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A type of ISDN service designed for larger organizations. PRI includes 23 B-channels (30 in Europe)
and one D-channel. PRI service is generally transmitted through E1/T1 lines.
Proxy server
A firewall component that manages Internet traffic to and from a network and provides other features
such as file caching and access control. A proxy server can also improve performance by caching
frequently requested web pages and can filter unauthorized user requests for access to files or
designated web sites.
PSN – Packet Switched Network
PSTN – Public Switched Telephone Network
Refers to the international telephone system based on copper wires carrying analog voice data.
Telephone service carried by the PSTN is often called POTS. See also POTS.
Public-key encryption
A cryptographic system that uses two keys -- a public key known to everyone and a private or secret
key known only to the recipient of the message.
An important element to the public key system is that the public and private keys are related in such a
way that only the public key can be used to encrypt messages and only the corresponding private key
can be used to decrypt them. Moreover, it is virtually impossible to deduce the private key if you know
the public key.
PVC – Permanent Virtual Circuit
A virtual circuit that is permanently available. The only difference between a PVC and a switched
virtual circuit (SVC) is that an SVC must be reestablished each time data is to be sent. Once the data
has been sent, the SVC disappears. PVCs are more efficient for connections between hosts that
communicate frequently and play a central role in Frame Relay networks. They are also supported in
some other types of networks, such as X.25.
PWE3 – Pseudo Wire Emulation Edge-to-edge
QoS – Quality of Service
A networking term that specifies a guaranteed throughput level. The ATM technology supports QoS
levels which allows ATM providers to guarantee to their customers that end-to-end latency will not
exceed a specified level.
R2 – ITU-T Signaling System R2
RBS – Robbed Bit Signaling
Replay attack
Capturing and storing a password-included packet and then reissuing that packet in an attempt to gain
unauthorized access.
RIP – Routing Information Protocol
A protocol for exchanging routing information among gateways and other hosts.
RPC – Remote Procedure Call
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Multi Service Edge Device HL950
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Administrator's Guide
EN/LZT 108 5995 R3
June 2003
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