PDN Gateway Overview
▀ Features and Functionality - Inline Service Support
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
74
framework-10. Stateful NAT64 is available as part of the existing NAT licenses from the current system
implementation. The NAT44 and NAT64 will co-exist on the chassis and share the resources needed for NATing.
Peer-to-Peer Detection
Allows operators to identify P2P traffic in the network and applying appropriate controlling functions to ensure fair
distribution of bandwidth to all subscribers.
Peer-to-Peer (P2P) is a term used in two slightly different contexts. At a functional level, it means protocols that interact
in a peering manner, in contrast to client-server manner. There is no clear differentiation between the function of one
node or another. Any node can function as a client, a server, or both—a protocol may not clearly differentiate between
the two. For example, peering exchanges may simultaneously include client and server functionality, sending and
receiving information.
Detecting peer-to-peer protocols requires recognizing, in real time, some uniquely identifying characteristic of the
protocols. Typical packet classification only requires information uniquely typed in the packet header of packets of the
stream(s) running the particular protocol to be identified. In fact, many peer-to-peer protocols can be detected by simple
packet header inspection. However, some P2P protocols are different, preventing detection in the traditional manner.
This is designed into some P2P protocols to purposely avoid detection. The creators of these protocols purposely do not
publish specifications. A small class of P2P protocols is stealthier and more challenging to detect. For some protocols
no set of fixed markers can be identified with confidence as unique to the protocol.
Operators care about P2P traffic because of the behavior of some P2P applications (for example, Bittorrent, Skype, and
eDonkey). Most P2P applications can hog the network bandwidth such that 20% P2P users can generate as much as
traffic generated by the rest 80% non-P2P users. This can result into a situation where non-P2P users may not get
enough network bandwidth for their legitimate use because of excess usage of bandwidth by the P2P users. Network
operators need to have dynamic network bandwidth / traffic management functions in place to ensure fair distributions
of the network bandwidth among all the users. And this would include identifying P2P traffic in the network and
applying appropriate controlling functions to the same (for example, content-based premium billing, QoS modifications,
and other similar treatments).
Cisco’s P2P detection technology makes use of innovative and highly accurate protocol behavioral detection techniques.
Important:
For more information on peer-to-peer detection, refer to the
Application Detection and Control
Administration Guide
.
Personal Stateful Firewall
The Personal Stateful Firewall is an in-line service feature that inspects subscriber traffic and performs IP session-based
access control of individual subscriber sessions to protect the subscribers from malicious security attacks.
The Personal Stateful Firewall supports stateless and stateful inspection and filtering based on the configuration.
In stateless inspection, the firewall inspects a packet to determine the 5-tuple—source and destination IP addresses and
ports, and protocol—information contained in the packet. This static information is then compared against configurable
rules to determine whether to allow or drop the packet. In stateless inspection the firewall examines each packet
individually, it is unaware of the packets that have passed through before it, and has no way of knowing if any given
packet is part of an existing connection, is trying to establish a new connection, or is a rogue packet.
In stateful inspection, the firewall not only inspects packets up through the application layer / layer 7 determining a
packet's header information and data content, but also monitors and keeps track of the connection's state. For all active
connections traversing the firewall, the state information, which may include IP addresses and ports involved, the
sequence numbers and acknowledgement numbers of the packets traversing the connection, TCP packet flags, etc. is
