University Campus Network System Design

1. Project Overview & Requirements Analysis

• Campus Profile:

  • Students: 30,000

  • Area: 3,000 Acres (Requires long-distance fiber optic connectivity)

  • Teaching Buildings: 50

  • Dormitory Buildings: 80

  • Concurrent Network Users: ~5,000

• Key Requirements:

  • Universal Coverage: All teaching and dormitory buildings.

  • Minimum Bandwidth: 10 Mbps guaranteed per user.

  • Scalability & Performance: Must support high-density connectivity, network segmentation, and future growth (e.g., Wi-Fi 6/7, 25G/100G uplinks).

  • Reliability & Security: Carrier-grade uptime, threat prevention, and policy enforcement.

2. Network Architecture: Core-Aggregation-Access

This classic three-tier model provides scalability, redundancy, and clear functional separation.

• Core Layer: The network's backbone. Its sole purpose is to switch traffic as fast as possible.

• Aggregation/Distribution Layer: Aggregates access switches, enforces policies (QoS, ACLs), and routes between VLANs.

• Access Layer: Connects end-users (students, faculty, devices) to the network.

3. Detailed Hardware & Technology Specification

Here is a breakdown of the hardware, including the specific optical modules and transceivers for each layer.

A. Core Layer (The High-Speed Backbone)

This is the heart of the campus network, located in the primary data center.

• Core Switches:

  • Quantity: 2 (for full redundancy, using protocols like MLAG/VSS).

  • Specification: High-performance chassis-based switches.

  • Model Example: Cisco Nexus 9500 Series or Arista 7280R Series.

  • Key Requirements:

    • Ports: Multiple 400G QSFP-DD ports for high-speed interconnects.

    • Switching Capacity: > 100 Tbps.

    • Forwarding Rate: > 10 Bpps.

• Optical Modules & Transceivers (Core):

  • For Interconnecting the two Core Switches:

    • Technology: 400G Bidirectional (BiDi) or Standard.

    • Module: 400G QSFP-DD FR4 or 400G QSFP-DD DR4.

    • Rationale: FR4 supports up to 2km over duplex single-mode fiber (SMF), which is sufficient for connecting redundant cores, even if they are in different rooms. DR4 is suitable for shorter, intra-data center links.

  • For Uplinks to Aggregation Switches and Data Center Servers:

    • Technology: 100G or 400G, depending on the aggregation switch capability.

    • Module: 100G QSFP28 LR4 or 400G QSFP-DD FR4/LR4.

    • Rationale: LR4 supports up to 10km, which is necessary for the long-distance fiber runs across a 3000-acre campus to aggregation nodes.

B. Aggregation/Distribution Layer (The Policy Enforcement Point)

Aggregation switches are deployed in key distribution frames (IDFs) across campus, typically one per building cluster (e.g., a group of dormitories or a science quad).

• Aggregation Switches:

  • Quantity: ~10-15 strategically placed nodes.

  • Specification: High-performance, fixed-configuration or modular switches.

  • Model Example: Cisco Catalyst 9500 Series or Juniper EX4650 Series.

  • Key Requirements:

    • Uplink Ports: 2-4 x 100G/400G QSFP28/QSFP-DD ports (to Core).

    • Downlink Ports: 48 x 10/25G SFP28 ports (to Access switches).

    • Features: Must support L3 routing, QoS, and advanced security features.

• Optical Modules & Transceivers (Aggregation):

  • For Uplinks to Core:

    • Module: 100G QSFP28 LR4 or 400G QSFP-DD LR4.

    • Rationale: The long distances (potentially several kilometers) between aggregation nodes and the core data center mandate long-reach optics like LR4.

  • For Downlinks to Access Switches:

    • Module: 25G SFP28 LR or 10G SFP+ LR.

    • Rationale: LR (10km) optics provide the reach needed from a central aggregation point to individual buildings. The choice between 10G and 25G depends on the bandwidth requirements of the building.

C. Access Layer (The User Connection Point)

These switches are located in the wiring closets of every teaching and dormitory building.

