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A data exchange technology
What is
Data exchange technology is the basis for a host of data exchange network edge network core of large-scale
- Edge of the network: the network is connected to all the terminal devices (including the host)
- Core network: switching node (e.g., router) and a set of the transmission medium (the communication link), also referred to as subnetworks
Network as shown:
Under ordinary appreciated that data exchange technology is to allow two hosts for data transmission, message exchange
Two, three methods of data exchange technology
Circuit switched 2.1
The transmission data as shown in step three
- Establishing circuit: establishing a dedicated physical link between two hosts via intermediate switching node is
- Data transmission: using the communication circuit
- Removal circuit: a release signal through a physical link each node
It is the largest circuit-switched telephone network,
as the picture shows
Circuit-switched advantages and disadvantages
advantage
- Real-time high: a circuit to establish a fixed data rate transmission
- Delay smaller: the intermediate node does not process data
Shortcoming
- Channel utilization is low: a dedicated circuit connection is established, the data transmission should not occupied by circuit
- Single transfer rate: fixed rate data transmission
In summary
Is a circuit switched connection for voice and video services and real time
2.2 message exchange
Why?
Exchanging data between the host burst using the circuit switched channel capacity waste will be proposed message exchange
what is?
= + Packet data transmission / receiving host addresses and other control information
in units of packets stored in the respective nodes - a method of transmitting forward
- Storage - forward: entire packet to the adjacent node, look after all the memory forwarding, forwarding a next node
During transmission each node as follows
Exchange messages with respect to the advantages and disadvantages of the circuit switched
Advantages:
high channel utilization: only if packet forwarding busy channel, there is no idle occupation
Disadvantage:
When the extension: the node to buffer packets, packets queued for transmission
loss: When the cache is full node, then the packet is discarded
2.3 Packet Switched
What is
- The packet is divided into small packets of data blocks, each block of control information together with the address
- Each independent transmission packet to the destination, the destination of the packet reassembly, the packet is reduced to
Relationship between packets and packets
Packet switched transmission
Relative advantages and disadvantages of packet switching
Advantages :
1. Low switching device storage capacity requirements
- Packet switching cache the entire message
- Packet switching cache only small packets
2. switching speed
- Message when it is possible to relatively large external memory storage, low read speed
- Small packets stored in memory, the block read speed
3. Reliable transmission rate
- An error message will retransmit the entire message
- Packet re-transmission of small packets only
4. fairer:
-
Packet switching unfair: if the size of the packets along the same path to the same destination, the front and large packets, in the exchange process, small packets only until the transfer is completed large packet, the router node receiving, before transmission . Small packets require more time to reach the destination
-
Packet switching fair: the size of the entire packet is split into groups, independent transmission, generally small packets larger than the packet reaches the destination first
Disadvantages:
consumption of resources: Additional more packet control information when splitting assembly
Third, the summary data exchange technology
Circuit Switched
- Entire data (packets) from the source bit stream continuously to the end
Message switching
- The entire message is then sent to neighboring nodes, to find all the memory after forwarding, is forwarded to the next node (peer transmission finished, the next transmission)
Packet switching
- A single packet (message portion) is transmitted to an adjacent node, after storage down to find the forwarding table, forwarding to the next node (pipelined)
Advantages and disadvantages of three methods are relative to the previous terms, thenCertainly better than circuit switching packet switching it?
Not necessarily, when the real-time communication is required, it still has a circuit switched arena
