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127 ../../principles/dv.rst:15
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `R[d].time` is the timestamp of the last distance vector containing destination `d` 83/10000 · 83
128 ../../principles/dv.rst:17
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — A router that uses distance vector routing regularly sends its distance vector over all its interfaces. This distance vector is a summary of the router's routing table that indicates the distance towards each known destination. This distance vector can be computed from the routing table by using the pseudo-code below. 319/10000 · 319
129 ../../principles/dv.rst:31
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — When a router boots, it does not know any destination in the network and its routing table only contains its local address(es). It thus sends to all its neighbors a distance vector that contains only its address at a distance of `0`. When a router receives a distance vector on link `l`, it processes it as follows. 315/10000 · 315
130 ../../principles/dv.rst:54
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The router iterates over all addresses included in the distance vector. If the distance vector contains a destination address that the router does not know, it inserts it inside its routing table via link `l` and at a distance which is the sum between the distance indicated in the distance vector and the cost associated to link `l`. If the destination was already known by the router, it only updates the corresponding entry in its routing table if either : 459/10000 · 459
131 ../../principles/dv.rst:56
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the cost of the new route is smaller than the cost of the already known route `((V[d].cost + l.cost) < R[d].cost)` 114/10000 · 114
132 ../../principles/dv.rst:57
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the new route was learned over the same link as the current best route towards this destination `(R[d].link == l)` 114/10000 · 114
133 ../../principles/dv.rst:59
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The first condition ensures that the router discovers the shortest path towards each destination. The second condition is used to take into account the changes of routes that may occur after a link failure or a change of the metric associated to a link. 253/10000 · 253
134 ../../principles/dv.rst:61
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — To understand the operation of a distance vector protocol, let us consider the network of five routers shown below. 115/10000 · 115
135 ../../principles/dv.rst:117
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Assume that router `A` is the first to send its distance vector `[A=0]`. 72/10000 · 72
136 ../../principles/dv.rst:119
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `B` and `D` process the received distance vector and update their routing table with a route towards `A`. 105/10000 · 105
137 ../../principles/dv.rst:120
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `D` sends its distance vector `[D=0,A=1]` to `A` and `E`. `E` can now reach `A` and `D`. 88/10000 · 88
138 ../../principles/dv.rst:121
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `C` sends its distance vector `[C=0]` to `B` and `E` 52/10000 · 52
139 ../../principles/dv.rst:122
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `E` sends its distance vector `[E=0,D=1,A=2,C=1]` to `D`, `B` and `C`. `B` can now reach `A`, `C`, `D` and `E` 110/10000 · 110
140 ../../principles/dv.rst:123
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `B` sends its distance vector `[B=0,A=1,C=1,D=2,E=1]` to `A`, `C` and `E`. `A`, `B`, `C` and `E` can now reach all five routers of this network. 144/10000 · 144
141 ../../principles/dv.rst:124
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `A` sends its distance vector `[A=0,B=1,C=2,D=1,E=2]` to `B` and `D`. 69/10000 · 69
142 ../../principles/dv.rst:126
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — At this point, all routers can reach all other routers in the network thanks to the routing tables shown in the figure below. 125/10000 · 125
143 ../../principles/dv.rst:203
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — To deal with link and router failures, routers use the timestamp stored in their routing table. As all routers send their distance vector every `N` seconds, the timestamp of each route should be regularly refreshed. Thus no route should have a timestamp older than `N` seconds, unless the route is not reachable anymore. In practice, to cope with the possible loss of a distance vector due to transmission errors, routers check the timestamp of the routes stored in their routing table every `N` seconds and remove the routes that are older than :math:`3 \times N` seconds. 573/10000 · 573
144 ../../principles/dv.rst:205
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — When a router notices that a route towards a destination has expired, it must first associate an :math:`\infty` cost to this route and send its distance vector to its neighbors to inform them. The route can then be removed from the routing table after some time (e.g. :math:`3 \times N` seconds), to ensure that the neighboring routers have received the bad news, even if some distance vectors do not reach them due to transmission errors. 439/10000 · 439
145 ../../principles/dv.rst:207
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — Consider the example above and assume that the link between routers `A` and `B` fails. Before the failure, `A` used `B` to reach destinations `B`, `C` and `E` while `B` only used the `A-B` link to reach `A`. The two routers detect the failure by the timeouts in the affected entries in their routing tables. Both routers `A` and `B` send their distance vector. 360/10000 · 360
146 ../../principles/dv.rst:209
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `A` sends its distance vector :math:`[A=0,B=\infty,C=\infty,D=1,E=\infty]`. `D` knows that it cannot reach `B` anymore via `A` 126/10000 · 126