Russ

Author Archives: Russ

IS-IS Multi Instance: RFC8202

Multi-Instance IS-IS
One of the nice things about IS-IS is the ability to run IPv6 and IPv4 in the same protocol, over a single instance. So long as the two topologies are congruent, deploying v6 as dual stack is very simply. But what if your topologies are not congruent? The figure below illustrates the difference.

In this network, there are two topologies, and each topology has two different set of level 1/level 2 flooding domain boundaries. If topology 1 is running IPv4, and topology 2 is running IPv4, it is difficult to describe such a pair of topologies with “standard” IS-IS. The actual flooding process assumes the flooding domain boundaries are on the same intermediate systems, or that the two topologies are congruent.

One way to solve this problem today is to use IS-IS multi-topology, which allows the IPv6 and IPv4 routing information to be carried in separate TLVs so two different Link State Databases (LSDBs), so each IS can compute a different Shortest Path Tree (SPT), one for IPv4, and another for IPv6. Some engineers might find the concept of multi-topology confusing, and it seems like it might be overkill for other use cases. For instance, perhaps you do Continue reading

Forthcoming: Computer Networking Problems and Solutions

The new book should be out around the 29th of December, give or take a few days. For readers interested in what Ethan and I (and Ryan, and Pete Welcher, and Jordan Martin, and Nick Russo, and… the entire list is in the front matter), the general idea is essentially grounded in RFC1925, rule 11. There is really only a moderately sized set of problems computer system needs to solve in order to carry data from one application to another. For instance, in order to transport data across a network, you need to somehow format the data so everyone can agree on how to write and read it, ensure the data is carried without errors, ensure neither the sender nor the receiver overrun or underrun one another, and find some way to allow multiple applications (hosts, etc.), to talk over the same media. These four problems have somewhat proper names, of course: marshaling, which involves dictionaries and grammars; error control; flow control; and multiplexing. So the first step in understanding network engineering is to figure out what the problems are, and how to break them apart.

Once you understand the problems, then you can start thinking about solutions. As Continue reading

Adminstravia 20171009

Where’s Russ?

This is my second week of PhD seminars this fall—the only time in this program I intend to take two seminars back to back. One of the two was, in fact, very deep philosophy, so I was pretty taxed trying to pull the material together.

At the same time, the book has passed through technical review, and is now in author review. I hope it soon be in proofs. The combination of these two things, the book and the PhD work, along with multiple other things, is what caused me to call a pause in blogging for these two weeks. The date to watch is the 29th of December. It might be released earlier, but it is hard to tell right now. I will do a post a little later this week describing the book for those who are interested.

Tonight (Monday) I will be recording a new Network Collective show on the Intermediate System to Intermediate System (IS-IS) protocol, and we have a long list of History of Networking guests to bring on. The history material has turned out to be absolutely fascinating; I am thankful we have the connections available, and the recording venue, and someone Continue reading

The History of Networking: Tony Li on BGP

The Network Collective has another History of Networking up; this time we’re chatting with Tony Li about the History of BGP. Tony was not involved in the original origins of BGP (the famous napkin, a picture of which you can see in this book), but he did start working on it in around 1996, the year I joined Cisco as a lowly TAC engineer.

The post The History of Networking: Tony Li on BGP appeared first on rule 11 reader.

Light/No Blogging this Week

I’m trying to get through the final bits of this new book (which should publish at the end of December, from what I understand), and the work required for a pair of PhD seminars (a bit over 50 pages of writing). I probably won’t post anything this week so I can get caught up a little, and I might not be posting heavily next week.

I’ll be at SDxE in Austin Tuesday and Wednesday, if anyone wants to find me there.

The post Light/No Blogging this Week appeared first on rule 11 reader.

1 76 77 78 79 80 162