Network Layer Review Flashcards

Flashcards covering key concepts from network layer lectures, including routing protocols, IP addressing, and link layer protocols.

Sender (Network Layer)

Encapsulates segments into datagrams and passes them to the link layer.

Receiver (Network Layer)

Delivers segments to the transport layer protocol.

Data Plane

Local, per-router function that determines how a datagram arriving on a router input port is forwarded to a router output port.

Control Plane

Network-wide logic that determines how a datagram is routed among routers along the end-to-end path from a source host to a destination host.

Longest Prefix Matching

Using the longest address prefix that matches the destination address when looking for a forwarding table entry.

Tail Drop

Drops the arriving packet when buffers are full.

Priority (Buffer Management)

Drops or removes packets based on priority when buffers are full.

First Come, First Served (FCFS)

Packets are transmitted in the order of their arrival to the output port.

Priority Scheduling

Arriving traffic is classified and queued by class, with packets sent from the highest priority queue that has buffered packets.

Round Robin (RR) Scheduling

Arriving traffic is classified and queued by class, with the server cyclically scanning class queues and sending one complete packet from each class in turn.

CIDR

Classless Inter-Domain Routing; subnet portion of address of arbitrary length.

Subnet

Device interfaces that can physically reach each other without passing through an intervening router.

DHCP (Dynamic Host Configuration Protocol)

Protocol that allows a host to dynamically obtain an IP address from a network server when it joins the network.

DHCP additional capabilities

Returns more than just an allocated IP address, such as the address of the first-hop router, DNS server, and network mask.

NAT (Network Address Translation)

Allows all devices in a local network to share just one IPv4 address as far as the outside world is concerned.

Tunneling

IPv6 datagram carried as payload in IPv4 datagram among IPv4 routers.

Generalized forwarding

Match bits in arriving packet, take action.

Flow

Defined by header fields and simple packet handling rules.

Routing protocol goal

Determine good paths (routes) from sending hosts to receiving host through network of routers.

Dijkstra’s Link-State Routing Algorithm

Network topology and link costs known to all nodes; computes least cost paths from one node to all other nodes.

Dx(y)

Cost of least-cost path from x to y.

Distance Vector Algorithm iterations

Each local iteration caused by local link cost change or DV update message from neighbor.

Autonomous Systems (AS)

Aggregate routers into regions.

Intra-AS Routing

Routing among routers within the same AS.

Inter-AS Routing

Routing among ASes.

OSPF (Open Shortest Path First) routing

Floods OSPF link-state advertisements to all other routers in AS.

Hierarchical OSPF

Two-level hierarchy: local area, backbone.

BGP (Border Gateway Protocol)

Allows subnet to advertise its existence, and the destinations it can reach, to the rest of Internet.

eBGP, iBGP connections

Logical connectivity for gateway routers to run both eBGP and iBGP protocols.

Policy-based routing

Gateway receiving route advertisement uses import policy to accept/decline path.

Hot Potato Routing

Choose local gateway that has least intra-domain cost.

Logically centralized control plane advantages

Easier network management, greater flexibility of traffic flows.

Links

Communication channels that connect adjacent nodes along communication path.

Single bit parity

Detects single bit errors.

Channel Partitioning

Divides the channel into smaller pieces (time slots, frequency, code) and allocates a piece to a node for exclusive use.

TDMA: time division multiple access

Access to channel in rounds, each station gets fixed length slot (length = packet transmission time) in each round

FDMA: frequency division multiple access

Channel spectrum divided into frequency bands, each station assigned fixed frequency band

Polling

Centralized controller invites other nodes to transmit in turn

Token passing

Control token message explicitly passed from one node to next, sequentially

MAC (or LAN or physical or Ethernet) address

Function: used “locally” to get frame from one interface to another physically-connected interface

ARP: address resolution protocol

Determines interface’s MAC address, knowing its IP address?

ARP Protocol

Uses ARP to find B’s MAC address, A broadcasts ARP query, containing B's IP addr

Ethernet Switch

Takes an active role to Store, forward Ethernet (or other type of) frames

Switch: self-learning

Switch learns which hosts can be reached through which interfaces

Virtual Local Area Network (VLAN)

port-based VLAN : switch ports grouped (by switch management software) so that single physical switch operates as multiple virtual switches

trunk port

carries frames between VLANS defined over multiple physical switches

EVPN: Ethernet VPNs (aka VXLANs)

Ethernet frames carried within IP datagrams between sites