Computer Network Diagram

Having a well managed Computer Network Diagram of your networking infrastructure where you are responsible with, is a must for documentation. It is not just for documentation purposes, you can use this LAN Network Diagram to develop risk security assessment or develop a critical assets register.

Unfortunately not all the network administrators develop their LAN network diagramparticularly for small business or SOHO. But for medium-sized to enterprise class organizations, having a complete Computer network diagram is a must. Besides as documentation purposes, Computer network diagram can help you as the network administrators to maintain andtroubleshoot the networking problem as well as managing the network.

In the computer network diagram, all the networking devices should be identified by the IP addresses and be provided with well-managed labeling. If we are talking about the IP address, we should make a clear distinction in our LAN network diagram between the public (global) IP address and the private (internal) IP address. The private addresses must be hidden from the public network (the Internet) by a NAT mechanism configured in the firewall. Typically a firewall is a barrier or a border line between the trusted-network (our private – internal network) and the un-trusted network (the internet). Therefore the firewall must be a secured system. See also guidelines in firewalls security and the IP address classes.

Simple Back to Back Computers

The basic computer networking diagram can start with two computers which is configured in back to back. This configuration is typically used to transfer large amount of data between the two computers such as for full backup prior reinstallation of the OS platform. You can also perform full backup by using hard disk backup.

The figure 1 shows a computer network diagram for two computers configured in back to back. You need to use the UTP cross cable and connect each end of the cable into each of the NIC adapter ports (RJ-45 port). Or you can use a Switch to connect more than two computers to form a workgroup network. For connecting the computers to the Switch, you need to use the straight through type UTP cable. If your Switch supports the autosensing feature, you can use either cross or straight through network cable.

Figure 1 - Two computers network diagram

Computer Network Diagram – Share the Internet

Generally computer network diagram can be shown in the following figure. The LAN network diagram can be divided by two different networks: the private network (which sites behind the firewall) and the public network (that faces to the internet). The networking devices that sit in the public network typically consist of the CSU/DSU (which connect direct to the local loop of the Telco central office), a networking perimeter router (as the first line of defense against the internet threats), and the firewall.

Typically in home usage, the manufacturers ship the three devices into a single all-in-one product particularly for broadband internet connection such as SURFboard SBG900 by Motorola (for Cable services) or DGND3700 wireless ADSL modem router (for ADSL services). But many products ship with the function of the wireless router and the firewall separate from the modem such as Linksys E4200 N750 and WNDR4000 N750 wireless routers. Both are wireless gigabit simultaneous dual band routers with N750 technology (speeds up to 450Mbps in 5GHz band and up to 300Mbps in 2.4GHz band).

Figure 2 shows the conceptual computer network diagram that consists of private and public networks in block diagram. There are many routers with built-in modem that integrate the firewall, the router and the modem into a single device.

Please note that the IP addresses used must be different between the internal network (use the private IP address) and the public network (use the global IP address provided by your ISP).

Figure 2 - Shared internet - conceptual network diagram

In home usage, the wireless router typically has one WAN port (that connects direct to the LAN port of the modem with public IP address assignment) and 4 LAN ports with private address. The figure 3 shows a typical home wireless computer network diagram which uses a wireless router with shared printer, a modem that connects to the internet and some wireless clients including the Laptops with Wi-Fi enabled and XBOX game console with wireless adapter.

Figure 3 - Home Wireless router diagram

There several wireless routers that include a USB port that can be used to host a shared printer eliminating a print-server adapter.

Computer Network Diagram – Powerline

With the large house or multi-floor building, running the network backbone cable can be a hard work to complete. Drilling the walls to shorten the cable length or opening the ceilings to hide the clutter of the wires would be a lot of works to do. Not many users do mind with hassle of running the network cable. On other hand, building wireless network to cover the farthest corner of the building with a good signal strength is likely not possible particularly for streaming high definition media. The ideal solution for this type of network is by deploying Powerline adapter kits. See also home computer network – with powerline Ethernet adapter.

The figure 4 shows a computer networking diagram that uses Powerline adapter kits. The first floor where you build a wireless network, you connect the wireless router to the modem to share the internet. By adding a Powerline adapter connecting to the router Ethernet port, you enable the electrical wiring within the building as the virtual transmission medium for the network. Add a Powerline adapter with multi-port Ethernet in the second floor to let you join the home theater devices including XBOX, Blu-Ray player and HDTV to the internet.

Figure 4 Computer network diagram using powerline AV adapter

Redundant Computer Network Diagram

In medium to enterprise-class LAN network diagram, the computer network diagram is very complicated which might contain VLANs, redundant links, and sometimes contains multiple DMZs behind the firewalls.

