Many different manufacturers produce various models of computers, they run a completely different operating system, but TCP / IP protocol components allow them to communicate with each other. This is very surprised because it has far exceeded the initial ideas. TCP / IP originated in a group exchange network research project funded by the US government in the late 1960s, and now has developed into the most commonly used networking form between computers in the 1990s. It is a real open system because the definition of the protocol component and a variety of implementations can be made publicly available without spending money or spending very little money. It became the basis called "global Internet" or "Internet", which has more than 1 million units around the world.
A layered
Network protocols typically develop different levels, each of which is responsible for different communication functions. A protocol component, such as TCP / IP, is a combination of multiple protocols at different levels. TCP / IP is often considered a four-layer protocol system.
Four levels of TCP / IP protocol components
1. Link layer, sometimes referred to as a data link layer or network interface layer, typically includes a device driver in an operating system, and a corresponding network interface card in the computer. They process the details of the physical interface with the cable (or any other transport medium).
2. Network layers, sometimes referred to as interconnect mesh, handling packets in the network, such as the route selection of packets. In the TCP / IP protocol component, the network layer protocol includes an IP protocol (Internet Protocol), ICMP protocol (Internet Internet Connection Packet Protocol), and IGMP protocol (Internet Group Management Protocol).
3. Transportation layer, mainly providing end-to-end communication on both applications on two hosts. In the TCP / IP protocol component, there are two transmission protocols mutually different: TCP (Transfer Control Protocol) and UDP (User Data News Agreement).
TCP provides high reliability data communication for two hosts. It works to include the data to which the application is divided into the following network layers to confirm the received packet, and set the timeout clock that transmits the last confirmation packet. Since the transport layer provides high-reliability end-to-end communication, the application layer can ignore all of these details.
On the other hand, UDP provides a very simple service for the application layer. It just sent packets called a datagram from one host to another, but does not guarantee that the data is allowed to reach the other end. Any necessary reliability must be provided by the application layer.
These two transport layer protocols have different uses in different applications.
4. Application layer is responsible for handling specific application details. Almost a variety of different TCP / IP implementations provide the following general applications:
• Telnet remote login
• FTP file transfer protocol
• SMTP Simple Mail Transfer Protocol for Email
• SNMP Simple Network Management Agreement
Second, two networks connected by router
In the TCP / IP protocol component, network layer IP provides an unreliable service. That is, it is only as quickly as possible to send the packet from the source knot to the destination node, but does not provide any reliability guarantee. On the other hand, TCP provides a reliable transport layer in an unreliable IP layer. To provide this reliable service, TCP uses mechanisms such as timeout retransmission, transmission, and receiving end-to-end confirmation packets. It can be seen that the transportation layer and the network layer are responsible for different functions.
From the definition, a router has two or more network interface layers (because it is connected to two or more networks). Any system with multiple interfaces is called MultiHomed with multiple interfaces. A host can also have multiple interfaces, but generally not referred to as a router unless its function simply simply transmits the packet from an interface to another. Similarly, the router does not necessarily mean that the special hardware box used to forward the packet in the interconnection network. Most TCP / IP implementations also allow a multi-interface host to act as a router, but the host must conduct a special configuration for this. In this case, we can call the system as the host (when it runs an application, such as FTP or Telnet), it can also be called a router (when it forwards the packet from a network to another. ). We use different terms under different situations. One of the objectives of the interconnect is to hide all physical details in the application. Although this is not obvious in the interconnection network consisting of two networks, the application layer cannot be careful (nor care) a host is on Ethernet, and the other host is on the token ring, they pass the router Perform interconnection. With different types of physical networks, there may be 20 routers, but the application layer is still the same. The hidden physical details makes the interconnection network function is very powerful and very useful.
Another way to connect to the network is to use the bridge. The bridge is interconnected on the link layer, while the router is interconnected on the network layer. The bridge makes multiple local area network (LAN) together, so that the upper layer is like a local area network.
TCP / IP tends to connect to the network using a router instead of a bridge
Third, TCP / IP protocol components
TCP and UDP are two most famous transport level protocols, both of which use IP as a network layer protocol.
Although TCP uses unreliable IP services, it provides a reliable transport layer service.
