1. Characteristics of Scaleable Internetworks
M Clements
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2. Last Week IP Addressing Crisis and Solutions
CIDR vs. classful addressing
Supernetting
NAT/ PAT
IPv6 primer
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3. This week……….. Characteristics of Scaleable Internetworks
3 Layer Design Model
Reliability and Availability
24/7 access, transparency, routing failure plans
Responsiveness
QoS without latency
Efficiency in use of BW
Adaptability
Accessibility and Security
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4. Three Layer Design Model
Used for planning a new network
Hierarchical design now possible
Caters for the operation of the network
Design considerations
User access
Traffic segmentation and efficiency
High speed inter-site delivery
OSI model would be no use here!
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5. Flat Versus Hierarchical Topologies
Flat network topology ok for very small networks - no hierarchy
Each router/ switch has essentially the same job
Network not divided into layers or modules and is easy to design and implement
Easy to maintain, as long as it stays small
Flat network undesirable as network grows
Lack of hierarchy makes locating a fault difficult
May need to inspect the entire network
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6. Top Two Layers Core Layer Distribution Layer
For high speed switching of traffic
Lowest latency required here
Distribution Layer
For separating Core traffic from the rest of the network
Uses policies for:
Routing updates
Route summaries
Address aggregation
VLAN traffic
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7. Lower Layer - Access Layer
Allows traffic and users into the network
Low capability routers or switches may be used here
Can operate over remote access technologies such as POTS, ISDN, Frame Relay for remote site connectivity
Security policies should be implemented
ACLs, PAP, CHAP etc.
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8. Three Layer Design Model (Campus Network)
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9. Functions of the Layers
Core layer - optimal transport between sites
Distribution layer connects network services to the access layer
Implements policies regarding security, traffic loading and routing etc.
In a campus network, the access layer provides switches for end-user access
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10. Your design is right ………
When you already know how to add a new building, floor, WAN link, remote site, e-commerce service etc.
When new additions cause only local changes to the directly connected devices
When your network can double or triple in size without major design changes
When troubleshooting is easy because there are no complex protocol interactions to confuse matters
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11. Network Design Goals Reliability Availability Responsivity Efficiency
Adaptability
Accessibility and Security
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12. Reliability and Availability
Scaleable Routing Protocols
Alternate Paths to destinations where possible
Load Balancing
Per packet
Per destination
Protocol Tunnels
Dial-Backup
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13. Responsivity This brings in ideas such as queuing and priorities
End users of the network notice responsivity at the desktop.
1.First-in,first-out queuing (FIFO) 2.Priority queuing 3.Custom queuing 4.Weighted fair queuing
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14. Efficiency (of bandwidth)
This is the attempt to conserve bandwidth (BW) over (costly) WAN links
Local proxy server to hold frequently requested files
Reduce size and frequency of routing updates
Use Access Control lists to filter traffic
Snapshot Routing
Compression over WAN
Dial-on-demand routing
Route summarisation
Incremental routing updates.
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15. Adaptability
Allows several protocols to co-exist across a network – less important today
IP, IPX, SNA, APPLETALK etc.
Consideration must be paid to certain non-routable protocols such as SNA which may suffer unless catered for
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16. Accessibility and Security
Accessibility is allowing access to the network by users either on-site or remotely
Security is making sure that the users are authenticated so that the users are those who should be allowed access
Technologies such as ACLs, PAP, CHAP can be used here
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17. Small Enterprise Design Profile
The Enterprise Design Profile delivers the foundational network design that all enterprise services, applications, and solutions use to interact and communicate with one another.
The Enterprise Design Profile is constructed in a fashion that supports all the applications and services that will ride on it.
Additionally, these profiles must be aware of the type of traffic traversing and treat each application or service with the correct priority based on the needs and importance of that application.
Read on…
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18. Summary
Three Layer Hierarchical Design Model is used to simplify the complex tasks of network design
Basics of internetwork scaleability
Reliability and Availability
Responsivity
Efficiency
Adaptability
Accessibility and Security
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19. References http://images.ientrymail.com/networknewz/020604figure2.jpg
Small Enterprise Design Profile Reference Guide, Cisco, 2010
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