What are examples of TCP and UDP in real life

Question

I know the difference between the two on a technical level   But in real life  can anyone provide examples  the more the better  of applications  uses  of TCP and UDP to demonstrate the difference

User · Answer

TCP guarantees packet delivery AND order. Order is almost as important as the delivery in the first place when reconstructing data for files such as executables, etc.

UDP does not guarantee delivery NOR order. Packets can arrive (or not!) in any order.

Common uses for TCP include file transfer where the integrity of the packets is paramount. Voice/video applications can afford to lose some data while still maintaining acceptable quality, and so usually use UDP.

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TCP    World Wide Web HTTP  E-mail  SMTP TCP  File Transfer Protocol  FTP  Secure Shell  SSH    UDP    Domain Name System  DNS  Streaming media applications such as movies Online multiplayer games Voice over IP  VoIP  Trivial File Transfer Protocol  TFTP

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The classic standpoint is to consider TCP as safe and UDP as unreliable   But when TCP-IP protocols are used in safety critical applications  TCP is not recommended because it can stop on error for multiple reasons  Whereas UDP lets the application software deal with errors  retransmission timers  etc   Moreover  TCP has more processing overhead than UDP   Currently  UDP is used in aircraft controls and flight instruments  in the ARINC 664 standard also named AFDX  Avionics Full-Duplex Switched Ethernet   In ARINC 664  TCP is optional but UDP is used with the RTOS  real time operating systems  designed for the ARINC 653 standard  high reliability control software in civil aircrafts    For more information about real time controls using IP and UDP in AFDX  you can read the pages 27 to 50 in http   www afdx com pdf AFDX Training October 2010 Full pdf

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UDP  Anything where you don t care too much if you get all data always   Tunneling VPN  lost packets are ok - the tunneled protocol takes care of it  Media streaming  lost frames are ok  Games that don t care if you get every update Local broadcast mechanisms  same application running on different machines  discovering  each other    TCP  Almost anything where you have to get all transmitted data   Web  SSH  FTP  telnet SMTP  sending mail IMAP POP  receiving mail   EDIT  I m not going to bother explaining the differences  since you state that you already know and every other answer explains it anyway

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Real life examples of both TCP and UDP tcp -  a phone call  sms or anything specific to destination UDP -  a FM radio channel  AM   Wi-Fi

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TCP    Transmission Control Protocol is a connection-oriented protocol  which means that it requires handshaking to set up end-to-end communications  Once a connection is set up  user data may be sent bi-directionally over the connection   Reliable     Strictly only at transport layer  TCP manages message acknowledgment  retransmission and timeout  Multiple attempts to deliver the message are made  If it gets lost along the way  the server will re-request the lost part  In TCP  there s either no missing data  or  in case of multiple timeouts  the connection is dropped   This reliability however does not cover application layer  at which a separate acknowledgement flow control is still necessary   Ordered     If two messages are sent over a connection in sequence  the first message will reach the receiving application first  When data segments arrive in the wrong order  TCP buffers delay the out-of-order data until all data can be properly re-ordered and delivered to the application   Heavyweight     TCP requires three packets to set up a socket connection  before any user data can be sent  TCP handles reliability and congestion control  Streaming     Data is read as a byte stream  no distinguishing indications are transmitted to signal message  segment  boundaries   Applications of TCP  World Wide Web  email  remote administration  and file transfer rely on TCP   UDP    User Datagram Protocol is a simpler message-based connectionless protocol  Connectionless protocols do not set up a dedicated end-to-end connection  Communication is achieved by transmitting information in one direction from source to destination without verifying the readiness or state of the receiver   Unreliable     When a UDP message is sent  it cannot be known if it will reach its destination  it could get lost along the way  There is no concept of acknowledgment  retransmission  or timeout   Not ordered     If two messages are sent to the same recipient  the order in which they arrive cannot be predicted   Lightweight     There is no ordering of messages  no tracking connections  etc  It is a small transport layer designed on top of IP   Datagrams     Packets are sent individually and are checked for integrity only if they arrive  Packets have definite boundaries which are honored upon receipt  meaning a read operation at the receiver socket will yield an entire message as it was originally sent  No congestion control     UDP itself does not avoid congestion  Congestion control measures must be implemented at the application level   Broadcasts     being connectionless  UDP can broadcast - sent packets can be addressed to be receivable by all devices on the subnet   Multicast     a multicast mode of operation is supported whereby a single datagram packet can be automatically routed without duplication to very large numbers of subscribers   Applications of UDP  Numerous key Internet applications use UDP  including  the Domain Name System  DNS   where queries must be fast and only consist of a single request followed by a single reply packet  the Simple Network Management Protocol  SNMP   the Routing Information Protocol  RIP  and the Dynamic Host Configuration Protocol  DHCP    Voice and video traffic is generally transmitted using UDP  Real-time video and audio streaming protocols are designed to handle occasional lost packets  so only slight degradation in quality occurs  rather than large delays if lost packets were retransmitted  Because both TCP and UDP run over the same network  many businesses are finding that a recent increase in UDP traffic from these real-time applications is hindering the performance of applications using TCP  such as point of sale  accounting  and database systems  When TCP detects packet loss  it will throttle back its data rate usage  Since both real-time and business applications are important to businesses  developing quality of service solutions is seen as crucial by some   Some VPN systems such as OpenVPN may use UDP while implementing reliable connections and error checking at the application level

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REAL TIME APPLICATION FOR TCP   Email   Reason  suppose if some packet words statement  is missing we cannot understand the content It should be reliable   REAL TIME APPLICATION FOR UDP   video streaming       Reason     suppose if some packet frame sequence  is missing we can understand the content Because video is collection of frames For 1 second video  there should be  25 frames image  Even though we can understand some frames are missing due to our imagination skills  Thats why UDP is used for video streaming

