1. Cics 515 – Summer 2012 © Dr. Son Vuong 1 CICS 515 (Part 2) University of British Columbia CICS 515 (Part 2) Computer Networks Lecture 5b-c – IPv6 and Other Protocols Instructor: Dr. Son T. Vuong Email: vuong@cs.ubc.ca The World Connected

2. Cics 515 – Summer 2012 © Dr. Son Vuong 2 IPv6 n Initial motivation: 32-bit address space soon to be completely allocated. n Additional motivation: u header format helps speed processing/forwarding u header changes to facilitate QoS IPv6 datagram format: u fixed-length 40 byte header u no fragmentation specified in basic header

3. Cics 515 – Summer 2012 © Dr. Son Vuong 3 IPv6 Header (Cont) Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of“flow” not well defined). Next header: identify upper layer protocol for data

4. Cics 515 – Summer 2012 © Dr. Son Vuong 4 Other Changes from IPv4 n Checksum: removed entirely to reduce processing time at each hop n Options: allowed, but outside of header, indicated by “Next Header” field n ICMPv6: new version of ICMP u additional message types, e.g. “Packet Too Big” u multicast group management functions

5. Cics 515 – Summer 2012 © Dr. Son Vuong 5 Transition From IPv4 To IPv6 n Not all routers can be upgraded simultaneous u no “flag days” u How will the network operate with mixed IPv4 and IPv6 routers? n Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers

6. Cics 515 – Summer 2012 © Dr. Son Vuong 6 Tunneling A B E F IPv6 tunnel Logical view: Physical view: A B E F IPv6 C D IPv4 Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Src:B Dest: E Flow: X Src: A Dest: F data Src:B Dest: E A-to-B: IPv6 E-to-F: IPv6 B-to-C: IPv6 inside IPv4 B-to-C: IPv6 inside IPv4 Dual IPv6/IPv4 Router

7. Cics 515 – Summer 2012 © Dr. Son Vuong 7 IPv6 – Peer Instruction – Question 5.2 IPv6 supports the following features: A. 128-bit IP address B. Auto-configuration (plug-and-play) (stateless) as well as dynamic IP address via a DHCPv6 server (stateful) C. More options via extension headers including Jumbogram of greater than 64KB D. Efficient header processing E. All the above F. A, B and C

8. Cics 515 – Summer 2012 © Dr. Son Vuong 8 IPv6 – Peer Instruction – Question 5.3 An IPv6 datagram is 80,000 bytes. What extension header must be used? A. Destination option B. Fragmentation C. Authentication D. Hop-by-hop E. None of the above

9. Cics 515 – Summer 2012 © Dr. Son Vuong 9 IPv6 – Peer Instruction – Question 5.4 The IPv6 jumbogram option gives rise to the following issues: A. Fragmentation B. 16-bit length of UDP C. 16-bit MSS option of TCP D. Checksum calculation E. All of the above F. B and C

10. Cics 515 – Summer 2012 © Dr. Son Vuong 10 Ch 4: Network Layer and Routing  The IP Protocol  IP Format, Addressing, fragmentation,  Internet Control Protocols (ICMP)  Routing  RIP (Routing Information Protocol)  OSPF (Open Shortest Path First)  The Interior Gateway Routing Protocol  BGP – The Exterior Gateway Routing Protocol  IPv6  Internet Multicasting  Mobile IP

11. Cics 515 – Summer 2012 © Dr. Son Vuong 11 What’s next ? n IPv4, IPv6 n Internet Control Message Protocol (ICMP) n Address resolution (ARP) n Getting (dynamic) addresses (DHCP) n DNS What have we covered? n Routing protocols (RIP, OSPF, BGP)

12. Cics 515 – Summer 2012 © Dr. Son Vuong 12 CICS 515 (Part 2) University of British Columbia CICS 515 (Part 2) Computer Networks Lecture 5c – ICMP, ARP, DHCP, DNS Instructor: Dr. Son T. Vuong Email: vuong@cs.ubc.ca The World Connected

13. Cics 515 – Summer 2012 © Dr. Son Vuong 13 Lect. 5c – Other IP protocols ICMP, ARP, DHCP (Sect. 4.4.3, 5.4) DNS (Sect. 2.5 ) n Internet Control Message Protocol (ICMP) (Sect 4.4.3) n Address Resolution (ARP) (Sect 5.4) n Dynamic IP address assignment (DHCP) (Sect 5.4) n Domain Name System (DNS) (Sect2.5)

14. Cics 515 – Summer 2012 © Dr. Son Vuong 14 ICMP: Internet Control Message Protocol RFC 792 n Used by hosts & routers to communicate network-level information u error reporting: unreachable host, network, port, protocol u echo request/reply (used by ping) n Network-layer “above” IP: u ICMP msgs carried in IP datagrams n ICMP message: type (1B), code (1B), checksum (2B) plus part of IP datagram causing error (header + first 8 bytes of data)

15. Cics 515 – Summer 2012 © Dr. Son Vuong 15 ICMP datagram structure n ICMP msgs carried in IP datagrams n ICMP data contains part of IP datagram causing error (IP header + first 8 bytes of data)

16. Cics 515 – Summer 2012 © Dr. Son Vuong 16 ICMP: Internet Control Message Protocol Type Code description 0 0 echo reply (ping) 3 0 dest. network unreachable 3 1 dest host unreachable 3 2 dest protocol unreachable 3 3 dest port unreachable 3 6 dest network unknown 3 7 dest host unknown 4 0 source quench (congestion control - not used) 5 0-3 redirect a host to a better router 8 0 echo request (ping) 9 0 route advertisement 10 0 router discovery (solicitation) 11 0 TTL expired 12 0 bad IP header

