Routing, Routed and Non-RoutableProtocols

ROUTING PROTOCOLS

ROUTING PROTOCOLS are the software that allow routers to dynamically advertise and learn routes, determine which routes are available and which are the most efficient routes to a destination. Routing protocols used by the Internet Protocol suite include:

• Routing Information Protocol (RIP and RIP II)
• Open Shortest Path First (OSPF)
• Intermediate System to Intermediate System (IS-IS)
• Interior Gateway Routing Protocol (IGRP)
• Cisco's Enhanced Interior Gateway Routing Protocol (EIGRP)
• Border Gateway Protocol (BGP)

Routing is the process of moving data from one network to another network. Within a network, all hosts are directly accessable and do not need to pass data through a default gateway. All hosts on the same network are directly connected and can communicate directly with each other.

ROUTED PROTOCOLS

ROUTED PROTOCOLS are nothing more than data being transported across the networks. Routed protocols include:

• Internet Protocol
  • Telnet
  • Remote Procedure Call (RPC)
  • SNMP
  • SMTP
• Novell IPX
• Open Standards Institute networking protocol
• DECnet
• Appletalk
• Banyan Vines
• Xerox Network System (XNS)

Outside a network, specialized devices called ROUTERS are used to perform the routing process of forwarding packets between networks. Routers are connected to the edges of two or more networks to provide connectivity between them. These devices are usually dedicated machines with specialized hardware and software to speed up the routing process. These devices send and receive routing information to each other about networks that they can and cannot reach. Routers examine all routes to a destination, determine which routes have the best metric, and insert one or more routes into the IP routing table on the router. By maintaining a current list of known routes, routers can quicky and efficiently send your information on it's way when received.

There are many companies that produce routers: Cisco, Juniper, Bay, Nortel, 3Com, Cabletron, etc. Each company's product is different in how it is configured, but most will interoperate so long as they share common physical and data link layer protocols (Cisco HDLC or PPP over serial, Ethernet etc.). Before purchasing a router for your business, always check with your Internet provider to see what equipment they use, and choose a router which will interoperate with your Internet provider's equipment.

NON-ROUTABLE PROTOCOLS

NON-ROUTABLE PROTOCOLS cannot survive being routed. Non-routable protocols presume that all computers they will ever communicate with are on the same network (to get them working in a routed environment, you must bridge the networks). Todays modern networks are not very tolerant of protocols that do not understand the concept of a multi-segment network and most of these protocols are dying or falling out of use.

• NetBEUI
• DLC
• LAT
• DRP
• MOP

What you mean by RIP v1,v2,OSPF,IGRP,EIGRP?

What you mean by RIP v1,v2,OSPF,IGRP,EIGRP?

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By karthickjck

ROUTING PROTOCOL

RIP V1: It is a simple distance vector protocol. It has been enhance with various techniques, including Split Horizon and Poison Reverse in order to enable it to perform better in complicated network

The longest path cannot exceed 15 hops.

RIP uses static metrics to compare routes.

ADMINISTRATIVE DISTANCE:120

METRIC:HOB COUNT

What you mean by RIP v2?

RIP V2: It added several new features.

External route tags.

Subnet masks

Next hop router addresses.

Authentication.

Multicast support.

METRIC:SAME AS RIP V1

Explain about OSPF?

OSPF: Open Shortest Path First is a dynamic routing protocol for use in Internt Protocol(IP networks).It is a link state routing protocols. It falls into the group of interior gateway protocols, operating within an autonomous system(AS). Link-State routing protocol that calls for the sending of link-state advertisements (LSAs) to all other routers within the same hierarchial area. Information on attached interfaces, metrics used, and other variables is included in OSPF LSAs. As OSPF routers accumulate link-state information, they use the SPF algorithm to calculate the shortest path to each node.

METRIC: COST=bandwidth/interface bandwidth

AD:110

Explain about EIGRP?

EIGRP: EIGRP is a Cisco proprietary routing protocol derived from IGRP. EIGRP can be called as hybrid protocol or an advanced distance-vector routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and procession power in the router. Routers that support EIGRP will automatically redistribute route information to IGRP neighbors by converting the 32 bit EIGRP metric to the 24 bit IGRP metric. Most of the routing optimizations are based on the Diffusing update Algorithm(DUAL).

MERIC: Load, delay,bandwidth, reliability and MTU

Explain about IGRP?

IGRP:IGRP is a distance vector Interior Gateway Protocol(IGP). Distance vector routing protocols mathematically compare routes using some measurement of distance. This measurement is know as distance vector. Routers using a distance vector protocol must send all or a portion of their routing table in a routing-update message at regular intervals to each of their neighboring routers. As routing information proliferates through the network, routers can identify new destinations as they are added to the network, learn of failures in the network, and, most improtanly, calculate distances to all know destinations. IGRP uses a composite metric that is calculated by factoring weighted mathematical values for internetwork delay, bandwidth, reliability, and load. Network administrators can set the weighting factors for each of these metrics. Default metrics are Reliability and load.

