Information Technology Reference
In-Depth Information
Network view updates bandwidth cost.
If we define the update frequency
as
/1
, and the number of NOSes is
. Then, in time
1/
, the amount of link
utility change in each domain is
. EWBridge will transfer
×
information, while DHT is:
×
.
Thus, EWBridge is
×
less than DHT.
Size of network view storage.
We assume the size of the global SDN network view
information is
X
. In DHT, each domain just stores
. In reality, the controller needs
the entire view of all the SDN networks when computing path. It stores the rest size of
outside the DTH table. So the total size storage for each domain is the
same. EWBrige can also store the local network view of
in high speed database
and store the rest in relative lower speed database if there is a limitation in high speed
database.
Data query speed.
The EWBridge and DHT are both based on the “key-value” sto-
rage system, but DHT has routing issues (multi-hop routing), while EWBridge is sin-
gle-hop routing in more than 99.5% scenarios (will be shown in Section IV.D). Here a
hop may really mean multiple physical hops in the underlying network, so EWBridge
is faster than DHT in the data query speed.
In summary, EWBridge and Onix are designed for different deployment scenarios.
Onix adopts the DHT storage and focuses on large scale network while EWBridge
focuses on enterprise/ DC/ intra-domain networks. Onix is more scalable than EW-
Bridge for large scale networks. EWBridge is more efficient than Onix when they are
working in enterprise / DC / intra-domain networks.
4.4
Scalability
EWBridge supports the network abstraction strategy to improve scalability. As shown
in Section III.B, EWBridge supports network view abstraction. A large network can
be abstracted into a small virtual network only with the edge switches, or even into a
virtual node. To achieve large-scale scalability, each NOS should treat other SDN
networks as an abstract node with multi-ports. We use a mathematical model to eva-
luate the intra-domain level scalability:
Table 2.
Symbol Definition
Symbol
Meaning
Requestsacontrollercandealinonesecond
Requestsacomputergeneratesinonesecond
z
Number of computers one person has
Number of people in an AS/DC/enterprise
