RFC 1242 (rfc1242) - Page 2 of 12

Benchmarking terminology for network interconnection devices

RFC 1242                Benchmarking Terminology               July 1991


        Issues:
                List of issues or conditions that effect this term.

        See Also:
                List of other terms that are relevant to the discussion
                of this term.

3.  Term definitions

3.1  Back-to-back

        Definition:
                Fixed length frames presented at a rate such that there
                is the minimum legal separation for a given medium
                between frames over a short to medium period of time,
                starting from an idle state.

        Discussion:
                A growing number of devices on a network can produce
                bursts of back-to-back frames.  Remote disk servers
                using protocols like NFS, remote disk backup systems
                like rdump, and remote tape access systems can be
                configured such that a single request can result in
                a block of data being returned of as much as 64K octets.
                Over networks like ethernet with a relatively small MTU
                this results in many fragments to be transmitted.  Since
                fragment reassembly will only be attempted if all
                fragments have been received, the loss of even one
                fragment because of the failure of some intermediate
                network device to process enough continuous frames can
                cause an endless loop as the sender repetitively
                attempts to send its large data block.

                With the increasing size of the Internet, routing
                updates can span many frames, with modern routers able
                to transmit very quickly.  Missing frames of routing
                information can produce false indications of
                unreachability.  Tests of this parameter are intended
                to determine the extent of data buffering in the
                device.

        Measurement units:
                Number of N-octet frames in burst.

        Issues:

        See Also:




Benchmarking Methodology Working Group