CMPE 148 Final

ICANN

(_________)Internet Corporation for Assigned Names and Numbers: allocates addresses, manages DNS, assigns domain names, resolves disputes

DHCP

Dynamic Host Configuration Protocol (_____): allow host to dynamically obtain its IP address from network server when it joins network. host broadcasts "DHCP discover" msg [optional], DHCP server responds with "DHCP offer" msg [optional], host requests IP address: "DHCP request" msg, DHCP server sends address: "DHCP ack" msgcan. plug-n-play. client-server protocol.

switch

Filtering is the switch function that determines whether a frame should be for- warded to some interface or should just be dropped. Forwarding is the switch function that determines the interfaces to which a frame should be directed, and then moves the frame to those interfaces. Switch filtering and forwarding are done with a _______ table.

true

For a given modulation scheme, the higher the SNR, the lower the BER? For a given SNR, a modulation technique with a higher bit transmission rate (whether in error or not) will have a higher BER? Dynamic selection of the physical-layer modulation technique can be used to adapt the modulation technique to channel conditions?

HOL

Head-of-the-Line (_____) blocking: queued datagram at front of queue prevents others in queue from moving forward

11

IEEE 802.__ Wireless LAN: all use CSMA/CA for multiple access. all have base-station and ad-hoc network versions. Basic Service Set (BSS) (aka "cell") in infrastructure mode contains: wireless hosts, access point (AP): base station, ad hoc mode: hosts only. Uses CSMA/CA

20

IP datagram has a __ byte header.

trunking

In the VLAN __________ approach, a special port on each switch (port 16 on the left switch and port 1 on the right switch) is configured as a trunk port to interconnect the two VLAN switches. The trunk port belongs to all VLANs, and frames sent to any VLAN are forwarded over the trunk link to the other switch.

ICMP

Internet control message protocol(_____): used by hosts & routers to communicate network-level information; ex: error reporting, echo request/reply. lies above IP. messages have a type and a code field, and contain the header and the first 8 bytes of the IP datagram that caused the ICMP message to be generated in the first place

NAT

Network Address Translation (_____): local network uses just one IP address as far as outside world is concerned. can change addresses of devices in local network without notifying outside world. can change ISP without changing addresses of devices in local network. devices inside local net not explicitly addressable, visible by outside world (a security plus).

management

Network ________________ includes the deployment, integration and coordination of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate, and control the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost.

interconnection

Switching via _____________________ network: Overcome bus bandwidth limitations. banyan networks (multi-stage), crossbar, other interconnection nets initially developed to connect processors in multiprocessor

slotted aloha

assume all frames same size, time divided into equal size slots (time to transmit 1 frame), nodes start to transmit only slot beginning, nodes are synchronized. when node obtains fresh frame, transmits in next slot. if no collision: node can send new frame in next slot. if collision: node retransmits frame in each subsequent slot with prob. p until success. By retransmitting with probability p, we mean that the node effectively tosses a biased coin; the event heads corresponds to "retransmit," which occurs with prob- ability p. The event tails corresponds to "skip the slot and toss the coin again in the next slot"; this occurs with probability (1 - p). All nodes involved in the collision toss their coins independently. Pros: single active node can continuously transmit at full rate of channel. highly decentralized: only slots in nodes need to be in sync. simple. Cons: collisions, wasting slots. idle slots. nodes may be able to detect collision in less than time to transmit packet. clock synchronization. at best: channel used for useful transmissions 37% of time!

prefix

longest ______ matching: when looking for forwarding table entry for given destination address, use longest address prefix that matches destination address.

MIB

managed devices contain managed objects whose data is gathered into a Management Information Base (____). Two ways to convey info, commands: request/response or trap

AS

scalability and administrative autonomy can be solved by organizing routers into autonomous systems (___s), with each ___ consisting of a group of routers that are under the same administrative control. identified by globally unique number (ASN)

servers

software-defined networking (SDN): implemented in (remote) ___________

bus

switching via ____: datagram from input port memory to output port memory via a shared bus. bus contention: switching speed limited by bus bandwidth. only one packet can cross bus at a time

memory

switching via ________: traditional computers with switching under direct control of CPU. packet copied to system's memory. speed limited by memory bandwidth (2 bus crossings per datagram)

routers

traditional routing algorithms: implemented in ________

SDN

The control-plane approach is at the heart of software-defined networking (_____), where the net- work is "software-defined" because the controller that computes forwarding tables and interacts with routers is implemented in software.

SNR

The signal-to-noise ratio (_____) is a relative measure of the strength of the received signal (i.e., the information being transmitted) and this noise. a larger SNR makes it easier for the receiver to extract the transmitted signal from the background noise.

