first of all, thanks for the research. it makes sense now that I've read through it.
it appears that things have changed a lot since the days of ISAM/VSAM and hashed lookups. I recall reading a bit about CEF, and coming to a similar conclusion - that the Computer Science people have done extensive research and made substantial improvements to table lookup algorithms. one more reason why I love this newsgroup. ""Michael L. Williams"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > First let me say that I was looking for a book to recommend to a friend, and > I picked up this same book in the store and thumbed through.... I actually > happen to stop on the part where it talked about how a switch (bridge) > builds a routing table etc....... I put the book down, pointed at it, and > told my friend "Don't by this book!" I am appalled at what passes for > techincal books (I guess I'm more sensitive about networking topics)..... > but in the technical field, one must be careful about the terms they use > because they can mean different things..... packet -vs- frame, etc..... > > > Cisco calls the mac table a "content addressable memory" table. without > > spending more time than I have at the moment, I can't find a history on > CCO > > as to why they do this. > > Here is some info I found on CAM....... basically, you can use the data to > find itself in memory (as opposed to having to know it's address in > memory)...... (all of the following info is from various web pages found > through Google) > > Content-Addressable Memory (CAM): In this information-handling model, each > possible piece of information has one and only one possible storage > location. The data is its own key. It is important to differentiate CAM from > a hash key or traditional index. With conventional indexing schemes the > data content is used with a hash or index to produce the address location of > the data. The address has no real or direct relationship with the > information contained in the data. With CAM, the data describes its own > storage location. This also means all like data will always be found close > together in the physical data structure. There is a direct relationship > between the information in the data and its location in the physical data > store. > > In a symbolic system information is stored in an external mechanism. In the > example of the computer it is stored in files on the disks. As the > information has been encoded in some form of file system in order to > retrieve that information one must know the index system of the files. In > other words, data can only be accessed by certain attributes. In a > connectionist system the data is stored in the activation pattern of the > units. Hence, if a processing unit receives excitatory input from one of its > connections, each of its other connections will either be excited or > inhibited. If these connections represent the attributes of the data then > the data may be recalled by any one of its attributes, not just those that > are part of an indexing system. As these connections represent the content > of the data, this type of memory is called content addressable memory. This > type of memory has the advantage of allowing greater flexibility of recall > and is more robust. > > You can compare CAM to the inverse of RAM. When read, RAM produces the data > for a given address. Conversely, CAM produces an address for a given data > word. When searching for data within a RAM block, the search is performed > serially. Thus, finding a particular data word can take many cycles. CAM > searches all addresses in parallel and produces the address storing a > particular word. You can use CAM for any application requiring high-speed > searches, such as networking, communications, data compression, and cache > management. > > Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=45035&t=44649 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