The figure 5 is the example of the computer network diagram which contains redundant links for WAN connections, and also redundant links for each of the uplink switches.

Figure 5 Redundancy computer network diagram

In the above computer network diagram, the uplink switches are supplied from different two core switches. All the switches must be STP enabled if you configure multiple switches redundantly to avoid broadcast storm. See also STP protocol for more detail about Spanning tree protocol.

If you also configure multiple VLANs, in your LAN network diagram should mark each of the computers with each VLAN IDs. The use of layer 3 Switching will improve the performance of the LAN network if the VLANs are implemented. See more detail VLAN tutorial about VLAN ID.

In large networks, computer network diagram helps you to identify the critical items within the network, and you can make additional control for future disaster recovery. See also business continuity and disaster recovery plan and example of risk assessment.

LAN Topology

Talking about the Local area network, we should be familiar with the concept of the LAN topology that we use. There are many types of LAN topologies for different types of networks. We should also be familiar between physical topology and logical topology. Physical topology describes the layout of a network media such as copper cable, fiber optic cable, and most popular today is the wireless. While the logical topology is concerned about logical path through the network that data can take from one place to another.

See also Local area network topology in the real world deployed in industry.

The following are basic types of LAN topology:

• Bus
• Star
• Ring
• Mesh
• Hybrids

Bus Topology

The first type of LAN topology is the Bus topology which is the first type used in Ethernet network and consists of coaxial cable connected to all the computers on the LAN network. Each computer connected to the coaxial cable through a BNC-style T-connector. The following figure shows typical Bus topology.

All the computer network devices communicate through the same shared bus – so that’s why a bus is also a logical topology. Typically, collision detection (CD) or collision avoidance (CA) algorithms are used in bus topologies to arbitrate network access along with concepts such as “broadcasts” to reach every device on the cable.

Pro:

• LAN Bus topology is very simple and inexpensive to implement, there is only one main trunk.

Cons:

• LAN Bus topology requires proper termination on both ends of the bus. Improper termination will cause the network to be malfunction.
• One single trunk cable becomes a single point of failure, one break, causes all the network impact.
• Difficult in troubleshooting since you only have one single cable to share for all the computers on the network.

This type of bus LAN topology is not popular today, and it is part of the past and it is difficult today to find any types BNC type LAN adapter at the market.

LAN Star Topology

The second LAN topology is the Star topology. If you run a network cable from each computer to a centralized point such as a Switch, that is a simple concept behind the star topology. The switch handles the repeating or switching the traffic out to the other nodes on the network. The following figure shows the LAN Star topology.

Pro:

• Management is easy through the Switch at the port level. Administration and management can be done remotely by the authorized administrator. See also switch configuration.
• Any single failure of the port will not impact the whole network. See also network troubleshooting.
• Installation of the cable in each port will not disrupt LAN services
• No termination needed like in bus topology.

You should note that nearly every popular network technology today uses a star topology for its physical implementation.

Ring Topology

The third LAN topology is the Ring topology. Compared to bus and star topologies, ring topologies are more complex but they offer some attractive features. Nodes logically communicate in a ring formation, with each node communicating only directly with its upstream and downstream neighbors.

The following figure shows ring topology. Actually Ring topology is physically implemented using star topology.

In a ring topology, access to the network is controlled through a token that is passed from node to node as the arbitration mechanism. Each node takes its turn at claiming the token as the token passes from neighbor to neighbor, and when a node possesses the token, it takes its turn to transmit onto the ring. A data packet is transferred from one node to the next until it reaches its destination node. After the destination node has received the packet, it modifies the packet to acknowledge receipt and passes it on. Eventually, the packet makes it completely around the ring, and the transmitting node receives it and notes that the receipt has been acknowledged. When the transmitting node is finished, it releases the token to its neighbor, and the process repeats.

Ring topology is primary used by the Token-Ring networks.

Pro:

• No collision detection mechanism is required, so Token ring provides greater overall bandwidth use.
• Troubleshooting is easy by the fact that each node only knows its upstream and downstream neighbors.

Cons:

• The firmware required to manage the ring is somewhat complicated and must be on every network card that participates in the ring
• Expensive to implement and mostly the LANs today use Ethernet technology which dominate the market today.

Mesh Topology

Other LAN topology is a mesh topology which is an interlacing of multiple connections among several nodes. Typically, a mesh is done for one purpose: redundancy. Any serious campus network must incorporate a mesh to achieve the level of redundancy and fault tolerance that businesses demand from their data networks. There are two types of mesh: full and partial.

