REST is almost always going to be faster. The main advantage of SOAP is that it provides a mechanism for services to describe themselves to clients, and to advertise their existence.
REST is much more lightweight and can be implemented using almost any tool, leading to lower bandwidth and shorter learning curve. However, the clients have to know what to send and what to expect.
In general, When you're publishing an API to the outside world that is either complex or likely to change, SOAP will be more useful. Other than that, REST is usually the better option.
Simple Object Access Protocol (SOAP) and Representational State Transfer (REST) are two answers to the same question: how to access Web services. The choice initially may seem easy, but at times it can be surprisingly difficult.
SOAP is a standards-based Web services access protocol that has been around for a while and enjoys all of the benefits of long-term use. Originally developed by Microsoft, SOAP really isn’t as simple as the acronym would suggest.
REST is the newcomer to the block. It seeks to fix the problems with SOAP and provide a truly simple method of accessing Web services. However, sometimes SOAP is actually easier to use; sometimes REST has problems of its own. Both techniques have issues to consider when deciding which protocol to use.
Before I go any further, it’s important to clarify that while both SOAP and REST share similarities over the HTTP protocol, SOAP is a more rigid set of messaging patterns than REST. The rules in SOAP are important because without these rules, you can’t achieve any level of standardization. REST as an architecture style does not require processing and is naturally more flexible. Both SOAP and REST rely on well-established rules that everyone has agreed to abide by in the interest of exchanging information.
A Quick Overview of SOAP
SOAP relies exclusively on XML to provide messaging services. Microsoft originally developed SOAP to take the place of older technologies that don’t work well on the Internet such as the Distributed Component Object Model (DCOM) and Common Object Request Broker Architecture (CORBA). These technologies fail because they rely on binary messaging; the XML messaging that SOAP employs works better over the Internet.
After an initial release, Microsoft submitted SOAP to the Internet Engineering Task Force (IETF) where it was standardized. SOAP is designed to support expansion, so it has all sorts of other acronyms and abbreviations associated with it, such as WS-Addressing, WS-Policy, WS-Security, WS-Federation, WS-ReliableMessaging, WS-Coordination, WS-AtomicTransaction, and WS-RemotePortlets. In fact, you can find a whole laundry list of these standards on Web Services Standards.
The point is that SOAP is highly extensible, but you only use the pieces you need for a particular task. For example, when using a public Web service that’s freely available to everyone, you really don’t have much need for WS-Security.
The XML used to make requests and receive responses in SOAP can become extremely complex. In some programming languages, you need to build those requests manually, which becomes problematic because SOAP is intolerant of errors. However, other languages can use shortcuts that SOAP provides; that can help you reduce the effort required to create the request and to parse the response. In fact, when working with .NET languages, you never even see the XML.
Part of the magic is the Web Services Description Language (WSDL). This is another file that’s associated with SOAP. It provides a definition of how the Web service works, so that when you create a reference to it, the IDE can completely automate the process. So, the difficulty of using SOAP depends to a large degree on the language you use.
One of the most important SOAP features is built-in error handling. If there’s a problem with your request, the response contains error information that you can use to fix the problem. Given that you might not own the Web service, this particular feature is extremely important; otherwise you would be left guessing as to why things didn’t work. The error reporting even provides standardized codes so that it’s possible to automate some error handling tasks in your code.
An interesting SOAP feature is that you don’t necessarily have to use it with the HyperText Transfer Protocol (HTTP) transport. There’s an actual specification forusing SOAP over Simple Mail Transfer Protocol (SMTP) and there isn’t any reason you can’t use it over other transports. In fact, developers in some languages, such as Python and PHP, are doing just that.
A Quick Overview of REST
Many developers found SOAP cumbersome and hard to use. For example, working with SOAP in JavaScript means writing a ton of code to perform extremely simple tasks because you must create the required XML structure absolutely every time.
REST provides a lighter weight alternative. Instead of using XML to make a request, REST relies on a simple URL in many cases. In some situations you must provide additional information in special ways, but most Web services using REST rely exclusively on obtaining the needed information using the URL approach. REST can use four different HTTP 1.1 verbs (GET, POST, PUT, and DELETE) to perform tasks.
Unlike SOAP, REST doesn’t have to use XML to provide the response. You can find REST-based Web services that output the data in Command Separated Value (CSV), JavaScript Object Notation (JSON) and Really Simple Syndication (RSS). The point is that you can obtain the output you need in a form that’s easy to parse within the language you need for your application.