BGP

____: prefix + attributes = "route". prefix=CIDRized representing subnet(s) of format a.b.c.d/x. AS-PATH: list of ASes through which prefix advertisement has passed. NEXT-HOP: indicates specific internal-AS router to next-hop AS - router interface that begins AS-PATH. router may learn about more than one route to destination AS, selects route based on: local preference value attribute: policy decision, shortest AS-PATH, closest NEXT-HOP router: hot potato routing

Rate

_____ adaptation: base station, mobile dynamically change transmission rate (physical layer modulation technique) as mobile moves, SNR (Signal-to-Noise Ratio) varies

OSPF

_____ advanced features: security: all messages authenticated (to prevent malicious intrusion). multiple same-cost paths allowed. for each link, multiple cost metrics for different TOS (e.g., satellite link cost set low for best effort ToS; high for real-time ToS). integrated uni- and multi-cast support. hierarchical OSPF in large domains.

link

_____ layer services: framing, reliable delivery, flow control, error detection, error correction, half-duplex and full-duplex

link

_____ layer: datagram transferred by different link protocols over different links: e.g., Ethernet on first link, frame relay on intermediate links, 802.11 on last link. each link protocol provides different services. implemented in "adaptor" (aka network interface card NIC) or on a chip in each and every host.

Data

_____ plane: local, per-router function. determines how datagram arriving on router input port is forwarded to router output port. forwarding function. operates in nanosecond.

OSPF

_____(Open Shortest Path First): Intra-AS. a link-state protocol that uses flooding of link-state information and a Dijkstra's least-cost path algorithm. With OSPF, each router constructs a complete topological map (that is, a graph) of the entire autonomous system. Each router then locally runs Dijkstra's shortest-path algorithm to determine a shortest-path tree to all subnets, with itself as the root node. "open" = publicly available. IS-IS nearly identical

pure

_____(unslotted) aloha: no synchronization. when frame first arrives transmit immediately. collision probability increases. efficiency=18%.

CSMA/CD

_____/__: carrier sensing, deferral as in CSMA. collisions detected within short time. colliding transmissions aborted, reducing channel wastage

IPv6

_____: fixed-length 40 byte header. no fragmentation allowed. 128 bit IP address. header format helps speed processing/forwarding. header changes to facilitate QoS.

NAT

_____: router gets its address from the ISP's DHCP server, and the router runs a DHCP server to provide addresses to computers within network.

VLAN

_____: traffic isolation: frames to/from ports 1-8 can only reach ports 1-8. dynamic membership: ports can be dynamically assigned among VLANs. forwarding between VLANS: done via routing (just as with separate switches).

token passing

______ _______: When a node receives a token, it holds onto the token only if it has some frames to transmit; otherwise, it immediately forwards the token to the next node. If a node does have frames to transmit when it receives the token, it sends up to a maximum number of frames and then forwards the token to the next node. Token passing is decentralized and highly efficient. concerns: token overhead, latency, single point of failure (token)

DHCP

______ can return more than just allocated IP address on subnet: address of first-hop router for client, name and IP address of DNS sever, network mask (indicating network versus host portion of address)

error

______ detection & correction: Error types: singular, bursty. Hamming distance (dh): # of corresponding positions in which 2 codewords differ. Minimum distance (dmin): smallest dh between any 2 codewords in a code. For 2^d possible data messages: 2^n possible codewords. dmin = e + 1 to detect e error. dmin = 2e + 1 to correct e errors

Control

______ plane: network-wide logic. determines how datagram is routed among routers along end-end path from source host to destination host. operates in millisecond

inter

______-AS routing: routing among AS'es. gateways perform inter-domain routing (as well as intra-domain routing)

Cyclic redundancy

_______ _____________ check: Consider the d-bit piece of data, D, that the send- ing node wants to send to the receiving node. The sender and receiver must first agree on an r + 1 bit pattern, known as a generator, which we will denote as G. We will require that the most significant (leftmost) bit of G be a 1. The key idea behind CRC codes is shown in Figure 6.6. For a given piece of data, D, the sender will choose r additional bits, R, and append them to D such that the resulting d + r bit pattern (interpreted as a binary number) is exactly divisible by G (i.e., has no remainder) using modulo-2 arithmetic. The process of error checking with CRCs is thus simple: The receiver divides the d + r received bits by G. If the remainder is nonzero, the receiver knows that an error has occurred; otherwise the data is accepted as being correct.