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Since tcp usages are pretty straightforward from other answers  I ll mention some interesting UDP use-cases   1 DHCP - Dynamic Host Configuration Protocol  which is being used in order to dynamically assign IP address and some other network configuration to the connecting devices  In simple words  this protocol allows you just connect to the network cable or wifi  and start using the internet  without any additional configurations  DHCP uses UDP protocol  Since the settings request message is being broadcasted from the host and there is no way to establish a TCP connection with DHCP server you don t know it s address  it s impossible to use TCP instead   2 Traceroute - well-known network diagnostic tool which allows you to explore which path in the network your datagram passes to reach it s destination and how much time it takes   By default  it works by sending UDP datagram with unlikely destination port number ranging from 33434 to 33534  to the destination with the ttl time-to-live  field set to 1  When the router somewhere in the network gets such datagram - it finds out that the datagram is expired  Then  the router drops the datagram and sends to the origin of the datagram an ICMP Internet Control Message Protocol  error message indicating that the datagram s ttl was expired and containing router s name and IP address  Each time the host sends datagrams with higher and higher TTL  thus increasing the network part which it succeeds to overcome and getting new ICMP messages from new routers  When it eventually reaches it s destination datagrams TTL is big enough to allow it  - the destination host sends  Destination port unreachable  ICMP message to the origin host  This way  Traceroute knows that the destination was reached  Since the TCP guarantees segments delivery it would be at least inefficient to use it instead of UDP which  in turn  allows datagram to be just dropped without any resend attempts resend is implemented on the higher level  with continuously increasing TTL as described above

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TCP guarantees  in-order  packet delivery  UDP doesn t    TCP - used for traffic that you need all the data for  i e HTML  pictures  etc  UDP - used for traffic that doesn t suffer much if a packet is dropped  i e  video  amp  voice streaming  some data channels of online games  etc

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SCTP vs TCP vs UDPServices Features       SCTP        TCP       UDP Connection-oriented                       yes         yes       no Full duplex                               yes         yes       yes Reliable data transfer                    yes         yes       no Partial-reliable data transfer            optional    no        no Ordered data delivery                     yes         yes       no Unordered data delivery                   yes         no        yes Flow control                              yes         yes       no Congestion control                        yes         yes       no ECN capable                               yes         yes       no Selective ACKs                            yes         optional  no Preservation of message boundaries        yes         no        yes Path MTU discovery                        yes         yes       no Application PDU fragmentation             yes         yes       no Application PDU bundling                  yes         yes       no Multistreaming                            yes         no        no Multihoming                               yes         no        no Protection against SYN flooding attacks   yes         no        n a Allows half-closed connections            no          yes       n a Reachability check                        yes         yes       no Psuedo-header for checksum                no  vtags   yes       yes Time wait state                           vtags       4-tuple   n a

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UDP is mailing a letter at the post office   TCP is mailing a letter with a return receipt at the post office  except that the post master will organize the letters in-order-of mailing and only deliver them in-order   Well  it was an attempt anyway

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UDP is applied a lot in games or other Peer-to-peer setups because it s faster and most of the time you don t need the protocol itself to make sure everything gets to the destination in the original order  UDP does not garantee packet delivery or delivery order    Web traffic on the other hand is over TCP   I m not sure here but I think it has to do with the way the HTTP protocol is built   Edited because I failed at UDP

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TCP  will get there in meaningful order UDP  god knows  maybe

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TCP is appropriate when you have to move a decent amount of data     1 kB   and you require all of it to be delivered  Almost all data that moves across the internet does so via TCP - HTTP  SMTP  BitTorrent  SSH  etc  all use TCP   UDP is appropriate when you have small messages which you can afford to lose  and would like to send them as efficiently as possible  One reason you might be able to afford to lose them is because you can re-send them if they get lost  The main example on the internet is DNS - DNS consists of small queries saying things like  what is the IP number for stackoverflow com    and the responses are correspondingly small  Computers make a lot of these queries  so they should be made efficiently  but if they get lost en route  it s easy to time out and re-send them

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TCP is a connection oriented protocol  It establishes a path  or a virtual connection all the way through switches routers proxies etc and then starts any communication  Various mechanisms like routing djikstras shortest path algorithm exist to establish the virtual end to end connection  So it finds itself used while browsing HTML and other pages  making payments and web applications in general   UDP is a connectionless protocol - it simply has a destination and nodes simply pass it along if it comes as best as they can  So packets arriving out of order  along various routes etc are common  So Instant messengers and similar software developers think UDP an ideal solution   In real life if you want to throw data in the net  without worrying about time taken to reach  order of reaching use UDP  If you want a solid path before you start throwing packets  and want same order and latency for your data packets use TCP - I will use UDP for Torrents and TCP for PayPal

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One additional thought on some of the comments above that talks about ordered delivery      It must be clarified that the destination computer may receive packets out of order on the wire  but the TCP at the destination is responsible for  rearranging out-of-order data  before passing it on to the upper layers of the stack   When you say TCP guarantees ordered packet delivery  what that means is it will deliver packets in correct order to the upper layers of the stack

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TCP  I will not send data anymore until i get an acknowledgment    this process is slow  It is used for security purpose  example  web  sending mail  receiving mail etc  UDP  Here i have no headache with acknowledgment   this process is faster but here data can be lost    example   video streaming   online games etc  TCP   UDP   SMTP example   mobile telephone

[tcp] What are examples of TCP and UDP in real life?

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