The standard SMPP Connect form covers most vendors. Some vendors need extra settings: TLS binds, a stricter keep-alive, a smaller in-flight window, or prefix restrictions. Extra Attributes lets you set these per connect without changing any other connect.
Where to find it
SMPP Client → Connects → Edit the connect → scroll to the bottom → Extra Attributes. Choose an Attribute, enter a Value, and click Save Changes. Add one attribute per entry.
Most useful attributes
Connection stability
| Attribute | Use |
|---|---|
enquire-link-interval | Seconds between keep-alive (enquire_link) packets. Lower it if the vendor or a firewall drops idle binds |
reconnect-delay | Seconds to wait before re-binding after a disconnect. Increase it if the vendor blocks rapid re-binds |
connection-timeout | How long to wait when opening the connection |
wait-ack / wait-ack-expire | How long to wait for a submit_sm_resp, and what to do when it doesn’t arrive |
Throughput and flow control
| Attribute | Use |
|---|---|
max-pending-submits | Maximum unacknowledged submits in flight (the window). Lower it if the vendor throttles or disconnects under load |
Security
| Attribute | Use |
|---|---|
use-ssl | Bind over TLS when the vendor requires an encrypted SMPP port |
ssl-client-certkey-file | Client certificate, if the vendor requires mutual TLS |
Addressing and filtering
| Attribute | Use |
|---|---|
allowed-prefix / denied-prefix | Only send (or never send) numbers with these prefixes on this connect. A safety net against sending traffic to destinations the vendor doesn’t cover |
preferred-prefix / unified-prefix | Prefix preference and number normalisation for this connect |
source-addr-ton/npi, dest-addr-ton/npi, bind-addr-ton/npi, source-addr-autodetect | Override TON/NPI handling when the TON/NPI tab isn’t enough |
address-range, service-type, interface-version, my-number | Vendor-specific bind parameters |
Message handling
| Attribute | Use |
|---|---|
validityperiod | Message validity sent to the vendor. Useful for OTP routes, so stale OTPs expire instead of arriving late |
esm-class, alt-dcs, alt-charset, alt-addr-charset, max-sms-octets | Encoding and message-class adjustments for vendors with non-standard handling |
msg-id-type | How the vendor’s message IDs are read (e.g. hex vs decimal). Fix this when DLRs don’t match their messages |
Diagnostics
| Attribute | Use |
|---|---|
log-level, log-format | More detailed logging on one connect while troubleshooting. Turn it back down afterwards |
Applying changes
Extra attributes are bind-level settings. After saving, reload/reconfigure the connect from its Connection manager, and restart the Connect Manager (System → Controls → SMPP Client) if the change doesn’t take effect. Do this in a low-traffic window.
Good practice
- Change one attribute at a time and watch sessions, queue and DLRs before changing the next.
- Record why each attribute was set (vendor ticket, date) in the connect’s Description.
- DLRs not matching messages is almost always
msg-id-type. Ask the vendor whether their IDs are hex or decimal insubmit_sm_respand indeliver_sm.
Related articles
- How to Add a New SMPP Connect
- What is the keep-alive frequency set for SMPP client?
- Enquire link in SMPP server
- TON and NPI in SMPP