Highlight's & Comprimises:

Physical Topology

Pros

• Fast design -1 T1 line is interconnected between each school and the core network.
• Redundany - Inconnections between regional Hubs (in the core network) are via 4 T1s
  • unless all 4 of these connections fail the router can still operate (it will simply load share between the remaining connections).
• Furthermore, we poposing running an extra 4 (unused) redundant cables between each regional Hub (budget permitting)
  • allows us to immedialtely replace any connections that fail
  • useful if network administrator decides load sharing between more than 4 T1s is necessary.
  • read the bottom of section "(1) User Requirements " (use the menu bar) to see why this is a good idea.

Cons

• Single point of failure - all traffic heading outbound to the internet must pass through 1 router (Data Center) if this router fails no school will be able to connect to the Internet.

• Each regional Hub in the WAN core presents a potential point of failure for eleven schools

• If the single T1 connecting to a school breaks, that school has vastly reduced Internet connectivity.

  • the proposal is to integrate emergency ISDN connections as a redundancy backup into the WAN, but 144 Kbps is no sustitute for 1.54 Mbps.

Logical Design

Pros

• This WAN network is easy to implement & troubleshoot because of its two-layer hierarchical design
• Most Internet administration can be done from a single point (at the Data Center)
  • all public access servers are in the one area (in the Data Center).
  • ACLs in the firewall ensure no-one from the outside world has access to the district WAN.
• If any school encounters a network problem they can use the emergency dial-in ISDN line to inform network administrators at the school's regional Hub
  • hopefully the issue can be resolved quickly and the school can return to using the T1 line to connect to the outside world.
  • this ISDN is only connected when needed.
    
    
• The use of PPP (between regional Hubs and schools) lets us use password authentication through CHAP.
  • this security feautre can prevent one school hacking into another.
  • note that PAP was not choosen because it is vulnerable to brute force attacks.
• PPP works with non-cisco equipment, meaning if a school choses to purchase a non-cisco router it can still opertate as part of the WAN

Cons

• Each schools must still inplement security/ACLs to prevent security breaches from other schools (since there is only one firewall on WAN)