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EIGRP vs OSPF – Take 2

First a bit of disclosure.  I have worked for Cisco over 15 years, much of that time as the lead developer for EIGRP. I think I understand its strengths and weakness’ very well, and have spent a great deal of energy minimizing them.

I often find comparing protocols similar to the old “tab vs spaces” or “emacs vs vi” wars.  There are valid reasons to choose one over the other and in the grand scheme of things it comes down to a wash; often preference or ‘religion’.  EIGRP seems to victim to this .  I mean where are the “ISIS vs OSPF” debates?  With EIGRP, network engineers that love it – love it. Those that don’t, well they don’t. Arguing its merits often results in an equally long list of “yea but” demerits.

For example, most everyone would agree eigrp is “simple to deploy”, but detractors would argue that simplicity leads to sloppy designs and only though complexity can we force network engineers to “do their job” and design the network properly. Read More »

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A Unified L2/L3 IP Based Overlay for Data Centres: another use-case for The Location Identity Separation Protocol

It is amazing how the data centre world has changed in the last few years.  A Data Centre used to be a collection of network elements to interconnect static servers (and their associated storage), with traffic patterns that were highly predictable and mostly north-south.  Cloud and virtualization have changed all of this: a data centre is now a collection of compute and storage resources which can be securely sliced up into virtual networks and placed anywhere according to real time needs, interconnected by a fabric.  The virtualization of servers, network services such as firewalls and load balancers, and even network devices such as switches and routers, has created a very dynamic landscape in terms of how fast you could configure a virtual network, in a way where location shouldn’t really matter, and where compute and storage resources can be added on the fly, based on demand.  Multi-tenant Data Centres, such as the one to deploy Virtual Private Clouds, need to support 10000’s of these virtual networks.  And every one of these virtual networks needs a lot of different service instances to stitch together the virtual network across virtual servers, virtual switches, virtual firewalls, virtual load-balancers, and virtual routers.  Traffic patterns have shifted to East-West, because of the new applications which spread processing across many hosts, and because of the ‘location freedom’ that virtualization allows.  Network infrastructure needs to be cost-effective to handle all this traffic, while the increased lookup-table size caused by the any to any traffic patterns often led to increased cost.  Read More »

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History as a guide to SDN’s coming evolution

I developed Intelligent Network (IN) services and platforms during the early 1990s.  With IN, Unix based controllers were connected to traditional telephone switches to perform both obscure as well as massively deployed phone services.  Some of these services had very large centralized routing databases controlling the ultimate trunk/path selection of calls. Read More »

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New Technologies for the Delivery of Services

Reduction in the complexity of deploying and managing services, accelerating new service introduction, and reducing capital/operational expenditure overhead are key priorities for network operators today. These priorities are in part driven by the need to generate more revenue per user. But competitive pressures and increasing demand from consumers are also pushing them to experiment with new and innovative services. These services may require unique capabilities that are specific to a given network operator and in addition may require the ability to tailor service characteristics on a per-consumer basis. This evolved service delivery paradigm mandates that the network operator have the ability to integrate policy enforcement alongside the deployment of services, applications, and content, while maintaining optimal use of available network capacity and resources. Read More »

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Distributed? Centralized? Both?

Part of the interest in programmatic interfaces is fueled by the desire to logically centralize network control functions. A global view of network state can have many benefits but it does not preclude the use of distributed protocols within the network.  Network Programming Interfaces (NPIs) provide a facility to construct global state, mutate that state and distribute that state to the network which in combination with distributed protocols can aid in achieving greater network efficiencies, improve visibility, robustness and add to the value of the network overall. When used the right way, these NPIs will help set a new balance between centralized and distributed control.  Key to this balance will be domain or deployment specific constraints. Read More »

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