TCP IP Data Encapsulation

TCP IP Data Encapsulation

Data Encapsulation is a process in which, some additional information (such as header or tailor) is added in to the data while travelling from one host to another host over the network through the OSI layer.

It is about creating and wrapping user’s data with the control information layer by layer. 

To communicate information, each layer uses Protocol Data Units (PDUs) that holds the control information attached to the data at each layer of the model.

The data encapsulation works at transmitting host like;

• User information is converted in to data for transmission on the network.
• Data is converted to segments and a reliable connection is made.
• Segments are converted to TCP packet or UDP datagrams. A logical address is added at header.
• Then the converted segment are sent to network layer where they are converted to frames for transmission on the local network.
• Frames are converted to bits then and sent to receiver address.

De-encapsulation

This is the reverse of encapsulation process. The additional information is removed at receiver end from physical layer to application layer. The physical layer receives the bits data, de-encapsulates them in to frames and then sends them to upper layer.

The benefits of encapsulation

The prime benefit of encapsulation is security in transmission. Further it enhances maintenance, increases usability. 

-DR

Basics of Protocols

Protocols:

Protocols or Communication protocol is is a system of Digital message format or some rules, guidelines, some syntax  for exchanging message or information in between the computer systems or network devices.

Protocol is a set of rule for communication. 

Example of single protocols :Apple talk, ATM, Bluetooth.

There are various types of protocols in network lifecycle.  Also there are multiple protocols work in a single protocol called Protocol Suite. for Example : IP ( internet Protocol )

List Of Network protocols :

1.ARCNET

2.Apple talk

3.Bluetooth

4.ATM

5.Ethernet

6.FDDI

7.IP suite

8.IEEE 802

9.IPX

10.USB

11.Frame Relay

12. X.25 protocol suite

13. SS7

14.Decnet

15.H.323

16.PPP

And many more used for telecommunication field. But we can discuss here only IP suite which is more vital for network operations.

IP PROTOCOL SUITE ( TCP/IP):

IP Protocol Suite works in network devices ,interfaces, systems, Routers , Switches , Network Security Devices. The protocols inside the IP suite or known as TCP/IP suite  are as;

ARP/RARP, ATMP, BGMP, BGP-4, COPS, DCAP, DHCP, DHCPv6, DNS, DVMRP, EGP, EIGRP, ESP, FANP, Finger, FTP, GOPHER, GRE, HSRP, HTTP, ICMP, ICMPv6, ICP, ICPv2, IDRP, IGMP, IGRP, IMAP4, IMPP, IP, IPv6, IPDC, IRC, L2F, L2TP, LDAP, LDP, MARS, MDTP, Megaco (ASCII + ASN.1), Mobile IP, MZAP, NARP, Nat, NetBIOS/IP, NHRP, NTP, OSPF, PIM, POP3, PPTP, Radius, RIP2, RIPng for IPv6, RSVP, RTSP, RUDP, SCSP, SCTP, SDCP , SLP, SMPP,SSH, SMTP, SNMP, SOCKS, TACACS+, TCP, TELNET, TFTP, TRIP, UDP, Van Jacobson, VRRP, WCCP, XOT, X-Window.

As per requirement of protocols in an organization from small to large size up to data center ,  protocols are configured in router and L3 switches. 

We will see details Later  in configuration /and as Application Layer Protocols.

-DR

   

Basics of OSI Model and TCP/IP Model

OSI MODEL

OSI Layer

To run a network OSI (Open systems interconnection) model is just act as A guideline prepared by ISO (International organization for Standardization).

It provides a framework for building and implementing networking standards, devices and other interconnections. 

When a communication system is designed in this manner it is called Layered architecture. 

Now a days many devices work at the all seven layers of OSI model.

The OSI have seven layers. This is further divided in to two groups. The top three layers (Session, Presentation and Application) define how the application communicates with each other and with users. The down four layers (Physical, Datalink, Network and Transport) shows how data is communicated end to end. 

The Seven (7) Layers are as below;

7. Application Layer

6. Presentation Layer

5. Session Layer

4. Transport Layer

3. Network Layer

2. Data link Layer

1. Physical Layer

Now a days new model is working i.e TCP/IP model.

• Layers 7, 6, and 5 correspond to Application layer in TCP/IP model
• Layer 4 correspond to Transport layer in TCP/IP model
• Layer 3 corresponds to Internet layer in TCP/IP model
• Layer 2 and 1 correspond to Network Interface layer in TCP/IP model
• Protocols that were not originally part of the TCP/IP specifications are referred not by position in TCP/IP model but by OSI model.    

Protocols, their port numbers and layers in TCP/IP model :-

• Protocol number - is used to define a stream of data associated with a specific service.
• The transport is provided by TCP and UDP protocols.
• Internet layer protocols are ARP, IP and ICMP.
• HTTP - hypertext transfer protocol TCP port 80 (application layer).
• SSL - Secure socket layers TCP port 443.
• SMTP - TCP port 25. Files stored in LocalDrive:\Inetpub\Mailroot.
• SNMP - simple network management protocol used to provide information about TCP/IP hosts, UDP port 161.
• FTP - only basic authentication allowed, TCP port 20 (data) TCP port 21 (control). Files stored in LocalDrive:\Inetpub\Ftproot (application layer)
• POP - TCP port 110
• DNS - UDP port 53 (query) TCP port 53 (zone transfer)
• NNTP - TCP port 119. Files stored in LocalDrive:\Inetpub\Nntpfile\Root
• PPTP - Point to point tunneling protocol TCP port 1723; protocol number 47
• L2TP/IPSec - UDP ports 500, 1701 and 4500; protocol number 50
• ARP, ICMP and IP (internet layer).  

