Characteristics of Scaleable Internetworks M Clements Level 2 networking

Last Week IP Addressing Crisis and Solutions CIDR vs. classful addressing Supernetting NAT/ PAT IPv6 primer Level 2 networking

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 Level 2 networking

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! Level 2 networking

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 Level 2 networking

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 Level 2 networking

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. Level 2 networking

Three Layer Design Model (Campus Network) Level 2 networking

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 Level 2 networking

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 Level 2 networking

Network Design Goals Reliability Availability Responsivity Efficiency Adaptability Accessibility and Security Level 2 networking

Reliability and Availability Scaleable Routing Protocols Alternate Paths to destinations where possible Load Balancing Per packet Per destination Protocol Tunnels Dial-Backup Level 2 networking

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 Level 2 networking

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. Level 2 networking

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 Level 2 networking

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 Level 2 networking

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… Level 2 networking

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 Level 2 networking

References http://images.ientrymail.com/networknewz/020604figure2.jpg http://www.edrawsoft.com/Hierarchical-Network-Design.php http://images.ientrymail.com/networknewz/020604figure2.jpg Small Enterprise Design Profile Reference Guide, Cisco, 2010 Level 2 networking