The following figure is a typical full mesh LAN topology, each devices has connection to each other devices on the network.

Pros:

• Partial meshes are designed to provide redundancy where it is needed

Cons:

• Except in the smallest network, a full mesh is not very practical
• The cost of the full mesh implementation is very expensive.

Hybrid Topologies

In large network environment, you can attach Switches one to another to create larger LAN to support more devices. Hybrid topologies combined the above topologies together to form three popular hybrid topologies: tree, hierarchical star, and star-wireless.

Tree Hybrid Topology

The figure below shows combination topology: the star topology combined together with the bus topology.

Pro:

• A single computer failure will not bring the entire network to halt.
• If one hub malfunctions, it disables only the workstations that are attached to it from communicating on the network. The remaining workstations on the other hubs can continue to function normally

Cons:

• If any problem with the backbone, each groups of the Switches will become segmented into individual Switch.

Hierarchical Star Topology

For large network environment you can configure switches in hierarchical star topology as shown in the following figure.

Pros:

• Can be used to build large networks.
• Switches can be configured redundantly to avoid single point of uplink failures

Cons:

• Size restrictions due to address space and timing issues without introduction of routing technology. See also Layer 3 Switching

Star Wireless

The most recent hybrid topology has arrived with the advent of wireless technology. Wireless LAN technology in its current implementation requires a user to be in the vicinity of a wireless access point attached to the wired network. See also wireless LAN for more detail.

The star topology is necessary to combine the many access points spread across a building to ensure wireless coverage. All the access points collapse back into the main star hub, where server resources would reside on the network. As wireless technologies continue to evolve, so will the topologies that support them.

http://www.computer-network.net/lan-topology

Firewall Topology

Firewall should cover the use of a suitable firewall, firewall topology and firewall security policy

The use of a suitable firewall, firewall topology and security policy is critical in ensuring protection against network security threats. A secured firewall must be used to provide protection against threats from external public (un-trusted) networks, such as the Internet. Networks must be segmented if distinct security boundaries are to be enforced.

A firewall is a system than controls the flow of traffic between networks and provides a mechanism for protecting hosts against network based security threats. It should be noted that firewalls cannot control (and protect against) traffic that does not flow through the security gateway (eg. a dialup modem will bypass any firewall), nor can it protect against internal or authorized attacks. Firewalls are only as secure as the firewall system and the implemented security policy (firewall rule base). Due to the number and variety of developing threats and security vulnerabilities being easily distributed on the Internet firewalls can never provide 100% protection against all possible threats. A suitable firewall must be used to interconnect to any external, public or un-trusted network (i.e. the Internet). This is mandatory due to the security threats that exist and the sensitive nature of information located within the corporate. A DMZ (De-Militarized Zone) must be used to provide segmentation of the network when hosting public resources, such as Internet web servers.

External Firewall with DMZ

Multiple DMZ’s may be used if a requirement exists for multiple network segments with differing security policies (levels). This has applications for extranets, intranets, web hosting and remote access gateways (as shown below).

External Firewall with multiple DMZ

The use of internal firewalls within the corporate is not encouraged due to the complications associated with ensuring that corporate core services such as Active Directory and Exchange messaging are not affected. An internal firewall may inadvertently deny these core services which are critical to the operations of the corporate network.

If an internal firewall is to be used, it must be configured using an appropriate security policy (gateway rule base). This is a requirement to ensure that core services such as DNS, DHCP, Active Directory and Exchange messaging is globally available.

The minimum requirement with regards to “Firewall Topology” in the firewall security standards are:

1. A suitable firewall must be used for all external connections.

2. Networks with differing security requirements must be segmented and protected with a firewall (eg. Internal (trusted) vs. Internet (un-trusted)).

3. A DMZ is mandatory for systems (eg. web servers) that are accessible from any public (un-trusted) network. These externally accessed hosts must not be placed on the corporate internal (business) networks.

4. Multiple DMZ’s may be used to provide network segments with multiple security classifications (or zones).

5. All physical firewall connections must be secure and appropriately label. It is recommended to use a color coding scheme to differentiate between private, public or DMZ networks.

6. All Internet (external facing) firewalls must be configured to deny all traffic unless explicitly permitted.

A suitable firewall topology ensures the ability to identify security boundaries within the network and to apply a valid security policy (rule base) to the security gateway (firewall).

Another series of firewall security standards, you should read about firewall requirement.

http://www.computer-network.net/firewall-topology