T OP -D OWN N ETWORK D ESIGN C HAPTER T HREE C HARACTERIZING THE E XISTING I NTERNETWORK Oppenheimer

To judge how to meet expectations for network scalability, performance, and availability O BJECTIVES AAB To learn about the topology and physical structure, and assessing the network’s performance To describe techniques and tools in characterizing an incumbent network

T HE E XISTING N ETWORK  We now know where we want to go based on the analysis that was just done  We next need to determine where we are starting from  If this is an entirely new network, this step does not need to be done AAB

C HARACTERIZING THE NETWORK INFRASTRUCTURE Developing a set of network maps and learning the location of major internetworking devices and network segments. AAB

D EVELOPING A NETWORK MAP  Need to understand the traffic flow by learning the location of major hosts, interconnecting devices and network segments.  Goal is to obtain the network map/maps of the already implemented network.  Tools for developing network map:  Some customer don’t have existing map  Find good network-diagramming tool i.e. Cisco work, HP open view etc.. AAB

G ET A N ETWORK M AP : P URPOSE Learn the location of major hosts, interconnection devices, and network segments  for better understanding of traffic flow. Remember! Your aim at this step is to obtain a map (or set of maps) of the already-implemented network. You are one step ahead if the customers are already have maps for the new network design  designer have to check the detailed analysis of business and technical requirements AAB

I NFORMATION TO C OLLECT  Characterize the existing internetwork in terms of:  Its infrastructure Logical structure  Logical topology = illustrates the architecture of the network  It can be flat or hierarchical, structured or unstructured, layered or not  Its also describes methods for connecting devices in a geometric shape – star, ring, bus, hub or mesh  Discuss further in chapter 5!! Physical structure/components Developing a modular block diagram – figure 3-2 page 69  Addressing and naming  Wiring and media  Architectural and environmental constraints AAB

G ET A N ETWORK M AP : I NFORMATION TO COLLECT  A network map is the first thing to work on  This map should include  Geographic locations  WAN connections between sites Labeled with type/speed/protocols/media/service provider  Buildings and floors where equipment will be  Connections between buildings and floors Labeled with type/speed/protocols/media AAB

G ET A N ETWORK M AP : I NFORMATION TO COLLECT  Location of connection points like routers and switches  Internet connections  Remote access points  A baseline will be needed as this will tell you where the network is today AAB

G ET A N ETWORK M AP - EXAMPLE AAB Gigabit Ethernet Eugene Ethernet 20 users Web/FTP server Grants Pass HQ 16 Mbps Token Ring FEP (Front End Processor) IBM Mainframe T1 Medford Fast Ethernet 50 users Roseburg Fast Ethernet 30 users Frame Relay CIR = 56 Kbps DLCI = 5 Frame Relay CIR = 56 Kbps DLCI = 4 Grants Pass HQ Fast Ethernet 75 users Internet T1

C HARACTERIZE A DDRESSING AND N AMING  IP addressing for major devices, client networks, server networks, and so on  Any addressing oddities, such as discontiguous subnets?  Discontiguous subnet = is a subnet that is divided  Figure 3-3 pg 69 (text book)  Any strategies for addressing and naming?  For example, sites may be named using airport codes San Francisco = SFO, Oakland = OAK AAB

C HARACTERIZE THE W IRING AND M EDIA Single-mode fiber Multi-mode fiber Shielded twisted pair (STP) copper Unshielded-twisted-pair (UTP) copper Coaxial cable Microwave Laser Radio Infra-red AAB

W HAT SHOULD BE DOCUMENTED ??? To meet scalability and availability goals for new network design, it is important to understand the cabling and wiring of the existing network. documenting the existing cabling can help in designing for an enhancement and identify potential problems. It is also good to document the cable distance as this information is useful when selecting data link layer technologies based on distance restrictions Should document also the connections between buildings. Include the info on the number of pairs of wires and the type of wiring/wireless tech in use. should also indicate the distance between buildings- this help in selecting new cabling, i.e. upgrade from copper to fiber hence the distance between building can be much longer. AAB

Telecommunications Wiring Closet Horizontal Wiring Work-Area Wiring Wallplate Main Cross-Connect Room (or Main Distribution Frame) Intermediate Cross-Connect Room (or Intermediate Distribution Frame) Building A - HeadquartersBuilding B Vertical Wiring (Building Backbone) Campus Backbone C AMPUS N ETWORK W IRING AAB

E XAMPLE : BUILDING WIRING AAB

A RCHITECTURAL C ONSTRAINTS  Make sure the following are sufficient  Air conditioning  Heating  Ventilation  Power  Protection from electromagnetic interference  Doors that can lock AAB

A RCHITECTURAL C ONSTRAINTS  Make sure there’s space for:  Cabling conduits  Patch panels  Equipment racks  Work areas for technicians installing and troubleshooting equipment AAB

C HECKING A SITE FOR A WIRELESS INSTALLATION  Wireless site survey – to describe the process of analyzing a site to see if it will be appropriate for wireless transmission.  It starts with a draft WLAN design.  Decide on placement of the wireless access point.  the initial placement of the AP is based on an estimate of the signal loss that will occur between the AP and the users of the AP. AAB

I SSUES FOR W IRELESS I NSTALLATIONS Reflection-Reflection causes the signal to bounce back on itself. Absorption-Some of the electromagnetic energy of the signal can be absorbed by the material in objects through which it passes, resulting in a reduced signal level. Refraction-When an RF signal passes from a medium with one density into a medium with another density, the signal can be bent, much like light passing through a prism. Diffraction-similar to refraction, results when a region through which the RF signal can pass easily is adjacent to a region in which reflective obstructions exist. Spreading occurs in the diffraction process [ AAB

C HECK THE H EALTH OF THE E XISTING I NTERNETWORK  Performance  Availability  Bandwidth utilization  Accuracy  Efficiency  Response time  Status of major routers, switches, and firewalls AAB

N ETWORK U TILIZATION IN M INUTE I NTERVALS AAB

N ETWORK U TILIZATION IN H OUR I NTERVALS AAB

C HARACTERIZE P ACKET S IZES AAB

Node A Node B Node C Node D Node ANode BNode CNode D X X X X C HARACTERIZE R ESPONSE T IME AAB

C HECK THE S TATUS OF M AJOR R OUTERS, S WITCHES, AND F IREWALLS  show buffers  show environment  show interfaces  show memory  show processes  show running-config  show version AAB

T OOLS  Protocol analyzers  Multi Router Traffic Grapher (MRTG)  Remote monitoring (RMON) probes  Cisco Discovery Protocol (CDP)  Cisco IOS NetFlow technology  CiscoWorks  Cisco IOS Service Assurance Agent (SAA)  Cisco Internetwork Performance Monitor (IPM) AAB

AAB

S UMMARY  Characterize the exiting internetwork before designing enhancements  Helps you verify that a customer’s design goals are realistic  Helps you locate where new equipment will go  Helps you cover yourself if the new network has problems due to unresolved problems in the old network AAB

R EVIEW Q UESTIONS What factors will help you decide if the existing internetwork is in good enough shape to support new enhancements? When considering protocol behavior, what is the difference between relative network utilization and absolute network utilization? Why should you characterize the logical structure of an internetwork and not just the physical structure? What architectural and environmental factors should you consider for a new wireless installation? AAB