UDP sends and receives the datagram for the application. A datagram refers to an information unit (eg, information specified by the sender) from the sender to the receiver (eg, information specified by the sender). However, with TCP is that UDP is unreliable, it does not guarantee that data teleconcaps arrive at the end of the ultimate goal. SNMP (Simple Network Management Protocol) also uses the UDP protocol, but because it also handles many other protocols, it is left behind to discuss it.
IP is the primary protocol on the network layer and is used by TCP and UDP. Each set of data for TCP and UDP is transmitted in the interconnection network through the end system and the IP layer in each intermediate router.
ICMP is an accessory protocol for IP protocols. The IP layer uses it to exchange error messages and other important information with other hosts or routers. Although ICMP is mainly used by IP, the application may also access it. Two popular diagnostic tools, ping, and traceroute, they all use ICMP.
IGMP is an Internet group management protocol. It is used to broadcast a UDP datagram (send a UDP datagram to all hosts on a specified network) to multiple hosts.
ARP (address resolution protocol) and RARP (inverse address resolution protocol) are special protocols used by certain network interfaces such as Ethernet and token ring networks to convert the address used by IP layers and network interface layers.
Fourth, the address of the interconnection network
Each interface on the interconnect must have a unique Internet address (also known as an IP address). IP address length 32 bit. The Internet address does not use the address space in planar form, such as 1, 2, 3, etc. The IP address has a certain structure. These 32-bit addresses typically write four decimal numbers, each of which corresponds to one byte. This representation is referred to as "Dotted Decimal Notation).
It is necessary to point out that the multi-interface host has multiple IP addresses, each of which corresponds to an IP address. Since each interface on the interconnection must have a unique IP address, there must be a management agency to assign an IP address to the network access network. This management is called Internet Network Information Center (Internet Network Information Center). INTERNIC is only assigned a network number. The allocation of the host number is responsible by the system administrator.
The Internet Registration Service (IP address, and DNS domain name) passed by NIC, its network address is nic.ddn.mil. On April 1, 1993, INTERNIC was established. Now, NIC is only responsible for handling the registration request of the defense data network, and all other Internet user registration requests are handled by Internet, and its URL is: rs.internic.net.
In fact, INTERNIC has three components: RS.Internic.NET, directory, and database service (DS.Internic.net), and information service (is.internic.net).
The IP address has three categories: single-graph transmission address (target is a single host), broadcast transmission address (destination is all hosts on a given network), and multi-purpose transmission address (all hosts in the same group).
V. Domain name system
Although the network interface on the host can be identified via the IP address, the host is accessed, but people like to use or host names. In the TCP / IP field, the Domain Name System (DNS) is a distributed database that provides mapping information between IP addresses and hostnames.
Now, we must understand that any application can call a standard library function to view the IP address of the host of the given name. Similarly, the system also provides an inverse function - the IP address of a given host, see the host name it corresponds to.
Most applications using hostnames as parameters can also use IP addresses as parameters. For example, when we use Telnet to log in remotely, we can specify a host name or specify an IP address.
Six, packaging
When the application is transmitted with TCP, the data is sent to the protocol stack, and then each layer is passed by each layer by one by one as a bunch bitstream. Each of these layers increases some of the first information (sometimes adding the tail information). The data unit transmitted to the IP is referred to as a TCP message segment or a TCP Segment. The IP transmitted to the network interface layer is referred to as an IP Data (IP DataGram). Bit streams transmitted by Ethernet are called frames. The physical characteristics of the Ethernet data frame are between 46-1500 bytes.
All Internet standards and most books about TCP / IP use OcTet this term to represent bytes. The use of this excessively carved term is historical reason, because many of TCP / IP works on the DEC-10 system, but it does not use the 8 bit of bytes. Since almost all computer systems use 8 Bit bytes, we use this term here.
More specifically, the data unit transmitted between IP and network interface layers should be a packet. Grouping can be an IP datagram, or a piece of FRAGMENT.
UDP data is basically consistent with TCP data. The only difference is that the UDP is transmitted to IP, referred to as UDP DataGram, and the head of UDP is 8 bytes.
