Protecting Against Tcp Out Of Order Dos Attacks; Limiting Buffers Per Router - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

NOTE: Disabling PAWS does not disable other processing related to the TCP
timestamp option. This means that even though you disable PAWS, a fabricated
timestamp that already exists in the network can still pollute the database and result
in a successful DoS attack. Enabling PAWS resets the saved timestamp state for all
connections in the virtual router and stops any existing attack.
tcp paws-disable

Protecting Against TCP Out of Order DoS Attacks

You can use the group of tcp resequence-buffers commands to help protect the
router from TCP out-of-order DoS attacks.
TCP guarantees that applications receive data in order. This means that TCP buffers
any out-of-order packets it receives until ordered delivery can occur. To prevent
buffers from consuming too many resources, TCP limits the amount of data it accepts
to the number of data bytes that the receiver is willing to receive and buffer.
TCP does not take into account the buffering scheme that the receiver uses. If the
receiver uses a fixed-size receive buffer (that is, buffering all packets) regardless of
length, a packet that contains only one data byte might consume many data bytes
of buffer space, but only one byte of TCP space.
Under these conditions, an attacker can send a large number of 1-byte packets to
an E Series router in which each packet is buffered, consuming an entire packet
buffer and eventually consuming a large amount of resources.
To defend against this sort of attack, you can set defaults and limits on the number
of outstanding buffers on reordering queues. You can configure these defaults and
limits on a per-router, per-virtual router, or per-connection basis.

Limiting Buffers per Router

The tcp resequence-buffers global-maximum command enables you to limit the
number of outstanding buffers on the entire router.
tcp resequence-buffers global-maximum
Use to disable the Protect Against Wrapped Sequence (PAWS) number option
in TCP segments.
You can specify a VRF context for which you want PAWS disabled.
Example
host1(config)#tcp paws-disable
Use the no version to restore PAWS processing (the default mode).
See tcp paws-disable
Chapter 1: Configuring IP
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IP Routing