computer networking A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ma ...

, source routing, also called path addressing, allows a sender of a

packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a form ...

to partially or completely specify the

route Route or routes may refer to: * Route (gridiron football), a path run by a wide receiver * route (command), a program used to configure the routing table * Route, County Antrim, an area in Northern Ireland * ''The Route'', a 2013 Ugandan film * Ro ...

the packet takes through the network. In contrast, in conventional

routing Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...

, routers in the network determine the path incrementally based on the packet's destination. Another routing alternative,

label switching Label switching is a technique of network relaying to overcome the problems perceived by traditional IP-table switching (also known as traditional layer 3 hop-by-hop routing). Here, the switching of network packets occurs at a lower level, namely ...

, is used in connection-oriented networks such as

X.25 X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts a ...

Frame Relay Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Se ...

Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by American National Standards Institute (ANSI) and ITU-T (formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of ...

and

Multiprotocol Label Switching Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints the labels identif ...

. Source routing allows easier troubleshooting, improved

traceroute In computing, traceroute and tracert are computer network diagnostic commands for displaying possible routes (paths) and measuring transit delays of packets across an Internet Protocol (IP) network. The history of the route is recorded as th ...

, and enables a node to discover all the possible routes to a host. It does not allow a source to directly manage network performance by forcing packets to travel over one path to prevent congestion on another. Many high-performance interconnects including

Myrinet Myrinet, ANSI/VITA 26-1998, is a high-speed local area networking system designed by the company Myricom to be used as an interconnect between multiple machines to form computer clusters. Description Myrinet was promoted as having lower protocol ...

Quadrics In mathematics, a quadric or quadric surface (quadric hypersurface in higher dimensions), is a generalization of conic sections (ellipses, parabolas, and hyperbolas). It is a hypersurface (of dimension ''D'') in a -dimensional space, and it is de ...

IEEE 1355 IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC). IEC 14575 is a low-cost, low latency, scalable serial interconnection system, originally intended for communication between la ...

, and

SpaceWire SpaceWire is a spacecraft communication network based in part on the IEEE 1355 standard of communications. It is coordinated by the European Space Agency (ESA) in collaboration with international space agencies including NASA, JAXA, and RKA. ...

support source routing.

Internet Protocol

In the

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP h ...

, two header options are available which are rarely used: " strict source and record route" (SSRR) and " loose source and record route" (LSRR). Because of security concerns, packets marked LSRR are frequently blocked on the Internet. If not blocked, LSRR can allow an attacker to spoof an address but still successfully receive response packets by forcing return traffic for spoofed packets to return through the attacker's device. In

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

, two forms of source routing have been developed. The first approach was the Type 0 Routing header. This routing header was designed to support the same use cases as the IPv4 header options. Unfortunately there were several significant attacks against this routing header and its utilisation was deprecated. A more secure form of source routing is being developed within the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

to support the IPv6 version of

Segment Routing Segment routing, a form of computer networking, is a modern variant of source routing that is being developed within thSPRINGand IPv6 working groups of the IETF. In a segment routed network, an ingress node may prepend a header to packets that c ...

Software-defined networking

Software-defined networking Software-defined networking (SDN) technology is an approach to network management that enables dynamic, programmatically efficient network configuration in order to improve network performance and monitoring, making it more like cloud computing t ...

can also be enhanced when source routing is used in the forwarding plane. Studies have shown significant improvements in convergence times as a result of the reduced state that must be distributed by the controller into the network.

Myrinet

When using source routing with

, the sender of the packet prepends the complete route, one byte for every crossbar, to each packet header. Each crossbar examines the first routing byte of the packet. When using source routing, that byte indicates a particular port of that crossbar; when that port becomes available, the router discards that routing byte and sends the rest of the packet out that port.

SpaceWire

Each packet traveling through a SpaceWire network can use path addressing (source routing) or logical addressing or some combination. The router examines the first data character of the packet; when it indicates some specific port of the router, the router discards that routing character and sends the rest of the packet out that port. S.M. Parkes and C. McClements
"SpaceWire Networks"
2002. page 61.4.

References

External links

* {{cite web, url=http://www.iss.net/security_center/advice/Underground/Hacking/Methods/Technical/Source_Routing/default.htm , title=Source Routing , publisher=

IBM Internet Security Systems IBM Internet Security Systems, formerly Internet Security Systems, and often known simply as ISS or ISSX (after its former NASDAQ ticker symbol) is a security software and managed security services provider founded in 1994. The company was acquire ...