the art of network...

The Art of Network Architecture BRKRST-3114

Russ White

Scott Morris

Denise Donohue

© 2013 Cisco and/or its affiliates. All rights reserved. BRKRST-3114 Cisco Public

The Art of Network Architecture

Intersecting It

Driving It

Designing It

Selling It

3


The Intersection of Business and Technology

Why Let Business Drive Technology Decisions?

– Projects get funded

– Business succeeds

– You get a raise???

How Does Technology Drive Business Decisions?

– Technology Impact is Part of Design Discussion

– Future Growth Constraints

– Future Functional Constraints

4


Determining Business Requirements

Learn the Business Environment

– The Big Picture Information to gather

How to gather it

– The Competitive Environment Information to gather

How to gather it

How Does the Network Serve the Business

– Technologies and Applications in Use

– Network Evaluation

How Does the Network Serve its Customers

– Internal users

– External users

– Guest users

5


Learn the Business Environment The Big Picture

6

State of the Business

– Growing/shrinking/static

– Future plans

– Leadership

– Customers

Challenges

– And how can technology help?

Financial Health

– And how can technology help?

Company Website

Annual Report

Press About the Company

Talking to People

SWOT Analysis


Business Environment Example

Cisco Overview

Cisco Financial Report

Cisco Annual Report – Stockholder Letter

Cisco Annual Report – Full Report

Strengths Weaknesses Opportunities Threats

7

http://newsroom.cisco.com/overview

http://newsroom.cisco.com/press-release-content?type=webcontent&articleId=1136722

http://www.cisco.com/web/about/ac49/ac20/ac19/ar2012/letter/index.html

http://www.cisco.com/assets/cdc_content_elements/docs/annualreports/ar2012.pdf


Learn the Business Environment The Competitive Environment

8

State of the Market

– Lively/growing vs. stagnating

– Niche or broad?

Competitive Pressures

– How many competitors?

– How are they doing?

Competitors’ Use of Technology

Annual Report

Competitor’s Website

Press About Your Competitors

Talking to People


Competitive Environment Example

9


How Does the Network Serve the Business?

10

Does it hold you back…

Or take you where you

want to go?

http://www.google.com/url?sa=i&rct=j&q=picture+pulling+uphill&source=images&cd=&cad=rja&docid=yM7c2CCQMy0GqM&tbnid=TVgm6amr_WA-eM:&ved=0CAUQjRw&url=http://duf67.wordpress.com/tag/push-up-pull-up-pyramid-superset/&ei=hXFjUen2HeHA4AOk9YDACg&bvm=bv.44770516,d.dmg&psig=AFQjCNGyssHxe10QVluPiGWb14DGqI7Kdg&ust=1365557695800197


How Does the Network Serve the Business?

Technologies in Use

Applications in Use

Network Evaluation

– LAN

– WAN

– Security

– Flexibility

Where does the network…

– Support and improve business processes

– Hinder them?

11


How Does the Network Serve Its Customers?

Find out who are the network’s customers, and how they use its resources

– Internal users

– External users

– Guest users

12


Where Are There Gaps?

And How Can Technology Help?

– Update technologies to Improve processes

Reduce cost

Increase efficiency

– Add capabilities, such as VOIP/Video/Presence

Mobility (BYOD/CYOD)

– Redesign part (or all) of the network Equipment refresh is a good time for this

Technology or capability additions often require it

13

Drive It


Business Drivers

Capabilities

Continuity

Cost

Change

15


Capabilities as a Business Driver

Changing Expectations Changing Capability Needs Network Changes

Customer and employee expectations

Competitive expectations

16


Designing New Capabilities

How are changes in expectations and competition affecting the business?

How is ability to keep pace affecting business finances?

What mix of technologies will help them keep pace?

17


Designing New Capabilities

Changes required to business processes

Changes required to the network

Changes required to enterprise applications

User training required

18


Continuity as a Business Driver

Most businesses lose $$ if the network is unavailable

– Highly variable, dependant on the location within the network

– For instance, within a bank’s network: ATM machines can be down for days

without impact

Branches can be down for ten or fifteen minutes, but after that, losses mount quickly

On the trading floor, over $1 million lost in trading fees alone per minute (or second) of downtime

– Many large networks are now 24/7

19


Continuity

The trick question is: When is a network down?

This often isn’t easy to measure or understand

– Is a single application failing enough to call the entire network “down?”

– Is a single section of the network failing enough to call the network “down?”

Business requirements set the standards

– Critical applications

– Critical sites

– Critical portions of the network

20


Designing for Continuity

Design for failure

– Redundancy: links, servers, spares, etc.

– Hot or cold stand by

– Remote working

Plan for failure

– Detection

– Troubleshooting

– Repair

Test your plan

21


Designing for Continuity Worst Case Analysis

??

