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sign routing

The Border Gateway Protocol (BGP) is used to exchange routing information for the Internet and is primarily used by Internet Service Providers (ISPs). For detailed information about BGP and some tips for securing it, please see Cisco System's documentation or Team Cymru. A vulnerable situation arises due to the fact that BGP relies on long-lived persistent TCP sessions with larger window sizes to function. When a BGP session is disrupted, the BGP application restarts and attempts to re-establish a connection to its peers. This may result in a brief loss of service until the fresh routing tables are created.

In a TCP session, the endpoints can negotiate a TCP Window size. When this is taken into account, instead of attempting to send a spoofed packet with all potential sequence numbers, the attacker would only need to calculate a valid sequence number that falls within the next expected ISN plus or minus half the window size. Therefore, the larger the TCP Window size, the the larger the range of sequence numbers that will be accepted in the TCP stream. According to Paul Watson's report, with a typical xDSL data connection (80 Kbps, upstream) capable of sending of 250 packets per second (pps) to a session with a TCP Window size of 65,535 bytes, it would be possible to inject a TCP packet approximately every 5 minutes. It would take approximately 15 seconds with a T-1 (1.544 Mbps) connection. These numbers are significant when large numbers of compromised machines (often called "botnets" or "zombies") can be used to generate large amounts of packets that can be directed at a particular host.

Egress filtering

Egress filtering manages the flow of traffic as it leaves a network under your administrative control. There is typically limited need for machines providing public services to initiate outbound connections to the Internet.
In the case of BGP, only your BGP routers should be establishing connections to your peers. Other BGP traffic generated on your network could be a sign of an attempted attack.

Sign Routing

Please Contact Us to discuss your sign routing needs. You design it, we build it.

sign routing

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