State
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... This document describes the currently available tools as well as the
state of the art in accounting protocol design. A companion
document, RFC 2924 ...
... accounting protocol design. A companion
document, RFC 2924, reviews the state of the art in accounting
attributes and record formats.
...
... throughput. In
applications which require maintenance of session state, such as
simultaneous usage control, TCP and application-layer ...
... heartbeat capabilities provide a
mechanism for keeping track of session state.
When implementing UDP ...
... variables rather than expressing accounting data in terms of a change
from a previous data item. With cumulative data, the current state
can be recovered by a successful retrieval, even after many packets
have been lost. However, if the data is transmitted as a change then
...
... can be recovered by a successful retrieval, even after many packets
have been lost. However, if the data is transmitted as a change then
the state will not be recovered until the next cumulative update is
sent. Thus, such implementations are much more vulnerable to packet
loss ...
... connections within a single transport
connection, all maintaining the same congestion control state,
avoiding the "head of line blocking" issues that can occur with TCP.
...
... accounting
management systems may need to keep state on managed devices or
concurrent sessions. Since the number of devices is typically much
...
... smaller than the number of concurrent sessions, it is desirable to
keep only per-device state if possible.
...
... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| System | Per-device state |
| state | |
...
... | System | Per-device state |
| state | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
... accounting manager in a batch, resulting in an efficient transfer
process. In terms of Accounting Manager state, polling systems scale
with the number of managed devices, and system bandwidth usage scales
...
... roaming implementations.
Per-device state is typical of polling-based network management
systems, which often also carry out accounting management functions ...
... management functions,
since network management systems need to keep track of the state of
network devices for operational purposes. These systems offer
...
...
Per-session state is typical of event-driven systems without
batching. As a result, the event-driven approach scales poorly.
However, event-driven systems offer the lowest processing delay since
...
... providing the best of both worlds.
Where batching can be implemented, the state required in event-driven
polling can be reduced to scale with the number of active devices.
...
... active devices.
If portions of the network vary widely in usage, then this state may
actually be less than that of the polling approach. Note that
processing delay in this approach is higher than in event-driven
...
... | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Polling | Per-device state | Not robust |
| | Robust against | against device |
| | packet loss ...
... | | | Low efficiency |
| | | Per-session state |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Event-driven, | Single round-trip ...
... | | Per active device | |
| | state | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Event-driven | Batch transfers | Not robust |
...
... on multiple accounting events simultaneously, resulting in per-device
state. Management applications are able to retry requests when a
response is not received, providing resiliency against packet loss ...
... accounting records. As a result, these
systems result in per-active device state. Since accounting systems
using SMTP ...