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Hedge 126: George Michaelson on ISDN

ISDN, while an old technology, is still around in many parts of the world. When will it go away? George Michaelson joins Tom Ammon and Russ White to discuss the end of ISDN. The conversation then veers into old networking technologies, and the importance of ISDN in setting the terms and ideas we use today—ISDN is one of the key technologies around which network engineers built their mental maps of how to build and maintain networks.

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Upcoming Training: Network Troubleshooting

I’m teaching a three-hour webinar on troubleshooting on the 22nd of April:

This training focuses on the half-split system of troubleshooting, which is widely used in the electronic and civil engineering domains. The importance of tracing the path of the signal, using models to put the system in context, and the use of a simple troubleshooting “loop” to focus on asking how, what, and why are added to the half-split method to create a complete theory of troubleshooting. Other concepts covered in this course are the difference between permanent and temporary fixes and a review of measuring reliability. The final third of the course contains several practical examples of working through problems to help in applying the theory covered in the first two sections to the real world.

This is offered on Safari Books Online through Pearson. I think that if you register for the course, you can watch a recording later.

Register here.

Hedge: April Update

You can register for my network troubleshooting course here.

Information about the IEEE Network Softwarification Conference can be found here.

Our upcoming episodes for this month are George Michaelson on the death of ISDN and old networks; an update on the FR Routing project; and Rick Graziani on college and network engineering. Thanks for listening to the Hedge!

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Hedge 125: Brooks Westbrook and DC Fabric Design

DC fabric design is more of an art than a science—a lot of factors come into play, such as future growth, lifecycle management, security, and costs. How can network engineers balance these various factors—how do they even know what questions to ask? Brooks Westrbook joins Tom Ammon and Russ White to discuss three- and five-stage DC fabric design, OPEX, CAPEX, and other topics on this episode of the Hedge.

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BGP Policies (Part 4)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post, I’ll cover the first of a few ways to give surrounding autonomous systems a hint about where traffic should enter a network. Note this is one of the most vexing problems in BGP policy, so there will be a lot of notes across the next several posts about why some solutions don’t work all that well, or when they will and won’t work.

There are at least three reasons an operator may want to control the point at which traffic enters their network, including:

  • Controlling the inbound load on each link. It might be important to balance inbound and outbound load to maintain settlement-free peering, or to equally use all available inbound bandwidth, or to ensure the quality of experience is not impacted by overusing a single link.
  • Accounting for Continue reading

Hedge 124: Geoff Huston and the State of BGP

Another year of massive growth in the number and speed of connections to the global Internet—what is the impact on the global routing table? Goeff Huston joins Donald Sharp and Russ White to discuss the current state of the BGP table, the changes in the last several years, where things might go, and what all of this means. This is part two of a two part episode.

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BGP Policies (Part 3)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

There are many reasons an operator might want to select which neighboring AS through which to send traffic towards a given reachable destination (for instance, 100::/64). Each of these examples assumes the AS in question has learned multiple paths towards 100::/64, one from each peer, and must choose one of the two available paths to forward along.

In the following network—

From AS65001’s perspective

Assume AS65001 is some form of content provider, which means it offers some service such as bare metal compute, cloud services, search engines, social media, etc. Customers from AS65006 are connecting to its servers, located on the 100::/64 network, which generates a large amount of traffic returning to the customers.
From the perspective of AS hops, it appears the path from AS65001 to AS65006 is the same length—if this Continue reading

Hedge 123: Geoff Huston and the State of BGP

Another year of massive growth in the number and speed of connections to the global Internet—what is the impact on the global routing table? Goeff Huston joins Tom Ammon and Russ White to discuss the current state of the BGP table, the changes in the last several years, where things might go, and what all of this means. This is part 1 of a two part episode.

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DC Fabric Webinar

Sorry for the short notice … I’m teaching a three-hour webinar on DC fabrics and control planes this coming Friday, the 25th, through Safari Books Online. This course covers the basics of spine-and-leaf fabrics, as well as some high level information on various DC fabric control plane options (BGP, RIFT, and IS-IS). Please register here.

BGP Policies (Part 2)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

There are many reasons an operator might want to select which neighboring AS through which to send traffic towards a given reachable destination (for instance, 100::/64). Each of these examples assumes the AS in question has learned multiple paths towards 100::/64, one from each peer, and must choose one of the two available paths to forward along.

In the following network—

From AS65004’s perspective…

Transit providers primarily choose the most optimal exit from their AS to reduce the amount of peering settlement they are paying by using and maintaining settlement-free peering where possible and reducing the amount of time and distance traffic is carried through their network (through hot potato routing, discussed in more detail below).
If, for instance, AS65004 has a paid peering relationship with AS65002, and a contract with AS65003 which Continue reading

Hedge 121: Computing in the Network with Marie-Jose Montpetit

Can computation be drawn into the network, rather than always being pushed to the edge of the network? Taking content distribution networks as a starting point, the COIN research group is looking at ways to make networks more content and computationally aware, bringing compute into the network itself. Join Alvaro Retana, Marie-Jose Montpetit, and Russ White, as we discuss the ongoing research around computing in the network.

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