Learning BGP Module 1 Lesson 4: Intra-AS Models And Route Reflectors – Video
This lesson in Russ White’s BGP course delves into synchronization within an Autonomous System (AS) and confederation within an AS. It also discusses route reflectors, including how they prevent loops, route reflector clients, route reflector multi-path, and multi-path pros and cons. Russ White is a network architect, author, and instructor. You can subscribe to the […]
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Learning BGP Module 1 Lesson 3: How BGP Really Converges – Video
This lesson in Russ White’s BGP course gets into withdrawing a route, MRAI time, implicit withdraws, BGP Hunt, graceful restart, and other topics. Russ White is a network architect, author, and instructor. You can subscribe to the Packet Pushers’ YouTube channel for more videos as they are published. It’s a diverse a mix of content […]
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Hedge 129: Open Source Mentoring
Mentoring is a topic we return to time and again—because it’s one of the most important things we can talk about in terms of building your people skills, your knowledge, and your career. On this episode of the Hedge, Guedis Cardenas joins Tom Ammon and Russ White to talk about open source mentoring. We discuss how this is different than “regular” mentoring, and how it’s the same. Join us as we talk about one of the most important career and personal growth things you can do.
BGP Policy (Part 7)
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—the last post in this series—I’m going to cover do not transit options from the perspective of AS65001 in the following network—
There are cases where an operator does not traffic to be forwarded to them through some specific AS, whether directly connected or multiple hops away. For instance, AS65001 and AS65005 might be operated by companies in politically unfriendly nations. In this case, AS65001 may be legally required to reject traffic that has passed through the nation in which AS65005 is located. There are at least three mechanisms in BGP that are used, in different situations, to enforce this kind of policy.
Do Not Advertise Communities (Provider Specific)
Many providers supply communities a customer can use to block the advertisement of their routes to a particular AS. For instance, if Continue reading
Hedge May Update
A short update on upcoming classes and episodes of the Hedge for May, as well an update on what I’m working on and other places where I’m publishing material.
Live Training: How Routers Really Work
On the 27th of May, I’ll be teaching a three-hour course called How Routers Really Work? From the course description:
This training will peer into the internal components of a router, starting with an explanation of how a router switches packets. This walk through of a switching path, in turn, will be used as a foundation for explaining the components of a router, including the various tables used to build forwarding tables and the software components used to build these tables.
Hedge 128: Network Engineering at College
Have you ever thought about getting a college degree in computer networking? What are the tradeoffs between this and getting a certification? What is the state of network engineering at colleges—what do current students in network engineering programs think about their programs, and what they wish was there that isn’t? Rick Graziani joins Tom Ammon and Russ White in a broad ranging discussion on network engineering and college. Rick teaches network engineering full time in the Valley.
BGP Policy (Part 6)
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’m going to cover local preference via communities, longer prefix match, and conditional advertisement from the perspective of AS65001 in the following network—
Communities an Local Preference
As noted above, MED is the tool “designed into” BGP for selecting an entrance point into the local AS for specific reachable destinations. MED is not very effective, however, because a route’s preference will always win over MED, and because it is not carried between autonomous systems.
Some operators provide an alternate for MED in the form of communities that set a route’s preference within the AS. For instance, assume 100::/64 is geographically closer to the [65001,65003] link than either of the [65001,65002] links, so AS65001 would prefer traffic destined to 100::/64 enter through AS65003.
In this case, AS65001 can advertise 100::/64 with Continue reading
Learning BGP Module 1 Lesson 2: How BGP Builds Loop-Free Paths – Video
Russ White’s BGP series continues with a discussion of building loop-free paths with the Border Gateway Protocol (BGP). Topics include AS (Autonomous System) paths, loop prevention, why loop checks are inbound, and more on IBGP and EBGP. Russ White is a network architect, author, and instructor. You can subscribe to the Packet Pushers’ YouTube channel […]
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Learning BGP Module 1 Lesson 1: Why BGP? – Video
Russ White kicks off a ten-video series on the Border Gateway Protocol (BGP). The series is divided into two modules, with short lessons within each module. This first video covers a brief history of BGP and then gets into the purpose of BPG, reachability vs. a route, Autonomous System (AS) rules, problems that BGP solves, […]
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Is an IP Address Protected Information?
My third article on privacy and networking is up over at Packet Pushers—
Privacy And Networking Part 3: Is An IP Address Protected Information For Privacy?
Does an IP address need to be treated like other Personally Indentifiable Information (PII)?
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BGP Policies (Part 5)
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’m going to cover AS Path Prepending from the perspective of AS65001 in the following network—
Since the length of the AS Path plays a role in choosing which path to use when forwarding traffic towards a given reachable destination, many (if not most) operators prepend the AS Path when advertising routes to a peer. Thus an AS Path of [65001], when advertised towards AS65003, can become [65001,65001] by adding one prepend, [65001,65001,65001] by adding two prepends, etc. Most BGP implementations allow an operator to prepend as many times as they would like, so it is possible to see twenty, thirty, or even higher numbers of prepends.
Note: The usefulness of prepending is generally restricted to around two or three, as the average length of an AS Path in the Continue reading
On Securing BGP
The US Federal Communications Commission recently asked for comments on securing Internet routing. While I worked on the responses offered by various organizations, I also put in my own response as an individual, which I’ve included below.
I am not providing this answer as a representative of any organization, but rather as an individual with long experience in the global standards and operations communities surrounding the Internet, and with long experience in routing and routing security.
I completely agree with the Notice of Inquiry that “networks are essential to the daily functioning of critical infrastructure [yet they] can be vulnerable to attack” due to insecurities in the BGP protocol. While proposed solutions exist that would increase the security of the BGP routing system, only some of these mechanisms are being widely deployed. This response will consider some of the reasons existing proposals are not deployed and suggest some avenues the Commission might explore to aid the community in developing and deploying solutions.
9: Measuring BGP Security.
At this point, I only know of the systems mentioned in the query for measuring BGP routing security incidents. There have been attempts to build other systems, but none of these systems have been Continue reading
Hedge 127: FR Routing Update
The FR Routing project is a fully featured open-source routing stack, including BGP, OSPF, and IS-Is (among others), supported by a community including NVDIA, Orange, VMWare, and many others. On today’s episode of the Hedge, Tom Ammon and Russ White are joined by Donald Sharp, Alistair Woodman, and Quentin Young to update listeners on projects completed and underway in FR Routing.