• Access Switches:

  • Quantity: 130+ (One per building, plus multiples for larger buildings).

  • Specification: Stackable or standalone switches with Power over Ethernet (PoE++).

  • Model Example: Cisco Catalyst 9200/9300 Series or Aruba CX 6300 Series.

  • Key Requirements:

    • Uplink Ports: 2 x 10/25G SFP28 uplinks (for redundancy and capacity).

    • Downlink Ports: 48 x 1/2.5/5/10GBase-T Ethernet ports with PoE++.

    • PoE Budget: Sufficient to power Wi-Fi 6/7 Access Points, IP phones, and cameras.

• Optical Modules & Transceivers (Access):

  • For Uplinks to Aggregation Switches:

    • Module: 10G SFP+ LR or 25G SFP28 LR.

    • Rationale: Matches the downlink ports on the aggregation switches. LR optics are standard for building-to-building SMF links.

• Wireless Access Points (WAPs):

  • Quantity: ~2,000-3,000 (Based on density, typically 1 AP per 15-20 users/classroom).

  • Specification: Wi-Fi 6/6E (and future-proofed for Wi-Fi 7) Access Points.

  • Model Example: Aruba 500/600 Series or Cisco Catalyst 9100 Series.

  • Connection: Connected via Ethernet to the Access switches, receiving power via PoE++.

D. Data Center & Server Infrastructure

This supports campus applications (Learning Management System, email, file storage, etc.).

• Top-of-Rack (ToR) Switches:

  • Model Example: Cisco Nexus 3200 Series or Arista 7050X3.

  • Specification: High-speed, low-latency switches with 100G/400G uplinks to the core.

  • Optical Modules: 100G QSFP28 DR4/FR4 or 400G QSFP-DD DR4/FR4 for high-speed, short-reach connections to the core and between racks.

• Servers:

  • Specification: Rack-mounted servers.

  • Model Example: HPE ProLiant DL380 Gen11 or Dell PowerEdge R760.

  • Network Interface Cards (NICs):

    • For Application/Web Servers: 25G SFP28 or 10G SFP+ dual-port NICs.

    • For High-Performance Compute/Storage Servers: 100G QSFP28 dual-port NICs.

  • Optical Modules for Servers:

    • 10G Servers: 10G SFP+ SR (for short distances within a rack) or LR (for longer runs to a central switch).

    • 25G/100G Servers: 25G SFP28 SR or 100G QSFP28 SR4 for intra-rack connectivity to the ToR switch.

4. Bandwidth and Backbone Capacity Validation

• User Capacity: 5,000 users x 10 Mbps = 50 Gbps of guaranteed concurrent access layer bandwidth.

• Access Layer Uplink: Each building has a minimum 2 x 10G uplinks (20 Gbps aggregate). A large dormitory with 500 users would require 5 Gbps (500 users * 10 Mbps), which is well within a 10G uplink capacity.

• Aggregation to Core: With 10 aggregation nodes, each with a 100G uplink, the core has 1 Tbps of inbound capacity, easily handling the 50+ Gbps of user traffic plus internal data center traffic.

• Core Capacity: The 400G core interconnects provide a massive, non-blocking backbone.

5. Summary and Key Design Justifications

• Fiber Infrastructure: The entire design assumes a robust Single-Mode Fiber (SMF) plant throughout the campus, as it is the only medium that supports the long distances (LR: 10km) and high speeds (100G/400G) required.

• Why Optical Modules? They provide the flexibility to mix and match equipment from different vendors and adapt to different distance requirements without changing the core switch hardware.

• Redundancy: Every layer, from dual core switches to redundant uplinks from access switches, is designed for high availability.

• Scalability: The hierarchical model allows for easy expansion. Adding a new building simply requires an access switch and a fiber run to the nearest aggregation node. The core can be upgraded to 800G when needed.

This design provides a future-proof, high-performance, and reliable network foundation capable of supporting the academic and residential needs of a major university.