As an example of working with REST, you could create a URL for Weather Underground. The API’s documentation page shows an example URL of http://api.wunderground.com/api/Your_Key/conditions/q/CA/San_Francisco.json. The information you receive in return is a JSON formatted document containing the weather for San Francisco. You can use your browser to interact with the Web service, which makes it a lot easier to create the right URL and verify the output you need to parse with your application.
Deciding Between SOAP and REST
Before you spend hours fretting over the choice between SOAP and REST, consider that some Web services support one and some the other. Unless you plan to create your own Web service, the decision of which protocol to use may already be made for you. Extremely few Web services, such as Amazon, support both. The focus of your decision often centers on which Web service best meets your needs, rather than which protocol to use.
Soap Vs Rest
SOAP is definitely the heavyweight choice for Web service access. It provides the following advantages when compared to REST:
REST is easier to use for the most part and is more flexible. It has the following advantages when compared to SOAP:
Locating Free Web Services
The best way to discover whether SOAP or REST works best for you is to try a number of free Web services. Rolling your own Web service can be a painful process, so it’s much better to make use of someone else’s hard work. In addition, as you work with these free Web services you may discover that they fulfill a need in your organization, and you can save your organization both time and money by using them. Here are some to check out:
One common concern about using a free Web service is the perception that it could somehow damage your system or network. Web services typically send you text, not scripts, code, or binary data, so the risks are actually quite small.
Of course, there’s also the concern that Web services will disappear overnight. In most cases, these Web services are exceptionally stable and it’s unlikely that any of them will disappear anytime soon. I’ve been using some of them now for five years without any problem. However, stick with Web services from organizations with a large Internet presence. Research the Web service before you begin using it.
Working with the Geocoder Web Service
To make it easier to understand how SOAP and REST compare, I decided to provide examples of both using the same free Web service, geocoder.us (thank you to Mark Yuabov for suggesting it). This simple Web service accepts an address as input and spits out a longitude and latitude as output. You could probably mix it with the Google Maps API example I present in “Using the Google Maps API to Add Cool Stuff to Your Applications.”
Viewing a Simple REST Example
Sometimes, simple is best. In this case, REST is about as simple as it gets because all you need is an URL. Open your browser—it doesn’t matter which one—and type http://rpc.geocoder.us/service/csv?address=1600+Pennsylvania+Ave,+Washington+DC in the address field. Press Enter. You’ll see the output in your browser in CSV format:
You see the latitude, followed by the longitude, followed by the address you provided. This simple test works for most addresses in most major cities (it doesn’t work too well for rural addresses, but hey, what do you expect for free?). The idea is that you obtain the latitude and longitude needed for use with other Web services. By combining Web services together with a little glue code, you can create really interesting applications that do amazing things in an incredibly short time with little effort on your part. Everyone else is doing the heavy lifting. You can also test your REST API with simple to use tools like SoapUI.
Explaining a Simple SOAP Example
SOAP, by its very nature, requires a little more setup, but I think you’ll be amazed at how simple it is to use.
Begin this example by creating Windows Forms application using Visual Studio. The sample code uses C#, but the same technique works fine with other .NET languages (you’ll need to modify the code to fit). Add labels, textboxes, and buttons as shown here (the Latitude and Longitude fields are read-only).
Here’s where the automation comes into play. Right click References in Solution Explorer and choose Add Service Reference from the context menu. You’ll see the Add Service Reference dialog box. Type the following address into the address field: http://rpc.geocoder.us/dist/eg/clients/GeoCoder.wsdl and click Go. Type GeocoderService in the namespace field. Your dialog box should look like the one shown here.
Click OK. Visual Studio adds the code needed to work with Geocoder in the background.
At this point, you’re ready to use the Web service. All you need to do is to add some code to the Get Position button as shown here.
private void btnGetPosition_Click(object sender, EventArgs e)
{ // Create the client. GeocoderService.GeoCode_PortTypeClient Client = new GeocoderService.GeoCode_PortTypeClient();
// Make the call.
GeocoderService.GeocoderResult[] Result = Client.geocode(txtAddress.Text);
// Check for an error result.
if (Result != null) { // Display the results on screen. txtLatitude.Text = Result[0].lat.ToString(); txtLongitude.Text = Result[0].@long.ToString(); } else { // Display an error result. txtLatitude.Text = "Error"; txtLongitude.Text = "Error"; } }
The code begins by creating a client. This is a common step for any Web service you use with Visual Studio (or other environments that support SOAP natively). To see another version of the same step, check out the PHP example.
After you create the client, you use it to call one of the methods supported by the Web service. In this case, you call geocode() and pass the address you want to work with. The result of the call is stored in a GeocoderResult variable named Result. A single address could possibly end up providing multiple positions if you aren’t specific enough, so this information is passed back as an array.
