Can UMTS technology really provide useful WAN connectivity?
February 10th, 2009 | by Stefan Dominko |These days, a lot of companies want to use UMTS technology for backup WAN connectivity. Speeds seem to be very promising, and considerable even for primary WAN connections. But what about response times ? One of service providers is promising the following response times:
| Technology | Packet size 32 Bytes/1400 Bytes |
|---|---|
| GPRS | 600 ms/1800 ms |
| UMTS | 200 ms/600 ms |
| HSDPA | 75 ms/150 ms |
We have done some PING tests through UMTS/HSDPA connections, with the following results:
#ping 10.31.1.1 size 1400 repeat 100
Type escape sequence to abort.
Sending 100, 1400-byte ICMP Echos to 10.31.1.1, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 112/219/648 ms
#ping 10.31.1.1 size 36 repeat 100
Type escape sequence to abort.
Sending 100, 36-byte ICMP Echos to 10.31.1.1, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 68/158/620 ms
#
Of course, we must take into consideration that UMTS is not trustworthy connection. That’s why we have configured VPN site-to-site with 3DES encryption. Also, we use GRE tunnels; therefore, when looking at our PING test results, you must add some GRE/IPSec packet overhead.
To get an overview of response times over a long period, our NIL Monitor team has activated the NIL Monitor service for collecting PING test results every 5 minutes. The following printout shows PING tests with a packet size of 100 bytes.
As the image shows, there are a few packet losses (shown in blue), but not a critical number. Response times are stable, but in the range of 200–300 ms with a packet size of 100 bytes! This is too slow for many application types. Voice traffic is definitely not working well, with a 200–300 ms delay. It seems that WAN connections for critical applications should still be wired (DSL, fiber optic, …).
2 Responses to “Can UMTS technology really provide useful WAN connectivity?”
By dominico on Mar 20, 2009 | Reply
Try starting one ping with 100 bytes packet size and then after a another parralel ping with 1400 bytes packet size. You should notice decrease of response time for 100 bytes ping.
I get less than 70 ms response time for a 100 bytes packet size on HSDPA in a real network.
This is because of the radio resource allocation schemes.
If you are observing ping response times every five minutes for just a few packets ping that’s not the right approach as it takes approx 0.5 seconds for a base station to allocate new resources to terminal.
By Stefan Dominko on Mar 27, 2009 | Reply
I have noticed behaviour that you described. Of course I have done also tests with several hundred of pings with 100bytes nad 1400bytes packets and got same results as I have already mentioned in response time table. I think that response time primary depends on UMTS provider equipment, oversubscription, signal strength and free resources (cells) on base station in that particular moment. Regarding this, it is a low posibility to have the same response times in different countries or even different regions in same country. I have just done the test to show what one of the UMTS providers is promising and what you really get. Of course in our country (Slovenia).