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Under integrated mode, DECnet-Plus systems attempt to send packets in DECnet Phase V format unless:
Integrated mode routing is the only mode supported on OpenVMS systems preceding DECnet/OSI for OpenVMS Version 5.8.
Segregated mode routing handles DECnet Phase IV and Phase V as independent protocols. Routers do not translate messages between DECnet Phase IV and Phase V format. The routers must maintain separate network topologies in their internal databases to handle each type of protocol.
Under segregated mode, DECnet-Plus end systems transmit messages in the Phase IV address format if they have a DECnet Phase IV translatable destination address. All other messages are sent in DECnet Phase V format. If you use non-Digital routers that do not support Digital's technique of translating DECnet Phase V addresses to DECnet Phase IV, you may want to use segregated mode routing.
On OpenVMS systems, integrated mode is the default routing mode. To configure segregated mode, use the advanced configuration procedure or NCL. With NCL, you can switch from the default to segregated mode by setting the routing mode attribute, as in the following commands:
ncl> disable routing ncl> set routing routing mode = segregated ncl> enable routing
Note
If your OpenVMS system is running cluster alias, you must use integrated mode.
Use integrated routing mode in an integrated routing environment where the routers can handle Phase-IV-to-Phase-V or Phase-V-to-Phase-IV packet format conversions. Use segregated routing mode when the adjacent router(s) cannot perform Phase-IV-to-Phase-V or Phase-V-to-Phase-IV packet conversions.
An empty set for the manual network entity titlesattribute indicates the use of autoconfiguration. If the set is non-empty, autoconfiguration does not take place. To change the value of this routing attribute from an empty set to a non-empty set, or from a non-empty set to an empty set, the routingentity must be disabled.
Note
The dna address format attribute controls the interpretation of Phase IV addresses; it does not control whether autoconfiguration takes place.
DECnet Phase IV nodes cannot recognize DECnet Phase V addresses. However, DECnet Phase V nodes can recognize Phase IV addresses. For a DECnet Phase V node to communicate with a Phase IV node, the DECnet Phase V node must have a Phase IV address that conforms to the normal Phase IV limits (area number less than or equal to 63 and node number less than or equal to 1023). You must configure this Phase IV address on your DECnet-Plus system.
Use the DECnet-Plus configuration procedure or the following command to set up a Phase IV address. For this command to succeed, routing must not be enabled.
ncl> set routing phaseiv address 12.1
The Phase IV address along with a Phase IV address prefix is used to construct a Phase IV-compatible NSAP address. This is done by concatenating the Phase IV address prefix, the area portion of the Phase IV address, the Phase IV Ethernet address, and a transport selector. For example, if a system's Phase IV address is 12.1 and the Phase IV address prefix is 49::, the resulting NSAP addresses for NSP and OSI Transport are respectively:
49::000c:aa-00-04-00-01-30:20 49::000c:aa-00-04-00-01-30:21
In the same way that they learn their OSI network addresses, end systems learn their Phase IV address prefix from the routers in the subnetwork. Only if there are no DECnet Phase V routers present, does the end system use its own routing attribute phaseiv prefix to construct its Phase IV-compatible NSAP address.
For an end system to learn its Phase IV address prefix, you must configure it into the routers of the subnetwork in which the system resides. The default prefix for all systems is 49::. If you want to use a different initial domain part (IDP) and pre-DSP (domain-specific part), you can override the default by setting the phaseiv prefixattribute as follows. For this command to succeed, routing must not be enabled.
ncl> set routing phaseiv prefix 37:1234:
For example, if you configure a router in area 41 with the phaseiv prefix37:1234:, any DECnet-Plus end system with a Phase IV address in area 41 sets its Phase IV area as follows, where 41 decimal is converted to 29 hexadecimal:
37:1234:00-29:
This results in a Phase IV-compatible NSAP address of the form:
37:1234:00-29:aa-00-04-00-nn-nn:ss
All systems in the subnetwork should have the same Phase IV prefix, but because DECnet Phase V systems autoconfigure, you only need to set the prefix on the routers used by the end system. Digital, however, recommends that you ensure that the phaseiv prefix attribute is consistently set on all DECnet Phase V systems.
Note
For Digital Network Architecture (DNA) routing (via the Connectionless Network Protocol (CLNP)), DECnet-Plus does not support the configuration of NSAPs using decimal DSP (domain-specific parts) syntax. Digital supports X.121 format NSAPs (AFI=36) for the use of OSI transport over the Connection-Oriented Network Service (CONS), which requires the X.25 for OpenVMS product.
