1.4 Performance metrics for core IP routers

To study what network architecture is better, we need to have some performance metrics to compare the different options. In the network, there are two main stakeholders: the end users and the network carriers. Evidently, they have different concerns and views of the network. The most common use of the network is to request and download pieces of information^1.6 (be a web page, an image, a song, a video or a record in a database). After reachability, the end user is mainly interested in a fast response time, defined as the time since we request the object until the last byte arrives. Another important set of user applications (e.g., voice or video conferencing and streaming, or gaming) requires quality of service (QoS) guarantees, such as bounds on bandwidth, maximum delay, delay jitter or loss. These network guarantees are often expressed as a service level agreement between the network user and the ISP.

Network carries have a very different set of requirements. Tables 1.2 and 1.3 show a survey by BTexact of several IP backbone carriers about their current concerns and the features they will need in the next 2 years.

**Table 1.2:**

Concerns of carriers for network equipment in decreasing order of importance [25].
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**Table 1.3:**

New features required by carriers for network equipment in decreasing order of importance [25].
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After interconnectivity, which is always taken as a given, router reliability and stability are the greatest concern to carriers today. Significant improvements are required in these areas, particularly in the area of software reliability. It is highly undesirable to have equipment that fails, needs continuous attention, ties up valuable human resources and spoils the reputation of the carrier. Following in importance are scalability and performance. Even though the total cost of ownership comes last in the survey, the economic problems that numerous carriers currently face have probably increased its relevance; a good network has to come at a reasonable cost.

In terms of new features that carriers desire, the mitigation of Denial of Service (DoS) attacks ranks first, as such attacks can make the network connection unusable, damaging the reputation of the carrier. Improvements in performance come second, followed by better authentication and access security. Quality of service is last; however, it is more relevant for an operator that wants an integrated network that carries both low-margin data traffic and high-margin voice traffic.

In summary, end users care about low response time and quality of service, whereas network operators desire reliability, scalability and performance. As we will see end users will see no difference when using circuit switching or packet switching in the core of the network, whereas network carriers will clearly benefit from getting a network of higher capacity and reliability.