NETWORKING DAY 9 (Network Management,Secure Internet Management and SNMP, Remote Monitoring (RMON), Wireless network, Wireless Channels,The MAC level (link layer), TDMA , CSMA/CA, Channel access network design, )

DAY - 9

Network Management

Network management is a broad range of functions including activities, methods, procedures and the use of tools to administrate, operate, and reliably maintain computer network systems. Strictly speaking, network Management does not include terminal equipment (PCs, workstations, printers, etc.). Rather, it concerns the reliability, efficiency and capacity/capabilities of data transfer channels.

Network Administration: This involves tracking and inventorying the many network resources such as monitoring transmission lines, hubs, switches, routers, and servers; it also involves monitoring their performance and updating their associated software – especially network management software, network operating systems, and distributed software applications used by network users. Network Operation: This involves smooth network functioning as designed and intended, including close monitoring of activities to quickly and efficiently address and fix problems as they occur and preferably even before users are aware of the problem.

Network Maintenance: This involves timely repair and necessary upgrades to all network resources as well as preventive and corrective measures through close communication and collaboration with network administrators. Example work includes replacing or upgrading network equipment such as switches, routers and damaged transmission lines.

 Network Provisioning: This involves configuring network resources to support the requirements of a particular service; example services may be voice capabilities or increasing broadband requirements to facilitate more users.

Secure Internet Management and SNMP

The Simple Network Management Protocol (SNMP) is the standard operations and maintenance protocol for the Internet. SNMP-based management not only produces management solutions for systems, applications, complex devices, and environmental control systems, but also provides the Internet management solutions supporting Web services. SNMPv3, the most recent standard approved by the Internet Engineering Task Force (IETF), adds secure capabilities (like encryption).

Leadership, Experience, Reliability, and Support

SNMP Research provides comprehensive tools for secure management, policy deployment, and agent and manager development using SNMPv1, SNMPv2c, and SNMPv3. Products and services are used worldwide by end-users, Original Equipment Manufacturers, value-added resellers, and embedded systems suppliers.

Built Upon Open Standards

SNMP Research is a leading-edge producer of standards-based products and participates in the IETF SNMP open management standards working groups. SNMP Research was the first company to support SNMPv3. Dr. Jeff Case, founder of SNMP Research, and other engineers at SNMP Research authored or co-authored SNMPv1, SNMPv2c, SNMPv3, and many related

MIB (Management Information Bases) documents.

Remote Monitoring (RMON)

Remote Monitoring (RMON) performs extensive network-fault detection and provides performance-tuning data to NAs. Remote Monitoring (RMON) is a standard specification that facilitates the monitoring of network operational activities through the use of remote devices known as monitors or probes. RMON assists network administrators (NA) with efficient network infrastructure control and management.

RMON was initially developed to address the issue of remote site and local area network (LAN) segment management from a centralized location. The RMON standard specifies a group of functions and statistics that may be exchanged between RMON compatible network probes and console managers. RMON

RMON collects nine information types, including bytes sent, packets sent, packets dropped and statistics by host. NAs use RMON to determine network user traffic or bandwidth levels and website access information. Additionally, issue alerts may be preconfigured.

RMON uses certain network devices, such as servers, and contains network management applications that serve as clients. RMON controls the network by using its servers and applications simultaneously. When a network packet is transmitted, RMON facilitates packet status viewing and provides further information, in the event that a packet is blocked, terminated or lost.

Two RMON versions are available:

RMON1: Outlines 10 management information base (MIB) groups for standard network monitoring. MIB groups are viewable in most advanced network hardware.

RMON2: Focuses on higher traffic layers that exist above the medium access control (MAC) layer, Internet Protocol (IP) and application-level traffic. Facilitates network management applications to track all network layer packets.

Wireless network

What Is a Wireless Network?

A wireless local-area network (LAN) uses radio waves to connect devices such as laptops to the Internet and to your business network and its applications. When you connect a laptop to a WiFi hotspot at a cafe, hotel, airport lounge, or other public place, you're connecting to that business's wireless network

What Is a Wireless Network vs. a Wired Network?

A wired network connects devices to the Internet or other network using cables. The most common wired networks use cables connected to Ethernet ports on the network router on one end and to a computer or other device on the cable's opposite end.

 Wireless Network Benefits

Small businesses can experience many benefits from a wireless network, including: Convenience: Access your network resources from any location within your wireless network's coverage area or from any WiFi hotspot.

Mobility: You're no longer tied to your desk, as you were with a wired connection. You and your employees can go online in conference room meetings, for example.

Productivity: Wireless access to the Internet and to your company's key applications and resources helps your staff get the job done and encourages collaboration.

Easy setup: You don't have to string cables, so installation can be quick and cost-effective.

Expandable: You can easily expand wireless networks with existing equipment, while a wired network might require additional wiring.

Security: Advances in wireless networks provide robust security protections.

Cost: Because wireless networks eliminate or reduce wiring costs, they can cost less to operate than wired networks.

