DE10232945A1 - Forwarding Internet protocol packets in connectionless communications network involves selecting specially applied routing table in relevant transit router for identifier in Internet Protocol packet header - Google Patents

Abstract

In a connectionless communication network, the DSCP (Differentiated Service Code Point) bits in the header of the IP (Internet Protocol) packets are also used to select a special routing table in the transit router that is passed, in which the appropriate line for forwarding the IP packet is searched. The different routing tables correspond to quasi different traffic route structures within the network. Traffic balancing, QoS / policy routing, all of this can be achieved hereby without the need to create connection state memories in the individual network nodes.

Description

The subject of registration concerns a method for forwarding IP packets in a connectionless Communication network.

With internet data transmission the IP packets are generally after the shortest path forwarding (SPF) routing principle on the "shortest Route ".

Every router maintains this for these days exactly one routing table.

A transmission via different ways may become necessary due to QoS requirements (Quality of service), policy requirements (market behavior of the network operator) or Bandwidth requirements / availability.

But then a kind of connection had to be established up to now be, for the duration of the transfer a connection memory ("state") in the to be passed Routers / switches must be created (see RSVP Resource Reservation Protocol, see MPLS Multiprotocol Label Switching) of connection establishment messages (PATH / RESERVE or LABEL_REQUEST / LABEL_MAPuPING). These states are judged to be non-scalable.

An alternative approach, who avoids these states is through Differentiated Services (DiffServ) given, whereby IP packets are marked differently, so that they have different priorities in the passed routers Enjoy treatment can. See RFCs 3086, 3140, 3246, 3260. See also McGraw-Hill Encyclopedia of Networking and Telecommunications, 2001, pages 350 ff.

The present invention pursues the goal that the IP packets with different markings not only treated differently prioritized, but beyond can also be routed differently, and continue to do so no connection memory (= states) need to be created.

The goal is determined by the characteristics of claim 1 achieved.

According to the invention, each IP packet therefore receives one Marking or identification, subsequently with DiffRout Codepoint (DRCP) designated. According to the invention, the individual maintains Router not just one routing table but several, the routing table to be used based on the DRCP value in the header of the incoming IP packet is selected.

The DRCP could e.g. in the six DSCP bits be housed so that this on the one hand as a DiffServ Codepoint, but also as a DiffRout Codepoint would have to be interpreted. More generally: The DRCP could are passed along with the IP packets, the Protocol-Type, the six DSCP bits, the two CU bits, in the case of IPv6 the flow label, or parts of it must be used.

An overlay of the DSCP bits with another meaning ("differentiated routing "plus" differentiated service ") complicated things a little bit, is quite feasible because a) no 2 ** 6 = 64 differentiated services needed (a customer only pays for such differentiated services, their quality differences he actually perceive and feel can), and because b) the new additional meaning the wanted and so far achieved DiffServ effects downright reinforced.

The invention offers the possibility different traffic route structures on a given network to be defined, for example in analogy to the road system, where certain traffic participants, for example the pedestrians, preferred Sidewalks, but also country roads, but definitely not highways may use or where cars are country roads, Motorways, and only toll roads if you pay, but none on the other Allowed to drive on sidewalks, etc.

In this sense, traffic flows can be different mark, for example because they are of different traffic types (voice, video, data), or for different amounts of money-paying recipients are determined, and then one to route different traffic route structures accordingly.

The invention also offers the possibility of Balancing total traffic by overloading parts of the traffic are diverted to alternate traffic structures, or else to Traffic jams if possible Avoid from the start, parts of a traffic flow well proportioned across different Routes are routed.

By putting some traffic into one certain traffic route structure is forced, can at the same time other traffic route structures are to be kept free of this traffic.

Despite a multitude, there is always of established traffic route structures, ensured that all IP packets a certain “IP micro flows "the same Take route by simply having the same DRCP in the IP header to lead.

Several traffic route structures according to the invention are described below spelled out in detail. Before that, however, it should be pointed out that today's IP routing, namely according to the shortest path forwarding principle (SPF), a certain traffic route structure can be assigned and that the in this regard (and currently only) routing table by the same token special DRCP's is to be selected.

a) SPF

In the conventional SPF principle, each router calculates a Shortest Path Tree (SPT) with itself as the root to all other nodes in the network. In accordance with this SPT, the respective router creates a relevant routing table to which he stores, with regard to all accessibility (individual destination addresses, destination address blocks), which of the lines connected to him should be used for forwarding a corresponding IP packet. This conventional routing table is selected by the special DRCP = "SPF".

b) SPF-x

As a variant to a), any router can calculate an SPT such that total only lines are used which have a certain (designated x) Set of QoS / Policy / etc. additional requirements suffice. A policy requirement could be “anything just no toll roads "or" everything just not toll roads or highways ", Or “none Management which already belongs to this or that traffic route structure ".

For various such sentences x may the respective router creates its own routing table and it select on the basis of special DRCPs = "SPF-x".