23


Cost as a Business Driver

Most companies strive to reduce costs

– Unfortunately, cost often compromises the other design goals

– That can introduce risk

Two goals

– Managing costs

– Predicting costs

Two dimensions

– Operational Expense (OPEX)

– Capital Expense (CAPEX)

25


Managing Costs

Modularity

OPEX

• Reduces configuration complexity on individual devices

• Reduces build-out time

• Limits scope of equipment validation

• Reduces MTTR (keeping the network in service)

CAPEX

• Limits scope of equipment requirements

Management

OPEX

• Automates configuration management

• Worst case analysis provides scoping and prioritization

Security

OPEX

• Increases overall network service level

• Protects information and services

26


Predicting Costs

Modularity

OPEX

• Costs can be managed at the module, rather than equipment or network level

CAPEX

• Modules can be treated as a group for equipment upgrades, etc.

Management

• Provides analysis for predicting network needs over a longer period of time

• Externally facing OODA loop provides an environment of best practices and trends

on which to found modifications in the network

• Constant evaluation of the network in terms of business goals provides a “look

ahead” capability for predicting new problems to be solved and challenges to be met

• Worst case analysis provides a realistic estimate of what’s needed to meet real

world challenges

Security • Externally facing OODA loop picks up and anticipates new threats to the network

which need to be planned for and met

27


Change as a Business Driver

Business Growth

– Organic business growth

– Scope creep

– Mergers and acquisitions

Business Shrinkage

– Organic business decline

– Spin-offs

Changing Expectations

– Customers

– Employees

Modularity

– Set fixed limits on module sizes within a well defined plan

– Limit the size of each failure domain

– Keep configurations repeatable for faster rollouts and modifications

Management

– Accurate baseline and change measurement and analysis

– Project network needs into the future in a reliable way

28


Managing Change An Example

Organic growth isn’t always visible

– Start out with 500 remote locations in a hub-and-spoke network

– Add a new location every other day for a year

– 675 remotes after one year

This will probably work with no additional effort....

– It appears the network is handling the growth just fine

29



After a single link failure, however, the network doesn’t ever converge…

– The network administrators chase the problem to the hub router

– A bigger hub router is purchased, and readied for installation

Wait! This is really a design problem

– If the organic growth had been measured and planned for, the network wouldn’t have failed

30



How would modular design help here?

If the size of the hub-and-spoke module were intentionally limited…

– Based on testing, best practices, and documentation…

– Once the topology reached a predetermined size, an intentional decision could be made about what to do Build a second topology?

Increase the size of the hub router?

31


Managing Change Mergers and Acquisitions

Mergers and Acquisitions

– Often involves two or more routing protocols

– Often involves intense pressure to merge services quickly

– Often involves two completely different design philosophies, neither of which have been deployed correctly

32

Design It


Design Toolbox

Modularity

Resilience

Management

Security

34

© 2013 Cisco and/or its affiliates. All rights reserved. BRKRST-3114 Cisco Public 35

Modularity Repeatable Configurations

In this network, there are two hub and spoke topologies

– One uses a point-to-multipoint layer 2 technology the other point-to-point circuits

– One uses EIGRP, the other OSPF

This network is more difficult than it needs to be to manage

Each topology should be design and configured using the same tools where possible

OSPF

EIGRP


Modularity Assigning Functionality

Types of functionality

– Policy

– Filtering/aggregating reachability information

– Forwarding traffic over long(er) geographic distances

Modularity divides these pieces up into manageable chunks

– Much like we divide a piece of software into multiple modules, and connect them through an API

Packet Filtering

Aggregation


Modularity Fault Isolation

Where do we want to isolate faults?

– The control plane must calculate for each path between Routers A and B

If we split the network into two fault domains....

– Devices within each fault domain only compute paths within their fault domain

– This drags the network closer to the MTTR/MTBF balance point

Divide complexity from complexity

MTTR

MTBF

Incre

asin

g P

ara

llelis

m

A

B


Modularity How Do We Modularize?

Hide Information

Aggregate or filter control plane state

– Create a hierarchical design between the various network modules

Create multiple overlapping control planes

– BGP/IGP

– Virtualization (covered in more detail later)

Aggregation

BGP Overlay Overlay Topology


Modularity The Tradeoff

If modularity is good, why not build really small modules?

Hiding information introduces suboptimal traffic flow

– Suboptimal routing

– Stretch

A

2001:DB8:9168:1::/64 2001:DB8:9168:2::/64

Before

Aggregation

Aggregate to

2001:DB8:9168::/48


Resilience Redundancy

In principle, redundancy is easy

– Any system with more parallel paths through the system will fail less often

The problem is a network isn’t really a single system

– It’s a group of interacting systems

Adding paths is a tradeoff

– Increases MTBF in one layer

– Increases MTTR in another layer

The key is to balance MTBF and MTTR

MTTR

MTBF

Incre

asin

g P

ara

llelis

m


Resilience Redundancy

In the real world, the point where MTTR and MTBF meet is between two and three parallel structures

