QOS-Enabled Networks (eBook)

Tools and Foundations

Miguel Barreiros, Peter Lundqvist (Autoren)

eBook Download: EPUB

2015 | 2. Auflage
John Wiley & Sons (Verlag)
978-1-119-10912-9 (ISBN)

Infos

Updated second edition discusses the basic concepts of Quality of Service (QoS) and illustrates their application in practical scenarios. This edition includes data center and cloud computing specifics, and a new chapter on QoS in the Data Center.

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Written by two experts in the field who deal with QOS predicaments every day and now in this 2nd edition give special attention to the realm of Data Centers, QoS Enabled Networks: Tools and Foundations, 2nd Edition provides a lucid understanding of modern QOS theory mechanisms in packet networks and how to apply them in practice. This book is focuses on the tools and foundations of QoS providing the knowledge to understand what benefits QOS offers and what can be built on top of it.

Autor

Miguel Barreiros is the Data Center Practice Lead at Juniper Networks responsible for the EMEA region. Previously he was a Senior Solutions Consultant focused on both Data Centers and IP/MPLS networks Since he joined Juniper Networks in 2006 he has been focused in the creation and development of solutions, and involved in projects that span all stages of building and expanding networks, from design and testing through implementation and ongoing maintenance. He began his networking career in 2000, when as a hobby he was network administrator for a British multiplayer gaming website that hosted network servers for various video games. Miguel has a B.Sc. degree in Electronics and Computer Engineering from Instituto Superior Técnico. He holds Juniper Networks Certificate Internet Expert (JNCIE) 193 and is a Juniper Networks Certified Instructor. Peter Lundqvist, Systems Engineer, Arista Networks, Sweden Peter Lundqvist works in system engineering at Arista Networks since May 2014. Prior to this, he was a senior Beta Engineer at Juniper Networks, supporting the field test and rollout of new features and solutions before they are public available. He has been responsible for the testing of several of the newly deployed QOS features. Before working in the Engineering department, Peter worked as professional services engineer, in network design and implementation of large-scale networks, several of them including QOS features. Peter worked for more than 13 years at Juniper Networks, prior to which he worked in Cisco Systems as Consulting Engineer.

Rezensionen

"My long-time friends Miguel Barreiros and Peter Lundqvist have deep experience designing modern QoS strategies, and they share that experience in this book, from modern QoS building blocks to applied case studies. They'll equip you well for designing the best QoS approach for your own network."
--Jeff Doyle

"An excellent overview of the fundamentals of QoS tools and their application, "QoS-enabled Networks" can serve both as an introduction and as a reference. Free from vendor-specific implementation details and configuration knobs, the book focuses on core concepts and on how to apply them to real-world scenarios, making this complex topic come into sharp focus"
--Ina Minei, Network Architect, Google

"This book addresses the real world scenarios faced by many telcos across the globe. Prioritisation and scheduling at the forefront of network design is key to every telco's utopia of a fully converged, multiservice network. A great resource in the designers tool kit"
--Phill Magill, Head of Network Innovation at Talk Talk Group

"This is the first book about QOS that I actually enjoyed reading precisely because the authors focused on real-life QoS and not in academic discussions about it."
--Per Nihlen, IP Network Manager, NORDUnet

"This book provides a new approach of the complex realm which is the QoS . It offers a detailed theoretical explanation of QoS mechanisms but also great case studies of concrete QoS applications. This book allowed me to better grasp complex QoS configurations such as the hierarchical CoS in BNG environment."
--David Roy, IP/MPLS NOC engineer - Orange France

"This book contains useful scenarios and real world case studies which expertly convert theoretical knowledge in practical application"
--Matheu Leonards, Head of Architecture, Finance and Risk, Thomson Reuters

"Mercifully, this book is not a dry academic dissertation on QoS. Rather, it offers an accessibly written and useful insight into the concepts and mechanisms of QoS that augment the tool kit of today's Network Engineer"
--Russell Thompson, Network Engineer, Telstra

Textauszug

1
The QOS World

Quality of Service (QOS) has always been in a world of its own, but as the technology has been refined and has evolved in recent years, QOS usage has increased to the point where it is now considered a necessary part of network design and operation. As with most technologies, large-scale deployments have led to the technology becoming more mature, and QOS is no exception.

