Term
| Media Access Control Protocols |
|
Definition
| Arbitrate access if multiple hosts wish to transmit at the same time |
|
|
Term
|
Definition
| listen before transmitting (Media Access Control) |
|
|
Term
|
Definition
| listen while transmitting and stop on detecting collision (Media Access Control) |
|
|
Term
|
Definition
| Multiple nodes plugged into common 'bus' medium |
|
|
Term
|
Definition
| Multiple Access With Collision Avoidance for Wireless LANs. Basically: don't do collision avoidance. Sender sends RTS(Request to Send) with length of data frame. Receiver then replies with Clear to Send with echo of frame length. If sender gets CTS frame it sends data frame, if not it does exponential back-off before trying again. Receiver then sends ACK. |
|
|
Term
|
Definition
| distance vector-like algorithm. measures number of hops, up to 15, 16=infinity.Routing tables are exchanged with adjacent nodes every 30 seconds. If no communication happens after 180 seconds, the node/link is declared 'failed' |
|
|
Term
|
Definition
| Publicly available. Uses the link state minimum cost path computation algorithm. Advertisement carries one entry per adjacent node. Advertisements disseminate to an entire AS via flooding. All messages are authenticated to prevent malicious intrusion. Multiple same-cost paths allowed. For each link, multiple cost metrics for different network-layer 'services'. Hierarchical. |
|
|
Term
|
Definition
| Border Gateway Protocol. Send messages like:OPEN, UPDATE, KEEPALIVE, NOTIFICATION. Used in Inter-AS Routing. |
|
|
Term
| Inter vs Intra AS routing |
|
Definition
Inter- between networks. administrator wants control over how its traffic routed and who routes through its network. policy over performance.
Intra- in the same network. No policy decisions, but focus on performance. |
|
|
Term
|
Definition
| 32-bit network-layer address. It identifies a host or router's interface. Used to get datagram to destination network. Not portable. The upper bits are the network part, host part is the lower bits |
|
|
Term
|
Definition
| Ethernet address. Used to get datagram from one interface to another physically-connected interface in the same network. 48 bit MAC address burned into the adapter Read- only Memory. Address administration administered by IEEE. Manufactures buy some portion of MAC address space. MAC unstructured address is useful for portability. |
|
|
Term
|
Definition
| Like routers. They use the MAC address to forward frames. Large number of interfaces. Switches learn MAC addresses of hosts on each link. |
|
|
Term
|
Definition
| Address resolution protocol. ARP cache contains IP/MAC address mappings, along with TTL (Time to live; time after whch address mapping will be forgotten, like 20 mins). If a host, A, wants another host's, B, MAC address from B's IP address, it can broadcast a query, to which the B responds to with the MAC address to put into the A's ARP cache |
|
|
Term
|
Definition
| The protocol data unit at the IP network layer. |
|
|
Term
|
Definition
| connection between host or router and a physical link. Routers typically have multiple interfaces. IP addresses are associated with an interface, not the host or router. |
|
|
Term
|
Definition
| Inefficient use of address space, address space exhaustion. |
|
|
Term
|
Definition
| network portion of address has an arbitrary length. address format:a.b.c.d/x where x is the number of bits in network portion of address called the network mask. Used in routing tables, not IP datagram source/destination |
|
|
Term
|
Definition
| made up of IP protocol version, Header length, total IP datagram length, fragmentation info, Maximum number of remaining hops, Transport layer protocol, and the data. |
|
|
Term
|
Definition
| maximum transmission unit. Used to fragment IP datagrams. Fragments only reassemble at final destination. |
|
|
Term
|
Definition
| Internet control message protocol. Used by hosts, routers and gateways to communicate network-level information. Error reporting/echo request-reply. |
|
|
Term
|
Definition
| changed to fixed-length 40 byte header. No fragmentation allowed. Helps high speed processing. New 'anycast': route to 'best' of several replicated servers. chooses priority among datagrams in flow. Has an upper layer protocol for data. |
|
|
Term
| Global routing algorithms |
|
Definition
| all routers maintain the complete graph of the network. "link state" algorithms. |
|
|
Term
| Decentralized routing algorithms |
|
Definition
| router knows link costs to physically connected adjacent nodes. Run iterative algorithm to exchange information with adjacent nodes. has distance vector algorithms. |
|
|
Term
|
Definition
| Iterative, meaning nodes exchange cost information until each node has the current route cost, and the algorithm is self-terminating. Each iteration is caused by local link cost change or message from adjacent node that its least cost path to some destination has changed. It's asynchronous, meaning nodes don't have to exchange info at the same time. Each node communicates with directly attached adjacent nodes. Nodes can advertise incorrect path cost. each node's table used by others. |
|
|
Term
|
Definition
| -addressing: the means by which end systems identify each other. -path determination- the route taken by packets from source to destination. -Switching- the movement of packets from an input interface to an appropriate output interface. Call setup- the establishment of a virtual circuit from sender to receiver. |
|
|
Term
| link state flooding algorithm |
|
Definition
| The data stored for an edge in the graph made up of the cost from end to end, and a unique timestamp for the last update to each cost. A node that discovers a change in cost for one of its attached links forwards the update to all adjacent nodes. A node receiving an update forwards it based on a comparison of the update timestamp and the timestamp on its local data for the link. |
|
|
Term
|
Definition
2RTT+O/R
R-transmission speed.
