Summary
Switched networks' (including the Internet) nodal devices require buffers to hold packets during periods of congestion and when traffic streams on more than one input port need to access the same output port. Appropriately sizing the buffers has been a contentious issue among researchers over the last couple of years. Three main buffer sizing formulas have been reported in literature, which are: bandwidth‐delay product or BDP, small buffer, and the tiny buffer formulas. But researchers are largely agreed that the BDP formula results in unrealistically large and wasteful buffers, while a number of researchers have held with good reasons, that the small and tiny buffer formulas are theoretical formulations that cannot be generally and practically applied to real networks. Some researchers have even asserted that deriving a single, universal formula for sizing buffers may not be possible. The main purpose of this paper is to explain an approach, which we term “network topology point –of –view,” that we developed to derive a novel, empirical, generic, practical, easy‐to‐apply, closed‐form formula that can be used to obtain the buffer capacity that is optimal—in terms of the minimum capacity possible for lossless operation, for any switched network node, including nodes (switches and routers) in the Internet. The results obtained from utilizing the formula to specify typical nodal buffers' capacities are largely in agreement with the values of the tiny buffer formula in literature; but this paper's formula additionally specifies what we term “very tiny buffers.” The simple approach adopted for presenting this paper makes it a handy tutorial material that explains this “network topology point‐of‐view” concept.
All switched Local Area Networks (switched LANs) have a parameter that is common to them, known as, ‘bits-carrying capacity', which is one of the parameters that network managers and administrators use in managing the performances of these class of networks. However, there appears, to the best of the knowledge of the members in the research team involved in this work, no formal method (or methods) available in literature for determining this parameter. Reported in this chapter, is the formal derivation of a formula, which can be used to obtain the capacity of any switched LAN. Also reported, is a formula that can be used to obtain the capacity (that is, bits capacity, in units such as Mb or, Megabits; Gb, or Gigabits) to subscribe for, when a switched LAN needed to be connected to the network of a service provider, such as, connecting the network to the Internet via an ISP (Internet Service Provider). The practical utility of both formulas is also illustrated.
Carrier Service Providers define a Bandwidth Profile, which enables them bill for bandwidth usage and engineer their networks’ resources to provide performance assurances for in-profile Service Frames. The CBS (Committed Burst Size) is one of the parameters of this profile. Similarly, in the context of the guaranteed and controlled-load services’ provisioning of theInternet, IETF’s (Internet Engineering Task Force’s) T-SPEC (traffic specification) defines a parameter known as burst tolerance, b. Likewise, in the Intserv (Integrated Service) use of RSVP (Resource Reservation Protocol), a service type is specified and quantitative traffic parameters are expressed using the token (buffered leaky) bucket model: Maximum Burst Size, B is one of the parameters of this model. Therefore, a major question that is usually asked in these contexts is: How should applications determine the CBS or b or B of their flows? This basically will be for the purpose of engendering optimal use of network resources, specifically, the use of buffer capacities in nodal devices (switches/routers). In this paper, we describe the derivation of a formula for Nodal Devices Buffers’ Capacities Provisioning, for lossless data communication traffic flows.
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