| From: | Tzeentch tzeentch666@*********.net |
|---|---|
| Subject: | Virtual Realities 3.0: Bandwidth |
| Date: | Thu, 27 Jul 2000 14:05:35 -0700 |
Bandwidth is the speed at which data moves over a connection. Modern
connections are rated in the number of megapulses they can push through a
line per second.
Under these rules there are two kinds of bandwidth: *persona bandwidth* and
*transfer bandwidth*. Persona bandwidth carries commands and machine code
between the deck and his connection. Transfer bandwidth is used to transfer
other types of data. When determining how much data the user is actually
transferring, you total the persona and transfer bandwidth. This total
affects the users datatrail, which in turn affects how easily trace programs
can locate a decker.
The gamemaster is free to use one or both forms of bandwidth in his game.
The persona bandwidth rule is simple, while the transfer bandwidth rules are
a bit more complex. If the optional bandwidth rules are not used, then
assume that all Matrix transactions happen at virtually instantaneous
speeds. The decks I/O speed determines how fast the deck can upload or
download data in this case.
SYSTEM I/O SPEED
If the optional bandwidth rules are not being used then assume that all
Matrix transactions happen at the maximum I/O speed of the system. In order
to calculate a systems I/O speed in this case multiply the systems OS rating
by 40, rounding to the nearest multiple of 10. The deck may divide uploads
and downloads between this amount in Mp/Combat Turn.
For example, Ereskanti's system is running a rating 8 desktop OS. His system
I/O speed is (8 x 40) 320 MePS. He could upload a 200Mp and download 120Mp
per Combat Turn or any variation of the figure.
PERSONA BANDWIDTH
Also called 'icon bandwidth', persona bandwidth is representative of the
users persona programs loaded onto the host. It handles all the commands and
code transfer between the deck and the Matrix. The persona bandwidth is
equal to the sum of the users persona program ratings plus the ratings of
all of his utilities divided by 5, since all programs must be loaded into
the user space in order to interact with the host or grid.
Persona Bandwidth = (Total Persona Ratings) + (Total Ratings of Utility
Programs in Memory)/5
A user must set his persona bandwidth when he logs into the jackpoint. This
total remains constant throughout the run - the user must disconnect and
reconfigure his settings if he wishes to modify the usage (see Suspending
Persona Operations, for the sole exception to this rule). Even if his
program ratings are reduced during the course of a run, the user cannot
reallocate the totals in order to make his datatrail harder to follow.
One common tactic to reduce an intruder's signature on a network is to
intentionally reduce their persona program ratings so that they use less
bandwidth, and are thus harder to trace. The disadvantage to this is that
the ratings cannot be modified during the course of the run.
TRANSFER BANDWIDTH
Transfer bandwidth is representative of uploading and downloading
information. The starting transfer bandwidth a user has available is the
jackpoints base bandwidth minus the persona bandwidth. The remainder is what
the user has to play with. For example, a user sitting on a legal jackpoint
(base bandwidth of 20) with a persona bandwidth of 8 has 12 MePS of transfer
bandwidth. A decker may attempt to increase his base bandwidth by conducting
a Retrain operation.
Transfer Bandwidth = Current Bandwidth - Persona Bandwidth
In extreme cases the decker can suspend his persona programs and reassign
their bandwidth to increase his transfer bandwidth (see Suspending Persona
Operations).
Data Transmission
With 12 MePS of transfer bandwidth as user can download a music album in 10
seconds, or maintain four Full-X simsense transmissions. For most users this
is more then enough, even on their worst day the average user would have a
hard time saturating a legal jackpoints bandwidth. But for a decker, even a
few seconds can mean the difference between life and death. Every MePS
counts when staying ahead of snooping IC, uploading doctored datafiles, or
downloading that paydata, which is where the Retrain operation comes in.
Multiplexing
Multiplexing is the term used to perform multiple data transactions from a
single connection. A user may split his transfer bandwidth among different
jobs how he pleases. For example, a decker with 50 MePS of transfer
bandwidth could be downloading files at 20 MePS while also uploading 30 MePS
of data.
Multiplexing is handled automatically and requires no test or action on the
users part.
EXCEEDING THE BASE BANDWIDTH
Unless a Retrain system operation (see below) is performed, a user may not
exceed the base bandwidth of his jackpoint - no matter the actual System I/O
capability.
For example, an average illegal jackpoint has a base bandwidth of 20.
Without a Retrain the maximum bandwidth avialable (for both Persona and
Transfer) is 20 MePS. This limitation could force the decker or user to make
some hard choices about how he wants to set up his system.
Retrain
Retraining refers to the process of grabbing additional base bandwidth
during a Matrix run (see System Operations, p. xx, for further information).
The decker may never exceed the jackpoints maximum bandwidth through Retrain
operations.
Since increasing bandwidth in this manner has a significant effect on the
users signature versus trace programs, most deckers do not perform Retrain
operations until the last possible moment, dropping the extra bandwidth as
soon as its not needed.
To determine the effect of a Retrain, divide the decks current Bandwidth by
the Base Bandwidth, rounded down and multiplied by -1. This is applied as a
modifier for the decker's Evasion Factor for resisting the effects of Track
and Trace IC (see Trace IC, p. xx). Only apply this modifier if the user's
deck exceeds the base bandwidth for his connection.
Suspending Persona Operations
Users may stop persona operations in order to increase their transfer
bandwidth. However, this is an all-or-nothing action, the persona bandwidth
may not be reassigned in anything but the whole amount. Suspending persona
operations is a Free Action.
For example, a user with a persona bandwidth of 16 MePS that then suspends
persona operations could then assign that amount to his transfer bandwidth.
While suspended, all persona program ratings - Bod, Evasion, Masking, and
Sensor - drop to 1. The deck is automatically switched to running in
terminal mode (see Deck Modes, p. xx) and suffers the appropriate penalties
while his persona is suspended.
OPTIONAL RULE: REALISTIC BANDWIDTH
In a more realistic campaign, the gamemaster may impose additional
restrictions on the decker's bandwidth usage and availability.
RETRAIN
Under the realistic bandwidth rules the Retrain operation is not available.
It is a cinematic game aid to speed play.
BANDWIDTH THROTTLING
Under the realistic rules the deckers actual base bandwidth is equal to the
LOWEST value of his system I/O, his jackpoint bandwidth, or that of any
intervening grid or host.
In most cases bandwidth throttling is employed by firewalls to external
connections, in order to reduce the risk of denial of service attacks. Thus
while systems inside the firewall may have high ususable bandwidths per
connection, an outside user may be extremely limited. A typical limit is 10
MePS for all but accounts with superuser access. Thus for all intents and
purposes the decker would be limited to a base bandwidth of 10 to conduct
his business with.
OPENING THE THROTTLE
On systems that intentionally throttle available bandwidth, the gamemaster
is free to decide if the restrictions can be lifted with Control or Slave
tests. If security deckers are present they can oppose these tests as
normal.
Kenneth
"On two occasions I have been asked, 'Pray, Mr. Babbage, if you put into the
machine wrong figures, will the right answers come out?' I am not able to
apprehend the kind of confusion of ideas that could provoke such a
question."
-- Charles Babbage
