wan design ผศ. ดร. อนันต์ ผลเพิ่ม asst.prof.anan phonphoem, ph.d....
TRANSCRIPT
WAN design
ผศ.ดร. อนั�นัต์ ผลเพิ่ �มAsst.Prof.Anan Phonphoem, Ph.D.
[email protected]://www.cpe.ku.ac.th/~anan
Computer Engineering DepartmentKasetsart University, Bangkok, Thailand
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Types of WAN Service
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WAN Technology
Technology Typical Uses
Leased Line PPP networks, hub and spoke, back-ups
ISDN Remote-access, voice, video, back-ups
Frame Relay Fast, efficient mesh between remote sites
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WAN requirements Optimise WAN bandwidth Minimise cost Maximise the effective service to
end users
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LAN/WAN integration LAN/WAN, previously logically
separated, must now be fully integrated for seamless performance
Both now must be able to handle... Voice traffic (VoIP) Bandwidth intensive multimedia applications
Video conferencing On-line training
Increased business critical data access
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Goals Availability Total cost of ownership
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Concerns Environmental variables Performance constraints Networking variables
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WAN Design strategies Mesh
Network is flat All routers perform same function Expansion proceeds haphazardly
Hierarchical Organized in layers Easier to implement/Troubleshooting Scalability Predictability
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Important of Layers Designing networks using the OSI model
designed in layers simplify the tasks required for internetworking Design elements can be replicated as grows
Therefore, networks should be designed using a hierarchical model. Unfortunately, most networks are thrown
together into a mesh (“a mess!”) with little or no vision of future needs.
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Benefit of Hierarchical Design
Scalability allows for future growth without sacrificing
control or functionality Ease of Implementation
logically constructed layers specify the functions of each layer
Ease of troubleshooting well-defined functions at each layer aid in
the isolation of problems
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Benefit of Hierarchical Design Predictability
behavior of functional layers can be estimated and planned for
Protocol support allows easier implementation of future
technologies because the network has been logically constructed
Manageability All the above aids net. admin. in overall
management of the network
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The Hierarchical Design ModelThe Three-Layer
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The Hierarchical Design ModelThe Three-Layer
Core layer--provides transport between remote sites
Distribution layer--provides policy-based connectivity
Access layer--provides workgroup/user access to network
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Core Layer
Fast WAN connections between remote sites
Core links are normally point-to-point with no host devices
Core services include: T1/T3 Frame Relay ATM SMDS
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Distribution Layer Provides WAN services to multiple LANs Usually the campus backbone Uses Fast Ethernet (or Gigabit
Ethernet) Used on large sites to interconnect
blgs.
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Access Layer Usually a LAN or group of LANs Gives access to specific users and
workgroups This layer is where all hosts (including
servers) are attached to the network
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WAN Layer Functions Core Layer Functions Distribution Layer Functions Access Layer Functions
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Core Layer Functions Optimize Transport Between Remote
Sites Redundant paths to guard against circuit
outages Provide load sharing and rapid
convergence when link states change Efficient use of bandwidth by...
Implementing scalable routing protocols and Blocking local traffic access to the core
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Distribution Layer Functions
Policy-Based Connectivity Boundary definition & packet manipulation Control access to services of the core layer and
other distribution layer routers VLAN routing Address aggregation (i.e., subnets) & route
optimization ACLs and other security measures
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Access LayerFunctions
Workgroup & User Access to the Network Isolation of Broadcast Traffic Shared and Switched Bandwidth MAC-layer filtering Microsegmentation
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Other Hierarchical Options One-Layer Design Two-Layer Design
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One-Layer Design Only a few remote sites need to be
connected Servers are placed in farms or in each
workgroup to reduce traffic on the backbone
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Two-Layer Design WAN link is used to interconnect separate
sites Link does not have to be dedicated. An
alternative would be ISDN.
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Hierarchical Design Advantages
Controlling data traffic patterns through source/destination network layer addressing A packet only needs to travel up the
hierarchy as far as it needs to find the destination.
With good design, most traffic would be contained in the access layer with users accessing their workgroup servers
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Hierarchical Design Advantages
Server Placement Enterprise Servers needed by all
workgroups should be placed in the Distribution Layer (e.g. email, DNS, etc.)
Workgroup Servers needed by a unique set of users should be placed in the Access Layer, preferably in the same broadcast domain as the users
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References Cisco course material Allan Johnson’s material (from cisco) user:dam0c00k’s material (from cisco)