Measured Parameters
Basic measurement principles
Six Quarks SQ probes have software modules - quality agents that implement different types of tests. Presently the following quality assurance agents are available:
- Ethernet OAM agent;
- Echo-test agent;
- Network quality agent;
- Network service quality agent;
- Voice over IP quality agent;
- IPTV quality agent.
Six Quarks is constantly working on extending the list of available agents, so new quality agents are likely to come into service.
Ethernet OAM Agent
Ethernet OAM quality assurance agent controls channel quality, in conformity with ITU-T Y.1731. The response party may be any device supporting Ethernet OAM tests as provided by ITU-T Y.1731 specification. Two types of tests are maintained: one-way (ETH-LB) and two-way (ETH-DM).
The following parameters are available for assurance:
- Frames loss;
- Frames with modified priority;
- Frames reordering;
- Duplicate frames;
- Loss Distance;
- Round-trip delay.
For ETH-DM tests the following parameters are also available:
- One-way delay;
- Jitter.
Echo-test Agent
Echo-test agent makes measurements on the network layer generating test traffic and forwarding it to any third party device that supports traffic mirroring using the ICMP, UDP or TCP protocols. The external device sends received traffic back to Six Quarks SQ probe where echo-test agent receives and analyses it.
The following parameters are available for assurance:
- Packet loss;
- Packets with chaned priority;
- Packets reordering;
- Duplicated packets;
- Loss Distance;
- Round-trip delay.
Network Quality Assurance Agent
Network detailed quality assurance agent makes measurements (as the echo-test agent does) on the network layer but unlike the echo-test agent, which monitors basic parameters only, the network quality agent provides detailed information of the network quality.
The agent establishes a control connection with the agent on an other Six Quarks SQ probe. After that it generates test traffic and forwards it to the neighbouring probe. The probe that receives test traffic analyses it, then forms and sends response test traffic. After measurement session is over, agents exchange test results via control channel and compose the overall picture of the assured network quality.
The following parameters are available for assurance:
- Packet loss in forward direction;
- Packet loss in reverse direction;
- Round-trip delay;
- One-way delay;
- Jitter;
- Packets with changed priority in each direction;
- Packets reordering in each direction;
- Duplicated packets in each direction;
- Loss Distance.
Network Applications Quality Assurance Agent
Network applications quality assurance agent assesses customers' contentment with standard network applications. It is often the only instrument allowing to detect reasons of users' dissatisfaction when overall network quality level is acceptable. The agent controls quality of access to specific network services: clock synchronization (NTP), domain names resolution (DNS) and any network service running on a TCP port, for instance: HTTP, FTP or SSH server.
When making tests the network applications quality assurance agent connects to an existing application server as its client. After the session is over the agent creates a report on its quality.
The following parameters are available for assurance:
- False and unanswered queries;
- Packet loss;
- Server response delay;
- Packets with changed priority.
Besides, the following parameters are available for DNS service control:
- Errors in name resolution of specific user-defined names.
The following parameters are also available for NTP service control:
- Number of incorrect messages;
- Number of messages about server synchronization loss.
Voice over IP Delivery Quality Agent
VoIP delivery quality assurance agent creates control connection to a responding VoIP agent functioning on another Six Quarks SQ probe. After establishing control channel the first agent creates synthetic media traffic according to the selected codec and sends it to the recipient probe. The responding probe, in its turn, also creates synthetic media traffic according to the selected codec. In the end of session agents analyse session results.
The following parameters are available for assurance:
- MOS;
- R-factor;
- Packet loss in forward direction;
- Packet loss in reverse direction;
- Round-trip delay;
- One-way delay;
- Jitter;
- Packets with changed priority;
- Packet reordering;
- Duplicated packets;
- Loss Distance.
IPTV Quality Agent
IPTV quality assurance agent controls IPTV image quality using 92 metrics. The IPTV quality agent of Six Quarks SQ probe joins a multicast group. After that it analyses deeply the received MPEG-stream.
IPTV quality agent examines SPTS and MPTS transport streams, analyses their structure, elementary streams, identifying MPEG2, MPEG4, AVC video codecs and MPEG1, MPEG2 layer 1,2,3, AC3 audio codecs.
Quality parameters are analysed and controlled in conformity with the following protocols and recommendations:
- RFC 1889;
- RFC 2236;
- RFC 3550;
- RFC 4445;
- ETSI TR 101 290;
- ETSI EN 300 468;
- ISO/IEC 13818-1.
92 metrics are analysed and controlled at the following levels:
- Interface;
- Socket;
- Transport stream;
- Program;
- Elementary stream.