Images of wireless network

The following diagram shows a Smartphone controlling a lighting network via the Internet. The Smartphone application sends JIP commands to the lights, through the Internet and via the Internet Gateway into the JenNet-IP wireless network. The wireless microcontroller on each light in the network runs an application to interpret the JIP commands, control the light, and monitor energy consumption.

Wireless Channels

IEEE 802.11g/b wireless nodes communicate with each other using radio frequency signals in the ISM (Industrial, Scientific, and Medical) band between 2.4 GHz and 2.5 GHz. Neighbouring channels are 5 MHz apart. However, due to the spread spectrum effect of the signals, a node sending signals using a particular channel will utilize frequency spectrum 12.5 MHz above and below the centre channel frequency. As a result, two separate wireless networks using neighbouring channels (for example, channel 1 and channel 2) in the same general vicinity will interfere with each other. Applying two channels that allow the maximum channel separation will decrease the amount of channel cross-talk and provide a noticeable performance increase over networks with minimal channel separation.

The radio frequency channels used are listed in

Table 2-1. 802.11g Radio Frequency Channels
Channel	Centre Frequency	Frequency Spread
1	2412 MHz	2399.5 MHz - 2424.5 MHz
2	2417 MHz	2404.5 MHz - 2429.5 MHz
3	2422 MHz	2409.5 MHz - 2434.5 MHz
4	2427 MHz	2414.5 MHz - 2439.5 MHz
5	2432 MHz	2419.5 MHz - 2444.5 MHz
6	2437 MHz	2424.5 MHz - 2449.5 MHz
7	2442 MHz	2429.5 MHz - 2454.5 MHz
8	2447 MHz	2434.5 MHz - 2459.5 MHz
9	2452 MHz	2439.5 MHz - 2464.5 MHz
10	2457 MHz	2444.5 MHz - 2469.5 MHz
11	2462 MHz	2449.5 MHz - 2474.5 MHz
12	2467 MHz	2454.5 MHz - 2479.5 MHz
13	2472 MHz	2459.5 MHz - 2484.5 MHz

Wireless channel in Secure Public Systems

The top level of a wireless information network is shown in Figure 1. The public network (Internet and Phone) and the private network such as the one modeled as a university are usually not secure. The private networks modeled as an industry, a wireless service provider, and a private LAN are usually secure. Figure 1. also illustrates security firewalls for the secure private networks.

The MAC level (link layer)

This section of the document focus on the next layer up, the link layer. This mostly comprise the

MAC (Medium Access Control) protocol. Different MAC protocols and techniques are

presented.

Main channel access mechanisms

The main job of the MAC protocol is to regulate the usage of the medium, and this is done through a channel access mechanism. A channel access mechanism is a way to divide the main resource between nodes, the radio channel, by regulating the use of it. It tells each node when it can transmit and when it is expected to receive data. The channel access mechanism is the core of the MAC protocol. In this section, we describe TDMA, CSMA and polling which are the 3 main classes of channel access mechanisms for radio.

TDMA

In this chapter, we discuss TDMA as a channel access mechanism and not its applications and protocols based on it. TDMA (Time Division Multiplex Access) is very simple. A specific node, the base station, has the responsibility to coordinate the nodes of the network.

The time on the channel is divided into time slots, which are generally of fixed size.

Each node of the network is allocated a certain number of slots where it can transmit.

Slots are usually organised in a frame, which is repeated on a regular basis.

The base station specify in the beacon (a management frame) the organisation of the frame. Each node just needs to follow blindly the instruction of the base station. Very often, the frame is organised as downlink (base station to node) and uplink (node to base station) slots, and all the communications goes through the base station. A service slot allows a node to request the allocation of a connection, by sending a connection request message in it .In some standards, uplink and downlink frames are one different frequencies, and the service slots might also be a separate channel.

TDMA channel access mechanism:

TDMA suits very well phone applications, because those application have very predictable needs

(fixed and identical bit rate). Each handset is allocated a downlink and a uplink slot of a fixed size (the size of the voice data for the duration of the frame). This is no surprise why TDMA is used into all cellular phone standards (GSM in Europe, TDMA and PCS in the USA) and cordless phone standards (DECT in Europe). TDMA is also very good to achieve low latency and guarantee of bandwidth (where CSMA/CA is quite bad).

TDMA is not well suited for data networking applications, because it is very strict and inflexible.

IP is connectionless and generates burst traffic which is very unpredictable by nature, while TDMA is connection oriented (so it has to suffer the overhead of creating connections for single IP packets). TDMA use fixed size packets and usually symmetrical link, which doesn't suit IP that well (variable size packets). TDMA is very much dependant of the quality of the frequency band. In a dedicated clean band, as it is the case for cellular phone standard, TDMA is fine. But, because of it's inflexibility, and because it doesn't really take care of what's happening on the channel, TDMA can't cope and adapt to the busty interference sources found in the unlicensed bands (unless a retry mechanism is put on top of it).

