Reliable Internet Connectivity with BGP

Robert A. Van Valzah


Just What the Heck am I About to Read?

This is an unfinished book, but my hope is that you'll still find something of value here. It's over 100 pages when printed, so I think it's likely that you'll find something of interest if your goal is to learn more about reliable Internet connectivity. (Although the book is unfinished, this web site should be consistent. I.e., you shouldn't find broken links and the like.)

The outline is complete and you can see it in the Table of Contents below. Much of the Preface is "real," but it also contains material intended only for editors to consider. The architecture part contains two partial chapters. They still contain some "fleshless outline," but I've tried to nearly complete the Policies for Reliability chapter.

The other parts still exist largely in outline form. The appearance of text in

program listing font
is a sign of bones in need of flesh.

I started writing this book because I noticed that I was hearing a lot of the same questions over and over again. I get a kick out of helping people use computers and networks and I thought writing a book might allow me to help more people than I could ever help one-on-one. I'd never written a book before and became aware of tools like DocBook and Xfig that would allow me to prepare the material so it could be presented as a book or website. Starting on a book seemed like a good way to organize my thoughts in a consistent way that'd be useful to others while allowing me a chance to gain familiarity with these tools.

This was a "spare time" project for me, so I knew it'd get time only as long as it was more fun than work. I worked on it fairly hard in late 1999, completing about 100 pages before Thanksgiving with a few hundred hours worked. (About 1/2 of those pages are mostly complete and about 1/2 are still in outline form.) There are also 28 figures illustrating reliability connectivity issues.

I considered entering into a contract to complete the book with a technical publisher, but rejected the idea because I thought it'd likely tip the balance more toward work than fun. My pool of spare time was empty for the first 8 months of 2000 so the project sat in mothballs. I'd occasinally give copies of the material to clients who seemed to benefit from it. Then in September, 2000, I decided to make the material available as a web site under my copyright so that it at least stood a chance of helping a wider audience. (It certainly wasn't doing anybody any good just spinning around on my hard drive getting dizzy.) If it helps you (or leads you astray), please let me know. If I have time and there seems to be interest in it, I'll continue fleshing out the parts that're fun to write or are most often requested. At worst, it can just rest here as search engine fodder for the unwitting web spider or surfer.

One final warning: most of the links below in the table of contents will lead you to pages that're nothing but outline. See the preface or the policy chapter for something closer to finished material. The index might also be a place to start if you're hunting for something in particular.

Table of Contents
Preface
What is this Book Good For?
What this Book is Not Good For
Marketing
The Market for this Book
Market size
Competition
Length
What Lies Ahead?
Organization Rationale
Cross Referencing Consequences and Organizations Rejected
I. Introduction, Concepts, and Terminology
1. Introduction to Reliable Internet Connections
Issues in Reliable Internet Connectivity
How Hard is this Going to Be?
What is the Role of BGP in Reliable Internet Connectivity
A Crash Course in How Packets are Routed
Where Does Reliability Come From?
2. BGP Myths
You Need a $100,000 Router with Gobs of Memory to Run BGP
One Big Router is Better than Two Small Ones
Asymmetric Paths Cause Problems
Load Sharing with BGP Requires a Lot of Tweaking
Other Myths from Mike's Mindspring Contacts
BGP will Avoid Congestion
You always have to apply to a registry (e.g. ARIN) and receive an ASN before you can run BGP.
You have to run BGP on all your routers.
"Floating" Static Routes Detect All Link Failures
3. Concepts and Terminology
Autonomous Systems
Transit
Gateway Protocols
Entrances and Exits
Routes or "Prefixes"
BGP Decision Algorithm
BGP Communities
Perimeter Network ("DMZ")
II. Roadmap for Reliability
4. Coordination with Other Parties
Why Are So Many Parties Involved?
Who are They and What Roles do they Play?
Why they Might Depend on Each Other?
5. Steps to Reliability
Establish List of Routes Your AS will Originate
Arrange Address Delegation
Establish an Addressing Plan
Make Network Architecture Decisions
Order Routers and Lines
Make Policy Decisions
Establish Transition Plan
Configure Routers
Turn Up BGP
Testing
Configure Ancillary Services
III. Network Architecture and Policies: Decisions and Tradeoffs
6. Architectures for Reliability
Introduction
How Will Address Space be Assigned to Networks?
How Many Sites Should Have Internet Connections?
How Many Internet Connections are Required?
How Many ISPs are Required?
How Many Border Routers are Required?
What Route Subset Will You Request on Each Connection?
Private Networks
Border LAN Architecture
How Do Firewalls and NAT Interact with Reliable Internet Connectivity?
Budgeting: What Will Alternative Architectures Cost?
Architectural Transitions
7. Policies for Reliability
Policy and Load Balancing
The Questions of Policy
Asymmetric Paths
Influencing Entrance Selection and Controlling Exit Selection
Exit Selection Policies
Exit Selection Scenario with a Single ISP
Exit Selection Scenario with Multiple ISPs
Destination Independent Exit Policies
Destination Dependent Exit Policies
Influencing Entrance Selection
Originating Routes
Border Router Selection
Choosing an IGP
Choosing an IOS Version
Policy Transition Paths
IV. Router Configuration
8. Cisco Router Configuration for BGP
Static Default Route
Floating Static Default Route
Loopback Interfaces
BGP Router Process
Internal Neighbors
External Neighbor
Synchronization
Aggregation
Auto Summary
Static Route Origination
Semi-Dynamic Route Origination
Dynamic Route Origination
Pull Up Routes
Preventing Transit
Filtering Routes Originated
Filtering Routes Accepted
Setting MEDs
HSRP (Hot Standby Router Protocol)
Originating a BGP Default Route
9. Scenario: Adding Second Connection to your Existing ISP from Another Site
10. Scenario: Adding a Connection to a Second ISP from a Single Site
11. Scenario: Connections from Two Sites with a Firewall and Private Network
V. Big BGP
12. Reducing IBGP Complexity
Route Reflectors
AS Confederations
13. BGP Features for Large Networks
MD5 Authentication
Flap Damping
BGP Communities
VI. Transition tips, monitoring, testing and troubleshooting
14. Transition Tips
Telnet to an Interface in Each AS
15. Monitoring Tools and Techniques
16. Testing and Troubleshooting Tools and Techniques
17. Miscellaneous Tips
Index
Colophon

Copyright © 1999-2000 by Robert A. Van Valzah