Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 37)

Multi-Service IronWare Routing Configuration Guide 9
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Implementation of BGP4
NOTIFICATION message
When you close the BGP4 session with a neighbor, the device detects an error in a message
received from the neighbor, or an error occurs on the device, the device sends a NOTIFICATION
message to the neighbor. No further communication takes place between the BGP4 device that
sent the NOTIFICATION and the neighbors that received the NOTIFICATION.
REFRESH message
BGP4 sends a REFRESH message to a neighbor to request that the neighbor resend route updates.
This type of message can be useful if an inbound route filtering policy has been changed.
Implementation of BGP4
BGP4 is described in RFC 1771 and the latest BGP4 drafts. The implementation fully complies with
RFC 1771 and supports the following:
• RFC 1745 (OSPF Interactions)
• RFC 1997 (BGP4 Communities Attributes)
• RFC 2385 (TCP MD5 Signature Option)
• RFC 2439 (Route Flap Dampening)
• RFC 4456 (Route Reflection)
• RFC 2842 and 3392 (Capability Advertisement)
• RFC 3065 (BGP4 Confederations)
• RFC 2858 (Multiprotocol Extensions)
• RFC 2918 (Route Refresh Capability)
• RFC 3392 (BGP4 Capability Advertisement)
• Draft-ietf-idr-restart-10.txt (restart mechanism for BGP4)
Memory considerations
BGP4 can handle a very large number of routes and therefore requires a lot of memory. For
example, in a typical configuration with a single BGP4 neighbor, receiving a full internet route table,
a BGP4 device may need to hold up to millions of route updates. Many configurations, especially
those involving more than one neighbor, can require the device to hold even more routes. The
device provides dynamic memory allocation for BGP4 data. BGP4 devices automatically allocate
memory when needed to support BGP4 neighbors, routes and route attribute entries. Dynamic
memory allocation is performed automatically by the software and does not require a reload.
As a guideline, a device with a 2 GB Management module can accommodate 150 – 200 neighbors,
with the assumption that the device receives about one million routes total from all neighbors and
sends about eight million routes total to neighbors. For each additional one million incoming
routes, the capacity for outgoing routes decreases by about two million.