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B.5. MANAnet Shield by CS3

MANAnet Shield is a family of products that aim to offer protection from both incoming and outgoing DDoS attacks:

  • MANAnet FloodWatcher is a passive device that detects anomalies in network traffic that could be a sign of an incoming DDoS attack and alerts administrators.

  • MANAnet Linux Router implements path-enhanced IP (PEIP—CS3 technology to defeat IP spoofing). It also attempts to enforce fair sharing of network resources based on PEIP information using CS3 technology called Place-Based Fair Queueing (PLFQ). The router can deploy rate-limiting rules as a response to incoming DDoS attacks, at the request of its neighbors, or on its own accord.

  • MANAnet Firewall offers firewall functionality with PEIP and PLFQ and issues rate-limiting requests when a DDoS attack is detected.

  • MANAnet Reverse Firewall is an inline device that aims to detect and throttle outgoing DDoS attacks.

MANAnet FloodWatcher monitors incoming and outgoing network traffic, collecting statistics on multiple traffic parameters. The collected data is compared to operator-set thresholds to detect anomalies. Offending traffic is then profiled and network operators are alerted about the attack and provided with a devised attack signature.

MANAnet Linux Router is a router implementing two proprietary technologies: PEIP, with a goal to defeat IP spoofing; and PLFQ, with a goal to provide fair resource sharing among legitimate users. PEIP modifies each packet with additional information to discern the path that the packet takes through a MANAnet-protected network. The first router on the path will append its IP address to the packet. Subsequent routers will enumerate their incoming interfaces, and append the number of the interface on which a packet was received to the path information. Packets that are replies to service requests preserve the path information from the request. Reply-specific path information is appended to the preserved request path. This should provide useful information in case of reflector DDoS attacks, where the path of reply traffic would be the same in all packets, but the request paths would differ. For instance, assume that three attackers—A, B, and C—send DNS requests to server S, faking a victim's address V. All replies will carry an identical path from S to V, but they will also carry different paths for request packets indicating A, B, and C. PEIP information aims to help V drop offending replies (to requests from A, B, and C), while still being able to send DNS requests to S and receive replies. The IP address in the beginning of the path information is called a visible source. A MANAnet Linux Router subjects incoming traffic to the proprietary queueing algorithm PLFQ with a goal to assign a fair share of resources to each visible source. A visible source that is particularly misbehaving (sending large amounts of traffic) may be additionally restrained by the router deploying a rate limit on traffic from this source. Contiguous MANAnet routers organize themselves into cooperative neighborhoods and work together to build PEIP information and attempt to trace incoming attacks back to an ingress point into the neighborhood. Figure B.8 depicts two cooperative neighborhoods.

Figure B.8. MANAnet neighborhoods cooperate to defend against DDoS attacks. (Reprinted from MANAnet white paper with permission of CS3, Inc.)


MANAnet Firewall implements the standard firewall functionality and adds three new features:

  1. The ability to decode PEIP information and perform PLFQ packet scheduling.

  2. The ability to perform Historical Place-Based Fair Queueing (HPLFQ). The vendor does not offer much information on this option, except that the goal of HPLFQ is to ensure fair service to new requests with respect to the recent service history of their paths.

  3. The ability to detect and rate-limit packets that are deemed "unexpected" by the firewall. The MANAnet Firewall keeps track of each established TCP connection, defining a range of expected sequence numbers to be seen in the incoming packets. This range is inferred by observing the acknowledgment and TCP window information from the connection's outgoing packets. Incoming TCP packets with sequence numbers matching the defined range are called expected and sent to their destination. TCP packets that do not match the sequence number range, TCP SYN, UDP, and ICMP packets are called unexpected. These packets will be rate limited in case of an attack by being placed in different processing queues at the MANAnet Firewall and assigning a limited share of resources to each queue. Packets within the queue will be processed applying PLFQ. The product white papers specify that this creates a possibility for legitimate users to have their unexpected packets served even during a DDoS attack.

MANAnet Reverse Firewall applies MANAnet Firewall functionality to the outgoing traffic. It aims to detect outgoing DDoS attacks and responds by placing a rate limit on the amount of unexpected packets that are allowed to leave the network. In this case, packets that cannot be readily identified as replies to incoming TCP packets are called unexpected. The Reverse Firewall also deploys PEIP and PLFQ with a goal to offer fair service to legitimate users within the deploying network. The PEIP information in dropped packets should help network operators locate compromised machines within their network.

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