Prerequisites For Tcp; Restrictions For Tcp; Information About Tcp; Tcp Services - Cisco ASR 1000 Series Configuration Manual
Aggregation services router ip application services cisco ios xe release 3s
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- Software configuration manual (602 pages) ,
- Configuration manual (442 pages) ,
- Replacing (120 pages)
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Prerequisites for TCP
Prerequisites for TCP
TCP Time Stamp, TCP Selective Acknowledgment, and TCP Header Compression
Because TCP time stamps are always sent and echoed in both directions and the time-stamp value in the
header is always changing, TCP header compression will not compress the outgoing packet. To allow TCP
header compression over a serial link, the TCP time-stamp option is disabled. If you want to use TCP header
compression over a serial line, TCP time stamp and TCP selective acknowledgment must be disabled. Both
features are disabled by default. Use the no ip tcp selective-ack command to disable the TCP selective
acknowledgment once it is enabled.
Restrictions for TCP
The TCP Keepalive timer parameters can be configured only on vty and TTY applications.
Information About TCP
TCP Services
TCP provides reliable transmission of data in an IP environment. TCP corresponds to the transport layer
(Layer 4) of the Open Systems Interconnection (OSI) reference model. Among the services that TCP provides
are stream data transfer, reliability, efficient flow control, full-duplex operation, and multiplexing.
With stream data transfer, TCP delivers an unstructured stream of bytes that are identified by sequence
numbers. This service benefits applications because they do not have to divide data into blocks before handing
it off to TCP. Instead, TCP groups bytes into segments and passes them to IP for delivery.
TCP offers reliability by providing connection-oriented, end-to-end reliable packet delivery through an
internetwork. It does this by sequencing bytes with a forwarding acknowledgment number that indicates to
the destination the next byte that the source expects to receive. Bytes that are not acknowledged within a
specified time period are retransmitted. The reliability mechanism of TCP allows devices to handle lost,
delayed, duplicate, or misread packets. A timeout mechanism allows devices to detect lost packets and request
retransmission.
TCP offers efficient flow control, which means that the receiving TCP process indicates the highest sequence
number that it can receive without overflowing its internal buffers when sending acknowledgments back to
the source.
TCP offers full-duplex operation, and TCP processes can both send and receive data at the same time.
TCP multiplexing allows numerous simultaneous upper-layer conversations to be multiplexed over a single
connection.
TCP Connection Establishment
To use reliable transport services, TCP hosts must establish a connection-oriented session with one another.
Connection establishment is performed by using a "three-way handshake" mechanism.
IP Application Services Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
24
Configuring TCP
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