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Quality of Service

Quality of service allows some traffic to obtain a different network service from the norm.

A pamphlet explaining Quality of Service on AARNet3 is available as a pdf file (3Mb) and as a zip file (2.9 Mb) should you wish to download it, unzip it and modify the .odt file for your institution)

AARNet provides service classes for Admission-controlled Voice, Admission-controlled Video, Scavenger, and Best Effort traffic. Access by sites to classes other than Best Effort requires a request to the AARNet Network Operations Centre.

AARNet's services use the IETF's Differentiated Services model and AARNet provides a selection of traffic classes using the DiffServframework.

Admission-controlled Voice class

  • This class is for 3Mbps of low latency, low jitter traffic suitable for voice over IP applications within the AARNet network.
  • Traffic from the site is identified by the site marking the traffic with DSCP=EF.
  • Traffic from the site in excess of 3Mbps is re-marked into the Scavenger class.
  • Traffic to the site in excess of 10% of the link bandwidth is re-marked into the Scavenger class.
  • Router queues for this class are under 40ms, roughly half a VoIP phone jitter buffer.
  • Voice traffic is policed to 10% of any link's bandwidth on each hop of the AARNet network. This is intended to defeat distributed denial of service attacks which target QoS-enabled endpoints.
  • To allow backward-compatibility sites can also mark Admission-controlled Voice traffic with Precedence=5. This traffic will egress AARNet marked with DSCP=EF. Multicast traffic with DSCP=EF is placed in the Scavenger class and re-marked to DSCP=CS1.

Admission-controlled Video class

  • The class is for 30Mbps of bounded latency, low jitter traffic suitable for video over IP applications within the AARNet network.
  • Traffic from the site is identified by the site marking the traffic with DSCP=AF41.
  • Traffic from the site in excess of 30Mbps is re-marked into the Scavenger class.
  • Traffic to the site in excess of 30% of the link bandwidth is re-marked into the Scavenger class. Router queues for this class are under 100ms.
  • This class is not suitable for Access Grid nodes.
  • Traffic from the Access Grid is not admission controlled.Video traffic is policed to 30% of any link's bandwidth on each hop of the AARNet network.
  • This is intended to defeat distributed denial of service attacks which target QoS-enabled endpoints.
  • To allow backward-compatibility sites can also mark Admission-controlled Video traffic with Precedence=4. This traffic will egress AARNet marked with DSCP=AF41.
  • Multicast traffic with DSCP=AF41 is placed in the Scavenger class and re-marked to DSCP=CS1.

Scavenger class

  • This class is for at least 1% of link bandwidth at the worst queue servicing priority.
  • It is suitable for file transfers when there is no consideration of performance.
  • Traffic from the site is identified by the site marking the traffic with DSCP=CS1.
  • Traffic in excess of 1% is not policed, rather it is send to the Scavenger class output queue. If the output link is not loaded than the class will use whatever bandwidth meets the class's input traffic, but if the output link is loaded class will use only 1% of the output bandwidth.
  • This service is useful for download servers. For example, the large number of file transfers from the AARNet mirror on a Linux distribution's release date can lead to over half the flows of some sites being mirror downloads. If the mirror used Best Effort then fair queuing would result in the web browsing traffic to the site getting only 50% of the link bandwidth. Rather the mirror uses Scavenger, which results in no degradation of web browsing response times at the cost of slower download times during these busy periods.
  • To allow backward-compatibility sites can also mark Scavenger traffic with Precedence=1. This traffic will egress AARNet marked with DSCP=CS1.
  • Multicast traffic is accepted in the Scavenger class.

Best Effort class

  • Normal traffic uses the Best Effort class.
  • This class uses the link bandwidth with uncontrolled latency and jitter suitable for most applications.
  • Traffic from the site is identified by the site marking the traffic with DSCP=BE. Traffic is not policed.
  • The output queues are long enough to allow optimal TCP performance, that is 0.25 of the worst-case round-trip time at 1Gbps (Perth to Tomsk via Seattle and Amsterdam).
  • Multicast traffic is accepted in the Best Effort class.

Undefined traffic

  • Traffic which enters with a DSCP other than those above has the DSCP re-mapped to DSCP=BE and is placed in the Best Effort class.

Traffic with other networks

  • AARNet passes along and accepts the DSCP when it peers with providers with equivalent classes. When the provider does not provide an equivalent class we:
    • queue outgoing traffic depending upon its class but re-mark it with DSCP=BE as it is transmitted;
    • place incoming traffic into the Best Effort class and re-mark it with DSCP=BE.
  • For Admission-controlled Voice we accept the provider's DSCP=EF traffic into the Admission-controlled Voice class where the peer's network uses admission control, such as a SIP session border controller.
  • If the provider's network uses the DSCP=EF marking but does not use admission control we place the incoming traffic to Best Effort class and re-mark the traffic to DSCP=BE.
  • We police incoming DSCP=EF traffic to 3Mbps from each provider.
  • Admission-controlled Video is treated similarly to Admission-controlled Voice, with a limit of 30Mbps of traffic.
  • For Scavenger traffic from providers which implement a Scavenger or other “worst effort” class we accept any amount of traffic marked with DSCP=CS1 and pass on our Scavenger traffic into the provider's Scavenger class.
  • If the provider does not have an equivalent class we queue the outgoing traffic as Scavenger but re-mark it to DSCP=BE as it is transmitted.
  • Traffic from other providers with unknown DSCPs is placed into the Best Effort class and re-marked to DSCP=BE.

Admission-controlled classes

Sites which wish to use the Admission-controlled Voice or Admission-controlled Video class warrant to AARNet that the site performs admission control. This allows sites to use the control plane of their choice, such as their own SIP server. This is unlike other ISPs, which must be less trusting of their customers and must direct traffic through the ISP's SIP session border controller or H.323 proxy.

ICMP and IGMP traffic

ICMP and IGMP traffic which should not cross network boundaries is discarded. All other ICMP traffic is placed into the Scavenger class.

Network abuse traffic

Traffic which contains a bogus source address is discarded. Traffic with a destination address not in AARNet is discarded, the generation of a ICMP Network Unreachable depending upon the address. Traffic with other markings which indicates network abuse is discarded. Traffic which may be network abuse may be placed into the Scavenger class.

Prices

All traffic classes are incur identical charges.