Reliable InternetConnectivity with BGP

Robert A. VanValzah


Introduction

This is an unfinished book, but my hope is that you'llstill find something of value here. It's over 100 pages whenprinted, so I think it's likely that you'll find something ofinterest if your goal is to learn more about reliableInternet connectivity. (Although the book is unfinished, thisweb 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 Tableof Contents below. Much of the Preface is "real," but it also contains material intendedonly for editors to consider. The architecture part contains two partial chapters. Theystill contain some "fleshless outline," but I've tried tonearly complete the Policies forReliability chapter.

The other parts still exist largely in outline form. Theappearance 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 washearing a lot of the same questions over and over again. Iget a kick out of helping people use computers and networksand I thought writing a book might allow me to help morepeople than I could ever help one-on-one. I'd never written abook before and became aware of tools like DocBook and Xfig that wouldallow me to prepare the material so it could be presented asa book or website. Starting on a book seemed like a good wayto organize my thoughts in a consistent way that'd be usefulto others while allowing me a chance to gain familiarity withthese tools.

This was a "spare time" project for me, so I knew it'dget time only as long as it was more fun than work. I workedon it fairly hard in late 1999, completing about 100 pagesbefore Thanksgiving with a few hundred hours worked. (About1/2 of those pages are mostly complete and about 1/2 arestill in outline form.) There are also 28 figuresillustrating reliability connectivity issues.

I considered entering into a contract to complete thebook with a technical publisher, but rejected the ideabecause I thought it'd likely tip the balance more towardwork than fun. My pool of spare time was empty for the first8 months of 2000 so the project sat in mothballs. I'doccasinally give copies of the material to clients who seemedto benefit from it. Then in September, 2000, I decided tomake the material available as a web site under my copyrightso that it at least stood a chance of helping a wideraudience. (It certainly wasn't doing anybody any good justspinning around on my hard drive getting dizzy.) I have no plans to write more, so it sits here as search enginefodder for the unwitting web spider or surfer.

One final warning: most of thelinks below in the table of contents will lead you to pagesthat're nothing but outline. See the preface or the policychapter for something closer to finished material. The index might also be a place tostart if you're hunting for something in particular.

Table of Contents
Preface
What isthis Book Good For?
What this Bookis Not Good For
Marketing
TheMarket for this Book
Marketsize
Competition
Length
What LiesAhead?
OrganizationRationale
Cross ReferencingConsequences and Organizations Rejected
I. Introduction, Concepts, andTerminology
1. Introduction toReliable Internet Connections
Issues in Reliable Internet Connectivity
How Hard isthis Going to Be?
What is theRole of BGP in Reliable InternetConnectivity
A CrashCourse in How Packets are Routed
WhereDoes Reliability Come From?
2. BGP Myths
YouNeed a $100,000 Router with Gobs of Memory to RunBGP
One BigRouter is Better than Two Small Ones
AsymmetricPaths Cause Problems
Load Sharingwith BGP Requires a Lot of Tweaking
OtherMyths from Mike's Mindspring Contacts
BGP willAvoid Congestion
You always haveto apply to a registry (e.g. ARIN) and receive anASN before you can run BGP.
You haveto run BGP on all your routers.
"Floating"Static Routes Detect All Link Failures
3. Concepts andTerminology
Autonomous Systems
Transit
GatewayProtocols
Entrances andExits
Routes or"Prefixes"
BGPDecision Algorithm
BGPCommunities
PerimeterNetwork ("DMZ")
II. Roadmap forReliability
4. Coordination withOther Parties
Why Are So Many Parties Involved?
Who are Theyand What Roles do they Play?
Why theyMight Depend on Each Other?
5. Steps toReliability
EstablishList of Routes Your AS will Originate
ArrangeAddress Delegation
Establish an Addressing Plan
MakeNetwork Architecture Decisions
OrderRouters and Lines
Make PolicyDecisions
Establish Transition Plan
Configure Routers
Turn UpBGP
Testing
Configure Ancillary Services
III. Network Architecture andPolicies: Decisions and Tradeoffs
6. Architectures forReliability
Introduction
How WillAddress Space be Assigned to Networks?
How Many SitesShould Have Internet Connections?
How ManyInternet Connections are Required?
How Many ISPs areRequired?
How ManyBorder Routers are Required?
What RouteSubset Will You Request on EachConnection?
PrivateNetworks
Border LANArchitecture
How DoFirewalls and NAT Interact with Reliable InternetConnectivity?
Budgeting: WhatWill Alternative Architectures Cost?
Architectural Transitions
7. Policies forReliability
Policyand Load Balancing
TheQuestions of Policy
AsymmetricPaths
Influencing Entrance Selection and ControllingExit Selection
Exit SelectionPolicies
ExitSelection Scenario with a Single ISP
ExitSelection Scenario with Multiple ISPs
Destination Independent Exit Policies
Destination Dependent Exit Policies
InfluencingEntrance Selection
OriginatingRoutes
Border RouterSelection
Choosing anIGP
Choosing an IOSVersion
PolicyTransition Paths
IV. RouterConfiguration
8. Cisco RouterConfiguration for BGP
Static Default Route
FloatingStatic Default Route
LoopbackInterfaces
BGP RouterProcess
InternalNeighbors
ExternalNeighbor
Synchronization
Aggregation
AutoSummary
StaticRoute Origination
Semi-Dynamic Route Origination
DynamicRoute Origination
Pull UpRoutes
Preventing Transit
FilteringRoutes Originated
FilteringRoutes Accepted
SettingMEDs
HSRP (HotStandby Router Protocol)
Originating a BGP Default Route
9. Scenario:Adding Second Connection to your Existing ISP fromAnother Site
10. Scenario:Adding a Connection to a Second ISP from a SingleSite
11. Scenario:Connections from Two Sites with a Firewall andPrivate Network
V. Big BGP
12. Reducing IBGPComplexity
RouteReflectors
ASConfederations
13. BGP Features forLarge Networks
MD5Authentication
FlapDamping
BGPCommunities
VI. Transition tips, monitoring,testing and troubleshooting
14. TransitionTips
Telnetto an Interface in Each AS
15. MonitoringTools and Techniques
16. Testingand Troubleshooting Tools and Techniques
17. MiscellaneousTips
Index
Colophon

Copyright © 1999-2000 by RobertA. Van Valzah