Theo Flashcards
Sockets
- endpoints of logical connections
- consist of an IP address and a port number
Difference between TCP and UDP (+ sequence and acknowledgement numbers)
- Transmission Control Protocol (TCP) provides logical connections and reliability
- takes care of flow control
- Data divided into segments
- Each data byte has a number
- Sequence number: number of first data byte
- Receiver confirms with sending acknowledgment number and - flag
- resent
- E.g. Email, FTP
- User Datagram Protocol
- provides connectionless and unreliable IP service to the application layer
- package can be sent without prior connection
- not resent
- E.g real time applications, such as a video/audio streams or video games
Network Access Point or Internet Exchange Point (IXP)
- network node interconnecting networks of different internet service providers (ISPs)
- on layer 1 (using Ethernet)
- Border Gateway Protocol: to announce routes between participants of an IXP and makes routing decisions based on path, network policies and/or rule-sets
Routers
- forward data packages between different networks
- Network layer (read IP headers)
Gateway
- interconnects networks working with different protocols
- transport or even the application layer (translation between various protocols)
Internet Backbone
- main data routes between large networks and routers (traffc between countries and continents)
- hosted by high-capacity network centers
WAN
- Wide Area Network
- network across a large region (nation, state)
LAN
- Local Area Network
- Small network (single room up to several buildings)
Schaubild
split horizon with poisoned reverse
- he cost is set to infinity for every node which contains “B” in the column “Next
- does not protect against all forms of loops, but under special network situations against the count-to-infinity problem
MTU
- maximum transmission unit
- largest protocol data unit that the network protocol can pass onwards
- specified in bytes
- MTU = MSS + (IP & TCP) headers
MSS
- largest amount of data that the network protocol can handle in a single, unfragmented piece
- specified in bytes
ACK field
- maximal received sequence number (SEQ), up to which all bytes have been received correctly, plus 1
- Caution: storage of receive buffer
packet
- (or package)
- data unit sent over a packet-switched network
- Depending on layer and protocol: frame, datagram, segment
frame
- another name for packet on the second layer (data link layer)
- sent over a single link
datagram
- independent entity of data
- sufficient information to be routed from the source to the destination computer
- packets of an unreliable service
- third layer (IP and UDP)
segments
- packets exchanged on the transport layer
Recall
- relevant documents retrieved/all relevant documents
Precision
relevant documents retrieved/all documents retrieved
recall - precision
Native approach
Wenn was nicht passt, wort eine Stelle nach rechts und von neuem
Aufgabe: 2 aggregated search engines vs. all other single ones: recall and precision
IP-header Beispiele
TCP
TCP is a host-to-host protocol for reliable communication
Internet Protocol provides a connectionless and unreliable service for the transport layer
By what factor does IPv6 increase the address space if you compare it to IPv4?
objectives for the introduction of IPv6
increase the address space
OSI / ISO vs. TCP/IP Model
layered architecture allows to exchange the protocols more easily
e.g. IPv4 ↔ IPv6
Which network components use the information in the IP headers
disadvantages of IPv6 over IPv4
static vs. dynamic routing
Internet communication layers
advantage of a packet switching network over a circuit switching network
Internet vs. WWW
Internet is the general network
WWW is one of the (high level) services
DVR vs. Link-state-Algo
count-to-infinity problem
Link-State routing steps
step 3: compile the Link-State packets
step 4: the network is flooded with these Link-State packets
stept 5: shortest path from node A to every other node using Dijkstra’s algorithm
count to infinity problem
Erklärung
- As soon as the link between router C and router D fails, router C will no longer get any more distance information from router D
- but receives from router A that it can reach router D
- routing loop, causing all routers to increase their distances
- gradually reach infinity
- because just the indexed vectors with distances, but no corresponding links are being distributed
(Link-state Routing)
Link-State packets consist of
Editing distance
Levenshtein distance (a special form of the Editing distance)
formale
KMP Regel
!= oben
= unten
Bestcase
BM (mh)
O(n/m)
If the mismatch occurs at the rightmost symbol, the pattern can be moved by m positions (m stands for the number of letters in the pattern).
