Network Architecture Overview
Network Architecture Notes
Physical vs. Logical Networks
- Physical Network: Consists of physical wires and devices forming the network's infrastructure.
- Logical Network: Software-based partitions, segments, and connections overlaid on physical networks (e.g., Software Defined Networks).
Changes in Network Design
- Old Method: Each LAN required a separate physical network (e.g., distinct networks for sales and engineering).
- New Method: Single physical infrastructure with multiple VLANs (Virtual LANs) to segregate traffic.
Benefits of VLANs
- Ease of Management: VLAN assignments can change without physical movement of devices.
- Segmentation: Improves network management by dividing traffic into separate segments.
VLANs vs. Subnets
- Subnet: Routable network segment (e.g., 192.168.128.0/23); allows direct communication between devices.
- VLAN: Software construct grouping switch ports into LAN segments; it typically includes one subnet but can theoretically encompass multiple subnets.
- Broadcast Domains: VLANs define broadcast domains, minimizing traffic overload, while subnets are defined by an IP address range.
OSI Model
| Layer | Name | Description |
|---|---|---|
| 1 | Physical | Physical connection between devices (copper, fiber, wireless) |
| 2 | Data Link | MAC addressing and low-level error handling |
| 3 | Network | Logical addressing (e.g., IP) and routing protocols |
| 4 | Transport | End-to-end delivery of messages, error checking |
| 5 | Session | Managing connections and dialogues between systems |
| 6 | Presentation | Data formatting and encryption |
| 7 | Application | Application protocols like SMTP, HTTP, FTP |
Network Layer Details
Layer 1 - Physical Layer:
- Responsible for actual data transmission as bits.
- Functions include bit rate control and defining physical topologies.
- Modes: Simplex, half-duplex, full-duplex.
Layer 2 - Data Link Layer (DLL):
- Ensures node-to-node message delivery, error-free data transfer.
- Subdivided into Logical Link Control (LLC) and Media Access Control (MAC).
- Functions include framing, physical addressing, and flow control.
Layer 3 - Network Layer:
- Facilitates transmission between different networks and packet routing.
- Key functions: routing and logical addressing.
Infrastructure Considerations
- Main Distribution Frame (MDF): Central hub connecting IT and telecommunication lines to an internal network.
- Intermediate Distribution Frames (IDF): Connect various areas or floors of a building to the MDF.
Logical Network Design
- VLAN Segmentation:
- Small offices may feature a single large subnet; larger networks require segmentation.
- Security profile and change control levels dictate partitioning of VLANs.
- Misconceptions about VLANs: They do not inherently secure connections or increase bandwidth.
Network Access Control
- NAC Overview: Ensures devices authenticate correctly and are placed in the appropriate VLAN.
- Methods:
- MAC-based: Weakest method verifying MAC addresses.
- Authentication-based: Utilizes credentials or two-factor authentication.
- Certificate-based: One-time verification with certificates for seamless access.
Emergency Services Location
- Must enable IP address mapping to physical locations to assist emergency services.
- Use of VLANs to provide automatic location data based on area.
Wireless Office Networks
- Transition to WiFi: Wired connections are now supplemented or replaced by wireless.
- Physical Infrastructure:
- Requires enterprise-grade equipment for adequate coverage and bandwidth.
- Network Access Control (NAC): Unified access control measures for consistencies across wired and wireless networks are essential.
Datacenter Network Considerations
- Differences include higher density and bandwidth needs when compared to standard office LANs.
- Focus on flexibility and scalability in design, including subnet separation for security.
WAN Strategies
- WAN connects offices and datacenters and involves topology and technology considerations.
- Redundancy: Ensure multiple connections to avoid fail points and improve resilience.
- Topologies: Various topologies such as star and ring connect sites with their respective advantages and disadvantages.
Routing Strategies
- Static Routing: Simple but non-scalable; manual route configuration.
- Interior Routing Protocols: Dynamic routing via OSPF and EIGRP.
- Exterior Gateway Protocols (EGP): Manages routing between different networks, such as EBGP.
Internet Access Approaches
- Outbound Connectivity:
- Single connection is easy but has fault risks.
- Regional or site-by-site connections offer alternatives with respective benefits and complexities.
Corporate Standards
- Consistent standards aid in scaling and support across components.
- Logical design outlines user data flow while physical design pertains to actual hardware and topology.
Software Defined Network (SDN)
- SDN allows programmable routing to optimize traffic based on application needs, contrasting traditional routing that may disrupt overall network traffic.
IPv6 Deployment
- Need for IPv6: Overcoming IPv4's limitations with extensive address availability and multicast capability.
- Strategies for Deployment:
- Begin with internet-facing infrastructures, lesser critical networks, or set up test labs.
- Gradual rollout across internal networks as preparation for full deployment is needed.