If your end system is operating in an environment with one or more non-DNA routers, your DECnet-Plus end system cannot autoconfigure its network address or network entity title (NET). (The NET is the address that identifies the Network layer.) In this case, you can manually specify up to three NETs for your system. To do this, you need to know the following information about the node:
The following sequence of commands specifies the NET for a system:
ncl> create routing type endnode
ncl> set routing manual network entity titles -
_ncl> { 41:45418715:00-49:08-00-2b-00-01-02:00} (1)
ncl> enable routing
To make this change permanent, rerun the advanced configuration procedure or add these commands to the NET$ROUTING_STARTUP.NCL script file after the line create routing type endnode. (Replace the string (41:45418715:00-49:08-00-2b-00-01-02:00) with the correct NET for your node.) The next time you reboot the system, DECnet-Plus uses this new information.
Note
Phase IV backward compatibility is not supported when operating in a non-DNA environment. Therefore, the routing attribute phase iv address should be set to 0.0 or left unset.
This section explains how to configure routing circuit information and how to set up a multicircuit configuration.
The following example shows how to configure routing circuit information. The first three commands set up the routing type and addressing information, as described in Section 8.4.1. The remaining commands set up the routing circuit, as described below.
ncl> create routing type endnode
ncl> set routing dna address format true, lifetime 63, -
_ncl> manual network entity titles {}, probe rate 20
ncl> enable routing
ncl> create routing circuit hdlc-0 type hdlc (1)
ncl> set routing circuit hdlc-0 data link entity -
_ncl> hdlc link hdlc-0 logical station hdlc-0, - (2)
_ncl> manual data link sdu size 1492, - (3)
_ncl> template template-name (4)
ncl> enable routing circuit hdlc-0
| Circuit | Description |
|---|---|
| csma-cd | IEEE 802.3 LAN routing circuit |
| hdlc | Synchronous HDLC circuit |
| ddcmp | Synchronous DDCMP circuit |
| fddi | Fiber Distributed Data Interface (FDDI) for LANs |
| x25 static incoming | X.25 inward switched virtual circuit |
| x25 static outgoing | X.25 outward switched virtual circuit |
| x25 da | Dynamically-assigned X.25 virtual circuit |
| x25 permanent | Permanent X.25 virtual circuit |
Table 8-4 lists additional attributes to consider when setting up a routing circuit with CLNS. It also shows the circuits for which the attributes are valid.
| Attribute | Valid Circuit Type |
|---|---|
| idle timer | x25 da |
| inactive area address | csma-cd |
| initial minimum timer |
x25 static incoming
x25 static outgoing x25 da |
| manual routers | csma-cd |
| maximum call attempts | x25 static outgoing |
| maximum svc adjacencies | x25 da |
| recall timer | x25 static outgoing |
| reserved adjacency | x25 da |
| reserve timer | x25 da |
| x25 filters |
x25 static incoming
x25 da |
DECnet-Plus for OpenVMS supports up to 16 circuits. Hardware, OpenVMS, or WANDD software, however, can further limit the number of circuits you can have. For more information about possible limits, refer to your system and WANDD documentation.
When communicating with remote systems, data PDUs are sent over all circuits in turn. If the remote end system is directly connected on one or more circuits, only those circuits are used to reach the end system. Moreover, a single data PDU is transmitted over all circuits at the interval at which you set the probe rate.
The probe rateis a Routing module attribute that has a default value of 1000 on OpenVMS systems. Therefore, every thousandth data PDU bound for a specific end system is transmitted on all circuits. This helps ensure that all available paths are used.
When operating a DECnet-Plus end system in a multicircuit configuration, you must adhere to certain topology restrictions:
Failure to comply with these restrictions might result in unacceptable operation.
To create multiple circuits for an end system on a CSMA-CD LAN, use your DECnet-Plus configuration procedure. Digital recommends that you accept the default settings (used in the example in Section 8.4.2.2) for the various attributes and change these only if you need to. Refer to the DECnet-Plus Network Control Language Reference for more information about these attributes.
The following example shows the contents of the file NET$ROUTING_STARTUP.NCL, located by default in SYS$SPECIFIC:[SYSMGR]. This file is created by the DECnet-Plus for OpenVMS configuration procedure. The file enables routing, creates the Routing module, and creates CSMA-CD and FDDI circuits.
create node 0 routing type endnode set node 0 routing phaseiv address = 4.884 set node 0 routing phaseiv prefix = 49:: set node 0 routing dna address format true set node 0 routing default eshello timer 600 enable node 0 routing create node 0 routing circuit csmacd-0 type = csma-cd set node 0 routing circuit csmacd-0 data link entity = csma-cd station csmacd-0 set node 0 routing circuit csmacd-0 enable phaseiv address = false enable node 0 routing circuit csmacd-0 create node 0 routing circuit fddi-0 type = fddi set node 0 routing circuit fddi-0 data link entity = fddi station fddi-0 set node 0 routing circuit fddi-0 enable phaseiv address = true enable node 0 routing circuit fddi-0
Note
To delete and disable entities, see the information in Section 6.5.
