<sect>OSPF
+<sect1>Introduction
+
+<p>Open Shortest Path First (OSPF) is quite complex interior gateway
+protocol. Today's version for IPv4 is 2 and it's defined in RFC 2328<htmlurl
+url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt">. It's based on
+link-state of SPF technology. Each router maintains a database
+describing the Autonomous System's topology. Each participating router has
+has an identical database and all routers run the exact same algorithm
+calculatin shortest path tree with themselves as roots, in parallel.
+OSPF chooses the least cost path as the best path. In OSPF, the
+Autonomous System can be splitted into more areas. Topology
+of such area is hidden to the rest of the Autonomous System. This enables
+a reduction in routing traffic as well as protection other areas from bad
+routing data. Unfortunatelly multiple OSPF areas are not fully supported
+in this version of BIRD. Another very important feature of OSPF is that
+it can keep routing information from other protocols (like static or BGP)
+in it's link-state database as external routes. Each external route can
+be tagged by the advertising router, enabling the passing of additional
+information between routers on the boundary of the Autonomous System.
+
+<p>OSPF quickly detects topological changes in the Autonomous System (such
+as router interface failures) and calculates new loop-free routes after a
+period of convergence. This period of convergence is short and involves
+a minimum of routing traffic.
+
+<p>Each router joined in OSPF periodically sends hello messages out
+all its interfaces. This allows neighbors to be discovered dynamically.
+Then the neighbors exchange theirs parts of database. And keep it
+identical flooding updates. Flooding proces is reliable and ensures
+that each routes detects the change.
+
+<sect1>Configuration
+
+<p>
+
+<code>
+protocol ospf <name> {
+ rfc1583compat bool;
+ area <id> {
+ stub <bool>;
+ tick <num>;
+ interface <interface>
+ {
+ cost <num>;
+ hello <num>;
+ retransmit <num>;
+ priority <num>;
+ wait <num>;
+ dead count <num>;
+ type [broadcast|nonbroadcast|pointopoint];
+ authetication [none|simple];
+ password "<text>";
+ neighbors {
+ <ip>;
+ };
+ };
+ };
+}
+</code>
+
+<descrip>
+ <tag>rfc1583compat <M>bool</M></tag>
+ This option can disable or enable compatibility of routing table
+ calculation with RFC 1583<htmlurl
+ url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
+ value is no.
+
+ <tag>area <M>id</M></tag>
+ This specifies area id of configured OSPF area. It can be written
+ as a number or as an IPv4 number. The most important area is
+ the backbone (area id 0) to which every other area must be connected.
+
+ <tag>stub <M>bool</M></tag>
+ No external routes are flooded into stub area. Default value is no.
+
+ <tag>tick <M>num</M></tag>
+ The routing table calculation is not processed when any single
+ change comes. To lower the CPU utilization it's processed late
+ in periodical interval. The default value is 7.
+
+ <tag>interface <M>interface</M></tag>
+ This mean that specified interface (or interface pattern) belongs
+ to actual area.
+
+ <tag>cost <M>num</M></tag>
+ Specifies output cost of interface. Default value is 10.
+
+ <tag>hello <M>num</M></tag>
+ Specifies interval between sending hello messages. Beware, all
+ router on the same network has to have the same hello interval.
+ Default value is 10.
+
+ <tag>retransmit <M>num</M></tag>
+ Specifies interval between retransmiting unacknoledged update.
+ Default value is 5.
+
+ <tag>priority <M>num</M></tag>
+ On every multiple access network (like e.g ethernet) Designed
+ and Backup Designed router is elected. These routers have some
+ special functions in flooding process. Higher priority rices
+ preferences in elections. Routers with priority 0 are not
+ eligible. Default value is 1.
+
+ <tag>wait <M>num</M></tag>
+ After start, router waits specified interval between starting
+ election and building adjacency. Default value is 40.
+
+ <tag>dead count <M>num</M></tag>
+ When router does not receive any message from neighbor in
+ <dead count>*<hello> seconds, it will declare neighbor down.
+
+ <tag>type <M>broadcast</M><tag>
+ BIRD detects a type of connected network. However, sometimes is
+ necessary to change it. On broadcast networks are flooding
+ and hello messages sent using multicasting. (Single
+ packet to all neighbors.)
+
+ <tag>type <M>nonbroadcast</M></tag>
+ On nonbroadcast network are packets sent to each neighbor
+ separately because of lack of multicast messages.
+
+ <tag>type <M>pointopoint</M></tag>
+ Pointopoint network connects just 2 routers together. No election
+ is provided there, this reduces a number of sent messages.
+
+ <tag>authetication <M>none</M></tag>
+ No passwords are sent in OSPF's packets. This is default value.
+
+ <tag>authetication <M>simple</M></tag>
+ In every packet is sent an 8 bytes long password. Received packets
+ without this password are ignored. This autentication mechanism is
+ very weak.
+
+ <tag>password <M>text</M></tag>
+ An 8 bytes long password used for authentication.
+
+ <tag>neighbors</tag>
+ A set of neighbors to which hello messages on nonbroadcast networks
+ are sent.
+</descrip>
+
+<sect1>Attributes
+
+<p>OSPF defines 3 route attributes. Each internal route has a metric. External
+routes uses metric type 1 or metric type 2. Metric type one is comparable
+with internal metric. Metric type 2 is always longer then metric type 1
+or internal metric. Each external route can also carry a tag. Tag is
+32 bits long number and it's used for exporting routes to other protocols
+in link-state it has no funtion.
+
+<sect1>Example
+
+<p>
+
+<code>
+protocol ospf MyOSPF {
+ area 0.0.0.0 {
+ tick 8;
+ interface "eth*" {
+ cost 11;
+ hello 15;
+ priority 100;
+ retransmit 7;
+ authentication simple;
+ password "aaa";
+ };
+ interface "ppp*" {
+ cost 100;
+ };
+ };
+ area 120 {
+ stub yes;
+ interface "-arc0" , "arc*" {
+ type nonbroadcast;
+ authentication none;
+ wait 50;
+ dead count 6;
+ neighbors {
+ 192.168.120.1;
+ 192.168.120.2;
+ 192.168.120.10;
+ };
+ };
+ };
+}
+</code>
+
<sect>Pipe
<sect1>Introduction
projects / thirdparty / bird.git / commitdiff
