network design and administration
- 1. Network Design and Administration II RCS315
- 2. Network Design Background • Today's IT environment continues to grow in both design and complexity at a rapid pace. • Your business' success hinges on a well- designed, reliable network. • Designing, architecting, implementing and managing technology is what we do. • A great network design can help an organization grow, enhance its performance, and provide increased security. 2RCS315
- 3. Network Design Concept • Network design is a category of systems design that deals with data transport mechanisms. As with other systems' design disciplines, network design follows an analysis stage, where requirements are generated, and precedes implementation, where the system (or relevant system component) is constructed. • The objective of network design is to satisfy data communication requirements while minimizing expense. Requirement scope can vary widely from one network design project to another based on geographic particularities and the nature of the data requiring transport. 3RCS315
- 4. Network design Principals • Regardless of network size or requirements, a critical factor for the successful implementation of any network design is to follow good structured engineering principles. These principles include – Scalability: Scalable network designs can grow to include new user groups and remote sites and can support new applications without impacting the level of service delivered to existing users. – Availability: A network designed for availability is one that delivers consistent, reliable performance, 24 hours a day, 7 days a week. In addition, the failure of a single link or piece of equipment should not significantly impact network performance. – Security: Security is a feature that must be designed into the network, not added on after the network is complete. Planning the location of security devices, filters, and firewall features is critical to safeguarding network resources. – Manageability: No matter how good the initial network design is, the available network staff must be able to manage and support the network. A network that is too complex or difficult to maintain cannot function effectively and efficiently. • To meet these fundamental design goals, a network must be built on a hierarchical network architecture that allows for both flexibility and growth. 4RCS315
- 5. NERTWORK DESIGN METHODLOGY/analysis Step 1. Identify the network requirements. • The network designer works closely with the customer to document the goals of the project. • Goals are usually separated into two categories: – Business goals: Focus on how the network can make the business more successful – Technical requirements: Focus on how the technology is implemented within the network 5RCS315
- 6. Step 2. Characterize the existing network. – Information about the current network and services is gathered and analyzed. – It is necessary to compare the functionality of the existing network with the defined goals of the new project. – The designer determines whether any existing equipment, infrastructure, and protocols can be reused, and what new equipment and protocols are needed to complete the design. 6RCS315
- 7. Step 3. Design the network topology and solutions – A common strategy for network design is to take a top-down approach. In this approach, the network applications and service requirements are identified, and then the network is designed to support them. – When the design is complete, a prototype (a model) or proof-of-concept test is performed. This approach ensures that the new design functions as expected before it is implemented. – Here logical design is simulated to see if it gives out the expected results. 7RCS315
- 8. NOTE: Determining the Scope of the Project • While gathering requirements, the designer identifies the issues that affect the entire network and those that affect only specific portions. • Failure to understand the impact of a particular requirement often causes a project scope to expand beyond the original estimate. • This oversight can greatly increase the cost and time required to implement the new design 8RCS315
- 9. Impacting the Entire Network • Network requirements that impact the entire network include the following: – Adding new network applications and making major changes to existing applications, such as database or Domain Name System (DNS) structure changes – Improving the efficiency of network addressing or routing protocol changes – Integrating new security measures – Adding new network services, such as voice traffic, content networking, and storage networking – Relocating servers to a data center server farm 9RCS315
- 10. Impacting a Portion of the Network. • Requirements that may only affect a portion of the network include the following: – Improving Internet connectivity and adding bandwidth – Updating access layer LAN cabling – Providing redundancy for key services – Supporting wireless access in defined areas – Upgrading WAN bandwidth 10RCS315
- 11. HIERARCHICAL NETWORK DESIGN • As from above, a hierarchical design is used to group devices into multiple networks. • The networks are organized in a layered approach thus A hierarchical network design involves dividing the network into discrete layers. • Each layer, or tier, in the hierarchy provides specific functions that define its role within the overall network. • This helps the network designer and architect to optimize and select the right network hardware, software, and features to perform specific roles for that network layer. 11RCS315
- 12. The hierarchical design model has three basic layers: • Core layer: – Connects distribution layer devices • Distribution layer: – Interconnects the smaller local networks • Access layer: – Provides connectivity for network hosts and end device 12RCS315
- 15. Or: Multi Building Enterprise Network Design RCS315 15
