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Introducing ATM Networking
ANA-5910/5930/5940 Use r’s Gui de
Stock Number: 51069 4-00, Rev. C Page: 2-7
Print Spec Number: 493081-00
Current Date: 5/28/97 ECN Date: 05/29/97
stands for User Datagr am Protocol. Both TCP and UDP have
associated processes and applications that produce the messages
and streams TCP and UDP receive and deliver. While TCP provides
a reliable data transport mechanism to host appl ications including
checksums, UDP provides applications-specific IP addresses but
only provides its applications access only to IP’s conne ctionless,
unreliable delivery.
Classical IP over ATM
Within contemporary ne tworks, host IP soft ware and IP routers g et
datagrams from network sources to ne twork desti nat ions . Within an
ATM network, the ATM adaptation la ye r intercepts and converts IP
datagrams to and from cells. This spans the message transmission
differences inherent within each communication design. However,
it does not address the behavorial differences between components
above this layer. For instance, unlike ATM, the legacy delivery
process does not itself guarantee reliable, in-order delivery.
Because TCP/IP applications were designed in LAN environments
that naturally provided broadcast services that are unavailable with
native ATM, other differenc es also require consid eration before ATM
can seamlessly transp or t IP datagrams. These me ch a ni sms resolve
IP addresses to ATM network addre sses and provide TCP/IP’s
Address Resolution Protocol (ARP) support. Many of these
considerations are resolved in the Internet Engineering Task Force
(IETF) Request For Comment 1577 (RFC 1577). This document
provides protocols, collectively referred to as Classical IP over ATM,
that introduce the concept of a