Skip to content

DA3. DiffServ and IntServ QoS Models

Statement

Quality of Service (QoS) can be implemented in three different models, namely; Best effort, Integrated Services (IntServ), and Differentiated Services (DiffServ).

  • Compare and contrast the Integrated Services (IntServ) and Differentiated Services (DiffServ) Quality of Service (QoS) models in a network environment.
  • When might it be most beneficial to implement one model over the other in a network environment? Share at least one justified example.

Answer

Quality of Service (QoS) is a set of technologies that are used to guarantee a certain load that a network can handle; it aims to provide the least delay and packet loss. There are 4 parameters to Qos: Bandwidth, Delay, Jitter, and Packet Loss. There are a few techniques that are used in implementing the models above Scheduling, Policing, Shaping, Queuing, Admission Control, and Resource Reservation (SK Wish, 2020).

Integrated Services (IntServ) is a QoS model that provides the most guaranteed level of message delivery; it involves using the Resource Reservation Protocol (RSVP) to reserve resources for a specific flow (connection). It requires the sender to reserve resources before sending packets, and that all links along the path have agreed and reserved resources for the transfer. In order to achieve this, all links must maintain a state for each transfer; the state is soft, and it is discarded as soon as the flow reaches its destination (Huawei, 2022).

Differentiated Services (DiffServ) is a QoS model that provides different treatments for each type of traffic, there is no pre-reservation of resources, however, each packet must contain information about its type or QoS class that the sender expects. At every router, the QoS information is examined, and the packet is marked with a Differentiated Services Code Point (DSCP) (Mishra, 2022), that determines the next steps that the router will take. Depending on the marking, the router will put the packet in a specific queue, or even decide if it should use the IntServ or Best Effort model for its communication with the next router (Huawei, 2022).

The Table below compares and contrasts the two models:

Feature Integrated Services (IntServ) Differentiated Services (DiffServ)
Treatment All traffic is treated equally Different classes of traffic are treated differently
Reservation Resources are reserved before sending packets No pre-reservation of resources
State Maintains a state for each transfer No state is maintained
Scalability Less scalable (state slows it down) More Scalable
Protocol Uses RSVP Uses DSCP

As per the discussion above, the IntServ model is most beneficial when the network requires guaranteed service for specific flows, such as video conferencing or voice-over IP, where the network only handles one type of traffic. The DiffServ model is most beneficial when the network handles different types of traffic and needs to prioritize them accordingly; which is the case for most networks including the Internet, LANs, and WANs.

As an example, an internal network in a company to facilitate communications between its employees can use the IntServ model to guarantee the best quality of service; while a general-purpose network must be able to handle different types of traffic, and can use the DiffServ model to deliver each type within the acceptable limits of its protocol.

References