CSE 550 Computer Network Design

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CSE 550 - Computer Network Design

• Dr. Marwan Abu-Amara
• 2nd Semester (T052)

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Network Topologies

• Questions to determine network topology
• Is a small LAN with a few workstations?
• Is a campus LAN or a massive enterprise
  implementation?
• Is scalability important?
• How about network management?
• What about cost?

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Network Topologies (cont.)

• No one topology is right for every network
  environment
• Each network topology can be an integral part of
  another topology design
• Redundant and secure topologies should be part of
  every network design

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Network Topologies (cont.)

• Network topologies covered
• Flat network topology
• Hierarchical network topology
• Mesh network topology
• Redundant network topology
• Campus/LAN network topology
• Enterprise/WAN network topology
• Secure network topology

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Flat Network Topology

• Generally used for very small networks
• Each network device (e.g. hub, switch, ) is used
  for a general rather than specific purpose
• Most network components are used for simple
  broadcasting and providing limited switching
  capabilities
• Based on a common broadcast domain
• Not generally created in a modular fashion
• Provide a consistent and easy-to-manage network
  environment
• Scalability is not usually an important design
  factor

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Flat Network Topology (cont.)

• Advantages
• Lower cost lower in initial cost due to the
  smaller size of network and lower equipment costs
  (special routing switching components are not
  used to a wide extent)
• Reliability due to the simplistic design
  general static nature of the topology
• Easy to design due to the lack of need for
  modularity scalability
• Easy to implement due to the lack of
  specialized switching equipment

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Flat Network Topology (cont.)

• Disadvantages
• Not modular changes to the environment will
  usually affect all internetworking devices
• Bandwidth domain most if not all devices are
  usually in the same bandwidth domain (i.e. share
  the same bandwidth)
• Broadcast domain same broadcast domain that can
  lead to congestion

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Hierarchical Network Topology

• Created in layers to allow specific functions
  features to be implemented in each of the layers
• Each component is carefully placed in a
  hierarchical design for maximum efficiency
  specific purpose
• Routers, switches, and hubs all play specific
  role in routing distributing data packet info
• Incorporates 3 key layers
• Core layer
• Distribution layer
• Access layer

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Hierarchical Network Topology (cont.)

• Core layer
• Provides the backbone, or high-speed switching
  component to the network
• Provides only the specialized task of switching
  data
• Distribution layer
• Demarcation point between core layer end-user
  access layer
• Provides packet manipulation, filtering,
  addressing, policy enforcement, and other
  data-manipulation tasks

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Hierarchical Network Topology (cont.)

• Access layer
• Provides end-user access to network
• Prioritization bandwidth switching can also be
  configured at the access layer to optimize use of
  network resources
• With modularity, hierarchical networks can limit
  the effect of each component change to the
  immediate area of change only
• Hierarchical networks are created to be scalable

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Hierarchical Network Topology (cont.)
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Hierarchical Network Topology (cont.)

• Advantages
• Scalable allows addition of routers, switches,
  , when needed with minimum impact to design
• High availability due to redundancy, alternate
  paths, optimization, and filtering
• Low delay routers delineating broadcast
  domains, and multiple paths for switching
  routing
• Fault isolation can facilitate change and
  improve fault isolation

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Hierarchical Network Topology (cont.)

• Advantages (cont.)
• Modular allows each component to perform a
  specific purpose in the internetwork leading to
  easier more organized network management
• Cost efficient due to ability to optimize
  tune switching routing paths
• Network management more automated easier to
  deploy
• Disadvantages
• Cost due to redundancy that is often integrated
  into the network topology switching equipment

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Mesh Network Topology

• Constructed with many different interconnections
  between network nodes
• 2 types
• Fully meshed
• Typically the backbone of the enterprise network
• Provides excellent redundancy reliability
• Frequently runs mission-critical services
  applications
• Partially meshed
• Similar to fully meshed except that each network
  node or switch does not necessarily have
  immediate connection to each other network node
  or switch

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Mesh Network Topology (cont.)

• Fully Meshed
• Each network node or switch will have a direct
  path to every other network node or switch
• Nodes are typically located at core level or
  backbone level of network
• Not a cost-effective solution
• Cant guarantee that server or application
  failures will be redundant with just a fully
  meshed backbone

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Mesh Network Topology (cont.)
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Mesh Network Topology (cont.)