Since both TCP, UDP, ICMP, and IGMP are transmitted to IP, IP must add some identity to the generated IP header to indicate which layer belongs to. To this end, IP stores a value of 8 bits in the header, referred to as a protocol. 1 is expressed as the ICMP protocol, 2 is expressed as the IGMP protocol, and 6 is represented as a TCP protocol, and 17 is represented as a UDP protocol. Similarly, many applications can use TCP or UDP to transmit data. The transport layer protocol is stored in an identifier of an application when generating a message header. Both TCP and UDP represent different applications with a 16-bit port number. TCP and UDP store the source port number and destination port number into the packet header, respectively.
The network interface is to send and receive IP, ARP, and RARP data, so some form of identity must also be added to the frame header of the Ethernet to indicate the network layer protocol to generate data. To this end, the frame header of the Ethernet also has a 16-bit frame type field.
Seven, Demultiplexing
When the destination host receives an Ethernet data frame, the data begins to rise from the protocol stack, and remove the header of the packets plus each layer protocol. Each layer protocol box is to check the protocol identity in the header of the packet to determine the upper level protocol of the received data. This process is called a distribution.
The positioning of ICMP and IGMP is always a very difficult thing for the ICMP and IGMP. We put the agreement ICMP and IGMP and IP on the same layer, that is because they are an IP's subsidiary protocol. But we put them on the IP layer, because ICMP and IGMP packets are packaged in IP datagrams.
We also encounter similar problems for ARP and RARP. Here we put them above the Ethernet device driver because they have their own Ethernet data frame types as they are in the IP datagram. However, we put the ARP as part of the Ethernet device driver, placed below the IP layer, which is logically reasonable.
When further describing the details of TCP, we will see that the protocol is indeed unbearable by destination port number, source IP address, and source port number.
Eight, customer server model
Most web applications are written and one end is a customer, the other end is a server, and its purpose is to allow the server to provide customers with some specific services.
We can divide this service into two types: repeat type or concurrent.
The repeat server interacts by the following steps:
1. Wait for a customer request.
2. Handle the customer request.
3. Send a response to a customer who sends a request.
4. Return to step 1.
The main problem of repeated server occurs in 2 states. At this time, it cannot serve other clients.
The concurrent hairstyle server uses the following steps:
1. Waiting for a customer request
2. Start a new server to process the customer's request. During this period, a new process, task or thread may generate, and rely on the support of the underlying operating system. How this step depends on the operating system. The generated new server processes all the requests of the customer. After processing, the new server is terminated.
3. Return to step 1.
The advantage of a concurrent server is that it is a process that generates other servers to handle the customer's request. That is, each customer has its own corresponding server. If the operating system allows multiple tasks, you can simultaneously serve multiple customers at the same time.
We are for the server, not the customer's classification.
In general, TCP servers are concurrent, and the UDP server is repeated, but there are some exceptions.
Nine, port number
We have pointed out that TCP and UDP use a 16-bit port number to identify applications. So how do these port numbers choose?
The server is generally identified by a port number well known. For example, for each TCP / IP implementation, the TCP port number of the FTP server is 21, each TELNET server TCP port number is 23, each TFTP (Simple File Transfer Protocol) server UDP port number is 69. Any TCP / IP implementation is provided with a well-known port number between 1-1023. The port numbers that these people are well known are managed by the Internet Accommbers Authority, IANA. Between 1992, the port numbers well known between 1-255. The port numbers between 256-1023 are usually occupied by UNIX systems to provide some specific UNIX services - that means of providing only UNIX systems, while other operating systems may not provide services. Now all port numbers between IANA management 1-1023.
A difference between the Internet extension service and UNIX-specific services is Telnet and Rlogin. They all allow us to log in to other hosts via a computer network. Telnet is a TCP / IP standard with a port number 23 and can be implemented on all operating systems. In contrast, Rlogin is only designed for UNIX systems (although many non-Unix systems now also provide this service), it is 513 in the early 1980s.
The client usually does not care about the port number it uses, and it is only necessary to ensure that the port number is unique on this unit. The client port number is also called a temporary port number (ie there is time very short). This is because it usually exists when the user runs the client, and the server will run as long as the host is turned.
Most TCP / IP implements a port number between 1024-5000 to the temporary port. The port number greater than 5000 is reserved for other servers (not commonly used on the Internet).