Parity

_______ checking: single bit = only detect single bit errors. two-dimensional bit: detect and correct single bit errors

CSMA

_______(carrier sense multiple access): listen before transmit, if channel sensed idle transmit entire frame, if channel sensed busy defer transmission. a transmitting node listens to the channel while it is transmitting. If it detects that another node is transmitting an interfering frame, it stops transmitting and waits a random amount of time before repeating the sense-and-transmit-when-idle cycle. end-to-end channel propagation delay of a broadcast channel—the time it takes for a signal to propagate from one of the nodes to another—will play a crucial role in determining its performance.

subnet

_______: device interfaces with same subnet part of IP address. can physically reach each other without intervening router. to determine the ________, detach each interface from its host or router, creating islands of isolated networks, each isolated network is called a _________

switch

_______: link-layer device: takes an active role. store, forward Ethernet frames. examine incoming frame's MAC address, selectively forward frame to one-or-more outgoing links when frame is to be forwarded on segment, uses CSMA/CD to access segment. transparent, hosts are unaware of presence of switches. plug-and-play, self-learning, switches do not need to be configured. no collisions. buffer packets. uses table.

taking turns

________ _______: MAC protocol. nodes take turns, but nodes with more to send can take longer turns. polling, token passing.

Simple Network

________ ___________ Management Protocol version 2 (SNMPv2) [RFC 3416] is an application-layer protocol used to convey network-management control and information messages between a managing server and an agent executing on behalf of that managing server.

random

________ access: MAC protocol. channel not divided, allow collisions. "recover" from collisions

power

________ management. node-to-AP: "I am going to sleep until next beacon frame". AP knows not to transmit frames to this node. node wakes up before next beacon frame. beacon frame: contains list of nodes whose frames have been buffered by AP. node goes back to sleep if no buffered frames; otherwise node explicitly requests buffered frames by sending polling message to AP

intra

________-AS routing: routing among hosts, routers in same AS ("network"). all routers in AS must run same intra-domain protocol. routers in different AS can run different intra-domain routing protocol. gateway router: at "edge" of its own AS, has link(s) to router(s) in other AS'es

polling

________: The polling protocol requires one of the nodes to be designated as a master node. The master node polls each of the nodes in a round-robin fashion. In particular, the master node first sends a message to node 1, saying that it (node 1) can transmit up to some maximum number of frames. After node 1 transmits some frames, the master node tells node 2 it (node 2) can transmit up to the maximum number of frames. (The master node can determine when a node has finished sending its frames by observing the lack of a signal on the channel.) The procedure con- tinues in this manner, with the master node polling each of the nodes in a cyclic manner. typically used with "dumb" slave devices. concerns: polling overhead, latency, single point of failure (master)

multiple access

_________ _________ protocol: distributed algorithm that determines how nodes share channel, i.e., determine when node can transmit. communication about channel sharing must use channel itself! no out-of-band channel for coordination. ideally when one node wants to transmit, it can send at rate R. when M nodes want to transmit, each can send at average rate R/M, fully decentralized, simple.

channel

_________ partitioning: MAC protocol. divide channel into smaller "pieces" (time slots, frequency, code). allocate piece to node for exclusive use. TDMA, FDMA.

bellman-ford

_________-____ Equation: let dx(y) := cost of least-cost path from x to y then dx(y) = min {c(x,v) + dv(y) }

distance-vector

_________-_________ algorithm is iterative, asynchronous, and distributed. It is distributed in that each node receives some information from one or more of its directly attached neighbors, performs a calculation, and then distributes the results of its calculation back to its neighbors. It is iterative in that this process continues on until no more information is exchanged between neighbors. The algorithm is asynchronous in that it does not require all of the nodes to operate in lockstep with each other. from time-to-time, each node sends its own distance vector estimate to neighbors, when x receives new DV estimate from neighbor, it updates its own DV using B-F equation:

priority

__________ scheduling: send highest priority queued packet. multiple classes, with different priorities class may depend on marking or other header info, e.g. IP source/dest, port numbers, etc.

preamble

__________: 7 bytes with pattern 10101010 followed by one byte with pattern 10101011. used to synchronize receiver, sender clock rates. at the start of ethernet frame.

ethernet

__________: connectionless: no handshaking between sending and receiving NICs. unreliable: receiving NIC doesn't send acks or nacks to sending NIC. data in dropped frames recovered only if initial sender uses higher layer rdt (e.g., TCP), otherwise dropped data lost. Ethernet's MAC protocol: unslotted CSMA/CD with binary backoff. different speeds:10 Mbps, 100 Mbps, 1Gbps, 10 Gbps, 40 Gbps, 100 Gbps. different physical layer media: fiber, cable

Network

___________ layer: transport segment from sending to receiving host. on sending side encapsulates segments into datagrams. on receiving side, delivers segments to transport layer

Ethernet

___________ with a bus topology is a broadcast LAN—all transmitted frames travel to and are processed by all adapters connected to the bus. with a hub-based star topology is also a broadcast LAN—whenever a hub receives a bit from one of its interfaces, it sends a copy out on all of its other interfaces. max data field size is 1500 bytes.

routing

___________: determine route taken by packets from source to destination. Like process of planning trip from source to destination

