User guide

New and Changed Information
20
Release Notes for Cisco 2500 Series for Cisco IOS Release 12.0 T
78-5563-07 Rev.H0
are replacing their traditional SNA network with an IP infrastructure that supports traffic from a variety
of clients, using a variety of protocols, requiring access to applications on a variety of platforms,
including SNA applications on Enterprise servers.
While SNA routing is still required when multiple servers must be accessed, the number of nodes
required to perform this function is decreasing as the IP infrastructure grows and as the amount of native
SNA traffic in the network decreases.
SNASw enables an enterprise to develop their IP infrastructure, while meeting SNA routing
requirements.
X.25 Closed User Groups
The X.25 specification for Closed User Groups (CUG):
• Provides an application access security service that restricts users who do not have subscribed
access to the host location.
• Provides a privacy technique that you can use to create private subnets or virtual networks out of a
public data network.
Note Previously, Cisco supported only the ability to specify the CUG value but did not enforce
restriction. Cisco currently enforces this security restriction.
X.25 Switch Local Acknowledgment
Cisco offers an X.25 switch function that creates virtual connections (VC) by connecting channels
between X.25 class services.
The following X.25 class services are supported:
• X.25, Connection-Mode Network Service (CMNS)
• X.25 over TCP (XOT)
• Switched Virtual Circuits (SVCs) and Permanent Virtual Circuits (PVCs) are both supported and
can be switched to each other (converted).
The current Cisco implementation provides end-to-end acknowledgment, which means that flow control
or window and packet size acknowledgment is between the originating and terminating data terminal
equipment (DTE).
Acknowledgment is not local to the DTE and data communications equipment (DTE), and the overall
effect is low throughput.
VPN Tunnel Management
The VPN Tunnel Management feature provides network administrators with two new functions for
managing VPN tunnels:
• The ability to set a limit for the maximum number of allowed simultaneous VPN sessions
• The ability to prevent new sessions from being established on a VPN tunnel without disturbing the
service of existing sessions (this function is called VPN tunnel soft shutdown)
These functions can be used on either end of a VPN tunnel—the Network Access Server (NAS) or on
the home gateway.