Reserved port number
The UNIX system has the concept of reserved port numbers. Only a process with superuser privileges allows it to allocate a reserved port number.
These port numbers are between 1 and 1023, some applications (such as famous rlogin) use part of the authentication between customers and servers.
Ten, standardization process
Who is controlling the TCP / IP protocol component, who is defining a new standard and other similar things? In fact, there are four groups responsible for Internet technology.
1. The Internet Association (ISOC: Internet Society) is a professional organization that drives, supports and promotes the growing and development of Internet, which puts Internet as an infrastructure for global research.
2. The Internet Architecture Commission (IAB: Internet Architecture Board) is a technical supervision and coordinated institution. It consists of 15 volunteers from different majors, and its functions are the last editing and technical review of Internet standards. IAB is part of ISOC.
3. Internet Engineering Special Team (IETF: Internet Engineering Task Force) is an organization-oriented organization that is divided into nine fields (applications, diameters, and addressing, security, etc.). IETF has developed a statute to become an Internet standard. In order to help the IETF Chair, the Internet Engineering Guidance Group (IESG: Internet Engineering Steering Group) is established.
4. The Internet Research Group is mainly studied for long-term projects.
IRTF and IETF are affiliated to IAB.
RFC
All formal standards on the Internet are published in the RFC (Request for Comment) documentation. In addition, a large number of RFCs are not formal standards, and the purpose of publication is to provide information. The space of the RFC is from 1 pages to 200 pages. Each item is identified by a number, such as RFC 1122, the bigger the number, the more the contents of the RFC. All RFCs can be grouped for free by email or with FTP from the Internet. If you send the email below, you will receive a list of ways to get RFC:
To: rfc-info@isi.edu
Subject: Getting RFCS
Help: ways_to_get_rfcs
The latest RFC index always searches the starting point of the information. This index lists the time of RFC alternative or partially updated.
Here are some important RFC documents:
1. Assign RFC (Assigned NumBers RFC) lists the numbers and constants used in all Internet protocols. As this book is published, the latest RFC number is 1340 [Reynolds and Postel 1992]. All famous internet port numbers are listed here.
When this RFC is updated (usually at least once a year), the index list will list the time of the RFC 1340 is replaced.
2. Internet official protocol standard, currently RFC 1600 [Postel 1994]. This RFC describes the standardization status of various Internet protocols. Each protocol is one of the following standardized states: standards, draft standards, proposals, experimental standards, information standards, and historical standards. In addition, there is a requirement for each protocol: necessary, suggested, optional, limited, or not recommended.
Like the assignment RFC, this RFC is regularly updated. Please check the latest version at any time.
3. Host requirements RFC, 1122, and 1123 [BRADEN 1989A, 1989B]. The RFC 1122 is directed to the link layer, the network layer, and the transport layer, and the RFC 1123 is for the application layer. These two RFCs have made a lot of corrective and explanations for early important RFC documents. If you want to see more detailed details of the protocol, they are usually an entry point. They list the characteristics of "must", "should", "can", "should not" or "can not", "" should not "or" can not ".
RFC 1127 [BRADEN 1989C] The discussion content and conclusions of the work group development host demand RFC process were informally summarized.
4. Router demand RFC, the official version is RFC 1009 [BRADEN AND POSTEL 1987], but a new version is close to complete [Aknqyust 1993]. It is similar to the host's demand RFC, but only describes the need for the router.
Standard simple service
There are some standard simple services to provide almost every implementation. The client usually chooses Telnet. When using TCP and UDP, the same port number is typically selected.
If you carefully check these standard simple services and other standard TCP / IP services (such as Telnet, FTP, SMTP, etc.), we have found that they are odd. This is historical reason, because these port numbers are derived from the NCP port number. (NCP, the network control protocol, is the transport layer protocol of Arpanet, the predecessor of TCP. NCP is single, not full-duplex, so each application requires two connections, need to reserve a pair of odd numbers and even numbers Port number. When TCP and UDP become a standard transport layer protocol, each application only needs one port number, so the odd number in NCP is used.
Eleven, interconnection network
The world's interconnection network -Internet, the first letter of this word is uppercase whether it has different meaning. Internet intends to connect multiple networks with a common protocol. The Internet refers to all host collections (more than 1 million units) through TCP / IP. Internet is an Internet, but the Internet is not equal to the Internet.