Weighted

____________ Fair Queuing (WFQ): generalized Round Robin. each class gets weighted amount of service in each cycle

Dijkstra

____________'s algorithm: uses edge weight as measure of distance. node labeled w/ its distance from source using shortest path. net topology, link costs known to all nodes. accomplished via "link state broadcast". computes least cost paths from one node ("source") to all other nodes. gives forwarding table for that node. iterative: after k iterations, know least cost path to k dest.'s

DOCSIS

____________: data over cable service interface spec. FDM over upstream, downstream frequency channels. TDM upstream: some slots assigned, some have contention. downstream MAP frame: assigns upstream slots. request for upstream slots (and data) transmitted random access (binary backoff) in selected slots

infrastructure

______________ mode: base station connects mobiles into wired network. handoff: mobile changes base station providing connection into wired network

forwarding

______________ table configured by both intra- and inter-AS routing algorithm. intra-AS routing determine entries for destinations within AS. inter-AS & intra-AS determine entries for external destinations

interface

______________: connection between host/router and physical link. router's typically have multiple. host typically has one or two (e.g., wired Ethernet, wireless 802.11). IP addresses associated with each.

fragmentation

______________: large IP datagram divided within net. "reassembled" only at final destination. IP header bits used to identify, order related fragments. the last fragment has a flag bit set to 0, whereas all the other fragments have this flag bit set to 1. the offset field is used to specify where the fragment fits within the original IP datagram.

forwarding

______________: move packets from router's input to appropriate router output. Like process of getting through single interchange.

generalized

_______________ forwarding: forward based on any set of header field values

decentralized

________________ switching: using header field values, lookup output port using forwarding table in input port memory ("match plus action"). goal: complete input port processing at 'line speed'. queuing: if datagrams arrive faster than forwarding rate into switch fabric

RTS

allow sender to "reserve" channel rather than random access of data frames, avoid collisions of long data frames. sender first transmits small request-to-send (____) packets to AP using CSMA. RTSs may still collide with each other (but they're short). AP broadcasts clear-to-send CTS in response to RTS. CTS heard by all nodes. sender transmits data frame, other stations defer transmissions

CIDR

Classless InterDomain Routing (______): internets adress assignment strategy. subnet portion of address of arbitrary length. address format: a.b.c.d/x, where x is # bits in subnet portion of address

CDMA

Code Division Multiple Access (_____): Each station transmits over entire frequency spectrum. Using coding theory to separate multiple transmissions. Each station is assigned a unique m-bit code, chip sequence (typically, m = 64 or 128). Chip sequences are pairwise orthogonal, normalized inner products of any 2 chip sequences is 0. encoded signal = (original data) X (chip sequence);For 1, station transmits its chip sequence; For 0, station transmits negative of its chip sequence; Silent, no transmission. decoding: inner-product of encoded signal and chip sequence

BGP

___(Border Gateway Protocol): the de facto inter-domain routing protocol. provides each AS a means to: eBGP: obtain subnet reachability information from neighboring ASes. iBGP: propagate reachability information to all AS-internal routers. determine "good" routes to other networks based on reachability information and policy. allows subnet to advertise its existence to rest of Internet: "I am here". semi-permanent TCP connection

Robin

Round ________ scheduling: multiple classes, cyclically scan class queues, sending one complete packet from each class (if available)

MAC

____ address: used 'locally" to get frame from one interface to another physically-connected interface (same network, in IP-addressing sense). each adapter on LAN has unique LAN address

true

Typically, small networks consisting of a few hundred hosts have a few LAN segments. Switches suffice for these small networks, as they localize traffic and increase aggregate throughput without requiring any configuration of IP addresses. But larger networks consisting of thousands of hosts typically include routers within the network (in addition to switches). The routers provide a more robust isolation of traffic, control broadcast storms, and use more "intelligent" routes among the hosts in the network?

ARP

____(address resolution protocol): translate between IP and MAC addresses. table: each IP node (host, router) on LAN has table. IP/MAC address mappings for some LAN nodes: < IP address; MAC address; TTL>. TTL (Time To Live): time after which address mapping will be forgotten (typically 20 min)

11

Within this 85 MHz band, 802.__ defines 11 partially overlapping channels. Any two channels are non-overlapping if and only if they are separated by four or more channels. The 802.11 standard requires that an AP periodically send beacon frames, each of which includes the AP's SSID and MAC address. Your wireless device, know- ing that APs are sending out beacon frames, scans the 11 channels, seeking beacon frames from any APs that may be out there (some of which may be transmitting on the same channel—it's a jungle out there!). Having learned about available APs from the beacon frames, you (or your wireless device) select one of the APs for association.

ad hoc

__ ___ mode: no base stations. nodes can only transmit to other nodes within link coverage. nodes organize themselves into a network: route among themselves

hot potato

___ ________ routing: choose local gateway that has least intra-domain cost (e.g., 2d chooses 2a, even though more AS hops to X): don't worry about inter-domain cost!