The current trend in the networking world is convergence, abandoning the concept of several separate physical networks in which each one carries specific types of traffic, moving toward a single, common physical network infrastructure. This is old news for the Internet and other service providers, however, a novelty in other realms such as the Data Center. The major business driver associated with this trend is cost reduction: one network carrying traffic and delivering services that previously demanded several separate physical networks requires fewer resources to achieve the same goal.

One of the most striking examples is voice traffic, which was previously supported on circuit-switched networks and is now delivered on the “same common” packet-switched infrastructure. Also, in modern Data Centers the operation of a server writing into the hard drive, the disk, is done using a networking infrastructure that is shared with other traffic types.

The inherent drawback in having a common network is that the road is now the same for different traffic types, which poses the challenge of how to achieve a peaceful coexistence among them since they are all competing for the same network resources.

Allowing fair and even competition by having no traffic differentiation does not work because different types of traffic have different requirements, just like an ambulance and a truck on the same road have different needs. There is always the temptation of simply making the road wider, that is, to deploy network resources in an over-provisioned manner following the logic that although the split of resources was not ideal, so many free resources would be available at all times that the problem would be minimized. However, this approach has some serious drawbacks. First, in certain networks, the traffic flows and patterns are not predictable making it impossible to know the required resources beforehand. Secondly, it works against the major business driver behind network convergence, which is cost reduction. And third, such over-provisioning needs to be done not only for the steady state but also to take into account possible network failure scenarios.

QOS does not widen the road. Rather, it allows the division of network resources in a nonequal manner, favoring some and shortchanging others instead of offering an even split of resources across all applications. A key point with QOS is that a nonequal split of resources implies that there cannot be “win–win” situations. For some to be favored, others must be penalized. Thus, the starting point in QOS design is always to first select who needs to be favored, and the choice of who gets penalized follows as an unavoidable consequence.

In today’s networks, where it is common to find packet-oriented networks in which different types of traffic such as voice, video, business, and Internet share the same infrastructure and the same network resources, the role of QOS is to allow the application of different network behaviors to different traffic types.

Hence, for a specific traffic type, two factors must be considered, characterizing the behavior that the traffic requires from the network and determining which QOS tools can be set in motion to deliver that behavior.

1.1 Operation and Signaling

The QOS concept is somewhat hard to grasp at first because it is structurally different from the majority of other concepts found in the networking world. QOS is not a standalone service or product but rather a concept that supports the attributes of a network by spanning horizontally across it.

QOS can be split into two major components: local operation and resource signaling. Local operation is the application of QOS tools on a particular router (or a switch, a server, or any QOS-capable device).

Resource signaling can be defined as the tagging of packets in such a way that each node in the entire path can decide which QOS tools to apply in a consistent fashion to assure that packets receive the desired end-to-end QOS treatment from the network.

These two components are somewhat similar to the IP routing and forwarding concepts. Routing is a task performed jointly by all routers in the network. All routers exchange information among them and reach a consistent agreement in terms of the end-to-end path that packets follow. As for forwarding, each router performs the task individually and independently from the rest of the network using only local information.

Routing is comparatively more complex than forwarding, because it involves cooperation among all the routers in the network. However, routing does not need to work at wire speed. Forwarding is simpler. It is a task performed by a router individually and independently. However, it must operate at wire speed.

An analogy between routing and forwarding, and QOS resource signaling and local operation, can be drawn. QOS resource signaling is somewhat analogous to the routing concept. It involves all routers in the network but has no requirement to work at wire speed. QOS local operation is analogous to the forwarding concept. Like forwarding, QOS local operation is, in concept, simpler, and each router performs it independently and individually. Also, QOS local operation must operate at wire speed.