Twelve, realization
The TCP / IP software that is both true standards is realized from the University of California, California, California. Historically, the software is published with the 4.x BSD system (Berkeley Software Distribution). Its source code is the basis of many other implementations.
The time issued by various BSD versions is listed below, and important TCP / IP features are marked. Column BSD network version on the left, all of its network source code can be disclosed: including protocol itself and many applications and tools (such as Telnet and FTP).
4.2BSD (1983) The first widely available TCP / IP release
4.3BSD (1986) TCP performance is improved
4.3bsd Tahoe (1988) starts slow, congestion avoidance measures
BSD Network Software 1.0 (1989): Net / 1
4.3BSD RENO (1990) TCP header prediction, SLIP first compression routing table modification
BSD Network Software 2.0 (1991): Net / 2
4.4BSD (1993) multicast, long fat pipeline modification
4.4BSD-Lite (1994) is also known as NET / 3
Thirteen, application programming interface
Applications using TCP / IP protocols typically use two application programming interfaces (APIs): Socket and TLI (transport layer interface: Transport Layer Interface). The former is sometimes referred to as "Berkeley Socket" indicating that it is developing from Berkeley. The latter initially developed by AT & T, sometimes referred to as XTI (X / Open Transfer Interface) to recognize the work of X / Open's own definition of standard international computer producers. XTi is actually a supercoming of TLI.
(One)
TCP / IP should be a protocol set, according to the seven-layer theory of OS, TCP / IP is divided into four layers. They are applications, transfer, INTERNE, and web interfaces, respectively.
We generally say TCP in the transport layer, while IP is in the Internet layer.
TCP / IP applications include ping, telnet, ftp, finger, usually usually used in us.
Configuring TCP / IP includes IP addresses, subnet masks, and default gateways
Correct TCP / IP four steps: ping 127.0.0.1 (loopback address) If the TCP / IP has been loaded, ping himself indicates that the client is normal (mainly the network card), the PING gateway indicates that the local area network is normal, the PING routing address Expressed is completely normal, of course, you can also carry out the fourth step, generally don't have this trouble, but theory is the foundation :-)
The IP address is composed of four-segment binary number, IP is divided into four types of addresses A, B, C, D, E E.
The high end of the A category is 0, from 1.xYZ ~ 126.xyz .b high end is 10, from 128.xYz ~ 191.xyz C high end of 110, from 192.xYz ~ 223.xyz D high end 1110 is reserved The IP address E high end is 1111, which is the IP address used by research.
Where 255 is the broadcast address, 127 is the internal return address
(2) The following is the setting of the subnet
If the company is not in the Internet, it will not worry about iPaddress, because all iPaddress can be used, whether it is aclass or bclass, this time does not think of the Subnet, but if the Ipaddress is precious, it is precious. At present, IPAddress has become more and less, and IPAddress applied is currently conservative, and IPADRESS can only be used in Internet, but can apply to a cclass to a cclass, Ipaddress for some companies. But there are multiple points to use, then the Subnet is required, this short document shows the principle of the Subnet and how to plan.
Introduction to SubnetMask
Setting any equipment on any online whether you are host, PC, Router, etc. need to set ipaddress, and follow the iPaddress's so-called NetMask, this NetMask's main purpose is to get NetWorkNumber in ipaddress, that is, iPaddress Get NetWorkNumber as Netmask, as shown below
Ipaddress 192.10.10.6110000000000001010.00001010.000001010
Netmask 255.255.255.011111111111111111111111111111.00000000
And ------------------------------------- ------------------
Etworknumber 192.10.10.011000000.00001010.000000000000001010.00001010.00000000
Netmask has a so-called preset value, as shown below
ClassipAddress range Netmask
A 1.0.0.0-126.255.255.255255.0.0.0
B 128.0.0.0-191.255.255.255255.255.0.0
C 192.0.0-223.255.255.255255.255.255.0
There is only 255 values in the preset NetMask, and this value is not necessarily 255 when talking to SubnetMask.
