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Cross Country Network Bandwidth (RFC0567)

IP.com Disclosure Number: IPCOM000003658D
Original Publication Date: 1973-Sep-06
Included in the Prior Art Database: 2001-Oct-24
Document File: 1 page(s) / 2K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

L.P. Deutsch: AUTHOR


The following computation of cross-country network bandwidth was contributed by Butler Lampson of PARC.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Network Working Group                             L. Peter Deutsch  (PARC-MAXC)

Request for Comments: 567                                     September 6, 1973

NIC #18970


The following computation of cross-country network bandwidth was

contributed by Butler Lampson of PARC.

Consider what happens when a TIP user on the West Coast, connected to a

full-duplex Host on the East Coast, strikes a key on his terminal.

The TIP sends a one-character message (1 packet).

The destination IMP sends a RFNM (1 packet).

The destination Host sends an ALLocate - this seems to be the strategy

used by TENEX Hosts, at least (1 packet).

Thc TIP sends a RFNM for the ALLocate (1 packet).

The same sequence repeats itself, with roles interchanged, for the echo

character (4 packets).

This constitutes 4 packets or 4OOO bits in each direction. The current

cross-country transmission capability of the ARPANET is 3 5OKb phone

lines; ergo, it can only support 3*50000/4000=37.5 such characters per


It may be that RFNMs are transmitted between IMPs more efficiently; at

best this can only double the network capacity.

This computation may help explain why cross-country TIP users (e.g. the

substantial West Coast community of BBN-TENEX users) experience such

bad echo response, at least in bursts: the network itself may be

experiencing momentary peak loads.

If this argument is correct, the proposed remote echoing facilities of

the new TELNET protocol could have a major effect on network operation.