Routing
Routing is the process of mapping a path to send a packet to its destination
Internet address. Routing can be direct or indirect. Direct routing is used when the
source and destination nodes are on the same physical network. When direct
routing is used, the source node sends the packet on the network with the
destination hardware address in the link layer protocol header. The destination node
hardware detects its own address in the packet header and accepts the packet.
Indirect routing is used when the source and destination nodes are not on the same
physical network. The source node uses its routing tables to determine which router
will forward packets to the destination node. The packet is put on the network with
the router’s hardware address in the network header, and the destination’s Internet
address in the IP header.Thus, the router hardware receives the packet from the
network, and the router IP software determines the packet’s destination from the IP
header.
Introduction to TCP/IP Protocols on AS/400
Network protocols are sets of rules that control the communication and transfer of
data between two or more devices in a communications system. The term TCP/IP
refers to a family of nonproprietary network protocols, of which TCP, providing
host-to-host transmission, and IP, providing data routing from source to destination,
are two important parts.
The topics that follow discuss only those protocols that are available on the AS/400
business computing system.
TCP/IP consists of a layered structure of protocols that range from low-level,
hardware-dependent programs, to high-level applications. Each TCP/IP layer
provides services to the layer above it and uses the services provided by the layer
below it.
The layers are defined as follows:
Application
Provides a way for a process to cooperate with another process on the
same or a different host.
Transport
Provides communication from one application program to another. Such
communication is often called end-to-end data transfer.
Internetwork
Makes the entire physical network seem like a single virtual network. This is
achieved by shielding the higher levels from the underlying network
architecture.
Network Interface or Data Link
Provides the interface to the actual network hardware. Examples are
token-ring and Ethernet.
Hardware
This layer is not part of the TCP/IP family and is represented by dotted
lines. This layer consists of the hardware-specific network protocols.
12 OS/400 TCP/IPConfiguration and Reference V4R4