Differences Between Dlsw V1.0 And Dlsw V2.0 - 3Com MSR 50 Series Configuration Manual

212 C 7: DLS C
HAPTER W ONFIGURATION
n
Differences between
DLSw v1.0 and DLSw
v2.0
network cost. In addition, DLSw v2.0 provides enhancements by means of UDP
explorer frames sent in multicast and unicast modes. When the peer is also
running DLSw v2.0, the two ends can use UDP packets to explore reachability, and
a TCP connection is established only when data transmission is required.
SDLC is a data link layer protocol developed by IBM for IBM SNA networks.
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For more information on LLC, refer to IEEE 802.2 standard.
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Problems with DLSw v1.0
TCP connection
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In DLSw v1.0, immediately after a pair of peers is configured, the local peer
attempts to establish a TCP connection with the remote peer (by first establishing
two TCP connections and bringing down one of them after capabilities exchange),
regardless whether a connection is needed. All packets, including explorer frames,
circuit setup requests and data packets, are transmitted over the TCP connection.
This wastes network resources.
Excessive broadcasts
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Although a local acknowledgement mechanism is provided in DLSw v1.0, explorer
frames may flood the WAN over the established TCP connections if the
reachability table of DLSw contains a small number of entries or no entries.
Low maintainability
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When a circuit is disconnected, DLSw v1.0 uses two types of messages to notify
the peer but cannot tell the disconnection cause. This adds to difficulty in locating
the reason for an abnormal circuit disconnection.
Enhancements in DLSw v2.0
DLSw v2.0 provides enhancements to address the above-mentioned problems
while it remains compatible with DLSw v1.0.
The components on a DLSw network are defined as follows:
Figure 35 DLSw v2.0 network
Origin LAN
Origin DLSw
station
router
In Figure 35, the origin station is the end station that originates communication,
the target station is the end station that accepts communication, the origin DLSw
router is a DLSw-enabled router connected to the origin station, and the target
DLSw router is a DLSw-enabled router connected to the target station. In this
document, an origin DLSw v2.0 router is a DLSw v2.0-capable router.
Using UDP packets to explore peer addresses
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To prevent unnecessary TCP connection setups, DLSw v2.0 sends explorer frames
by using UDP packets instead of over TCP connection, unless a TCP connection is
present). These UDP packets can be sent in two ways: multicast and unicast
UDP, TCP/IP
Target DLSw
router
SSP message
LAN
Target
station