However, there is a major difference between QOS resource signaling and routing; there are no standardized specifications (such as those which exist for any routing protocol) regarding what is to be signaled, and as a result there is no standard answer for what should be coded on all network routers to achieve the desired end-to-end QOS behavior. The standards in the QOS world do not give us an exact “recipe” as they do for routing protocols.

1.2 Standards and Per-Hop Behavior

The two main standards in the IP realm that are relevant to QOS are the Integrated Services (IntServ) and the Differentiated Services (DiffServ). IntServ is described in RFC1633 [1] and DiffServ in RFC2475 [2].

IntServ was developed as a highly granular flow-based end-to-end resource reservation protocol, but because of its complexity, it was never commonly deployed. However, some of its concepts have transitioned to the MPLS world, namely, to the Resource Reservation Protocol (RSVP).

The DiffServ model was developed based on a class scheme, in which traffic is classified into classes of service rather than into flows as is done with IntServ. Another major difference is the absence of end-to-end signaling, because in the DiffServ model each router effectively works in a standalone fashion.

With DiffServ, a router differentiates between various types of traffic by applying a classification process. Once this differentiation is made, different QOS tools are applied to each specific traffic type to effect the desired behavior. However, the standalone model used by DiffServ reflects the fact that the classification process rules and their relation to which QOS tools are applied to which type of traffic are defined locally on each router. This fundamental QOS concept is called per-hop behavior (PHB).

With PHB, there is no signaling between neighbors or end to end, and the QOS behavior at each router is effectively defined by the local configuration on the router. This operation raises two obvious concerns. The first is how to achieve coherence in terms of the behavior applied to traffic that crosses multiple routers, and the second is how to propagate information among routers.

Coherence is achieved by assuring that the routers participating in the QOS network act as a team. This means that each one has a consistent configuration deployed which assures that as traffic crosses multiple routers, the classification process on each one produces the same match in terms of which different traffic types and which QOS tools are applied to the traffic.

Unfortunately, the PHB concept has its Achilles’ heel. The end-to-end QOS behavior of the entire network can be compromised if a traffic flow crosses a number of routers and just one of them does not apply the same consistent QOS treatment, as illustrated in Figure 1.1.

Figure 1.1 End-to-end consistency

In Figure 1.1, the desired behavior for the white packet is always to apply the PHB A. However, the middle router applies a PHB different from the desired one, breaking the desired consistency across the network in terms of the QOS treatment applied to the packet.

The word consistent has been used frequently throughout this chapter. However, the term should be viewed broadly, not through a microscopic perspective. Consistency does not mean that all routers should have identical configurations. Also, as we will see, the tools applied on a specific router vary according to a number of factors, for example, the router’s position in the network topology.

The second challenge posed by the PHB concept is how to share information among routers because there is no signaling between neighbors or end to end. Focusing on a single packet that has left an upstream router and is arriving at the downstream router, the...

Produkt-Details

• Erscheint lt. Verlag: 21.12.2015
• Reihe/Serie: Wiley Series in Communications Technology
• Reihe/Serie: Wiley Series in Communications Technology
• Reihe/Serie: Wiley Series on Communications Networking & Distributed Systems
• Sprache: englisch
• Themenwelt: Mathematik / Informatik ► Informatik ► Netzwerke
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• Themenwelt: Technik ► Nachrichtentechnik
• Schlagworte: Communication Technology - Networks • Computer Science • Data centers • Drahtlose Kommunikation • Electrical & Electronics Engineering • Elektrotechnik u. Elektronik • Informatik • Kommunikationsnetze • Mobile & Wireless Communications • Networking • Networks • Netzwerke • Quality of Service (QoS)
• ISBN-10: 1-119-10912-4 / 1119109124
• ISBN-13: 978-1-119-10912-9 / 9781119109129