Antonio González Torres Switches Antonio González Torres

Hierarchical Network Design The design of larger LANs includes identifying the following: An access layer that connects end users into the LAN A distribution layer that provides policy-based connectivity between end-user LANs A core layer that provides the fastest connection between the distribution points

LAN design goals Functionality Scalability Adaptability Manageability

Functionality The network must work. The network must allow users to meet their job requirements. The network must provide user-to-user and user-to-application connectivity with reasonable speed and reliability.

Scalability The network must be able to grow. The initial design should grow without any major changes to the overall design.

Adaptability The network must be designed with a vision toward future technologies. The network should include no element that would limit implementation of new technologies as they become available.

Manageability The network should be designed to facilitate network monitoring and management to ensure ongoing stability of operation.

LAN design considerations The function and placement of servers Collision detection issues Segmentation issues Broadcast domain issues

Server Placement Enterprise servers Workgroup servers support all the users should be placed in the main distribution facility (MDF). Workgroup servers support a specific set of users should be placed in the intermediate distribution facility (IDF).

Segmentation the process of splitting a single collision domain into smaller collision domains reduces the number of collisions allows for greater utilization of bandwidth Using Layer 2 devices such as bridges and switches Routers reduce the size of the collision domain and the size of the broadcast domain at Layer 3

LAN design methodology Gather requirements and expectations Analyze requirements and data Design the Layer 1, 2, and 3 LAN structure, or topology  Document the logical and physical network implementation

Availability measures Availability measures the usefulness of the network. things that affect availability: Throughput Response time Access to resources Every customer has a different definition of availability.

Design LAN Structure The most common LAN topologies are star and extended star The topology structure can be broken into OSI layers to determine devices to use

LAN design documentation OSI layer topology map LAN logical map LAN physical map Cut sheets VLAN logical map Layer 3 logical map Addressing maps

Document Logical Diagram the flow of data in a network A snapshot view of all LAN implementation

OSI layer topology map This diagram shows how the devices and telecommunication closets are connected

Cut sheets Cut sheets store detail information about the different connections in the network

VLAN logical map VLAN logical maps show the inter VLAN and Intra VLAN interconnection using a router or trunking ports

Layer 3 logical map These diagrams show the logical addresses different devices use to send and receive information

Addressing maps Addressing maps show the logical addresses configured for each network device

Layers design

Layer 1 Design One of the most important components to consider when designing a network is the physical cabling.

Layer 1 Design Issue: Type of Cabling copper or fiber-optic? the overall structure of the cabling

Some rules on Cabling Fiber-optic cable should be used in the backbone and risers in all cable designs. Category 5e UTP cable should be used in the horizontal runs. The cable upgrade should take priority over any other necessary changes. Enterprises should also make certain that these systems conform to well-defined industry standards, such as the TIA/EIA-568-A specifications.

Star Topology Using Cat. 5 UTP

Typical MDF in Star Topology In a simple star topology with only one wiring closet, the MDF includes one or more horizontal cross-connect (HCC) patch panels. HCC patch cables are used to connect the Layer 1 horizontal cabling with the Layer 2 LAN switch ports. The uplink port of the LAN switch, depending on the model, is connected to the Ethernet port of the Layer 3 router using a patch cable. At this point, the end host has a complete physical connection to the router port.

Multi-Building Campus When hosts in larger networks exceed the 100-meter limitation for Cat. 5e UTP, more than one wiring closet is required. Multiple wiring closets mean multiple catchment areas. The secondary wiring closets are referred to as IDFs.

Extended-Star Topology in a Multi-Building Campus VCC is used to interconnect the various IDFs to the central MDF. IDFs should be connected to the MDF by vertical cabling, also called backbone cabling. Fiber-optic cable is normally used because the vertical cable lengths are typically longer than 100 meters

Logical Diagram the locations and identification of the MDF and IDF wiring closets the network topology model without all the details of the exact installation paths of the cables the basic road map of the LAN the number of spare cables the type and quantity of cables used to interconnect the IDFs with the MDF

detailed documentation of all cable runs, the identification numbers, and the port the run is terminated on at the HCC or VCC.

Devices at Layer 2 determine the size of the collision domains. Layer 2 Design Devices at Layer 2 determine the size of the collision domains. 

Asymmetric Switching provides more bandwidth to vertical cabling, uplinks, and servers

The desired capacity of a vertical cable run is greater than that of a horizontal cable run.

Determine the number of 10 Mbps and 100 Mbps ports review of the user requirements for the number of horizontal cable drops per room and the number of total drops in any catchment area. This includes the number of vertical cable runs. E.g.: four horizontal cable runs per room; total 18 rooms; require 72 LAN switch ports

Collision Domain Size with Hubs

Layer 2 Switch Collision Domains

An Acceptable Solution Using Hubs Must make sure bandwidth to the host is provided in accordance to the specifications gathered in the requirements phase of the network design process

Layer 3 Design

Layer 3 Router for Segmentation All data traffic from Network 1 destined for Network 2 has to go through the router. There are two broadcast domains

Logical Addressing Mapped to the Physical Network A standard convention should be set for addresses of important hosts on the network.

Address Map and Logical Network Map provides a snapshot of the network

helps to troubleshoot the network Physical Network Map helps to troubleshoot the network

VLAN Environment combines Layer 2 switching and Layer 3 routing technologies limits both collision domains and broadcast domains provides security with the creation of VLAN groups

Hierarchical LAN Design easier to make changes to the network as the organization grows

Access layer switches the entry point for user workstations and servers to the network provides services such as VLAN membership. Access layer functions also include MAC layer filtering and microsegmentation

Distribution layer Networks are segmented into broadcast domains Policies are applied and ACLs can filter packets. Switches in this layer operate at Layer 2 and Layer 3 Distribution layer functions: Aggregation of the wiring closet connections Broadcast/multicast domain definition Virtual LAN (VLAN) routing Any media transitions that need to occur Security

Distribution layer The following Cisco switches are suitable for the distribution layer:  Catalyst 2926G Catalyst 5000 family Catalyst 6000 family

Core layer The core layer is a high-speed switching backbone. If the switch does not have a router module, an external router is used for the Layer 3 function. This layer should not perform any packet manipulation. A core infrastructure with redundant alternate paths gives stability to the network Asynchronous Transfer Mode (ATM) or Ethernet switches can be used.

Core layer The following Cisco switches are suitable for the core layer: Catalyst 6500 series Catalyst 8500 series IGX 8400 series Lightstream 1010