In a complete set of CCLASS, such as 203.67.10.0-203.67.10.255.0, 203.67.10.0 called NetWorkNumber (IPADDRESS and NETMASK as AND), and 203.67.10.255 is Broadcast's iPaddress, so this? Can't use, actually only 254 iPaddress, etc. 203.67.10.1--203.67.10.254, which is the result of Netmask at 255.255.255.0, and the so-called SubnetMSK can divide the entire set of C Class into the array of NetWorkNumber, which is in Netmask. Hand feet, if you want to divide the entire set of CCLASS to set to 255.255.255.192, if you want to divide the whole group CCLASS into 8 groups of NetWorkNumber, NetMask is 255.255.255.224, how come, from the above knowing NetWorkNumber is From IP Address and NetMask as And, it is known that 1 will be reserved by binary binary representation, and 0. Remove
192.10.10.193--11000000.00001010.00001010.10000001
255.255.255.0--111111111111111111.11111111.00000000
-------------------------------------------------- ----------------
192.10.10.0--11000000.00001010.00001010.0000000000
The above is the result of 255.255.255.0 is Netmask, NetWorkNumber is 192.10.10.0, if used in the use of 255.255.255.24492.10.10.193--110000000000001010.00001010.10000000
255.255.255.224--1111111111111111111111111111.11100000
-------------------------------------------------- ----------------
192.10.10.192--11000000.00001010.00001010.10000000
At this point, NetWorkNumber became 192.10.10.192, which is an Subnet.
How to decide that NetMask used, 255.255.255.224 in binary notation as 11111111.11111111.11111111.11100000, a change in the final set, 11100000 is 224 to three Bit 3 may represent a convenient 2 is 8 NetworkNumber
Netmask binary representation can be divided into several networks
255.255.255.0 11111111.11111111.11111111.000000001
255.255.255.128 11111111.11111111.11111111.100000002
255.255.255.192 11111111.11111111.11111111.110000004
255.255.255.224 11111111.11111111.11111111.111000008
255.255.255.240 11111111111111111111111111111111000016
255.255.255.248 11111111111111111111111111111111111111111111111111111111111111111111111111111111111
255.255.255.252 11111111.11111111.11111111.1111110064
The following use 255.255.255.224 will be divided into 8 groups of NetWorkNumber, each NetWorkNumber, and its BroadcastIPAddress and iPaddress.
NETWORKNUMBERBROADCAST iPaddress
1 203.67.10.0 203.67.10.31 203.67.10.1-203.67.10.30
2 203.67.10.32 203.67.10.63 203.67.10.33-203.67.10.62
3 203.67.10.64 203.67.10.95 203.67.10.65-203.67.10.94
4 203.67.10.96 203.67.10.127 203.67.10.97-203.67.10.126
5 203.67.10.128 203.67.10.159 203.67.10.129-203.67.10.158
6 203.67.10.160 203.67.10.191 203.67.10.161-203.67.10.190
7 203.67.10.192 203.67.10.223 203.67.10.193-203.67.10.222
8 203.67.10.224 203.67.10.255 203.67.10.225-203.67.10.254
Verify that the iPadDress used is as shown in the above table.
203.67.10.115--11001011.01000011.00001010.01110011
255.255.255.224--1111111111111111111111111111.11100000
-------------------------------------------------- ----------------
203.67.10.96--11001011.01000011.00001010.01100000
203.67.10.55--11001011.01000011.00001010.00110111255.255.255.224--11111111.11111111.11111111.11100000
-------------------------------------------------- ----------------
203.67.10.32--11001011.01000011.00001010.00100000
The other NetMask divided into NetWorkNumber can be built by the above method.
Subnet application
Using Subnet is to solve the problem with only a group of CCLASS but require a few networkNumber, not to solve the problem of iPadDress is not enough, because the iPaddress that can be used with Subnet can be used, Subnet is usually used in Taipei in Taipei, but The company uses the Router connection between the two, and also on the Internet, but only to a group of cclassipaddress, after ROUTER needs to use different network, so this must be used, of course the second office can Remotebridge, REMOTEBRIDGE Connection, there is no problem with Subnet, which does not discuss this, so the online connection architecture and ipaddress use in the above cases.