Sometimes +total stall time. |
|
|
Term
|
Definition
| sender adjusts its transmission rate so as not to overwhelm the receiver. |
|
|
Term
|
Definition
| the senders adjust their transmission rate so as not to overwhelm routers in the network. Congestion can lead to lost packets and long delays |
|
|
Term
|
Definition
| all the links are fully utilized but no data is delivered to applications |
|
|
Term
| End-to-end congestion control |
|
Definition
| end-systems receive no feedback from network. Congestion inferred by observing loss and/or delay. |
|
|
Term
| hop-by-hop congestion control |
|
Definition
| routers provide feedback to end systems. Network determines an explicit rate that a sender should transmit at. Network signals congestion by setting a bit in a packet's header. |
|
|
Term
|
Definition
| maximum segment size, for segments in windows. |
|
|
Term
| slow start congestion control |
|
Definition
| ramp up the transmission rate until loss occurs. The window size increase exponentially each RTT until a loss occurs or the size of the window equals threshold. If there's a loss, it starts back over. |
|
|
Term
|
Definition
| keep connection close to sustainable bandwidth. It increases the window size by 1 segment each RTT, decrease by a factor of 2 when packet loss is detected. |
|
|
Term
| slow start vs. congestion avoidance |
|
Definition
| threshold is an estimate of a safe level of throughput that is sustainable in the network. This determines whether a window uses slow start or congestion avoidance according to it. |
|
|
Term
|
Definition
| loss signaled by timeout. |
|
|
Term
|
Definition
Fast retransmit-receipt of 3 duplicate ACKs also signals a packet loss
Fast recovery-skips slowstart and continue in congestion avoidance new slowstart threshold. |
|
|
Term
|
Definition
| point to point transport layer protocol. Bi-directional, reliable, in-order, connection oriented, pipelined, congestion controlled, flow controlled |
|
|
Term
|
Definition
| Byte stream index of the first byte in the segment's payload. |
|
|
Term
|
Definition
| Sequence number of next byte expected from the other side. |
|
|
Term
|
Definition
| to avoid premature timeouts and keep high performance, the sample RTT is calculated to set the time for the timeout. Timeout is estimated RTT plus safety margin |
|
|
Term
|
Definition
| The whole window (size n) is sent. If a NACK is received, then the last n packets will be sent again. |
|
|
Term
| transport layer vs network layer |
|
Definition
| transport layer: data transfer between end systems Network layer: data transfer between network components |
|
|
Term
|
Definition
| multiplexing, demultiplexing. Error detection, reliable data delivery. pipelining. flow control. congestion control |
|
|
Term
|
Definition
| uses destination IP addr, destination port number to identify the socket. Socket it owned by some processes, allocated by the OS. fast. No handshaking, best effort sending. DNS, SNMP, and routing protocols use it. |
|
|
Term
|
Definition
| TCP uses source IP and port number, and destination IP address and port #. Connection and socket are owned by some process |
|
|
Term
|
Definition
| contains all the info about a torrent. It has tracker-info, creation date, comment, created by. hash of all pieces are present in info field. |
|
|
Term
|
Definition
| transfer transfer protocol. Uses client/server model. FTP maintains state. |
|
|
Term
|
Definition
| uses TCP sockets. stateless. |
|
|
Term
|
Definition
| email. push protocol . Uses HTTP. persistent connections |
|
|
Term
|
Definition
| time to put bits onto the link. packet length/link bandwidth |
|
|
Term
|
Definition
| time to get from one end to the other. length of physical link/signal propagation speed. |
|
|
Term
|
Definition
La/R
L-packet length
a-average packet arrival rate
R-link transmission speed |
|
|
