Chapter 6 Network Hardware

Chapter 6 Network Hardware

As it stated in the book “To understand the process it’s helpful to compare data transmission to the means by which the Canadian Postal Service delivers mail: Mail trucks, airplanes, and delivery staff serve as the transmission system that moves information from place the place. ” Network hardware is the transmission system that moves our data around the world to the correct recipient.

NICs (Network Interface Cards) act as mailboxes (Transceiver on both Physical and Data Link Layer of the OSI model) on the servers and workstations where the data is transmitted and received. Advances in NIC technology have made it so many NICs can also perform prioritization, network management, buffering and traffic filtering. Most new computers come with Gigabit NICs installed however, if you purchase a NIC today purchase Gigabit NIC and verify it is backward compatible!

The following are the two internal bus NICs:
• PCI is the most popular using a PCI slot on the mother board for installation.
• PCIe is also popular using the PCI Express slot on the motherboard.

The following are the four external bus NICs:
• Personal Computer Memory Card International Association or PCMCIA used mainly with laptops.
• USB (universal serial bus) NIC port using two USB standards 1.1: transfer rate of 12 Mbps and 2.0: transfer rate of 480 Mbps In the future there will be USB 3.0: transfer rate of 4.8 Gbps.
• Fire wire is another connection type developed by Apple Computer (1980s)–IEEE 1394 standard (1995) Traditional Firewire connection: 400 Mbps (max)Newer version: 3 Gbps
• CompactFlash NIC Latest standard: 4.0 Data transfer rate: 133 Mbps, connects devices too small for PCMCIA slots.

Wireless NIC’s are supported and installed on all bus types.

Interpreting LED Indicators
ACT - Indicates that the NIC is either transmitting or receiving data.
LNK - Indicates the NIC is functional.
TX - Indicates the NIC is functional and transmitting frames to the Network.
RX - Indicates the NIC is functional and receiving frames to the Network.

IRQ (Interrupt Request) – is a message to the computer that instructs it to stop what it was doing and pay attention to something else. NICs are devices installed most likely on IRQ 9, 10, or 11.

Repeater & Hubs operate on the physical layer of the OSI model and therefore, have no means to interpret the data they transmit. They can’t detect and/or improve bad or erroneous data they merely just repeat it. They share one connection (collision domain) with all other devices. These are becoming rarer in modern day networks.

Bridges operate at the data link layer of the OSI model. A bridge connects two network segments adding length beyond the segments maximum limits. Hence the name a bridge determines if the node needs to cross the bridge to talk with and another node. If it recognizes the node is on its side/segment it doesn’t cross over the bridge keeping local traffic on its side/segment of the bridge however, if it recognizes the node is trying to communicate with a node on the other side/segment it crosses over expanding the reach of the node.

Switches operate traditionally at data link layer of the OSI model switches operate at layers 3(Network) and 4(Transport). So instead of having 2 hubs with a bridge between them you can use a switch (multi port bridge) to connect and separate collision domains (hubs). Each channel on the switch represents its own collision domain limiting the potential for collisions.

Switching methods although there are four methods, the two following basic methods are most popular. Cut-Through Mode: The switch reads frame’s header (the first 14 bytes contains destination MAC address) and forwards before receiving entire packet. Although it can detect runts (shortened packets) it can’t detect corrupt packets which may increase the number of errors found on a network. The other method is Store-and-Forward Mode: The switch reads entire data frame into memory taking more time, then checks for accuracy before transmitting accurate information. Used in larger LAN mixed environments transferring data between segments running different transmission speeds.

With Switches you can create VLANs (virtual local area networks) and Trunking to logically separate networks within networks, by grouping a number of ports into a broadcast domain. One potential problem is that by grouping together certain nodes, you are also excluding another group. Planning needs to be carefully thought out so that you aren’t creating an Administrative nightmare so, use caution if you think you need to set one up. Personally I think for security could use the NO (Network Operating System) and really only seeing this used maybe for some type of high speed line access?

To prevent looping Switches use STP (Spanning Tree Protocol) technology that operates in the Data Link layer calculating paths avoiding potential loops and artificially blocking links completing loop. It takes the following three steps to do this, it first selects a root bridge, examines the possible paths between them the disables paths/links that are not part of the shortest path avoiding a loop back.

Switches operate at the data link layer of the OSI model and routers operate in the network layer of the OSI model. Now manufactures are producing Content and Multilayer Switches that are similar to routers and able to also operate on the Network and Transport layer know as a Layer3 and 4 switches. They are also producing switches that interpret Layer 4 through Layer 7 data know as content/application switches. Giving these types of switches the ability to do advance filtering, statistic recording and security functions.

Routers as noted earlier operate at the Network layer of the OSI model. Multiport connectivity device used to integrate and direct data through LANs and WANs. They operate at different transmission speeds, protocols and are slower than switches and bridges. From my experience these mainly have been used to tie in T1 or other internet connections to the LAN. They determine shortest, fastest path between two nodes connecting dissimilar network types.

The following are the six common routing protocols under the three sections, Distance-Vector, Link-State and Hybrid to give the Best path most efficient route from one node to another. Routers do this by looking at current information, hops between nodes, network activity, transmission speed, link availability, topology… This is characterized as convergence time the time it takes for a router to recognize a best path.

Distance-Vector: Determine best route based on distance to destination (Hops, latency, network traffic conditions). The following three protocols are distance-vector protocols.
RIP (Routing Information Protocol) and RIPv2 Only factors in number of hops between nodes.
BGP (Border Gateway Protocol) is configurable to follow policies which makes them the most complex to use.

Link-State: Is a protocol that enables routers to share information. This information is then used by each router independently maps network to determine the best path. It relies on their neighbors’ data path information. The following two protocols are distance-vector protocols.
OSPF (Open Shortest Path First) It uses interior or border router for it information. Unlike RIP there is no hop limit and uses a more complex algorithm to determine best path.
IS-IS (Intermediate System to Intermediate System) was originally codified by ISO, which referred to routers and “intermediate systems”. IS-IS is designed only for use on interior routers.

Hybrid: EIGRP (Enhanced Interior Gateway Routing Protocol) is the most popular which uses Link-state and distance-vector characteristics. These are easy to setup and has a fast convergence time with low network overhead. It supports multiple protocols
and accommodates very large, networks.

Gateways and Other Multifunction Devices are combinations of networking hardware and software used to connect two dissimilar networks using different formatting, communications protocols, and architecture to repackaging information.
They reside on servers, microcomputers, connectivity devices, mainframes. Examples of these are E-mail gateways, Internet gateways, LAN gateways, Voice/data gateways, and Firewalls.