Srivathsan Ananthachari wrote: > > Hi, > > This might have something to do with the protocol design . I was > wondering whether all the connection-oriented / reliable > protocols use " > Windowing " .
No, a lot of connection-oriented protocols and a lot of reliable protocols don't use windowing. There are three separate issues here: connection-oriented, reliability, and flow control. Those characteristics can be combined in many ways, as in a protocol that is reliable, not connection-oriented, and doesn't use flow control (such as TFTP); or a protocol that is connection-oriented and reliable and doesn't use flow control (like NetWare Core Protocol with no burst mode); or a protocol that is connection-oriented but not reliable and doesn't do windowing, such as Frame Relay. Wow, how many other combinations could I come up with? :-) Connection-oriented means that there's some sort of formal establishment of the connection. Examples are Frame Relay, ATM, TCP. Dare I bring up NetBIOS again? :-) In a TCP/IP environment, NetBIOS depends on TCP for connection establishment (and reliability and windowing flow control). In a NetBEUI environment, NetBIOS handles reliability and connection establishment. It also relies on LLC type 2 for those 2 things (it's pretty inefficient) and windowing flow control. With NWLink (NetBIOS on IPX), NetBIOS does connection establishment and realibility on its own, and has no windowing flow control. Reliable means that data delivery is guaranteed. This usualy requires sequence numbers and ACKs. There are protocols that are reliable but not connection-oriented and that don't use flow control. An example is OSPF when it exchanges database description messages. This is a reliable protocol with sequence numbers, but there's no formal connection establishment first. Neighbors discover each other with hellos, but they don't establish a connection. They don't use windowing either. Many command/reply protocols, such as DNS, are reliable. The client retransmits if it doesn't get an asnwer. But they aren't connection-oriented and they don't use flow control. Flow control coordinates the amount of data that can be sent to a receiver. It can be handled in two different ways: Stop-and-wait flow control: The sender waits for an ACK after every frame. Examples of protocols that do this are Bysync (BSC), NetWare Core Protocol when burst mode isn't used, Network File System (NFS), Trivial File Transfer Protocol (TFTP). Some of those (like NCP) are connection-oriented and reliable, but they don't use windowing. Some of them (like TFTP) are reliable, but not connection-oriented. Sliding window flow control: The sender can transmit several frames before needing an ACK. TCP uses this, as does X.25, LLC Type 2, HDLC (though not Cisco's HDLC), SDLC. Those are all connection-oriented and reliable also. There are quite a few protocols that aren't connection-oriented or reliable and don't do flow control: Ethernet, Token Ring, Cisco's HDLC, IP, UDP, etc. Priscilla > > Can the group add elaborate on this please..? > > TIA > Srivathsan A > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71364&t=71333 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]