(three)
TCP / IP (Transfer Control Protocol / Network Protocol) is a network communication protocol that specificallys all communication devices on the network, especially a host between the host and another host and the transmission method. TCP / IP is the foundation protocol of the Internet and a standard method for computer data packaging and addressing. In data transfer, it is possible to understand that there are two envelopes, TCP and IP are like envelopes. The information to be transmitted is divided into several segments. Each segment is plugged into a TCP envelope, and records on the letter cover The information of the section number, then put the TCP envelope into the IP large envelope, send the Internet. In the receiving end, a TCP package collects the envelope, extracts the data, restores the order before sending, and checks. If the error is found, the TCP will request retransmission. Therefore, TCP / IP can transmit data without error in the Internet.
In any physical network, each site has a machine identifiable address, which is called a physical address. There are two physical addresses.
Features:
The length, format, etc. of the physical address is part of the physical network technology, the physical network is different, the physical address is different.
Site on different networks may have the same physical address.
The above two points are determined, and network network communication cannot be performed with physical networks.
In the web terminology, the protocol is predetermined in advance to exchange data between two computers. TCP / IP is not one but a lot of agreements, which is why you often hear it represents a protocol set, while TCP and IP are just two basic protocols.
The TCP / IP software you put in computer provides a tool platform including TCP, IP, and TCP / IP protocol concentrated. In particular, it includes some high-level applications and FTP (file transfer protocols) that allow users to transmit network files on the command line.
TCP / IP is a research outcome of US government funded senior research programs (ARPA) in the 1970s, used to enabling a global research network to form a virtual network, which is an international Internet. original
The Internet is formed by converting existing networks, such as Arpanet to TCP / IP, and this Internet finally became a backbone network of today's Internet.
Today, TCP / IP is so important that it allows stand-alone grid to join the Internet or organization to form a private intranet (Intranet). Each network constituting the internal network is physically coupled to a device that is a router or IP router. The router is a computer used from a network to another network to transfer packets. In an inner network for use TCP / IP, information is transmitted by using a separate IP packet (IPPACKET) or IPDATAGRAMS). The TCP / IP software makes each other on the network to "see" on the network, in fact it hides the router and basic network architecture and makes it look like a big network. Like a 48-bit Ethernet address, it is necessary to confirm a 32-bit IP address as if you need to confirm an Ethernet address. We represent it with a point of decimal number, such as 128.10.2.3. Given the IP address of a remote computer, the local computer on an internal network or Internet can send data to the remote computer like two computers in the same physical network. TCP / IP provides a solution to solve how to exchange data between two computers belonging to the same internal network and sub-physical networks. This program includes a number of parts, while each member of the TCP / IP protocol set is used to solve some part of the problem. For example, the most basic protocol of the TCP / IP protocol-I -IP protocol is used to exchange data in the internal network and perform an important feature: Routing - Select Datashers From A Host to the path to the path, the path will pass, and use appropriate The router completes the span (HOP) between different networks.
TCP is a higher level it allows running data streams to run on different hosts. TCP scores data streams into small segments called TCP data segments (TCPSEGMENTS) and transmits using IP protocols. In most cases, each TCP data segment is installed in an IP datagram. However, if desired, TCP will divide the data segment into multiple datagrams, and the IP data decomposition is compatible with the physical data frame of transmitting bitstream and byte streams between different hosts in the same network. Since IP does not guarantee the order in which the received datagram, TCP will match the TCP data segment and form an uninterrupted data stream. FTP and Telnet are two TCP / IP applications that rely on TCP.
Another important TCP / IP protocol set is a user Data Ravel Agreement (UDP), which is similar to TCP but is much larger than TCP. TCP is a reliable protocol because it has error checks and handshake confirmation to ensure the complete arrival destination. UDP is a "unreliable" protocol because it does not guarantee the same sequence of data reports, and even if they arrive. If there is a reliability requirement, the application avoids it. SNMP (Simple Network Management Protocol) with many TCP / IP tools is an application example of using UDP protocols.
Other TCP / IP protocols work after the TCP / IP network, but also play an important role. For example, Address Translation Protocol (ARP) converts IP addresses to physical network addresses such as Ethernet addresses. Instead, the corresponding reverse address conversion protocol (RARP) is the opposite work, the physical network address is converted to an IP address. The Internet Control Packet Protocol (ICMP) is a support protocol that uses IP to complete the control information of IP datagram in transmission and error information. For example, if a router does not send an IP datagram, it will use ICMP to tell the sender here.