The primary function of the Routing layer is to identify the best path to a given destination. DECnet Phase V systems have multiple mechanisms to determine such a path. Under most circumstances, these mechanisms work automatically without any need for special configuration. This section describes the routing mechanisms and explains how to use them to handle special circumstances.
DECnet-Plus uses the following rules in order of precedence to determine where to send each packet:
DECnet Phase IV and Phase V end systems and routers regularly advertise their existence on their attached data links. DECnet-Plus nodes listen for these advertisements and automatically build (autoconfigure) an adjacency database. For LANs, the adjacency database contains the list of routers attached to each circuit. For WAN circuits, the adjacency database identifies the type of node attached to the other end of the circuit, router or endnode. DECnet-Plus also automatically records OSI systems from other vendors in its adjacency database as OSI-only nodes.
If the routers in a subnetwork do not adhere to the DECnet Phase V routing protocol (in other words, they are non-DNA routers), DECnet Phase V end systems are unable to create physical connections to them.
Normally, a DECnet Phase V end system learns about its routers through the ES-IS protocol. If your LAN has only routers that do not implement the ES-IS protocol, you must identify the LAN address of the routers that the DECnet Phase V end system uses. Included in the following sequence of commands is a command needed for specifying the LAN address for a CSMA-CD data link. The command is called out ( (1) ).
Note
You do not need to do this if there are routers on the LAN that support ES-IS.
ncl> create routing type endnode
ncl> enable routing
ncl> create routing circuit csmacd-0 -
_ncl> type csmacd
ncl> set routing circuit csmacd-0 manual routers -
_ncl> { 08-00-2b-00-01-03, 08-00-2b-00-03-04 } (1)
ncl> set routing circuit csmacd-0 -
_ncl data link entity csma-cd station csmacd-0
ncl> enable routing circuit csmacd-0
Displaying Adjacencies
Display routing adjacencies by using the following NCL command:
ncl> show routing circuit circuit_name adjacency * all
The following example shows two adjacencies for circuit csmacd-0:
$ mc ncl show routing circuit csmacd-0 adj * all
Node 0 Routing Circuit CSMACD-0 Adjacency RTG$0001
at 1996-07-24-09:48:29.181-04:00I22.051
Identifiers
Name = RTG$0001
Status
Type = Autoconfigured (1)
State = Up
LAN Address = 08-00-2B-A2-08-B9
Neighbor Node Type = Phase V Router (2)
Router NETs =
{
47:24:02-01-0A-04:08-00-2B-A2-08-B0:00 ,
49::00-04:AA-00-04-00-F5-13:00 (DEC:.LKG.LKISL2)
}
Node 0 Routing Circuit CSMACD-0 Adjacency RTG$0002
at 1996-07-24-09:48:29.191-04:00I22.051
Identifiers
Name = RTG$0002
Status
Type = Autoconfigured
State = Up
LAN Address = AA-00-04-00-FF-13 (LOCAL:.A04NIS)
Neighbor Node Type = Phase V Router
Router NETs =
{
47:24:02-01-0A-04:08-00-2B-A0-17-90:00 ,
49::00-04:AA-00-04-00-FF-13:00 (LOCAL:.A04NIS)
}
Connectivity from a DECnet Phase V end system to a Phase IV node through a router that does not support Phase IV backward compatibility is not possible. A non-DNA OSI router does not know how to translate a DECnet Phase V address to a Phase IV address, or convert Network layer data protocol data unit (PDU) formats. The following are possible solutions to consider:
If you have configured your DECnet-Plus end systems to have a Phase IV-compatible address and you are operating in a non-DNA environment, you must ensure that all level 2 non-DNA OSI routers advertise the complete set of area addresses for the level 1 networks to guarantee connectivity between your DECnet-Plus end systems.
The Routing module stores information about remote systems (including NSAP addresses) to which data transfer is in progress. This information is known as the end system cache, and the data stored in this cache allows the Routing layer to quickly choose the correct data link address to which packets should be forwarded, as well as which format (Phase IV or OSI) should be used. The cache entries are created automatically, based upon the receipt of data and/or routing redirect packets, and indicate if the remote system is on-LAN (direct), or reachable by way of a router (indirect or reverse).
PROFILE_VMS_009.HTML OSSG Documentation 2-DEC-1996 12:35:00.53
Copyright © Digital Equipment Corporation 1996. All Rights Reserved.