Cisco WS-C3550-48-EMI Bedienungsanleitung PDF herunterladen (Seite 3)

Cisco Systems, Inc.

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Intelligence in the Network

Networks of today are evolving to address four new developments at the network edge:

• Increase in desktop computing power

• Introduction of bandwidth-intensive applications

• Expansion of highly sensitive data on the network

• Presence of multiple device types, such as IP phones and wireless LAN access points

These new demands are contending for resources with many existing mission-critical applications. As a result,

IT professionals must view the edge of the network as critical to effectively manage the delivery of information

and applications.

As companies increasingly rely on networks as the strategic business infrastructure, it is more important than ever

to ensure their high availability, security, scalability and control. By adding Cisco intelligent functionality to the

wiring closet, customers can now deploy network-wide intelligent services that address these requirements in a

consistent way from the desktop to the core and through the WAN.

With Cisco Catalyst Intelligent Ethernet switches, Cisco enables companies to realize the full benefits of adding

intelligent services into their networks. Deploying capabilities that make the network infrastructure highly available to

accommodate time-critical needs, scalable to accommodate growth, secure enough to protect confidential information,

and capable of differentiating and controlling traffic flows are key to further optimizing network operations.

Network Control through Advanced Quality of Service and Rate Limiting

The Cisco Catalyst 3550 offers superior Layer 3 granular QoS features to ensure that network trafﬁc is classiﬁed,

prioritized, and congestion is avoided in the best possible manner. Conﬁguration of QoS is greatly simpliﬁed through

automatic QoS (Auto QoS), a feature that detects Cisco IP phones and automatically conﬁgures the switch for the

appropriate classiﬁcation and egress queuing. This optimizes trafﬁc prioritization and network availability without

the challenge of a complex conﬁguration.

The Catalyst 3550 can classify, reclassify, police, and mark the incoming packets before the packet is placed in the

shared buffer. Packet classiﬁcation allows the network elements to discriminate between various trafﬁc ﬂows and

enforce policies based on Layer 2 and Layer 3 QoS ﬁelds.

To implement QoS, ﬁrst, the Catalyst 3550 switches identify trafﬁc ﬂows, or packet groups, and classiﬁes or

reclassiﬁes these groups using the Differentiated Services Code Point ﬁeld (DSCP) and/or the 802.1p class of service

(CoS) ﬁeld. Classiﬁcation and reclassiﬁcation can be based on criteria as speciﬁc as the source/destination IP address,

source/ destination Media Access Control (MAC) address or the Layer 4 Transmission Control Protocol (TCP)/User

Datagram Protocol (UDP) port. At the ingress, the Catalyst 3550 will also perform policing and marking of the

packet. Control plane and data plane ACLs are supported on all ports to ensure proper policing and marking on a

per packet basis.

After the packet goes through classiﬁcation, policing, and marking, it is then assigned to the appropriate queue before

exiting the switch. The Catalyst 3550 supports four egress queues per port, which allows the network administrator

to be more discriminating and speciﬁc in assigning priorities for the various applications on the LAN. At egress, the

switch performs scheduling and congestion control. Scheduling is an algorithm/process that determines the order in

which the queues are processed. The switches support Weighted Round Robin (WRR) scheduling and strict priority

queuing. The WRR queuing algorithm ensures that the lower priority packets are not entirely starved for bandwidth

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Cisco WS-C3550-48-EMI Bedienungsanleitung Seite 3