Specifications

80
Release Notes for Cisco 7000 Family for Cisco IOS Release 12.1 T
78-10811-05
New and Changed Information
OSPF Flooding Reduction
Platforms: Cisco 7100 series, Cisco 7200 series, and Cisco 7500 series routers
The explosive growth of the Internet has placed the focus on the scalability of Interior Gateway
Protocols such as Open Shortest Path First (OSPF). The networks using OSPF are becoming larger
every day and will continue to expand to accommodate the demand to connect to the Internet.
Internet service providers and customers with large networks have regularly complained that OSPF has
a traffic overhead, even when the network topology is stable.
By design, OSPF requires link-state advertisements (LSAs) to be refreshed as they expire after 3600
seconds. Some implementations have tried to improve the flooding by reducing the frequency to refresh
from 30 minutes to approximately 50 minutes. This solution reduces the amount of refresh traffic but
requires at least one refresh before the LSA expires.
The OSPF Flooding Reduction feature works by reducing unnecessary refreshing and flooding of
already known and unchanged information. To achieve this reduction, the LSAs are now flooded with
the higher bit set, thus making them DoNotAge LSAs.
PRI QSIG on the Cisco 7200
Platforms: Cisco 7200 series routers
QSIG protocol support allows Cisco voice switching services to connect PBXs, key systems, and
central office switches that communicate by using the QSIG protocol, which is becoming the standard
for PBX interoperability in Europe and North America. QSIG is a variant of ISDN D-channel signaling.
With QSIG, Cisco networks emulate the functionality of the public-switched telephone network
(PSTN), and QSIG signaling messages allow the dynamic establishment of voice connections across a
Cisco WAN to a peer router, which can then transport the signaling and voice packets to a second private
integrated services network exchange (PINX). In addition, QSIG support can enable a toll-bypass
application.
Virtual Profile CEF Switched
Platforms: Cisco 7100, Cisco 7200 series, and Cisco 7500 series routers
Using the Virtual Profile CEF Switched feature you can apply a per-user level configuration onto an Async
and ISDN B-channel interface. VP CEF previously supported process switching and low-end system fast
switching.
VP CEF switching provides improved performance by using Forwarding Information Base (FIB) to look up
a route for a forwarding packet. FIB look-ups are superior to the cache tables used in fast switching because
they are populated by routing topology rather than traffic and use the optimal switching decision.
VP CEF switching enables you to use VP in other new technologies that requires CEF switching, such as
MPLS/BGP VPN, and dCEF with ISDN interfaces.