
directory as well.
Network Directory
The network directory is a set of files that contain information used by
the node to communicate with other nodes in the internetwork.
You use NMMGR to perform the following network directory functions:
* Add, modify, and delete entries in the directory.
* Review and inspect directory information.
* Merge a remote directory with a directory on the local node.
* Automatically update directories on a group of remote nodes by
using a background stream job controlled from a central
administrative node.
See chapter 11 for more information on configuring the network directory
through NMMGR. More information on merging directories and on central
administrative nodes is included in this chapter.
When a Network Directory is Required.
A network directory must be configured on nodes with X.25.
Point-to-point nodes that do not use domain name services require network
directory configuration. You must also configure a network directory
when non-HP nodes are part of an HP IEEE802.3/Ethernet or FDDI LAN or
token ring and you are not using domain name services. At least one node
on IEEE802.3/Ethernet or FDDI LANs must have a network directory if any
of the nodes on that network are to communicate with the internet and you
are not using domain name services.
The network directory of a node in a point-to-point network must contain
the IP address of all other nodes that you want the node to be able to
reach. When configuring the network directory for a point-to-point
network, make sure that the IP address you enter in the network
directory matches the data in the mapping screens (path name
NETXPORT.NI.NIname.MAPPING.mapentry).
For nodes on an X.25 network, the network directory maps the X.25 address
key to an IP address to allow a node to communicate within the X.25
network. You must configure a network directory for nodes using X.25.
Planning The Network Directory.
There are two theories about how network directories should be planned
and configured on a network, as follows:
* Centralized network directories.
* Decentralized network directories.
The centralized theory requires each node on the internet to have the
same network directory.This means that every node in the network must
have an entry in the network directory. The advantage to this is that
you update the network directory in one place, then copy it to the rest
of the world. The disadvantage is that network directories for large
internets are going to be large.
The recommended way to create and maintain your network directory using
the centralized method is to assign a single node as the central
administrative node.You configure the network directory on this node and
then copy it to all other nodes on the network. When the network
directory is updated, it is updated on the central administrative node,
then copied to the other nodes. This procedure decreases the possibility
of incompatible directories. You may want to assign a central
administrative node for each network or for the entire internet.
The decentralized theory suggests that each network directory be
configured individually on each node. The advantage to this is that you
can customize the network directory on each node for security purposes
using local and global entries. The network directory will also be
smaller because it will only contain entries for that particular node.
However, updates must be done manually on each node.
Copying and Merging Network Directory Files.
The first time you configure the network directory, an entry for all
remote IP addresses must be added manually using the NMMGR screens.
After the first network directory is configured, you can use the MPE
STORE and RESTORE commands to copy the network directory to other
nodes.(This is assuming you have adopted the centralized method of
network directory maintenance. If you use the decentralized method, you
must always use NMMGR to create and maintain the network directory.)
NOTE The network directory uses a KSAM file pair. Therefore, when
copying a directory, be sure to copy both the data file and the key
file. The system names the key file automatically using the first
six letters of the network directory file name appended with a K.
For example, NSDIRK.NET.SYS is the name of the key file associated
with the data file NSDIR.NET.SYS.
Once a network directory has been established on each node in the
internet, you can set up a job stream to automate network directory
updates. The MERGEDIR command is part of a maintenance interface
provided primarily to support the updating of directories using a batch
job. Using this method, a job or series of jobs can be scheduled at
regular intervals to copy and then merge remote directories into the
local-system directory. See the MERGEDIR and the MAKESTREAM commands in
Using the Node Management Services (NMS) Utilities.
Probe and Probe Proxy
NS3000 LAN NIs with the IEEE 802.3 protocol enabled are able to make use
of a proprietary HP protocol called probe. Probe makes it possible for
nodes on an NS IEEE 802.3 LAN to communicate without a network directory
or domain names. A node can determine connection information about a
node on the same LAN by sending a multicast probe request out on the LAN.
The target node recognizes its address in the probe request and sends an
individually addressed probe reply with the necessary connection
information to the requesting node. The probe request/reply mechanism is
sufficient to obtain connection requirements in an HP LAN environment.
However, at least one node on an NS IEEE 802.3 LAN must have a network
directory if the nodes on that LAN are to communicate with other
networks. The node with the network directory on a LAN is called a proxy
server.By using the probe protocol, a LAN node without a network
directory can multicast a request for an internet address from the proxy
server. For backup purposes, you should designate at least two nodes on
a LAN to be proxy servers.
Address Resolution Protocol (ARP)
HP 3000 LAN, FDDI, and token ring NIs are able to make use of a standard
protocol called Address Resolution Protocol (ARP). ARP provides IP
address to station address resolution. ARP is enabled when the Ethernet
protocol or token ring is enabled.
Enabling Probe and ARP.
With the concurrent configuration of IEEE 802.3 and Ethernet on an NS
LAN, both the probe and ARP protocols are also enabled. Both protocols
broadcast requests to all nodes on the network to resolve the address of
a given remote node.
If you disable IEEE 802.3 on a LAN NI, you also disable the probe
protocol. Likewise, by disabling Ethernet, you disable the ARP protocol
associated with it. You cannot disable both of these protocols
simultaneously; at least one must be active on the LAN to facilitate
network communications.