 TCP/IP:

• The TCP/IP model is the newer networking model, OSI Open System Interconnection model is an older model
• Network interface - is the layer in the communications process that describes standards for physical media, for example ethernet. In OSI model it is both Physical layer and Data link layer.
• Internet - is the layer in the communications process during which information is packaged, addressed and routed to other network destinations. ARP is used for address resolution, IP for addressing and routing data and ICMP for reporting errors and exchanging limited control/status information. In OSI model this layer is called the Network layer.
• Transport - is the layer in the communications process during which the standards of data transport are determined. TCP protocol with its guarantees of delivery and connectionless unguaranteed but fast UDP protocol. This layer has the same name in the OSI model.
• Application - is the layer in the communications process during which end user data is changed, packaged and sent to and from transport layer, for example telenet. In OSI we have three layers, Session, Presentation and Application.

.Problems with TCP/IP connections:

• Network diagnostics - is a graphical tool that administrator can access from help and support tools menu. Users can save output to a file for examination by network administrator.
• Netdiag -  is a command line tool that is used to run different network tests. Administrator needs to install the tool first from the Windows CD, the support tools file is called suptools.msi.
• Tracert - shows the path a packet takes to reach given destination, this is done by setting different TTL values in the IP header of ICMP echo requests. Up to 30 hops, tells administrator when connectivity stops.
• Pathping - as tracert but shows the path that a packet takes to reach a given destination, however it also shows detailed analysis of traffic. Used to troubleshoot erratic network behaviour such as packets being delayed, where tracert is used for network connectivity.
• Arp - used to show the Arp cache on the PC. Sometimes local network computers can have wrong MAC addresses of each other cached and thus cannot communicate, use arp to check whatever addresses are correct. To cleat arp cache use arp -d command. Arp -a is used to check hardware address mappings, if it checks out look for hardware problem
• If the administrator is able to ping loopback address, PC own address and the local gateway but no other PCs the problem is most likely with arp cache being corrupted.
• Troubleshooting steps: loopback, local PC, default gateway, remote host by IP, remote host by name.

 -DR

Basics of a Repeater

Repeater

Repeater is a physical layer networking devices that amplifies and regenerates an incoming analogue/ digital signal before transmitting. The repeater simply works as a relay here and extends the coverage area.

Why it is required

Signals ideally loss or get attenuated during the transmission. A repeater reconstructs or regenerates the signal and transmits ahead. Thus it is also known as signal boosters. 

When the signal communicated in a channel, it gets attenuated depending upon the nature of the channel which seems a limitation of the LAN or cellular coverage. Repeaters installed in specific intervals can help in solving the problem. It restores the signal shape.

The best use of repeater is while it connects two LANs and creates a large LAN network. Multiple LAN can connect to make a single LAN.

There are different types of repeater available such as

• Digital Repeater
• Analogue Repeater
• Wired Repeater
• Wireless Repeater

Advantages

• They are simple to install and does not impact on network performance.
• They are cost effective
• It provides stability of the signals while eliminating the distance
• They can support dynamic networking
• They support all type of signals such as digital, analogue, electrical, light based. 

Demerit

• It cannot be managed.
• It cannot recognize packets, noises for any filtration purpose.

-DR

Basics of SWITCH

BASIC OF A SWITCH

A switch or network switch or called as LAN switch is a device that connects network devices as like hubs, Its more than a HUB. Its also referred as multi-port  network bridge.

• Switches operate at data link or network layer of OSI layer.
• It connects different type of network like ethernet ,fiber.
• A layer-2 switch provides hardware based bridging and uses application specific integrated circuits  ( ASICs).
• It is used to breakup the collision Domain.

• Switches create separate collision domain but a single broadcast domain.
• Main purpose of using a switch is to optimize the LAN performance and providing better bandwidth to LAN users. They only switch frame packets from one port to another.
• Switches provide dedicated collision domain and also independent bandwidth on each port.
• It comes with many Ports like hub, 12,24,28,  etc.
• Different vendors have different switches for wired and wireless LAN like Cisco, D-Link, Juniper ,Huawei, Aruba.
• Same as routers there also series of switches in cisco and other vendors.

In networking the switch is represented as symbol like :-

 

There are basic three switch Functions at layer-2 and are :

1.Address Learning

2.Forward/filter decisions

3.Loop avoidance

More information can be referred at section Basics of Switching under this Blog.

RPS

RPS a product from Cisco is Redundant Power System. It provides power supply redundancy and resiliency for switches and routers power requirement through POE (Power over Ethernet) mode.

Basically the RPS was used for catalyst models such as 3750-E, 3560-E. It avoids network downtime by preventing switch reboot after a internal switch failure. It is ease of use and ease of deployment. 

Virtual Switch:

Now a days there are virtual switches introduced in the market. A virtual switch works with virtual NIC. The virtual NIC is is software linked with unique MAC address that can be later used by a virtual machine to send and receive packets. 

-DR

Basics of HUB

Network HUB 

A HUB is a device, used in a LAN environment or used for connecting more than one computer. It has many number of PORTS for connection via UTP (RJ 45)cable. It is a small rectangular plastic box type having 4-5 PORTS. Similarly Large HUBS ranges from 8,12, 24 PORTS.

• When a message (DATA) is passed from one computer to the HUB, then the HUB broadcasts the message to all of its PORTS means all other computers can access in the same time. Which may occur Collision in the DATA access, transfer .
• One Advantage of using HUB is its very less expensive compared to switches.
• The Disadvantage is ,the ports lie in single collision domain. The message or data comes to the HUB repeats many time at ports. Its non secure as DATA can be tracked or hacked.

   

HUBs are physical layer ( L1 ) devices and may be called as multiport repeater. Due to the broadcast feature, the packet frame is passed through all ports. 

Its basically useful for Home use or smaller networks as they are unmanaged.

-DR