- 16. What Happens at the Core Layer? • The core layer is sometimes called the network backbone. Routers and switches at the core layer provide high-speed connectivity. • The core layer includes one or more links to the devices at the enterprise edge to support Internet, virtual private networks (VPN), extranet, and WAN access • The core layer is responsible for transporting large amounts of data quickly and reliably. • The designer must ensure that the core layer is designed with fault tolerance, especially because all users in the network can be affected by a failure. The ability to avoid unnecessary delays in network traffic quickly becomes a top priority for the network designer. 16RCS315
- 17. Goals of the Core Layer • The core layer design enables the efficient, high-speed transfer of data between one section of the network and another. • The primary design goals at the core layer are as follows: – Provide 100% uptime. – Maximize throughput. – Facilitate network growth 17RCS315
- 18. Core Layer Technologies • Technologies used at the core layer include the following: 1. Routers or multilayer switches that combine routing and switching in the same device 2. Redundancy and load balancing 3. High-speed and aggregate links 4. Routing protocols that scale well and converge quickly, such as Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF) Protocol 18RCS315
- 19. Redundant Links • Implementing redundant links at the core layer ensures that network devices can find alternate paths to send data in the event of a failure. • When Layer 3 devices are placed at the core layer, these redundant links can be used for load balancing in addition to providing backup. • In a flat, Layer 2 network design, Spanning Tree Protocol (STP) disables redundant links unless a primary link fails. This STP behavior prevents load balancing over the redundant links 19RCS315
- 20. Mesh Topology • Most core layers in a network are wired in either a full-mesh or partial-mesh topology. • A full-mesh topology is one in which every device has a connection to every other device. • Although full-mesh topologies provide the benefit of a fully redundant network, they can be difficult to wire and manage and are more costly. • For larger installations, a modified partial-mesh topology is used. In a partial-mesh topology, each device is connected to at least two others, creating sufficient redundancy without the complexity of a full mesh 20RCS315
- 21. Network Traffic Prioritization • Failures at the core layer can potentially affect all users of the network. Therefore, preventing failures becomes a daunting task. • The network designer has to incorporate features or additions to the design to minimize or eliminate the effects of a core layer failure. • The users on a network do not want to wait to complete their daily tasks because of a lack of care in the design. 21RCS315
- 22. Preventing Failures • The network designer must strive to provide a network that is resistant to failures and that can recover quickly in the event of a failure. Core routers and switches can contain the following: 1. Dual power supplies and fans 2. A modular chassis-based design 3. Additional management modules • Redundant components increase the cost, but they are usually well worth the investment. Core layer devices should have hot-swappable components whenever possible. Hot-swappable components can be installed or removed without first having to turn off the power to the device. Using these components reduces repair time and disruption to network services. • Larger enterprises often install generators and large uninterruptible power supply (UPS) devices. These devices prevent minor power outages from causing large-scale network failures. 22RCS315
- 23. Reducing Human Error • Human errors contribute to network failures. • Unfortunately, the addition of redundant links and equipment cannot eliminate these factors. • Many network failures are the result of poorly planned, untested updates or additions of new equipment. • Never make a configuration change on a production network without first testing it in a lab environment! • Failures at the core layer cause widespread outages. It is critical to have written policies and procedures in place to govern how changes are approved, tested, installed, and documented. Plan a back-out strategy to return the network to its previous state in case changes are not successful 23RCS315
- 24. Network Convergence • The choice of a routing protocol for the core layer is determined by the size of the network and the number of redundant links or paths available. • A major factor in choosing a protocol is how quickly it recovers from a link or device failure. 24RCS315
- 25. Convergence Definition and Factors • Network convergence occurs when all routers have complete and accurate information about the network. The faster the convergence time, the quicker a network can react to a change in topology. • Factors that affect convergence time include the following: – The speed at which the routing updates reach all the routers in the network – The time that it takes each router to perform the calculation to determine the best paths 25RCS315
- 26. Selecting a Routing Protocol for Acceptable Convergence Time • Most dynamic routing protocols offer acceptable convergence times in small networks. • In larger net- works, protocols such as Routing Information Protocol Version 2 (RIPv2) may converge too slowly to prevent disruption of network services if a link fails. • Generally, in a large enterprise network, EIGRP or OSPF provide the most stable routing solution. 26RCS315
- 27. Design Considerations with Convergence in Mind • Most networks contain a combination of dynamic and static routes. • Network designers need to consider the number of routes required to ensure that all destinations in the network are reachable. • Large routing tables can take significant time to converge. The design of network addressing and summarization strategies in all layers affects how well the routing protocol can react to a failure 27RCS315