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Thread: Need help to resolve the Terms

  1. #1
    Junior Member
    Join Date
    Aug 2003

    Question Need help to resolve the Terms

    this may be dum ... about the thread of W32.Blaster.Worm
    i would like to as a related thing about this worm.....
    Q: What's the difference between TCP and UDP?
    Q: What's "DCOM RPC"?

    well.... my question may not have direct relationship with the worm... but... these two things are the stuff that i don't understand

    i hope ppl can explain to me.... thanx......

    (is port 135 = dcom rpc )?

    Technology = Power

  2. #2
    Senior Member DeadAddict's Avatar
    Join Date
    Jun 2003
    Tcp is Transmission control protocol TCP enables two hosts to establish a connection and exchange streams of data.

    Udp is User datagram protocol provides very few error recovery services, offering instead a direct way to send and receive datagrams over an IP network. It's used for sending messages over a network.

    Port 135 is 135/tcp DCE endpoint resolution
    135/udp DCE endpoint resolution

    Dce is Distributed Computing Environment, a suite of technology services developed by The Open Group for creating distributed applications that run on different platforms. DCE services include:
    Remote Procedure Calls (RPC)
    Security Service
    Directory Service
    Time Service
    Threads Service
    Distributed File Service
    DCE is a popular choice for very large systems that require robust security and fault tolerance.

    Data Communications Equipment, a device that communicates with a Data Terminal Equipment (DTE)

    DCOM is Distributed Component Object Model

    DCOM uses the RPC mechanism to transparently send and receive information between COM components (i.e., clients and servers) on the same network

  3. #3
    Senior Member
    Join Date
    Feb 2003
    Memphis, TN

    That site will answer a lot of questions for you.

  4. #4
    Senior Member
    Join Date
    Aug 2003
    If you want the full details of TCP and UDP you can visit www.ietf.org and
    read the RFCs (request for comments) documents on the protocols.
    It is basically the white paper/blue print on how protocols work..

    Unfortunaltely, if you are new to TCP/IP , you may find the documentation a bit
    dry and too abstract to comprehend..

    So Im going to attempt and give you a quick simple understanding on what the 2 ptrotocols are and the differences between the 2.
    Here goes:

    TCP and UDP are transport layer protocols that are part of the TCP/IP suite..
    (operate on layer 4 of OSI model)

    Think of them as "trucks" that carry your applications.
    Not all applications use them. Some of well known applications that use them are:

    FTP, SMTP & POP3(which is Email), TELNET, DHCP, FTP,TFTP, HTTP, HTTPS, etc..
    You can also write your own TCP/IP application socket and use whatever transport
    protocol suits your needs.

    Now here is the difference between the two and why you may want to use one over the

    TCP is the reliable transport protocol. It is what they call connection oriented.
    It is very reliable because of the following:

    It establishes a 3-way handshake before sending any data to make sure first that
    a successful connection(virtual) can exist. In addition to that, TCP requires that an acknowledgement is received for every "chunk" of data that is sent. This way if any packets are dropped or error occurs while in transmission, it will retransmit the data therefore making it reliable..
    (there are other things TCP does that I wont bore you with here,,see RFC.)

    UDP on the other hand is what they call conncetionless. There are no 3 way handshake, no need for acknowledgements,,just send the data..If error occurs, the application is responsible for retransmitting.

    This makes UDP faster and simpler than TCP. TCP on the other hand is more reliable and more complex and with that reliability makes it slower than UDP..

    Now you might be asking when will I need to use the one over the other?
    To answer that question, i will use the following analogy referencing back to what I said earlier as "think of them as 2 different types of trucks"

    Ok here goes.
    Imagine you had to deliver across state antique furniture that was very expensive and you wanted to make sure that your #1 priority is that it gets to its destination without it being damaged. Now here you would hire professional movers who are insured and bonded who drive a brand new truck who all have a valid drivers license who all drive the speed limit and who all every now and then stop and check to make sure that the furniture is not damaged . They might be a bit expensive to hire but you are basically guaranteed that they will get the job done and are very reliable..Well this is kinda like what TCP is.

    Now on the other hand, assume you had old chairs in your basement that you wanted to donate to the local church. Here you wouldnt go to the extremes as to hiring the professional movers. You would ask your neighbor who drives a beatup old truck who may have his license suspended whos car stalls every now and then to perform the task for you. You buy him a 6 pack of beer and his happy. It costs you basically nothing and also its quick. And if so it happens that the chairs fall off the truck and get scratched, who cares, they're already scratched. Pick them up and toss back into truck... This is kinda like UDP.

    Sorry I got carried away...
    Hope this helps..

    With regards to DCOM RP
    I defer to deadaddict

  5. #5
    Junior Member
    Join Date
    Aug 2003
    Thnx alot.. great information

    Technology = Power

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