Juan Golbez's Networking Certification Blog: CCDA Notes: Network Design Methodology

Network Design Basics

Business forces that affect decisions for enterprise network include:

Return on Investment - Cost savings or increased productivity
Regulation - Meet industry regulations (HIPAA, DOD, etc)
Competitiveness - Technology needs to make business more competitive

Technology forces which affect decisions for network include:

Removal of borders - Network resources must be accessible from more places than before, like branch offices, teleworkers, mobile devices and business partners
Virtualization - Reduction in hardware/power/software needs as well as space considerations by virtualizing many services
Growth of Applications - As applications become larger and more demanding of resources, network resources are required to adapt

IT optimization areas can be split into three groups:

Data Centers
Networks
Applications

Three architectures provide for optimization within each group and inter-group as well:

Borderless Networks Architecture
Collaboration Architecture
Data Center/Virtualization Architecture

Borderless Networks Architecture

Policy/Control: Policies applied across all users/devices
Network Services: Resiliency and control
User Services: Services include performance, mobility, security
Connection Management: Delivers secure access anytime/anywhere

Collaboration Architecture

Communication/Collaboration Apps: conferencing, messaging, mobile apps, IP comms, social software
Collaboration Services: Services that supports the collaboration apps: policy/security management, contact management, session management, location, presence, client framework
Infrastructure: Allows collaboration anytime/anywhere on any device. This layer includes virtual machines, the network and storage.

Data Center/Virtualization

Data center/virtualization architecture is built on Cisco Data Center 3.0, which has a set of virtualization technologies/services that bring network/storage/computing/virtual platforms together

PPDIOO: The Cisco Lifecycle

Lowers cost of ownership by validating tech requirements, planning for infrastructure changes/resource requirements
Increases network availability through good network design
Improves business by establishing technology strategies/business requirements
Speeds access to applications through improved availability, reliability, scalability, security and performance

Lowering Cost Of Ownership:

Identify/validate tech requirements
Plan for infrastructure changes/resource requirements
Develop network design to mesh with business/technology needs
Improve network efficiency
Reduce operating expense by streamlining processes/tools

Increasing Network Availability

Assess the network and its ability to support design
Choose correct hardware/software and keep current
Create good network design and verify operation
Staging/testing before implementation
Improving engineer skills
Proactively monitor network for issues
Proactively identify security issues and remediation plan

Improve Business

Establish business/technology requirements
Ready sites to support design
Integrate technical needs and business needs into design
Expertly install system components
Continue to enhance performance after implementation

Speed Application Access

Improve operational readiness for current/planned network technology/service
Increase availability, capacity and performance of network
Manage/resolve issues affecting system, keep software current

PPDIOO Phases:

Prepare Phase

Establish requirements, develop network strategy, propose high-level network architecture

Plan Phase

Identify requirements by assessing current network and perform gap analysis between current/proposed

Design Phase

Provide high availability, scalability, reliability, security and performance in design

Implement Phase

Install/configure new equipment

Operate Phase

Analyze daily network operations and operational health

Optimize Phase

Proactive network management, propose modifications to design as needed

Design Methodology

1. Identify Customer Requirements

Identify network apps/services

Planned Applications
Concrete applications
Importance to business
Other Info/Comments

Define goals of organization, such as:

Increase competitiveness in field
Reduce costs
Improve customer relations (Better support, new services)

Identify possible constraints

Budget
Timeframe
Limited personnel
Policy limitation

Define technical goals

Improve network speed
Decrease failures
Simply management of network
Improve security
Improve scalability
Improve reliability
Tech refresh

Identify possible technical constraints

Legacy applications
Bandwidth allocation may not meet application needs
Existing infrastructure
Legacy equipment

2. Assess Current Network

Identify/Gather existing documentation about organization/network
Audit network to determine details of network
Analyze traffic for applications/protocols used

Identify/Gather Documentation

Include site designs, contacts, hours of operation/access and addresses, where network equipment is located and what infrastructure exists. Also gather info about LAN/WAN wiring and contact info for WAN providers. Especially look for IP/Vlan schema and IP allocation information, as well as network applications and servers in use

Network Audit

Use existing documentation, existing network management tools, and new tools to covers gaps in analysis. Audit should provide following:

List/naming convention for network devices
Hardware info for network devices
Software versions for network info as well as supported applications
Network configs
LAN/WAN speeds of vital links
Auditing tool output
WAN technology/provider info

Manual Analysis: review device configs, manually use show commands and collect output

show tech-support
show version
show log
show running-config
show process cpu
show process memory
show interface

Network Analysis Tools: Inspects packets for data flow/traffic analysis

Netform DesignXpert Enterprise: Desktop tool to discover/design/quote/propose solutions
CNS NetFlow Collector: Cisco hardware that collects network info
Cisco Embeded Resource Manager: Monitors IOS processes/utilization
Third-party tools: SolarWinds, NeTMRI, etc

After audit, check to make sure the following is true before moving on with design:

Network segments should be switched, not using hubs
WAN links are not saturated (70% or higher)
Response time acceptable (Generally 2ms on LAN, less than 100ms on WAN)
No segemts have more than 20% multi/broadcast traffic
No segment has more than 1 CRC per MB of data
Less than .1% of packets collide on ethernet segments
Network devices shouldn't have 75% CPU utilization for 5 min or over
Interface output drops shouldn't exceed 100 per hour
Interface input queue drops shouldn't exceed 50 per hour
Interface buffer misses shouldn't exceed 25 per hour
Interface ignored packets shouldn't exceed 10 per hour
QoS should be enabled for prioritization

3. Designing Network and Solutions

Top-Down

Start from top layer of OSI model and work downward, adapt infrastructure for application requirements. Analyze application requirements for top layers (Application, Preentation, Session) and develop infrastructure to support it for bottom layers (Transport, Network, Data Link, Physical)

Benefit:

Design meets current/future needs and organization requirement

Drawback:

Far more time-consuming

Bottom-Up

Start from bottom of OSI model and build upward. Utilize best practice and previous implementation experience to design network without taking specific application requirements into account

Benefit:

Allows for quick solution, based on best practice/previous experience