C) SST

While in the above cases a) and b) usually all Power lines for the transfer This is not the case in cases c) and d).

Each router calculates a smallest-size tree (SST), i.e. a (tree-like, meshless) topology graph the smallest size, which one between all edge point routers of a network. All of them are considered as edge point routers Router of a network understood, in which either participants (LANs, Hosts) and / or line interfaces to neighboring networks.

There are several SST topologies of the same minimum, so-called "tie-breaker" rules ensure that everyone Network node (supported based on identical network topology knowledge and based on the same set of parameters and parameter values) the identical SST topology is calculated (typical tie-breaker rule: If any intermediate minimum is determined in an iteration step but there are several equivalent options for this, so choose the one where the "involved" router is the smaller one Has an IP address). Each router thus comes to the same SST topology result. The respective router checks whether and where it appears in this SST topology and what it does adjacent lines are.

It creates an SST-related routing Table, i.e. it creates all target edge point routers and the "next hop." Zinc "entries he worry that this Routing table due to the well-determined DRCP = "SST" is selected. you note that each Edge of the SST topology graph is used bidirectionally.

d) SST-x

As under c) determine each router the same SST topology graphs, however, in such a way that Edges always have a set of QoS / bandwidth / policy / etc. additional requirements marked with an x suffice. Based on this, he creates a special routing table, which selected by the special DRCP = "SST-x".

This could also be the policy requirement here as stated under b).

Regarding the additional bandwidth requirement, it should be noted: If a certain bandwidth is required for the edges of the SST-x _i topology graph, the calculation algorithm must avoid those network edges that already exist in previously determined SST-x _k topology graphs and thereby in Sum have experienced a lot of bandwidth allocation.

e) "Overflow SST-x"

Regarding an SST-x traffic route structure, see d), one can identify certain substructures (approximately all Edges that have at least m start / finish edge node combinations the transfer are useful). Assign a "Disregard" bit to each of these edges and recalculate the SST-x tree.

The result is another smallest-size tree Topology graph, in which all edges again meet the specified boundary conditions x suffice but where none of the edges marked with Disregard occurs.

A node in this "overflow SST-x" traffic route structure occurs, there is a related one Routing table and makes it selectable by the DRCP = "overflow SST-x".

The network nodes of the SST-x topology graph on the edge of the sub-structures with disregard become dependent of locally available and current network load indicators, if applicable the packets arriving with DiffRout code point "SST-x" with the changed Forward diffrout code point "overflow-SST-x" and according to the attached Lines of the overflow tree "Overflow SST-x" instead of according to the adjacent one Lines of the "SST-x" topology graph.

f) "SPF-x, y best route"

Each network node determines the second best / third best / fourth best route to all network nodes, which is determined by this be that the excludes previously calculated, better routes (set DISREGARD bits!), with itself as a root node and taking into account all boundary conditions x.

The respective network node has its own routing table and makes this selection bar by DRCP = "SPF-x, y-best route".

You can, therefore, around the whole Balancing traffic, deliberately taking alternative routes, at the same time but for that make sure everyone Packets of a certain IP micro flow follow the identical route take the net (this is important to avoid packet overhauls, about the ability of the TCP namely for the to ensure correct alignment, not to overuse). More importantly is this ability for "TDM over IP" applications, such as z. B. Language over Internet VoIP (Voice over Internet Protocol).

Claims (8)

Procedure for forwarding IP packets in a connectionless Communication network formed with a plurality of network nodes is, in which an identifier contained in the header of an IP packet at the respective Transit router one in this regard specially created routing table selected in order to find the suitable one Line for determine the forwarding of the IP packet. A method according to claim 1, characterized in that the identifier is formed with the DSCP bits in the header of an IP packet. A method according to claim 1, characterized in that the identifier can be derived from any components in the IP header, for example from the components protocol type, DSCP bits, CU bits, and Flow label (if IPv6). Method according to one of the preceding claims, characterized in that the selected routing table using a Smallest-Size-Tree (SST) topology graph was created, which is bi-directional between the edge point routers, that is the routers with locally connected LANs, hosts or external Lines, stretches, and its topological shape from all of them routers occurring in it are recognized absolutely identically. A method according to claim 4, characterized in that the Determination of the SST topology graph further boundary conditions in the form QoS / bandwidth / policy requirements are taken into account. A method according to claim 1, characterized in that the selected Routing table from the respective router based on the results of a Shortest path tree calculation using itself as tree root node and considering additional boundary conditions in the form of QoS / policy requirements becomes. A method according to claim 5, characterized in that the selected A routing table of a traffic route structure is sufficient, some or all of it across from another, previously determined traffic route structure, an overflow traffic route structure and where certain nodes are based on locally available, current traffic load information, change the received identifier, namely appropriately on the relevant overflow traffic route structure, and forward the IP packets accordingly. A method according to claim 5 or 6, characterized in that the selected routing table compared to another, previously determined routing table the second best or third best, etc. routes considered, to support the balancing of total traffic in such a way that traffic congestion preferably not even arise.