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TCP/IP    

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TCP/IP


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Apr
20

TCP/IP

 

TCP/IP is the set of protocol suite as described under the OSI model for network communication in and on the Internet and Intranet networks.

 

It describes sub-netting and other similar methods to define networks and helps then communicate with one another.

 

The OSI Model can be referenced as a set of seven (7) layers, where in different applications work in close tie-up with one another to make possible the communication. They are:

 

Application Layer

 

Data

Presentation Layer

Session Layer

Transport Layer

Segment

Network Layer

Packets

Data Link Layer

Frame

Physical Layer

Bit

 

The first three layers response and receive / work on actual data.

Below that on the Transport Layer the Data is broken into segments.

Below that on the Network Layer Data is further broken into packets.

On the Data Link Layer Packets are further broken into Frames.

Below that on the Physical Layer the Frames are further broken into Bit(s) of data to be transferred.

 

 

A Little Description:

Suppose you have an xml file to be processed by your software;

Then the actual software processing the file :> This lies in the scope of Application Layer, the Presentation Layer and the Session Layer.

In this case Application Layer.

 

Transport and lower level layers are largely unconcerned with the specifics of application layer protocols. Routers and switches do not typically "look inside" the encapsulated traffic to see what kind of application protocol it represents; rather they just provide a conduit for it. However, some firewall and bandwidth throttling applications do try to determine what's inside, as with the Resource Reservation Protocol (RSVP). It is also sometimes necessary for network address translation (NAT) facilities to take account of the needs of particular application layer protocols.

 

Now, suppose you have a website open in a browser using the https protocol.

Then the SSL connection being used again lies in this scope (the top three layers). (Presentation Layer)

 

Named pipe (in Windows), Internet Proxies (using SOCKS), NFS and SMB also lie in this scope. (Session Layer)

 

Then the data they are processing is converted to segments.

As the TCP protocol in itself lies in the Transport layer

 

Then this segment is further broken to packets.

Packets are transferred using the IP protocol. And this lies in the Network Layer.

 

Now the Data Link Layer comes into picture; where these packets are again broken down to Frames.

The Devices working down under the Data Link Layer take care to transfer these frames.

Frames are further broken to bits which is transferred using the Physical Layer.

 

Devices like Routers work on the Network Layer.

Routers work on the network layer so they can filter data based on IP addresses. They have route tables to store network addresses and forward packets to the right port.

 

 

Hubs work on the lowest layer of OSI Model; which is the Physical Layer

            They don't possess a brain and just transfer bits.

 

There are mainly two types of hubs:

 

1. Passive: The signal is forwarded as it is (so it doesn't need power supply).

2. Active: The signal is amplified, so they work as repeaters. In fact they have been called multiport repeaters. (Use power supply)

           

Repeaters are simple devices that work at the physical layer of the OSI. They regenerate signals (active hubs does that too).

 

There is an important rule to obey while using repeaters/hubs to extend a local network and is called the 5-4-3 rule or the IEEE way. The rule forces that in a single collision domain there shouldn't be more than 5 segments, 4 repeaters between any two hosts in the network and only 3 of the segments can be populated (contain user connections).

This rule ensures that a signal sent over the network will reach every part of it within an acceptable length of time.

If the network is bigger, the collision domain can be divided into two parts or more using a switch or a bridge.

 

Switches on the other hand are more advanced. Instead of broadcasting the frames everywhere, a switch actually checks for the destination MAC address and forward it to the relevant port to reach that computer only. This way, switches reduce traffic and divide the collision domain into segments, this is very sufficient for busy LANs and it also protects frames from being sniffed by other computers sharing the same segment.

Switches have built-in hardware chips solely designed to perform switching capabilities, therefore they are fast and come with many ports. Sometimes they are referred to as intelligent bridges or multiport bridges.

Different speed levels are supported. They can be 10 Mb/s, 100 Mb/s, 1 Gb/s or more.

Most common switching methods are:

 

1. Cut-through: Directly forward what the switch gets.

2. Store and forward: receive the full frame before retransmitting it.

 

 

Switches work on the Layer II of OSI Model; which is the Data Link Layer; that's why they deal with frames instead of bits and filter them based on MAC addresses. Switches are known to be used for their filtering capabilities.