Administrative Distance:100

MERIC: Load, delay,bandwidth, reliability and MTU

What is CDMA?

CDMA=

CDMA stands for Code Division Multiple Access. It is a technique used for digital communication, and wireless technology in particular, that involves multiplexing. Whereas conventional communication systems use constant frequencies, CDMA uses multiple access, or multiplexing. Multiplexing, in this case accomplished through the specific type known as spread spectrum, uses varied frequencies to transmit audio signals. This, coupled with code division which requires a certain code to send and receive the frequency, further protects CDMA communications from interference.

Radio systems, one of the earliest forms of telecommunication, required users to have distinct frequencies. Two earlier forms of wireless communication illustrated the limits of methods previous to CDMA. Frequency Division Multiple Access or FDMA only allowed users to operate on a single frequency. For instance, when tuning in to a radio to get sound, a listener must select one frequency or the other. The listener must also tune the frequency to filter out noise in the spectrum that is not associated with one frequency or the other.

The other form of early radio communication was Time Division Multiple Access or TDMA. In this case, users could not share a frequency and each user had to coordinate his or her turn on that frequency in order to communicate. Both FDMA and TDMA posed restrictions for early users, particularly the military. As early as World War II, the military needed to communicate across vast distances that required wireless technology. That was also the case for their adversaries. Military communication units did not have time to wait their turn to transmit sound, or to find a frequency.

Previous telecommunication systems allowed military communication units to transmit sound into the same spectrum their adversaries used. The military’s signals needed a unique identification through a distinct code to avoid interference from enemy communication. The receiver of that message on the other end could similarly retrieve the message based on its unique code in the spectrum.

Just as the radio moved from military use to commercial use, so too was the case with the wireless technology. CDMA became the early choice for personal communication because it could allow multiple users to communicate within the spectrum, avoiding interference or blocking among users. In 1999, CDMA became the standard technology for the telecommunications industry for its growing wireless systems. Since there are large numbers of users in the system communicating at the same time, code division ensures that each user’s signal remains separate in the spectrum.

What is Firewall?

Firewall=
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

There are several types of firewall techniques:

Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.

Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.

Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.

Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

In practice, many firewalls use two or more of these techniques in concert.

A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.

what is VPN?

What is a virtual private network (VPN)?

A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.

A VPN works by using the shared public infrastructure while maintaining privacy through security procedures and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be "entered" by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also the originating and receiving network addresses.

ping command

he ping command is useful for determining the status of the network and various foreign hosts, tracking and isolating hardware and software problems, and testing, measuring, and managing networks

Some ping command options relevant to performance tuning are as follows:

-c

Specifies the number of packets. This option is useful when you get an IP trace log. You can capture a minimum of ping packets.

-s

Specifies the length of packets. You can use this option to check fragmentation and reassembly.

-f

Sends the packets at 10 ms intervals or immediately after each response. Only the root user can use this option.

If you need to load your network or systems, the -f option is convenient. For example, if you suspect that your problem is caused by a heavy load, load your environment intentionally to confirm your suspicion. Open several aixterm windows and run the ping -f command in each window. Your Ethernet utilization quickly gets to around 100 percent. The following is an example:

# date; ping -c 1000 -f 192.1.6.1 ; date
Thu Feb 12 10:51:00 CST 2004
PING 192.1.6.1 (192.1.6.1): 56 data bytes
.
--- 192.1.6.1 ping statistics ---
1000 packets transmitted, 1000 packets received, 0% packet loss
round-trip min/avg/max = 1/1/23 ms
Thu Feb 12 10:51:00 CST 2004

Note: The ping command can be very hard on a network and should be used with caution. Flood-pinging can only be performed by the root user.

In this example, 1000 packets were sent within 1 second. Be aware that this command uses IP and Internet Control Message Protocol (ICMP) protocol and therefore, no transport protocol (UDP/TCP) and application activities are involved. The measured data, such as round-trip time, does not reflect the total performance characteristics.

When you try to send a flood of packets to your destination, consider several points:

• Sending packets puts a load on your system.
• Use the netstat -i command to monitor the status of your network interface during the experiment. You may find that the system is dropping packets during a send by looking at the Oerrs output.
• You should also monitor other resources, such as mbufs and send/receive queue. It can be difficult to place a heavy load onto the destination system. Your system might be overloaded before the other system is.
• Consider the relativity of the results. If you want to monitor or test just one destination system, do the same experiment on some other systems for comparison, because your network or router might have a problem.

Telnet

A terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. To start a Telnet session, you must log in to a server by entering a valid username and password. Telnet is a common way to remotely control Web servers.

DHCP

Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task. This means that a new computer can be added to a network without the hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP addressing for dial-up users.

Difference in Hub, Switch, Bridge, & Router

Difference in Hub, Switch, Bridge, & Router

Hub
A hub is the simplest of these devices. Any data packet coming from one port is sent to all other ports. It is then up to the receiving computer to decide if the packet is for it. Imagine packets going through a hub as messages going into a mailing list. The mail is sent out to everyone and it is up to the receiving party to decide if it is of interest.