• Partially Meshed
• Can still provide redundancy through alternate
  paths, and, therefore, allowing mission critical
  application to continue processing
• If a network connection fails, the network will
  remain operational with reduced bandwidth and
  service levels
• More likely to be implemented in an enterprise
  network

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Mesh Network Topology (cont.)
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Mesh Network Topology (cont.)

• Advantages
• Redundancy provided by having multiple links
  connecting each network site
• Disadvantages
• Cost due to redundancy high circuit cost

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Redundant Network Topology

• Should be incorporated into all network designs
• Can be incorporated in transmission media,
  routers, servers, and workstations
• Extremely important at the core or backbone layer
• As an alternative to using multiple data circuits
  or multiple network providers, you can select 2
  media types to provide redundancy (e.g. satellite
  data circuits)
• Need to consider redundancy in routers,
  workstations, and servers

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Redundant Network Topology (cont.)
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Redundant Network Topology (cont.)

• Advantages
• Provides high network availability
• Secures data transactions from hardware failures
• Allows easier more cost-effective network
  management of redundant nodes
• Disadvantages
• Could be costly if not well designed

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Redundant Network Topology (cont.)

• Must include a backup path consisting of routers,
  switches, and individual backup links
• Must take into account
• How much capacity does the backup path support?
• How quickly will network begin to use backup
  path?
• Can use backup path for load balancing
• Some protocols dont support load balancing (e.g.
  running RIP on IPX)

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Campus/LAN Network Topology

• Uses more specific technology that is not
  necessary broadcast based
• Progression of network complexity
• Traditional networks
• Examples Netware Windows NT
• Share data within an office, building, or smaller
  internetworking environments
• Topologies Ring (Token Ring FDDI), Bus
  (Ethernet), Star
• Switched LANs
• Can provide dedicated bandwidth to specific users
• VLANs

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Campus/LAN Network Topology (cont.)

• Common practice to design redundant links between
  LAN switches
• Most LAN switches implement IEEE 802.1d spanning
  tree algorithm ? Loops in network traffic can be
  avoided
• Algorithm guarantees that there is 1 active path
• No load balancing!
• Can combine IEEE 802.1d VLANs in some switches
  to implement one spanning tree per VLAN ? Can
  offer load balancing

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Campus/LAN Network Topology (cont.)
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Campus/LAN Network Topology (cont.)

• Advantages
• Can provide dedicated bandwidth to the desktop
• More efficient use of network resources at LAN
  level
• Cost due to easier physical implementation
• Disadvantages
• Possibility that newer technologies are
  implemented too early dont take full advantage
  of network components that are already in place
  (may cause interoperability issues)

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Enterprise/WAN Network Topology

• Should be built to serve the applications that
  are needed to support the business, not the other
  way around!
• 3 main types
• Remote Access Networks
• Driven by telecommuters business travel
• Uses dialup, ISDN, cable access, and DSL
• Intranet/Internet
• Tracking security is of extreme importance
• WAN
• Combines intranet services, Internet access, and
  remote access to allow corporations to
  communicate with distributors, clients, and
  suppliers
• Technologies used include ATM Frame Relay

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Enterprise/WAN Network Topology

• VPNs
• Network design alternative
• Can connect business suppliers distributors
  through a third-party proprietary network
• Cost saving no need for support staff on
  backbone infrastructure, and less equipment to
  purchase maintain
• Keeps up on latest technology for backbone
• Control of network infrastructure is not in your
  hand!

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Enterprise/WAN Network Topology

• Advantages
• Must have for enterprises!
• Disadvantages
• Staffing support to implement maintain the
  network (can be solved by outsourcing)

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WAN Link Options
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WAN Topologies
Full-Mesh
Star or Hub-and-Spoke
Partial-Mesh
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Three-layer design model (WAN version)
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Secure Network Topology

• 3 main areas
• Policy Standardization
• Allow network users freedom to use network
  services securely
• Access management (different levels for different
  ranks)
• Remote access management
• Data encryption authentication
• Firewalls
• Physical security!
• Implementation
• Firewalls are commonly used
• Not everyone needs to know what level of security
  is implemented!

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Secure Network Topology

• 3 main areas (cont.)
• Audit Review
• Review audit of network security is critical
• Should be aware of latest news on hacker activity
  threats to your network systems
• Stay current on new technologies as well as
  latest software patches, security holes, and
  enhancements

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Secure Network Topology (cont.)

• Advantages
• Business can be conducted electronically
  quicker than in non-secure environment
• Disadvantages
• Cost