TCP / IP foundation (4)
Network designers often use ISO / OSI (International Standardized Organization / Open System Interconnect) seven-layer model when solving network architecture, each of which represents a certain level of network function. The bottom is the physical layer, which represents the physical media that performs data transmissions, in other words, the network cable. It is the data link layer, which provides services through the network interface card. The uppermost layer is the application layer, which runs the application using the network service. TCP / IP is equivalent to ISO / OSI model. When a data unit is flowing from the network application to the network interface card, it passes a list of TCP / IP modules. Each of this, the data unit will be packed together with the information required for the other end of the network. Thus when the data is finally transmitted to the NIC, it has become a standard Ethernet frame (assuming that the physical network is an Ethernet). The receiving TCP / IP software retakes the original data by stripping the Ethernet frame and transmitting the data over the TCP / IP stack to the receiving state (a method of understanding the TCP / IP work, It is information using the probe program to observe the information added by the different TCP / IP modules in the flow in the network).
In order to outline TCP / IP played in the Real Network World, consider the situation that occurs when you use the HTTP (Hyper Text Transfer Protocol) to get a page HTML data from the web server on the Internet. In order to form a virtual link with the web server, the browser uses a high-level software called a socket in abstraction. In order to get the web page, it writes the command to the web server by writing the httpget command to the socket to the socket. Next, the interface software uses the TCP protocol to issue the byte stream and bitstream containing the get command, TCP segment the data and transmits each independent segment to the IP module, which converts the data segment into a data report and sends it to Web server.
If the browser and server are transported - on different physical networks (in general), the datagram passes from a network to another network until the network where the server is located. Finally, the data is transmitted to the destination address and is re-assemble so that the web server gets the data main dry by reading their own sockets, and then view the continuous data stream. For browser and servers, data is written to the socket at this end and the other end appears as magic, but this is only a variety of complex interactions that occur under the bottom, which creates data that is seamlessly transmitted by the network.
This is what TCP / IP is done: Many small nets into a big network. And on this big network is also the service of communication with each other's communication on the Internet.
comment:
There are many talks for TCP / IP, but only three key points here:
· TCP / IP is a protocol used to form different physical networks together to constitute the Internet. The TCP / IP is connected to separate networks form a virtual network, which is used to confirm that various independent is not physical network addresses, but an IP address.
· TCP / IP uses multi-layer architecture, which clearly defines the responsibility of each protocol. TCP and UDP provide high-level data transfer services to web applications and require IP to transfer packets. IP is responsible for selecting the right route to the packet to the destination.
• On the Internet host, there are two running applications to move up and down by the TCP / IP stack of the host. Information on the transmitting end TCP / IP module is added to the data will be filtered off on the TCP / IP module corresponding to the receiving end and will eventually restore the original data.
If you are interested in learning more TCP / IP knowledge, there are two higher levels of information source RFC (RequestForcomment) 1180 - called "TCP / IP Tutorial" documentation, you can use many popular RFC Internet nodes Upload. The other is the first volume of Internetworkingwithtcp / IP: Principles, Protocols, And Architectures, author Douglase.comer (1995, Prentice-Hall). As the first part of the three trilog, many people think as a TCP / IP Bible. Www.net130.com's Cisco Tutorial / China-Pub Electronic Books / Columns:
TCPIP Detailed Volume 1 Agreement (http://www.net130.com/tutorial/chinapub/tcpip More 200 volumes 1 protocol .zip)
TCPIP Detailed Volume 2 Implement (http://www.net130.com/tutorial/chinapub/tcpip More 200 volume 2 Implement .zip)
TCPIP Detailed Volume 3 Transaction Agreement (
Http://www.net130.com/tutorial/chinapub/tcpip More 20 Volumes 3.Zip)
----------------
In the second, subnet settings.
192.10.10.193--11000000.00001010.00000000000000000000 should be 11000001
255.255.255.0--111111111111111111.11111111.00000000
192.10.10.193--11000000.00001010.000000000000000000000 should be 11000001
255.255.255.224--1111111111111111111111111111.11100000
-------------------------------------------------- ----------------
192.10.10.192--11000000.00001010.00001010.100000 should be 11000000