CSMA/CA

CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is the channel access mechanism used by most wireless LANs in the ISM bands. A channel access mechanism is the part of the protocol which specifies how the node uses the medium: when to listen, when to transmit... The basic principles of CSMA/CA are listening before talk and contention. This is an asynchronous message passing mechanism (connectionless), delivering a best effort service, but no bandwidth and latency guarantee (you are still following?).  It's main advantages are that it is suited for network protocols such as TCP/IP, adapts quite well with the variable condition of traffic and is quite robust against interferences.

CSMA/CA is fundamentally different from the channel access mechanism used by cellular phone systems CSMA/CA is derived from CSMA/CD (Collision Detection), which is the base of Ethernet . The main difference is the collision avoidance: on a wire, the transceiver has the ability to listen while transmitting and so to detect collisions (with a wire all transmissions have approximately the same strength). But, even if a radio node could listen on the channel while transmitting, the strength of its own transmissions would mask all other signals on the air. So, the protocol can't directly detect collisions like with Ethernet and only tries to avoid them

Channel access network design:

Direct communication between an 802.11 wireless network adapter and an AP occurs over a common channel corresponding to a frequency range in the S-Band ISM frequency range. You set the channel in the AP, and the wireless network adapter automatically tunes to the channel of the AP with the strongest signal. The wireless network adapter continues communication with the AP until the signal gets weak, at which time it attempts to locate another AP with a stronger signal.

To reduce interference between wireless APs, ensure that wireless APs with overlapping signals use unique channel frequencies. The 802.11b standard reserves 14 frequency channels for use with wireless APs. Within the United States, the Federal Communications Commission (FCC) allows channels 1 through 11. In most of Europe, you can use channels 1 through 13. In Japan, you have only one choice: channel 14.

Figure 11.4 shows the 11 802.11b frequency channels available in the United States. Notice that the 802.11b signals overlap with adjacent channel frequencies. As a result, you can only use three channels (in the United States, channels 1, 6, and 11) without causing interference between adjacent APs.

Figure 11.4   Channel Overlap for 802.11b APs in the United States

Standards:

Designing a local area network from scratch is the project most consultants dream of. When it finally lands in your inbox, do you know where to start? This checklist of six potential design issues will help ensure your LAN project is a success You finally have the consulting project you've been waiting for: A customer is building a new office and has asked you to design their entire local area network (LAN), as their present infrastructure is outdated and has ports failing by the day. This is a consultant's dream! However, it can become a nightmare for you and your company if you design the network improperly.

Let's look at some big network design issues to consider when designing a new LAN for your customers.

Plan the network's complexity to be in line with the customer's IT expertise Switches and routers come with hundreds of features and functions. However, engineering too many bells and whistles into the network can create support problems in the future, if the customer's IT staff does not have some basic understanding of the features and functions you implement. Recognize the business's needs without making the network overly complex.

To PoE, or not to PoE?

More and more customers are deploying wireless LAN technology and IP telephony. Wireless LAN access points are easiest to install when Power over Ethernet (PoE) is available. IP telephony utilizes phones that connect to and draw power from the LAN. The days of the traditional PBX system are numbered; every vendor out there is moving towards IP PBX systems and handsets. Many customers will tell you "We are not using wireless," or "We will never move to IP telephony." They may not now (at least as far as their manager knows), but if you do a good job on this project, your customer will keep their equipment for at least three to five years. You'll do a great service to your customer if you can convince them to purchase PoE switches now. Then, when the CIO decides to move to WLAN or IP telephony in 18 months, the non-PoE switches won't have to be replaced

Redundancy

Network uptime becomes more critical every year. Spend time planning a design that provides network redundancy from a physical and logical perspective. For example, utilize dual fiber-optic uplinks from the wiring closets to the core switches. Ensure that chassis-based core switches have dual CPU cards. Be sure to think about items like default gateway redundancy. You can design the most redundant physical network in the world, but if it's not properly configured to provide Layer 3 IP Default Gateway redundancy and a failure occurs, your customer's network will grind to a screeching halt and you can be sure they will call you to ask why.

10 Gigabit Ethernet? 100 Gigabit? Do I need that?

Just because 10 Gigabit Ethernet is here today and higher speeds are coming does not mean that you need those ports all over the LAN. All too often customers purchase the fastest equipment possible thinking they need it, even though their existing 100 Mbps network is only running at 5% capacity. While it is definitely prudent to ensure that core switches can support these higher speeds, you may be advising the customer to waste a lot of money if you tell them that 10 Gigabit switches are needed everywhere.

Standards and maintenance

When designing a corporate network, try to standardize on a few different types of devices, as opposed to using a different type of switch in every wiring closet, even if all your equipment is from the same manufacturer. Standardizing on a few different types of hardware simplifies configuration and troubleshooting. It also allows the customer to keep cold spares of each device with next-business-day maintenance, allowing for more rapid and cost-effective responses to device failures.