network layer data plane Flashcards
network-layer protocol provides…
…logical-communication between hosts.
network-layer role and functuinalities
role:
transport segment from sending to receiving host
* sender: encapsulates segments into datagrams, passes to link layer
* receiver: delivers segments to transport layer protocol
functionalities:
- forwarding (move packets from a router’s input link to appropriate router output link, local action, implementer in hardware)
- routing ( determine route taken by packets from source to destination, network action, implemented in software)
which devices does Network-layer protocols affects
not only end systems but hosts and routers
network layer routers task
- Examine header fields in all IP datagrams passing through it
- Move datagrams from input ports to output ports to transfer datagrams along end-end path
Network layer division
- data plane (local, per-router function, determines how datagram arriving on
router input port is forwarded to router
output port) - control plane (network-wide logic, determines how datagram is routed among routers along end-end path from source host to destination host)
2 control-plane approaches
- traditional routing algorithms: implemented in routers (per-router control plane) (Each router has a routing component that communicates with the routing component of other routers)
- software-defined networking (SDN): implemented in (remote) servers (separate remote controller computes and distributes the forwarding tables to be used by each router)
network layer provides service
best-effort service.
rules for forwarding
- Destination-based forwarding
- Generalized-based forwarding
what is an IP address
It is a binary number that univocally identifies a network interface of a host or router.
Pay attention: it does not identify the host, one host can have multiple interfaces
strategies to decide When the buffer is full, which packet to drop?
- tail drop: drop arriving packet
- priority: drop/remove on priority basis
strategies to determine the order in which queued packets are transmitted over an outgoing link
- first come, first served (FIFO)
- priority-based
- round robin
- weighted fair queueing
- …
we have 1 IP address for each…
host or router interface (=connection between host/router and physical link),
router’s typically have multiple interfaces.
what is a subnet
device interfaces that can physically reach each other without passing through a router
IP address structure
- subnet part: devices in same subnet have
common high order bits - host part: remaining low order bits
How to get the IP address
1)The network administrator might first contact its ISP, which would provide addresses from a larger block of addresses that had already been allocated to the ISP.
2)Internet Corporation for Assigned Names and Numbers (ICANN): Global authority that has ultimate responsibility for managing the IP address space and allocating address blocks to ISPs and other organizations
- Once an organization has obtained a block of addresses, it can assign individual IP addresses to its host and router interfaces.
- Host addresses could be configured manually (very tedious). Better use Dynamic Host Configuration Protocol (DHCP).
- A network administrator can configure DHCP so that a given host receives the same IP address each time it connects to the network, or a host may be assigned a temporary IP address that will be different each time the host connects to the network.
- DHCP is a client-server protocol.