Let’s assume that no errors occur (resulting in a null return value). The example assumes that you provided great information, so it places the information found in the first Result entry into the Latitude and Longitude output. So, this example isn’t really that complicated compared with REST, but as you can see, even a simple example is more work.
The Bottom Line: When To Use SOAP Or REST
Some people try to say that one process is better than the other, but this statement is incorrect. Each protocol has definite advantages and equally problematic disadvantages. You need to select between SOAP and REST based on the programming language you use, the environment in which you use it, and the requirements of the application. Sometimes SOAP is a better choice and other times REST is a better choice. In order to avoid problems later, you really do need to chart the advantages and disadvantages of a particular solution in your specific situation.
There’s one absolute you should get from this article. Don’t reinvent the wheel. It’s amazing to see companies spend big bucks to create Web services that already exist (and do a better job than the Web service the company creates). Look for free alternatives whenever possible. In many cases, the choice of Web service also determines your choice of protocol.
Actually there are two. Whether you pick between SOAP or REST for your web service, making sure you thoroughly test your APIs. Ready! API has a full suite of functional, performance, security and virtualization tools for your API testing needs. You can also learn how to test RESTful APIs, in our API Testing Resource Center.
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Wednesday, 18 January 2017
Understanding SOAP and REST Basics And Differences
Tuesday, 17 January 2017
OSI Seven Layers Model Explained With Examples
Please Do Not Throw Sushi and Pizza Away. (PDNTSPA).
Presentation layer prepares the data. It takes data from application layer and marks it with formatting code such as .doc, .jpg, .txt, .avi etc. These file extensions make it easy to realize that particular file is formatted with particular type of application. With formatting presentation layer also deals with compression and encapsulation. It compresses (on sending computer) and decompresses (on receiving computer) the data file. This layer can also encapsulate the data, but it’s uncommon as this can be done by lower layers more effectively.The Session Layer
OSI Model Seven Layers
OSI Layers model has seven layers; Application, Presentation, Session, Transport, Network, data link and physical.
Application Layer
Application layer provides platform to send and receive data over the network. All applications and utilities that communicate with network fall in this layer. For examples
Browsers :- Mozilla Firefox, Internet Explorer, Google Chrome etc
Email clients: - Outlook Express, Mozilla Thunderbird etc.
FTP clients :- Filezilla, sFTP, vsFTP
Application layer protocols that we should know for exam are following:
SNMP (Simple Network Management Protocol) — Used to control the connected networking devices.
TFTP (Trivial File Transfer Protocol) — Used to transfer the files rapidly.
DNS (Domain Naming System) — Used to translate the name with IP address and vice versa.
DHCP (Dynamic Host Configuration Protocol) — Used to assign IP address and DNS information automatically to hosts.
Telnet— used to connect remote devices.
HTTP (Hypertext Transfer Protocol) — Used to browse web pages.
FTP (File Transfer Protocol) — Used to reliably sends/retrieves files.
SMTP (Simple Mail Transfer Protocol) — Used to sends email.
POP3 (Post Office Protocol v.3) — Used to retrieves email.
NTP (Network Time Protocol) — Used to synchronizes clocks.
Presentation layer
Presentation layer prepares the data. It takes data from application layer and marks it with formatting code such as .doc, .jpg, .txt, .avi etc. These file extensions make it easy to realize that particular file is formatted with particular type of application. With formatting presentation layer also deals with compression and encapsulation. It compresses (on sending computer) and decompresses (on receiving computer) the data file. This layer can also encapsulate the data, but it’s uncommon as this can be done by lower layers more effectively.The Session Layer
Session layer deals with connections. It establishes, manages, and terminates sessions between two communicating nodes. This layer provides its services to the presentation layer. Session layer also synchronizes dialogue between the presentation layers of the two hosts and manages their data exchange. For example, web servers may have many users communicating with server at a given time. Therefore, keeping track of which user communicates on which path is important and session layer handle this responsibility accurately.
Transport Layer
So far CCNA exam is concern; this is the most important layer to study. I suggest you to pay extra attentions on this layer, as it is heavily tested in exam.
Transport layer provides following services: -
- It sets up and maintains the connection between two devices.
- It multiplexes connections that allow multiple applications to simultaneously send and receive data.
- According to requirement data transmission method can be connection oriented or connection less.
- For unreliable data delivery connection less method is used.
- Connection less method uses UDP protocol.
- For reliable data delivery connection oriented method is used.
- Connection oriented method uses TCP protocol.
- When Implemented a reliable connection, sequence numbers and acknowledgments (ACKs) are used.
