Network Design

1
Network Design

• A System Approach to Network design
• Traditional network design
• The analysis and design process
• Network services and services-based networking
• Systems and network services
• Characterizing services
• Concluding remarks

2
Traditional network design

• Network design is an art
• Evaluate and choose network technologies
• Knowledge about how
• Technologies
• Services and
• Protocols work
• Experience about what works and what doesnt

3
Traditional network design

• Traditionally
• Developing a set of general rules
• 80/20
• Bridge when you can route when you must
• Capacity planning
• Throw bandwidth at the problem

4
From traditional network design to new era

• Too many choices
• Interconnection strategies
• Routing protocols
• Topologies
• Technologies
• Optimize delay in the network
• Reliability
• Not just redundant paths/resilient routing
  protocols

5
The Analysis and Design Process

• Combination of several factors
• Design goals
• minimizing cost
• maximizing performance
• Trade offs
• Cost versus performance
• Simplicity versus function
• Balance between architecture and function
• Hierarchy
• Redundancy (trade-off between these too)

6
The Analysis and Design Process

• Analysis
• Requirements analysis
• Flow analysis
• Design
• Logical design
• Physical design
• Addressing and routing
• Implementation
• Management

7
Components of the Analysis and Design Process
8
The Analysis and Design Process

• Identify the services and performance levels that
  your design must satisfy
• Choose the best network technologies and services
  to meet your design goals

9
Network services and Services-based Networking

• Levels of performance
• Round-trip delay
• Bandwidth
• Reliability
• Availability
• Functions
• Security levels
• User groups for virtual networks

10
Services-based networking
11
Systems and Network Services

• Systems
• Set of components that work together to support
  or provide
• connectivity,
• communications, and
• network services to users
• Generic components
• Users
• Applications
• Hosts and
• Networks

12
Systems and Network Services

• Users
• Network and computer support
• Developers
• customers
• Applications
• Specific to a particular user/customer
• Generic to a customer base
• Generic to the entire network
• Hosts
• Subdivided to show the OS, device drivers, API
• Networks

13
Network Services

• Service descriptions for IP and ATM networks
  developed by
• The Internet Engineering Task Force (IETF)
• The ATM Forum
• Defined as
• Levels of performance
• Capacity
• Delay
• reliability
• Function
• Security, accounting, billing, scheduling and
  management

14
Network Services

• Service characteristics
• The service offering service request
• Important in configuring services in network
  elements (routers, switches, host OSs etc.)
• Used to configure, monitor, and verify services
  in the network

15
Network Services

• Service levels
• Service requirements or characteristics are
  grouped together to describe service levels for
  the network
• You can configure, measure and verify a service
  level instead of a number of service
  characteristics
• Also useful in accounting and billing

16
Network Services

• Describing service levels
• Committed information rates (CIRs)
• Classes of service (CoS)
• Types of service (ToS)
• Qualities of Service (QoS)

17
Characterizing Services

• Service requests
• Best effort
• Specified (deterministic and guaranteed) services
• Service offerings
• To meet requests
• ATM QoS
• Switched Multimegabit data service (SMDS) CoS
• Frame relay CIR

18
Characterizing Services

• Service performance requirements
• Reliability
• Capacity
• Delay

19
Characterizing Services

• Reliability
• A measure of the systems ability to provide
  deterministic and accurate delivery of
  information
• Completion time (e.g. 15 seconds for a sales
  transaction, round trip delay lt 40 ms for
  real-time banking transaction)
• Accuracy correct info received

20
Characterizing Services

• Capacity
• A measure of systems ability to transfer
  information
• Bandwidth the theoretical capacity of one or
  more elements in the system
• e.g. SONET OC-3c circuit 155.52 Mb/s excludes
  protocol overhead
• Throughput the realizable capacity of the system
  or its components
• e.g. SONET OC-3c circuit 80-128 Mb/s (measured)

21
Characterizing Services

• Delay a measure of the time differences in
  transmission of information across the system
  (source to destination).
• Propagation delay
• Transmission delay
• Queuing delay
• Processing delay
• Latency Delay incorporating application
  processing and task completion times