8.10 Dimensioni dell’MTU per l’SNMP WebGate
L’MTU (Maximum Transmission Unit) su reti Ethernet per WebGate è
impostato a 576 byte. Non vanno inviati pacchetti superiori a questo
valore, in quanto saranno eliminati e non riconosciuti dal WebGate.
9. Gestione Utenti
Il WebGate permette la gestione degli utenti.
La gestione degli utenti fornisce restrizioni di accesso a pagine HTML
e file system.
Il WebGate permette 4 livelli di accesso di base: “Administrator”
(accesso massimo), “Supervisor”, “User” e “Guest” (restrizioni
massime).
9.1 Restrizioni di Accesso
La gestione utenti permette le seguenti impostazioni:
• Limiti di accesso alle funzioni script.
L’accesso in lettura è permesso a tutti gli utenti, mentre l’accesso in
scrittura è limitato ad alcuni utenti in base al tipo di funzione, come
indicato al capitolo Funzioni Script del WebGate.
Ad esempio, l’accesso in scrittura alla funzione “Var” è limitato al
“Supervisor” e all’“Administrator”, per evitare che chiunque possa
modificare le impostazioni dei dispositivi collegati alla rete RS485.
L’associazione tra una funzione e il livello di accesso minimo richiesto è
fissa e non modificabile.
• Limiti di accesso al file system.
Le restrizioni in lettura e scrittura possono essere applicate a
qualunque file, utilizzando sia HTTP che FTP.
I livelli di accesso ai file vengono impostati attraverso l’FTP. Vedi il
capitolo File Transfer Protocol per un’approfondita descrizione dell’FTP.
8.10 MTU dimension for WebGate SNMP
The Ethernet MTU (Maximum Transmission Unit) for WebGate is set to
576 bytes. Do not send packets greater than this value, since they will
be trashed and not recognized by the WebGate.
9. User Management
WebGate is provided with some basic user management capabilities.
User Management provides access restrictions when using functions
and accessing to HTML pages and file system.
WebGate provides 4 basic access levels: “Administrator” (maximum
access capabilities), “Supervisor”, “User” and “Guest” (maximum
restrictions).
9.1 Access Restrictions
User Managements works in the following ways:
• Applying access restrictions to script functions.
Functions read access is allowed to everybody, but write access is
limited to some users on a function-by-function basis, as indicated in
chapter WebGate Script Functions.
For instance, the “Var” function write access is limited to “Supervisor”
and “Administrator” to avoid that everybody could change the settings
of devices connected to the RS485 network. The association between
a function and the minimum access level required is fixed and not
modifiable.
• Limiting access to the file system.
Read and write restrictions can be applied to any file, valid either using
HTTP and FTP.
File access levels are set through FTP. Please see chapter File Transfer
Protocol for an extensive description of FTP.
48
Manuale WebGate - cod. +030220230 rel. 1.0 - 16.09.2003
WebGate Error Messages
Error Messages
PDU
Possible cause and solution
type*
tooBig
G-GN
The length of the response message is too big. Try a new request querying for a number of variables less than the
previous one.
noSuchName
G-S
The manager is querying for one or more variables that doesn’t match anything in the MIBView of the WebGate.
The error index indicates which is the first variables that caused the error. Check the OID of the variable and retry.
Particular cases are querying for:
• MIB-II system variables different by sysContact, sysName, sysLocation;
• Objects not present in Carel-system subtree or under the Agent-parameters node;
• For a General-Units-Info subtree with node index > 9 or, in such subtrees, for units having address > Netsize:
• Unit with address > Netsize in the Carel-Instruments subtree.
• The Index of a unit variable is greater than MaxIndex=207 in the Carel-Units-Var subtrees.
Generally, when NMS asks for an object immediately successive at last in any subtree, WebGate sends this error
message.
GN
Along with the general case, with correct OID, some particular items are querying for:
• MIB-II system variables having OID-name less than sysUpTime or greater than sysName (the only system
variables defined are sysContact, sysName, sysLocation);
• Variable different by Agent-release in the Carel-system subtree;
• Variable different by Netsize in Agent-parameters node (Fig.8);
• Unit variable with index greater than MaxIndex-1.
readOnly
S
A set-request tried to write a variable that the operator is not allowed to write.
badValue
S
Particular cases are:
• Writing not alphanumeric strings or too long for system variables;
• Trying to set Netsize greater than 16 or wrong baudrate values;
genErr
G-GN-S
WebGate generally sends this error message when:
• NMS tries to read software-releases of High-level units;
• NMS tries operations on units that are off-line;
• NMS tries a Set-request to write a unit variable and output-message-queue is full;
Tab. 8.9.2
(*): G=Get-request, GN=GetNext-request, S=Set-request;