- Reliable connection controls flow through the uses of windowing or acknowledgements.
For exam purpose remember five main functions of transport layer.
- Segmentation
- Connection management
- Reliable and unreliable data delivery
- Flow control
- Connection multiplexing
Let’s understand these functions in more depth
Segmentation
Segmentation is the process of breaking large data file into smaller files that can be accommodated by network. To understand this process thinks about a 700 MB movie that you want to download from internet. You have 2MBPS internet connection. How will you download a 700MB movie on 2MBPS internet connection?
In this case segmentation process is used. On server transport layer breaks 700MB movie in smaller size of segments (less than your internet connection speed). Assume that 700Mb movie is divided in 700 segments. Each segment has file size of 1Mb that your PC can easily download at current connection speed. Now your PC will download 700 small files instead of one large file. So next time when you see download progress bar in browser, think it about segment receiver progress bar. Once your browser receives all segments from server, it will pop up a message indicating download is completed. Transport layer at your PC will merge all segments back in a single 700Mb movie file. End user will never know how a 700Mb movie makes its way through the 2Mbps connection line.
Connection management
Transport layer setup, maintain and tear down connections for session layer. Actual mechanic of connection is controlled by transport layer. Transport layer use two protocols for connection management UDP and TCP.
UDP
UDP is a connection less protocol. Connection-less transmission is said to be unreliable. Now, don't get worried about the term "unreliable" this doesn't mean that the data isn't going to get its destination; its only means that it isn't guaranteed to get its destination. Think of your options when you are sending a postcard, put it in the mailbox, and chances are good that it will get where it's supposed to go but there is no guarantee. There is always a chance of missing in the way. On the other hand, it's cheap.
TCP
TCP is a connection oriented protocol. Connection-oriented transmission is said to be reliable. Think TCP as registry AD facility available in Indian post office. For this level of service, you have to buy extra ticket and put a bunch of extra labels on it to track where it is going and where it has been. You get a receipt when it is delivered. In this method you have a guaranteed delivery. All of this costs you more—but it is reliable!
Reliability
Reliability means guaranteed data delivery. To insure delivery of each single segment, connection oriented method is used. In this approach before sending any segments three way handshake process is done.
Three way handshake process
- PC1 sends a SYN single to PC2 indicating that it wants to establish a reliable session.
- P2 replies with ACK/SYN signal where ACK is the acknowledgment of PC1’s SYN signal and SYN indicates that PC2 is ready to establish a reliable session.
- PC1 replies with ACK signal indicating that is has received SYN signal and session is now fully established.
Once connection is established data transmission will be initiated. To provide maximum reliability it includes following functions:-
- Detect lost packets and resend them
- Detect packets that arrived out of order and reorder them
- Recognize duplicate packets and drop extra packets
- Avoid congestion by implementing flow control
Flow control
The transport layer implements two flow control methods:
- Ready/not ready signals
- Windowing
Ready / not ready signals method
In this method sender sends data according to its buffer size. Receiver receives data in its buffer. When receivers buffer get filled, it send a not ready signal to sender, so sender can stop transmitting more segments. Receivers send ready signal when it becomes ready to receive next segments. This method has two problems.
- First, the receiver may respond to the sender with a not ready signal only when its buffer fills up. While this message is on its way to the sender, the sender is still sending segments to the receiver, which the receiver will have to drop because its buffer space is full.
- The second problem with the uses of this method is that once the receiver is ready to receive more segments, it must first send a ready signal to the sender, which must be received before sender can send more segments.
Windowing
In windowing a window size is defined between sender and receiver. Sender host will wait for an acknowledgement signal after sending the segments equal to the window size. If any packet lost in the way, receiver will respond with acknowledgement for lost packet. Sender will send lost packet again. Window size is automatically set during the three step handshake process. It can be adjust anytime throughout the lifetime of connection.
Connection Multiplexing/Application Mapping
Connection multiplexing feature allows multiple applications to connect at a time. For example a server performs a number of functions like email, FTP, DNS, Web service, file service, data service etc. Suppose server has a single IP address, how will it perform all these different functions for all the hosts that want to connect with it? To make this possible transport layer assigns a unique set of numbers for each connection. These numbers are called port or socket numbers. These port numbers allow multiple applications to send and receive data simultaneously.
Port numbers are divided into following ranges by the IANA
| Port number | Descriptions | ||||||||||||||||||||||||||||||||||||
| 0–1023 | Well-Known—For common TCP/IP functions and applications | ||||||||||||||||||||||||||||||||||||
| 1024–49151 | Registered—For applications built by companies | ||||||||||||||||||||||||||||||||||||
| 49152–65535 | Dynamic/Private—For dynamic connections or unregistered applications
Common TCP and UDP Port Numbers
Network Layer
Network layer is responsible for providing logical address known as IP address. Router works on this layer. Main functions of this layer are following:-
IP address
IP address a 32 bit long software address which made from two components:
Network component: - Defines network segment of device.