However, there are some Layer III switches present as well.

 

Bridges are used to extend networks by maintaining signals and traffic.

OSI: Bridges are on the data link layer so in principle they are capable to do what switches do like data filtering and separating the collision domain, but they are less advanced. They are known to be used to extend distance capabilities of networks.

 

In a comparison with switches, they are slower because they use software to perform switching. They do not control broadcast domains and usually come with less number of ports.

 

 

Layer 3 switches were conceived as a technology to improve on the performance of routers used in large local area networks (LANs) like corporate intranets. The key difference between Layer 3 switches and routers lies in the hardware technology used to build the unit. The hardware inside a Layer 3 switch merges that of traditional switches and routers, replacing some of a router's software logic with hardware to offer better performance in some situations.

 

Layer 3 switches often cost less than traditional routers. Designed for use within local networks, a Layer 3 switch will typically not possess the WAN ports and wide area network features a traditional router will always have.

 

Considering the design and cost factors Layer III switches have an advantage over Routers.

But, they don't have WAN Features so in any case; Routers are better.

 

What have been introduced so far are the main traditional devices used to build networks, understanding how they work helps to understand the logic behind networks designing, however, now that technology advance quickly, it is possible to find new products in the market combining two or more of these devices into one.

 

Examples are:

 

- Brouter: Works as a Bridge and as a Router.

- IP Switch or MultiLayer Switch (MLS): New switches with routing capabilities, they forward data based on IP addresses, work at the network layer too.

 

 

A set of protocol suites as they lie inside the Layers in the OSI Model:

 

OSI model

7. Application layer

NNTP SIP SSI DNS FTP Gopher HTTP NFS NTP SMPP SMTP SNMP Telnet DHCP Netconf (more)

6. Presentation layer

MIME XDR

5. Session layer

Named pipe NetBIOS SAP PPTP RTP SOCKS SPDY

4. Transport layer

TCP UDP SCTP DCCP SPX

3. Network layer

IP IPv4 IPv6 ICMP IPsec IGMP IPX AppleTalk X.25 PLP

2. Data link layer

ATM ARP SDLC HDLC CSLIP SLIP GFP PLIP IEEE 802.2 LLC L2TP IEEE 802.3 Frame Relay ITU-T G.hn DLL PPP X.25 LAPB Q.921 LAPD Q.922 LAPF

1. Physical layer

EIA/TIA-232 EIA/TIA-449 ITU-T V-Series I.430 I.431 PDH SONET/SDH PON OTN DSL IEEE 802.3 IEEE 802.11 IEEE 802.15 IEEE 802.16 IEEE 1394 ITU-T G.hn PHY USB Bluetooth RS-232 RS-449

 

A set of protocol suites as they lie in the Layers of TCP/IP Model:

Internet protocol suite

Application layer

DHCP DHCPv6 DNS FTP HTTP IMAP IRC LDAP MGCP NNTP BGP NTP POP RPC RTP RTSP RIP SIP SMTP SNMP SOCKS SSH Telnet TLS/SSL XMPP more...

Transport layer

TCP UDP DCCP SCTP RSVP more...

Internet layer (Network Layer)

IP IPv4 IPv6 ICMP ICMPv6 ECN IGMP IPsec more...

Link layer

ARP/InARP NDP OSPF Tunnels L2TP PTPP Media access control Ethernet DSL ISDN FDDI DOCSIS more...

TCP/IP Stack

The whole bunch of features as provided by TCP/IP are called as the TCP / IP stack

 

For communication purposes while troubleshooting we refer the whole set of features available under "Network Connections" as TCP/IP stack.

 

They are available by the short-cut key as described by "ncpa.cpl".

You can use it as follows:

            START > RUN > ncpa.cpl > Enter

 

There are two places where you can look for them after you open the windows using ncpa.cpl

On the top menu: under Advanced Settings

On the Individual NIC Card: Doing a Right-Click > Properties.

 

If the NIC for which you want to access the TCP/IP Stack is unavailable in the Window, then re-install its driver.

 

 

For further research, look here:

·        http://en.wikipedia.org/wiki/OSI_model

·        http://en.wikipedia.org/wiki/TCP/IP_stack

 



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ebhakt
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Author Name:         ebhakt
Author Location:    India
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