The biggest problem with hubs is their simplicity. Since every packet is sent out to every computer on the network, there is a lot of wasted transmission. This means that the network can easily become bogged down.

Hubs are typically used on small networks where the amount of data going across the network is never very high.

Bridge
A bridge goes one step up on a hub in that it looks at the destination of the packet before sending. If the destination address is not on the other side of the bridge it will not transmit the data.

A bridge only has one incoming and one outgoing port.

To build on the email analogy above, the bridge is allowed to decide if the message should continue on. It reads the address bob@smith.com and decides if there is a bob@smith.com on the other side. If there isn’t, the message will not be transmitted.

Bridges are typically used to separate parts of a network that do not need to communicate regularly, but still need to be connected.

Switch
A switch steps up on a bridge in that it has multiple ports. When a packet comes through a switch it is read to determine which computer to send the data to.

This leads to increased efficiency in that packets are not going to computers that do not require them.

Now the email analogy has multiple people able to send email to multiple users. The switch can decide where to send the mail based on the address.

Most large networks use switches rather than hubs to connect computers within the same subnet.

Router
A router is similar in a switch in that it forwards packets based on address. But, instead of the MAC address that a switch uses, a router can use the IP address. This allows the network to go across different protocols.

The most common home use for routers is to share a broadband internet connection. The router has a public IP address and that address is shared with the network. When data comes through the router it is forwarded to the correct computer.

This comparison to email gets a little off base. This would be similar to the router being able to receive a packet as email and sending it to the user as a fax.

What is LAN, MAN,WAN and SAN

LAN - Local Area Network

A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet.

In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring.

WAN - Wide Area Network

As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth.

A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.

A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances.

LAN, WAN and Home Networking

Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically a broadband router, to reach the ISP.

Other Types of Area Networks

While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others:

• Wireless Local Area Network - a LAN based on WiFi wireless network technology
• Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned an operated by a single entity such as a government body or large corporation.
• Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.
• Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel.
• System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.

The OSI Model vs. The Real World

The OSI Model vs. The Real World

The most major difficulty with the OSI model is that is does not map well to the real world!

The OSI was created after many of todays protocols were already in production use. These existing protocols, such as TCP/IP, were designed and built around the needs of real users with real problems to solve. The OSI model was created by academicians for academic purposes.

The OSI model is a very poor standard, but it's the only well-recognized standard we have which describes networked applications.

The easiest way to deal with the OSI model is to map the real-world protocols to the model, as well as they can be mapped.

Layer	Name	Common Protocols
7	Application	SSH, telnet, FTP
6	Presentation	HTTP, SMTP, SNMP
5	Session	RPC, Named Pipes, NETBIOS
4	Transport	TCP, UDP
3	Network	IP
2	Data Link	Ethernet
1	Physical	Cat-5

The difficulty with this approach is that there is no general agreement as to which layer of the OSI model to map any specific protocol. You could argue forever about what OSI model layer SSH maps to.

A much more accurate model of real-world networking is the TCP/IP model:

TCP/IP Model
Application Layer
Transport Layer
Internet Layer
Network Interface Layer

What is the OSI Model?

What is the OSI Model?

The OSI model is a reference model which most IT professionals use to describe networks and network applications.

he OSI model was originally intended to describe a complete set of production network protocols, but the cost and complexity of the government processes involved in defining the OSI network made the project unviable. In the time that the OSI designers spent arguing over who would be responsible for what, TCP/IP conquered the world.

The seven layers of the OSI model are:

Layer	Name
7	Application
6	Presentation
5	Session
4	Transport
3	Network
2	Data Link
1	Physical

The easiest way to remember the layers of the OSI model is to use the handy mnemonic "All People Seem To Need Data Processing":

Layer	Name	Mnemonic
7	Application	All
6	Presentation	People
5	Session	Seem
4	Transport	To
3	Network	Need
2	Data Link	Data
1	Physical	Processing

The functions of the seven layers of the OSI model are:

Layer Seven of the OSI Model

The Application Layer of the OSI model is responsible for providing end-user services, such as file transfers, electronic messaging, e-mail, virtual terminal access, and network management. This is the layer with which the user interacts.

Layer Six of the OSI Model

The Presentation Layer of the OSI model is responsible for defining the syntax which two network hosts use to communicate. Encryption and compression should be Presentation Layer functions.

Layer Five of the OSI Model

The Session Layer of the OSI model is responsible for establishing process-to-process commnunications between networked hosts.

Layer Four of the OSI Model

The Transport Layer of the OSI model is responsible for delivering messages between networked hosts. The Transport Layer should be responsible for fragmentation and reassembly.

Layer Three of the OSI Model

The Network Layer of the OSI model is responsible for establishing paths for data transfer through the network. Routers operate at the Network Layer.

Layer Two of the OSI Model

The Data Link Layer of the OSI model is responsible for communications between adjacent network nodes. Hubs and switches operate at the Data Link Layer.

Layer One of the OSI Model

The Physical Layer of the OSI model is responsible for bit-level transmission between network nodes. The Physical Layer defines items such as: connector types, cable types, voltages, and pin-outs.