94 Software Networks
Carrier-Grade Ethernet must possess functions that are found in
telecommunications networks – most notably the following:
– reliability, which means that there must be very few failures. The
MTBF (Mean Time Between Failures) needs to be at least
50,000 hours;
– availability, which must achieve the classic values in telephony –
i.e. a functioning state 99.999% of the time. This value is far from
being achieved by conventional Ethernet networks, which actually
only offer availability around 99.9% of the time;
– protection and restoration. When a failure occurs, the system
must be able to recover within a maximum of 50 ms. This duration
comes from telephony, where breakdowns lasting longer than this are
unacceptable. SONET networks, for example, reach this value for
their reconfiguration time. The solutions generally use redundancy,
either total or partial, which involves engaging another path, arranged
in advance;
– performance optimization by active or passive monitoring. The
operations are not all entirely homogeneous when the packet flows
vary. Thus, we need to adapt the flows so they can flow without a
problem;
– the network must be able to accept the SLAs (Service Level
Agreements). The SLA is a typical notion in an operator network
when a customer wants to negotiate a service guarantee. The SLA is
determined by a technical part – the SLS (Service Level Specification)
– and an administrative part whereby penalties are negotiated if the
system does not satisfy the requirements;
– management is also an important function of operator networks.
In particular, failure-detection systems and signaling protocols must
be available in order for the network to work.
From a technical standpoint, Carrier-Grade Ethernet is an
extension of VLAN technology. A VLAN is a local-area network in
www.it-ebooks.info
Carrier-Grade Ethernet must possess functions that are found in
telecommunications networks – most notably the following:
– reliability, which means that there must be very few failures. The
MTBF (Mean Time Between Failures) needs to be at least
50,000 hours;
– availability, which must achieve the classic values in telephony –
i.e. a functioning state 99.999% of the time. This value is far from
being achieved by conventional Ethernet networks, which actually
only offer availability around 99.9% of the time;
– protection and restoration. When a failure occurs, the system
must be able to recover within a maximum of 50 ms. This duration
comes from telephony, where breakdowns lasting longer than this are
unacceptable. SONET networks, for example, reach this value for
their reconfiguration time. The solutions generally use redundancy,
either total or partial, which involves engaging another path, arranged
in advance;
– performance optimization by active or passive monitoring. The
operations are not all entirely homogeneous when the packet flows
vary. Thus, we need to adapt the flows so they can flow without a
problem;
– the network must be able to accept the SLAs (Service Level
Agreements). The SLA is a typical notion in an operator network
when a customer wants to negotiate a service guarantee. The SLA is
determined by a technical part – the SLS (Service Level Specification)
– and an administrative part whereby penalties are negotiated if the
system does not satisfy the requirements;
– management is also an important function of operator networks.
In particular, failure-detection systems and signaling protocols must
be available in order for the network to work.
From a technical standpoint, Carrier-Grade Ethernet is an
extension of VLAN technology. A VLAN is a local-area network in
www.it-ebooks.info