Cisco 11.0 BT Manual de usuario descargar pdf (Pagina 19)

TN3270 Server Implementation 2-19

Note: If you need to use client LU nailing and provide redundancy, the solution is difﬁcult. With LU nailing,

requesting a speciﬁc LU for an IP address requires a connection to a speciﬁc PU andTN3270 Server. A secondary

TN3270 Server cannot be used to service these clients. In this case, we could use HSRP. HSRP provides

redundancy, but does not provide load balancing.

LocalDirector

LocalDirector dynamically load-balances trafﬁc between multiple servers to ensure timely access and response to

requests. It is independent ofdomain nameservers and applications;rather, it functions as afront endto agroup

of servers by load balancing trafﬁc demands between servers and speeding user access to server-based

applications. Servers can be added and removed transparently, but to end users LocalDirector provides the

appearance of a single, virtual server.

LocalDirector is a high-performance networking device with over 45 Mbps throughput. It supports up to 8,000

virtual IP addresses and domain names. It can also direct trafﬁc to 8,000 servers that can be a collection of

heterogeneous hardware platforms and operating systems, and it efﬁciently handles over 700,000 simultaneous

TCP connections.

In addition to its directing capabilities, LocalDirector also serves as a simple bridge to forward data packets

between its interfaces. This bridging ensures that LocalDirector does not interfere with network operation while

itis inserviceand itcanbe broughtonline immediatelyafterpowering upwithout affectingnetworkconnectivity.

The LocalDirector does not use Domain Name System (DNS) for domain name lookup. Networks without a

DNS or that do not require their TN3270 sessions to reference the DNS for mainframe connectivity are suited

to use the LocalDirector.

Most data centers implement a redundant CIP or CPA and TN3270 Server solution to create multiple IP

addresses for the end user to reference for host connectivity. LocalDirector is installed with the TN3270 Server

to provide consolidation of the IP addresses and load balancing.

The IP addressing consolidation is achieved by creating a virtual IP address on the LocalDirector. The real IP

addresses, as deﬁned in the TN3270 Server, are included in the LocalDirector. The real IP addresses are bound

to the virtual address creating a pool of host connection addresses. A typical conﬁguration binds all the real IP

addresses to a single virtual IP address, which creates a simple environment to administer. There is a range of

conﬁguration possibilities available, such as creating multiple virtual addresses and allocating a particular

address to a particular group or region. The best type of virtual address allocation will depend on the needs of

the company.

DistributedDirector

DistributedDirector can be run on either a Cisco 2500 or 4700-M router. With DistributedDirector, users need

only asingle DNS host nameor URL-embedded host namefor accessing a globallydistributed set of servers, thus

providing the appearance of a single virtual server. This eliminates the need for users to choose a server from a

list of possible sites.

DistributedDirector enables transparent distribution of all common TCP/IP network services, such as Hypertext

Transfer Protocol (HTTP), File Transfer Protocol (FTP), Telnet, TN3270, and gopher.

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Cisco 11.0 BT Manual de usuario Pagina 19