Clicks is a new software architecture for building flexible and configurable routers. A Click router is assembled from packet processing modules called elements. Individual elements implement simple router functions like packet classification, queuing, scheduling, and interfacing with network devices. A router configurable is a directed graph with elements at the vertices; packets flow along the edges of the graph. Several features make individual elements more powerful and complex configurations easier to write, including pull connections, which model packet flow drivn by transmitting hardware devices, and flow-based router context, which helps an element locate other interesting elements. Click configurations are modular and easy to extend. A standards-compliant Click IP router has 16 elements on its forwarding path; some of its elements are also useful in Ethernet switches and IP tunnelling configurations. Extending the IP router to support dropping policies, fairness among flows, or Differentiated Services simply requires adding a couple of element at the right place. On conventional PC hardware, the Click IP router achieves a maximum loss-free forwarding rate of 333,000 64-byte packets per second, demonstrating that Click's modular and flexible architecture is compatible with good performance.

The click modular router

Network Calculus.- Application of Network Calculus to the Internet.- Basic Min-plus and Max-plus Calculus.- Min-plus and Max-plus System Theory.- Optimal Multimedia Smoothing.- FIFO Systems and Aggregate Scheduling.- Adaptive and Packet Scale Rate Guarantees.- Time Varying Shapers.- Systems with Losses.

Network Calculus: A Theory of Deterministic Queuing Systems for the Internet

Click is a new software architecture for building flexible and configurable routers. A Click router is assembled from packet processing modules called elements. Individual elements implement simple router functions like packet classification, queueing, scheduling, and interfacing with network devices. Complete configurations are built by connecting elements into a graph; packets flow along the graph's edges. Several features make individual elements more powerful and complex configurations easier to write, including pull processing, which models packet flow driven by transmitting interfaces, and flow-based router context, which helps an element locate other interesting elements.We demonstrate several working configurations, including an IP router and an Ethernet bridge. These configurations are modular---the IP router has 16 elements on the forwarding path---and easy to extend by adding additional elements, which we demonstrate with augmented configurations. On commodity PC hardware running Linux, the Click IP router can forward 64-byte packets at 73,000 packets per second, just 10% slower than Linux alone.

/pdf/the-click-modular-router-1nn6g98t3q.pdf

The Click modular router

This document describes the use of RSVP (Resource Reservation Protocol), including all the necessary extensions, to establish label-switched paths (LSPs) in MPLS (Multi-Protocol Label Switching) Since the flow along an LSP is completely identified by the label applied at the ingress node of the path, these paths may be treated as tunnels A key application of LSP tunnels is traffic engineering with MPLS as specified in RFC 2702

RSVP-TE: Extensions to RSVP for LSP Tunnels

This document defines a general use Differentiated Services (DS) [Blake] Per-Hop-Behavior (PHB) Group called Assured Forwarding (AF). The AF PHB group provides delivery of IP packets in four independently forwarded AF classes. Within each AF class, an IP packet can be assigned one of three different levels of drop precedence. A DS node does not reorder IP packets of the same microflow if they belong to the same AF class.

Assured Forwarding PHB Group

Differentiated services enhancements to the Internet protocol are intended to enable scalable service discrimination in the Internet without the need for per-flow state and signaling at every hop. A variety of services may be built from a small, well-defined set of building blocks which are deployed in network nodes. The services may be either end-to-end or intra-domain; they include both those that can satisfy quantitative performance requirements (e.g., peak bandwidth) and those based on relative performance (e.g., "class" differentiation). Services can be constructed by a combination of:

/pdf/definition-of-the-differentiated-services-field-ds-field-in-4nifivtfq0.pdf

Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

The definition of PHBs (per-hop forwarding behaviors) is a critical part of the work of the Diffserv Working Group. This document describes a PHB called Expedited Forwarding. We show the generality of this PHB by noting that it can be produced by more than one mechanism and give an example of its use to produce at least one service, a Virtual Leased Line. A recommended codepoint for this PHB is given.

An Expedited Forwarding PHB

The differentiated services framework enables quality-of-service provisioning within a network domain by applying rules at the edges to create traffic aggregates and coupling each of these with a specific forwarding path treatment in the domain through use of a codepoint in the IP header. The diffserv WG has defined the general architecture for differentiated services and has focused on the forwarding path behavior required in routers, known as "per-hop forwarding behaviors" (or PHBs). The WG has also discussed functionality required at diffserv (DS) domain edges to select (classifiers) and condition (e.g., policing and shaping) traffic according to the rules. Short-term changes in the QoS goals for a DS domain are implemented by changing only the configuration of these edge behaviors without necessarily reconfiguring the behavior of interior network nodes.

/pdf/definition-of-differentiated-services-per-domain-behaviors-2mui2bmmpv.pdf

Definition of Differentiated Services Per Domain Behaviors and Rules for their Specification

Architectures for Internet quality of service (QoS) have been under discussion for over a decade and, with the commercialization of the Internet, the topic has become increasingly important. This paper gives a background and history of QoS for the Internet, then introduces and motivates the differentiated services (Diffserv) approach. The major advantages of the Diffserv approach are that it is a good match to the Internet architecture and that it can be initially deployed with a minimalist approach, adding complexity as needed. Despite the long history of discussion, the phrase "quality of service" does not have a universally accepted meaning. In this paper QoS is used to describe a set of measurable parameters, such as delay, throughput, and loss rate, that can be attached to some identifiable subset of the traffic of IP packets through a given network domain. The identifiable subset of traffic belongs to a "user" of IP QoS where "user" spans a range of granularities, from a single application program to an entire company. Providing guarantees about the values of network parameters requires the implementation and deployment of physical mechanisms throughout the network and then configuring these mechanisms in such a way that their effect, when viewed from the edges of the network, composes into the desired QoS. Diffserv uses simple mechanisms in a more complex composition, allowing the details of the composition to evolve while the mechanisms, part of the network infrastructure, can remain the same. The paper discusses the specifics of this approach and why it is well-matched to the Internet. Some practical issues for deployment are addressed. Further we address resource allocation and configuration questions, including simple possibilities for early deployment and some of the open questions for a more complex future deployment. This paper takes the position that it is possible to maintain reasonable QoS levels without recourse to any of the class of constrained routing approaches (including MPLS), though Diffserv can be used with these approaches if desired.

Differentiated services in the Internet

Nearly three decades after it was first diagnosed, the "persistently full buffer problem" recently exposed as part of "bufferbloat", is still with us and made increasingly critical by two trends. First, cheap memory and a "more is better" mentality have led to the inflation and proliferation of buffers. Second, dynamically varying path characteristics are much more common today and are the norm at the consumer Internet edge. Reasonably sized buffers become extremely oversized when link rates and path delays fall below nominal values.

https://dl.acm.org/doi/pdf/10.1145/2208917.2209336

Kathleen Nichols

Papers

Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

An Expedited Forwarding PHB

Definition of Differentiated Services Per Domain Behaviors and Rules for their Specification

Differentiated services in the Internet

Controlling Queue Delay: A modern AQM is just one piece of the solution to bufferbloat.