--- title: "Medium network design issues and proxy servers" subject: "Internet and Intranet" chapter: 5 key: "semester_8/internet_and_intranet:design-medium-network-proxy" source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/design-medium-network-proxy site: BCT Engineering --- # Medium network design issues and proxy servers Internet and Intranet · Chapter 5: Designing Internet Systems and Servers - Asked in: 2070 Magh, 3+8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/internet_and_intranet/design-medium-network-proxy - Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-5 ## Question What are the major design issues with its design criteria to be considered for a medium size network? Also discuss how proxy servers are managed for this network. ## Short answer Key design issues are scalability, performance, availability, security, manageability, cost, addressing, and wireless support, addressed with a hierarchical model, VLANs, redundancy, and QoS. Proxy servers are managed by placing them behind the firewall, configuring ACLs and authentication, enabling caching and content filtering, logging usage, controlling bandwidth, and providing high availability. ## Answer A **medium-size network** serves roughly 100-1000 users in one campus or office with several departments, servers and an internet link. Its design must meet current needs and grow without a redesign. #### Major design issues and criteria | Issue | Design criterion | |---|---| | Scalability | Hierarchical model (access, distribution, core); modular addressing; spare ports and rack space | | Performance | Enough bandwidth (Gigabit to desktops, 10G backbone); low oversubscription; QoS for voice and video | | Availability / reliability | Redundant links and core devices, RSTP or link aggregation, UPS, backup ISP | | Security | Firewall, DMZ for public servers, VLAN separation, ACLs, authentication, antivirus | | Manageability | Standard equipment, SNMP monitoring, labelled cabling, documentation, central logging | | Cost | Cost-effective equipment that meets need; consider total cost of ownership | | Addressing and routing | Private addressing with NAT, VLSM, DHCP, summarisation and a simple routing protocol (OSPF) | | Flexibility / standards | Open standards (IEEE 802.3, 802.1Q, TIA-568) so equipment from different vendors works | | Wireless support | Controller-managed APs, separate staff and guest SSIDs | #### Managing proxy servers A **proxy server** sits between the clients and the internet. Clients send web requests to it, and it fetches the pages on their behalf. Common software is Squid. **Placement.** The proxy is placed in the server segment (or DMZ) behind the firewall. Clients are pointed to it by browser settings or the WPAD file, or traffic is redirected transparently by the router or firewall (port 80 to 3128). **Management tasks** 1. **Access control**: define ACLs by IP range, user, time and site category. 2. **Authentication**: require login (LDAP or Active Directory) so usage can be tied to a user. 3. **Caching**: tune cache size, refresh rules and object size to cut bandwidth use and speed up repeated access. 4. **Content filtering**: block unwanted sites and file types, optionally with a filter list (for example SquidGuard). 5. **Logging and monitoring**: review access logs and reports to find heavy users and problems. 6. **Bandwidth control**: delay pools or QoS to limit large downloads. 7. **High availability**: two proxies with load balancing or failover; for larger sites, a cache hierarchy (parent and sibling proxies). 8. **Maintenance**: regular updates, log rotation, backup of configuration. ```text Sample Squid settings http_port 3128 acl lan src 192.168.10.0/24 acl blocked dstdomain "/etc/squid/blocked.txt" http_access deny blocked http_access allow lan http_access deny all cache_mem 512 MB ``` ```text Clients --> [Proxy/Cache] --> [Firewall] --> Internet | cache hit: reply locally | log, ACL, auth ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which design criterion supports availability in a medium network? A. Single ISP link B. Redundant links and core devices, RSTP or link aggregation, UPS C. Flat network D. More users per switch Answer: B. Availability relies on redundancy and power backup. (Key point: Availability) 2. Why use open standards such as IEEE 802.3 and 802.1Q? A. They lower cable length B. They make traffic encrypted C. So equipment from different vendors works together D. They remove the need for routing Answer: C. Open standards give flexibility across vendors. (Key point: Standards) 3. What is access control on the proxy? A. Defining ACLs by IP range, user, time and site category B. Increasing the cache size C. Rotating logs D. Updating software Answer: A. ACLs decide who can reach which sites and when. (Key point: Proxy access control) 4. How is high availability of proxies achieved? A. One large proxy B. Disabling caching C. Two proxies with load balancing or failover, or a cache hierarchy for larger sites D. Using only DNS Answer: C. Two proxies with balancing/failover, and parent and sibling caches for larger sites. 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