# Network Layer ###### tags: `computer network` ## Service of Network Layer * Send Packet from one source subnet to another destination subnet What the network layer does is to ***route*** the packet (sometimes called datagram) from source to destination with the optimal path by the ***routing algorithm*** ## Packet ![](https://i.imgur.com/Ogy3PSd.png) ## IP Address ![](https://i.imgur.com/fYcH2Ka.png) ## Routing Algorithm What the routing algorithm focus on are ***forwarding*** and ***routing***. * forwarding: forward input packet to which output within a router * routing: the overall routing within the network architecture There are two types of routing, ***adaptive and non-adaptive***. For adpative routing (or dynamic routing), there are algorithm such as Distance Vector Routing and Link-State Routing ![](https://i.imgur.com/8wmTDcz.png) ## Distance Vector Routing (Bellmond-ford) For full algorithm description, please refer to slide. Here, I would like to discuss more on the issue of Distance Vector Routing. Count-to-Infiniity Issue. For explanation, one could refer to [here](https://www.youtube.com/watch?v=C2_6womzsrk&ab_channel=FardinSaad) Some solution would be add Time-to-Live to packet to avoid a packet is passing between two node for a large amount of time.