8.2 - Packet-Switched Networks Flashcards
_______________ operate more like Ethernet and IP networks used in the LANs and BNs than like dedicated circuit networks
Packet-switched networks
With _______________ networks, a circuit is established between two communicating routers that provides a guaranteed data transmission capability that is available for use by ONLY those two devices
dedicated-circuit
In contrast, _______________ enable multiple connections to exist simultaneously between computers over the same physical circuit, just like LANs and BNs
packet-switched services
The user’s connection into the network is a ______________________________ (PAD) — which can be owned and operated by the customer or by the common carrier
packet assembly/disassembly device (PAD)
With packet-switched services, the user _______ a connection into the common carrier cloud
buys
The PAD converts the sender’s data into the ____________ layer and ______________ layer packets used by the packet network and sends them through the packet-switched network
network…data-link
At the other end, another _________ reassembles the packets back into the network layer and data link layer protocols expected by the destination
PAD
One of the key advantages of packet switched services is that different locations can have different _______________ into the common carrier cloud
connection speeds
Connections between the different locations in the packet network are called _____________________________ (PVCs)
permanent virtual circuits
Some carriers also permit the use of ______________________ (SVCs) — change dynamically based on traffic, although not common
switched virtual circuits
Organizations often lease a dedicated circuit from their offices to the packet-switched network _______________ (POP)
point of presence
The _______________ is the location at which the packet-switched network connects into the local telephone exchange
point of presence (POP)
Three types of packet-switched services
- Frame relay
- IP services
- Ethernet services
One of the oldest used packet-services
Frame relay
Said to replace frame relay as it is simpler to implement and uses IP, which every organization already uses
IP services
Introduced in the 2000s, used in LANs and BNs
Ethernet services
Uses T carrier and SONET as its wiring, so its speeds are identical to them (e.g., 15 Mbps, 45 Mbps, 155 Mbps, and 622 Mbps)
Frame relay
It is an unreliable packet service because it does not perform error control
Frame relay
It checks for errors, but simply discards packets with errors
Frame relay
It is up to the software at the source and destination to control for lost messages
Frame relay
The ______________________________ (CIR) is the data rate the PVC guarantees to transmit — if the network accepts the connection, it guarantees to provide that level of service
committed information rate
Most connections also specify a __________________________ (MAR), which is the maximum rate that the network will attempt to provide, over and above the _________________________ (CIR)
maximum allowable rate….committed information rate
The circuit will attempt to transmit all packets up to the MAR, but all packets that exceed the CIR are marked as _______________ (DE)
discard eligible
With _______________, the PAD at the sending site takes the outgoing message, strips off the _______________, and uses the IP packet to route the packet through the carrier’s packet-switched network to its final destination
IP services… Ethernet frame
Most IP services use _____________________________ (MPLS) as the data link layer protocol
multiprotocol label switching
Most organizations today use _____________ and IP in the LAN and BN environments, yet WAN packet network services (T carrier, SONET, and frame relay) use different layer 2 protocols
Ethernet
Any LAN or BN must be translated or _______________ into a new protocol and destination addresses generated for the new protocol — this takes time, slowing network thoroughput, adds complexity
encapsulated
