Day Of Exam Flashcards
TCP/IP
Transmission Control Protocol. Internet Protocol.
Four layers of TCP/IP
Link Layer (host / network interface layer), Internet Layer, Transport Layer, Application Layer.
Describe Link Layer:
Corresponds to OSI physical and data link layers.
Internet Layer, describe:
Defines IP. Two main functions: 1)host addressing & identification. 2) Packet Routing, forwarding packet to next router.
Transport Layer describe:
Same as OSI model. Creates distinct network connection. error control. application addressing (port numbers). Two end to end message transmission protocols: TCP & UDP
Application Layer describe:
Contains higher level protocols like FTP, DNS, SMTP
TCP?
Transmission Control Protocol (reliable connection oriented protocol).
UDP?
User Datagram Protocol (unreliable connectionless protocol).
MAC?
Medium Access Control. A component of the Link Layer.
What does MAC do?
This protocol deals with issues like addressing, assigning multiplex channels to different users, avoiding collisions. Resolves contention.
Channel Allocation Problem?
The problem of allocating a single broadcast channel amongst many users.
Channel Allocation Problem solutions?
Static: FDM, TDM. Dynamic: (Collision)Pure Aloha, Persistent CSMA, non-persistent CSMA, CSMA/CD. (non-collission) bit map protocl, binary countdown, adaptive tree walk.
When are collision based protocols good?
when network load is low.
When are collision free protocols good?
when network load is high
Pure Aloha:
Nodes send regardless of other nodes. Collision detected, wait then send again.
Slotted aloha:
Divide into intervals corresponding to frame. Efficiency doubled on pure aloha.
Carrier Sense?
Where a station can check if channel is in use.
CSMA / CD
Carrier Sense Multiple Access / Collision Detection.
Ethernet: 4 parts to it
Medium (lead), Segment (a single shared medium), Node (devices attached to the segment), Frame (nodes communicate in frames).
TCP header as list:6
Source destination port, sequence number, acknowledge number, checksum, window size, flags
TCP 4 characteristics:
Provides reliable delivery. User acknowledged delivery.
TCP header:
Source and destination port, sequence number, acknowledged number, checksum, window size, flags.
ARP?
Address resolution protocol. Solves problem of mapping MAC to IP.
ICMP?
Internet control message protocol. Internet monitored by routers, something wrong is reported by ICMP.
Subnet mask?
Separated IP into network and host addresses. Find subnet address by performing but wise AND operation on IP and subnet mask.
NAT?
Network address translation. Way to add more addresses. Translates packets going to Internet.
IP header?
Version, IHL, type of service, total length, ID, fragment offset, time to live, protocol, checksum, source address, destination address, options. 32 bits.
Conmectionless service?
Data sent between nodes without knowing if destination busy. UDP is connection less.
Connection less algorithms, static and dynamic?
Static: shortest path-examine each node in turn, dynamic: vector distance routing - router tables used.
Three way handshake?
H1 to h2: connection request (CR) TPDU with seq=x.
H2 to h1: replies with ACK TPDU ack=x and seq=y.
H1 to h2: sends data TPDU with ack=y, seq=x
Two types of releasing connection:
Asymmetric(1 can break), symmetric(communication after break).
TPDU? And layout?
Transport Protocol Data Unit. Frame header, packet header, TPDU header. Segment for TCP, Datagram for UDP.