Host component :- Defines the specific device on a particular network segment
Subnet mask is used to distinguish between network component and host component.
IP addresses are divided in five classes.
Following addresses have special purpose: -
0 [Zero] is reserved and represents all IP addresses;
127 is a reserved address and it is used for testing, like a loop back on an interface:
255 is a reserved address and it is used for broadcasting purposes.
IP packet
Network layer receive segment from transport layer and wrap it with IP header that is known as datagram.
Datagram
Datagram is just another name of packet. Network layer use datagram to transfer information between nodes.
Two types of packets are used at the Network layer: data and route updates.
Data packets
Data packets are used to transport the user data across the network. Protocols used by data packets are known as routed protocol. For example IP and IPv6
Route update packets
These packets are used to update the route information within internetwork. Routers use these packets. Protocols that send route update packets are called routing protocols; for example RIP, RIPv2, EIGRP, and OSPF
Data link layer
Main functions of data link layer are
MAC Address
MAC address is a 48 bit long layer two address. It is also known as hardware address. This address is burnt with device by manufacturing company.
The first six hexadecimal digits of a MAC address represent its manufacture company.
MAC addresses only need to be unique in a broadcast domain.
You can have the same MAC address in different broadcast domains.
Frame
Data link layer receive packet from network layer and wrap it with layer two Header that is known as frame. There are two specifications of Ethernet frame.
Key points to remember:-
Physical Layer
Physical layer deals with communication media. This layer receive frame from data link layer and convert them in bits. It loads these bits on actual communication media. Depending on media type these bit values are converted in single. Some use audio tones, while others utilize state transitions—changes in voltage from high to low and low to high.
Protocol data unit
Piece of data passed between layers collectively known as PDU (protocol data unit). Layers have different terms to describe it like (segment in transport layer, packet in network layer, frame at data link layer, and signal at physical layer.)
PDU include data file and a consistent body of information attached onto data at each successive layer. This information is called header and footer. It includes instructions on how to restore the file to its original state when it receives to the target system.
As a PDU passes through the layers, a header (and footer only on data link layer) is added to the packet with information to the peer layer on the destination system for reconstructing the data on its way back up through the layers of the destination network.
Data Exchange Process
In data exchange process, participating computers work in reverse mode. Layers on receiving computer perform the same task in reverse mode.
The receiving device takes delivery of, handles, and translates the data from the sending device at a particular layer. For example on sending computer presentation layer compress the data, same presentation layer on receiving computer decompress the data.
On sending computer
On receiving computer
In nutshell
At the sending device, each layer breaks the data down into smaller packets and adds its own header.
At the receiving device, each layer strips off the header and builds the data packets into larger packets.
Each protocol layer is blind to the headers of any other protocol layer and cannot process them.
TCP/IP Reference Model
TCP/IP protocol model is another popular layer model that describes network standards. For CCNA exam you should be aware about this model as well. This model has same names of layers as OSI reference model has. Don't be confuse with same name, layers at both model have different functionality in each model.
Let's see how TCP/IP model is different from OSI reference model
Application layer:
TCP/IP model combine the functionality of application layer, presentation layer and session layer from OSI model in single application layer. In TCP/IP model application layer do all tasks those are performed by upper layers in OSI model. Application layer deals with high level protocols, including data presentation, compression and dialog control.
Transport layer:
In TCP/IP model transport layer provides quality of services. TCP protocol is used for reliable data delivery. Flow control and error correction methods are used for guaranteed data delivery.
Internet layer:
In TCP/IP model Internet layer provide all the functionality that network layer provides in OSI model. Internet layer is responsible for finding the correct path for datagram [packet].
Network access layer:
Name of this layer may confuse you as OSI model has a layer of same name. In TCP/IP model network access layer deals with LAN and WAN protocols and all the functionality provided by physical and data link layer in OSI model.
Cisco's three-layer hierarchical model
Cisco's three layer hierarchical model is a set of networking specification provided by Cisco. This model describe which cisco device works on which layers.
Core Layer
High-speed layer-2 switching infrastructure works in this layer.
Distribution Layer
Distribution layer stands between access and core layers. Router and layer 3 switch works in this layer.
Access Layer
This layer provides user's initial access to the network via switches or hubs.
That’s all for this article. In next article I will explain another CCNA topic.
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