[Ericsson AB]

8 Performace comparison

8.1 Comparison of encoder/decoders

The Megaco/H.248 standard defines both a plain text encoding and a binary encoding (ASN.1 BER) and we have implemented encoders and decoders for both. We do supply a bunch of different encoding/decoding modules and the user may in fact implement their own (like our erl_dist module). Using a non-standard encoding format has its obvious drawbacks, but may be useful in some configurations.

We have made four different measurements of our Erlang/OTP implementation of the Megaco/H.248 protocol stack, in order to compare our different encoders/decoders. The result of each one is summarized in a line chart:

8.1.1 Encoded message size in bytes

message_size
Encoded message size in bytes

8.1.2 Encode time in micro seconds

encode_time
Encode time in micro seconds

8.1.3 Decode time in micro seconds

decode_time
Decode time in micro seconds

8.1.4 Sum of encode and decode time in micro seconds

total_time
Sum of encode and decode time in micro seconds

8.2 Description of encoders/decoders

In Appendix A of the Megaco/H.248 specification (RFC 3525), there are about 30 messages that shows a representative call flow. We have also added a few extra version 1, version 2 and version 3 messages. We have used these messages as basis for our measurements. The numbers within parentheses are the plain average values. Our figures have not been weighted in regard to how frequent the different kinds of messages that are sent between the media gateway and its controller.

The test compares the following encoder/decoders:

The actual encoded messages have been collected in one directory per encoding type, containing one file per encoded message.

Here follows an example of a text message to give a feeling of the difference between the pretty and compact versions of text messages. First the pretty printed, well indented version with long keywords:

MEGACO/1 [124.124.124.222] 
  Transaction = 9998 { 
    Context = - { 
      ServiceChange = ROOT { 
        Services { 
          Method = Restart, 
          ServiceChangeAddress = 55555, 
          Profile = ResGW/1, 
          Reason = "901 MG Cold Boot"
        }
      }  
    }
  }    

Then the compact text version without indentation and with short keywords:

!/1 [124.124.124.222] T=9998{
  C=-{SC=ROOT{SV{MT=RS,AD=55555,PF=ResGW/1,RE="901 MG Cold Boot"}}}}    

8.3 Setup

The measurements has been performed on a HP workstation xw4400 with an Intel Core 2 Duo 2.13 GHz, 3 GB memory and running SLES 10 SP1 i586, kernel 2.6.16.54-0.2.5-bigsmp Software versions was open source OTP R12B-1 and megaco-3.7.3.

8.4 Complete measurement result

This chapter details the effects of the possible encoding configurations for every codec. The result above are the fastest of these configurations for each codec. The figures presented are the average of all used messages.

For comparison, also included are performance figures for when both the test program and the codec's where hipe compiled. In the case of the binary codec's, the asn1 run-time was also inlined.

Codec performance
Codec and config Size Encode Decode Total
pretty 336 31 115 146
pretty [flex] 336 31 60 91
pretty hipe 336 18 58 76
pretty [flex] hipe 336 18 51 69
compact 181 26 91 117
compact [flex] 181 26 56 82
compact hipe 181 14 53 67
compact [flex] hipe 181 14 47 61
per bin 91 82 87 169
per bin [driver] 91 57 59 116
per bin [native] 91 63 63 126
per bin [driver,native] 91 35 38 73
per bin hipe+inline 91 38 38 76
per bin [driver] hipe+inline 91 33 36 69
per bin [native] hipe+inline 91 28 29 57
per bin [driver,native] hipe+inline 91 22 25 47
ber bin 165 45 70 115
ber bin [driver] 165 45 51 96
ber bin [native] 165 26 47 73
ber bin [driver,native] 165 26 28 54
ber bin hipe+inline 165 24 41 65
ber bin [driver] hipe+inline 165 24 30 54
ber bin [native] hipe+inline 165 14 31 45
ber bin [driver,native] hipe+inline 165 14 20 34
erl_dist 875 7 13 20
erl_dist [megaco_compressed] 405 8 9 17
erl_dist [compressed] 345 142 31 173
erl_dist [megaco_compressed,compressed] 200 111 18 129
erl_dist hipe 875 7 13 20
erl_dist [megaco_compressed] hipe 405 6 6 12
erl_dist [compressed] hipe 345 130 29 159
erl_dist [megaco_compressed,compressed] hipe 200 108 14 122

8.5 Summary

In our measurements we have seen that there are no significant differences in message sizes between ASN.1 BER and the compact text format. Some care should be taken when using the pretty text style (which is used in all the examples included in the protocol specification and preferred during debugging sessions) since the messages can then be quite large. If the message size really is a serious issue, our per encoder should be used, as the ASN.1 PER format is much more compact than all the other alternatives. Its major drawback is that it is has not been approved as a valid Megaco/H.248 message encoding.

When it comes to pure encode/decode performance, it turns out that:

If the pure encode/decode performance really is a serious issue, our erl_dist encoder could be used, as the encoding/decoding of the erlang distribution format is much faster than all the other alternatives. Its major drawback is that it is has not been approved as a valid Megaco/H.248 message encoding.

Note

Please, observe that these performance figures are related to our implementation in Erlang/OTP. Measurements of other implementations using other tools and techniques may of course result in other figures.


megaco 3.7.4
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