– One is almost always too little if you want resiliency

– Four is almost always too many

– And five is right out

This applies at all levels of redundancy

– Circuit/link

– Device

– Module

Core

Online

Data

Center

Backup

Data

Center

Redundant Modules

Redundant

Equipment

Redundant

Links


Resilience Fast Convergence

Three steps

– Detect

– Notify Link State Flooding

– Tuned flooding timers

– Reduce flooding domain

Distance Vector – Reduce update scope (query range)

– Calculate

– Switch

Make each step as fast as possible

– But not at the cost of network stability

Detect

Notify Calculate & Switch

42


Resilience Fast Reroute

Detect

Notify

– Link State Flooding Tuned flooding timers

Reduce flooding domain

– Distance Vector Reduce update scope (query range)

Calculate

Switch

Detect

Switch

Fast reroute eliminates these steps

Notify

Calculate

43


The OODA Loop Management and Security Background

Management

– A “slower” loop

– Reacts to organic threats Changes in the business, technology,

etc.

Business drivers

Security

– A “faster” loop

– Reacts to inorganic threats Attacks designed to deny service, obtain

access, discover information, etc.

44


Management

45

Network Documentation

Baseline Performance

Baseline Utilization

Change Analysis

Business Ecosystem

Business Processes

Technology Ecosystem

Design Modification

Replace Technology

Inject Technology

Add Services

Policy Modification

Best Fit Analysis

Root Cause Analysis

Business Trends

Best Practices

Case Studies

Shape to Models

Technology Trends

Business Trends

Best Practices

Case Studies

Change Management

Worst Case Analysis


Management Observe — What You Should Document

Topology

– Layer 2 and 3

Policy

– Where its applied

– The intent behind the policy

Modular Boundaries

– Where they are

– The intent behind the boundary

Per link utilization

– Time of day, seasonal, etc.

Normal failure rates


Management Orient — What You Should Know

Best practices

Network architecture models

Business models


Management Decide — What You Should Plan

There is no such thing as a free lunch

– Remember the tradeoffs

– Document the tradeoffs you’ve made

Follow best practices or not?


Management Act — What You Should Do

Make a plan for change

Know how to back out

– Or what your alternatives are in the case of failure

Worst case analysis


Security

50

Network Documentation

Baseline Performance

Baseline Utilization

Anomaly Detection

Design Modification

Replace Technology

Inject Technology

Add Services

Modify Policy

Best Fit Analysis

Root Cause Analysis

Security Trends

Best Practices

Case Studies

Shape to Models

Technology Trends

Best Practices

Change Management

Risks of Failure


Security Crunchy on the Outside…

A solid DMZ was once the best you could do in security design for your network…

Crunchy on the outside, chewy in the middle


Security Crunchy Through and Through

Every device has security

Automatic (fast) feedback loops

Crunchy through and through

IDS


Security Comparison of OODA Loops

Crunchy on the Outside

– Observe One of my machines has been zombied

– Orient What is the address of the master host?

On what port did they get through?

– Decide Where do I implement new filters to stop

this from happening in the future?

What is the best way to block this specific attack?

– Act Wait for a change window

Implement the new filters

Test

Crunchy Through and Through

– Observe Automated anomaly detection

Data analytics on network traffic

– Orient What type of attack?

From where?

– Decide Do I toss this traffic, scrub it, honeypot

it, or… ??

Do I need to change my edge policies?

– Act Allow the automated process to handle

Modify edge policies as needed

Selling It


“Selling” Your Design

Why should they spend this money / Implement this change?

How do you convey the need?

56

http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=NZFKM_jOdEzyIM&tbnid=Fa0KXegev9VJOM:&ved=0CAgQjRwwAA&url=http://fishcooking.about.com/od/oysterrecipes/r/angels_horsebk.htm&ei=VjVrUZevHojk4APc4oFQ&psig=AFQjCNGnEZkArhvxXjRzOI6i0MGR9jR91g&ust=1366066902555317


Tools for “Selling” Your Design

Justify Your Design: Create a Business Case

– How does it benefit the company?

– Risks and costs Include the risk and cost of doing nothing

– Tools – ROI analysis

– Worst-case analysis

Explain Your Design

– High level, but be prepared for low level details

57


Tools for “Selling” Your Design Typical Components of a Business Case

Executive Summary

Problem Assessment

Solution Information

– Overview

– Options

– Recommendation

Financial Analysis

– Costs

– Benefits

Assumptions and Risks

Timeline

Next Steps

58


Tools for “Selling” Your Design

ROI Illustrations

59


Summary

The “Art” of Network Architecture lies in the intersection between business needs and good technology

Network architects must be more than technical – they must have a foot in the business world also

Use your network design toolbox:

– Modularity

– Resilience

– Management

– Security

Good design is not enough, you must be able to

– Understand and design to the underlying business drivers

– Present the business as well as technical advantages of your design

60

‟You can't create a good design by adding Band-Aids to a poor design.”

• Terry Slattery

• CCIE #1026


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