Tuesday, February 9, 2016

CCNAv2 Terms To Know Pt. 1

cut-through:
appropriate for high performance computing applications
may forward invalid frames
forwarding process can begin after receiving the destination address

store-and-forward:
error checking before forwarding
only forwards valid frames
forwarding process only begins after receiving the entire frame

Flexibility: using all network resources to allow intelligent traffic load sharing.
Modularity: allows networks to expand and provide on-demand services.
Hierarchical: helps every device on every tier to employ a specific role.
Resiliency: provides a way for the network to always be accessible.

Hierarchical principal

the role of every device at each tier to simplify deployment, operation, management and fault domains at each tier

hierarchical

helps every device on every tier to employ a specific role

modularity principal

seamless network expansion and integrated service enablement on an on-demand basis

modularity

allows networks to expand and provide on-demand services

resiliency

keeping the network always on to satisfy user expectations

flexibility

using all network resources to allow intelligent traffic load sharing

access layer

network edge

access layer switch

connect to network layer switches

network layer switch

implement network foundation technologies such as routing, quality of service, and security

distribution layer

interfaces between the access layer and the core layer






distribution layer functions

Aggregating large-scale wiring closet networks
Aggregating Layer 2 broadcast domains and Layer 3 routing boundaries
Providing intelligent switching, routing, and network access policy functions to access the rest of the network
Providing high availability through redundant distribution layer switches to the end-user and equal cost paths to the core
Providing differentiated services to various classes of service applications at the edge of network

Core Layer

network backbone

core layer

can be combined with the distribution layer to provide for a collapsed design
the network backbone area for switching
provides fault isolation and high-speed backbone switch connectivity

distribution layer

includes redundancy as an important feature for switched network access
allows data to flow on equal-cast switching paths to the backbone
supports layer 2 broadcast domains and layer 3 routing boundaries
interfaces with the backbone and users to provide intelligent switching, routing and security

access layer

provides direct, switched network connectivity to the user
helps applications to operate on the switched network more safely and securely

ASIC

application-specific-integrated circuits

store and forward switching

reads header
computes FCS and if bad, drops the frame
if FCS is good forwards the frame

FCS

frame check sequences uses CRC field

automatic buffering

ingress buffering
supports a mix of Ethernet speeds

cut-through switching

makes forwarding decision as soon as MAC address is read & looked up in MAC table




rapid frame forwarding

forwards as soon as MAC address checked in table
may forward the frame while still receiving it
does not drop invalid frames

fragment free

waits for the entire collision window (64 bytes) before forwarding
able to drop runts

stack power

which enables power sharing among stack members

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