17. Cics 515 – Summer 2012 © Dr. Son Vuong 17 “Real” Internet delays and routes n What do “real” Internet delay & loss look like? n traceroute (tracert) program: provides delay measurement from source to router along end- end Internet path towards destination. For all i: u sends three UDP packets that will reach router i on path towards destination u router i will return packets to sender u sender times interval between transmission and reply. 3 probes

18. Cics 515 – Summer 2012 © Dr. Son Vuong 18 Traceroute and ICMP n Source sends series of UDP segments to dest u First has TTL =1 u Second has TTL=2, etc. u Unlikely port number n When nth datagram arrives to nth router: u Router discards datagram u And sends to source an ICMP message (type 11, code 0) u Message includes name of router& IP address n When ICMP message arrives, source calculates RTT n Traceroute does this 3 times Stopping criterion n UDP segment eventually arrives at destination host n Destination returns ICMP “port unreachable” packet (type 3, code 3) n When source gets this ICMP, stops.

19. Cics 515 – Summer 2012 © Dr. Son Vuong 19 Address Resolution Protocol (ARP) n How do we convert the IP address of each node (either the destination node, or a router) into the address on the local network? E.g. IP -> Ethernet. n Each machine keeps a mapping of IP address to physical addresses in a cache. n E.g. cascade.cs.ubc.ca 08:00:20:79:70:f5 dragon.cs.ubc.ca 08:00:09:27:b4:73 etc… n What if the mapping isn’t known, or has expired? Send an ARP (Address Resolution Protocol) broadcast message over the network.

20. Cics 515 – Summer 2012 © Dr. Son Vuong 20 ARP Packet Format TargetHardwareAddr (bytes 2-5) TargetProtocolAddr (bytes 0-3) SourceProtocolAddr (bytes 2-3) Hardware type = 1ProtocolType = 0x0800 SourceHardwareAddr (bytes 4-5) TargetHardwareAddr (bytes 0-1) SourceProtocolAddr (bytes 0-1) HLen = 48PLen = 32Operation SourceHardwareAddr (bytes 0-3) 081631

21. Cics 515 – Summer 2012 © Dr. Son Vuong 21 ARP Fields n Request format u HardwareType - Type of physical network (e.g., Ethernet) u ProtocolType - Type of higher layer protocol (e.g., IP) u HLEN & PLEN - Length of physical and protocol addresses (measured in bits) u Operation - Request for an address, or response to a request. u Source/Target Physical/Protocol addresses

22. Cics 515 – Summer 2012 © Dr. Son Vuong 22 ARP Comments n An ARP packet sits at the same level in the protocol graph as an IP packet. However ARP service is used by IP; thus ARP can also be viewed as a sublayer below IP. n ARP table entries timeout in about 10 minutes n Update the ARP table with information about the source when you are the target. Hence, both source/target physical/protocol addresses are in the packet.

23. Cics 515 – Summer 2012 © Dr. Son Vuong 23 How does a host get an IP address? n Fixed – assigned n Dynamic – changeable: via DHCP n why? Dynamic Host Configuration Protocol (DHCP)

24. Cics 515 – Summer 2012 © Dr. Son Vuong 24 Dynamic Host Configuration Protocol (DHCP) n DHCP allows config info (IP address etc) stored in DHCP server to be retrieved automatically by each host when booted or connected to network (via broadcast DHCPDiscover message) n that is, special IP address 255.255.255.255 n ignored by everyone except the DHCP server

25. Cics 515 – Summer 2012 © Dr. Son Vuong 25 DHCP (cont’d) n DHCP also allows dynamic assignment of IP addresses to hosts (DHCP server maintains a pool of available IP addresses to lease to host and host need to renew lease periodically). n It is not desirable to have a DHCP server on every network – instead, uses a relay agent for each network. n Relay agent unicasts DHCP request to server

26. Cics 515 – Summer 2012 © Dr. Son Vuong 26 DHCP with relay agent DHCP relay DHCP server Other networks Unicast to server Broadcast Host

27. Cics 515 – Summer 2012 © Dr. Son Vuong 27 DHCP Packet Format DHCP is derived from an earlier protocol called BOOTP OperationHTypeHLenHops Transaction ID (Xid) Client IP addr Your IP addr (yiaddr) Server IP addr Gateway IP addr Client hardware addr (chaddr) (16 bytes) Server name (64 bytes) file (128 bytes) options No. of secsFlags/unused

28. Cics 515 – Summer 2012 © Dr. Son Vuong 28 DHCP (cont’d) n Sent using UDP n Client puts hardware address in chaddr n Server replies with IP address in yiaddr (and other config info, e.g. gateway addr, server IP address, etc) n Types of DHCP packets (spec’d as options): u Discover, Offer, Request, Decline, Ack, Nack, Release n Scalability/manageability -- recurring theme (via relay/proxy)

29. Cics 515 – Summer 2012 © Dr. Son Vuong 29 DHCP Scenario DHCP ClientDHCP Server Discover Offer Request (or Decline) Ack (or Nack) Request Ack (or Nack) Release...

30. Cics 515 – Summer 2012 © Dr. Son Vuong 30 Layering Relationships between ICMP, ARP, DHCP and IP, UDP n ICMP/IP n IP calls ARP/Link(Ethernet) n DHCP(BOOTP) / UDP(67/68) (for simple configinfo) DHCP(BOOTP) / TFTP/UDP(69) (to get config file)

31. Cics 515 – Summer 2012 © Dr. Son Vuong 31 DNS: Domain Name System

32. Cics 515 – Summer 2012 © Dr. Son Vuong 32 Chapter 2: Application layer n 2.1 Principles of network applications n 2.2 Web and HTTP n 2.3 FTP n 2.4 Electronic Mail u SMTP, POP3, IMAP n 2.5 DNS n 2.6 P2P file sharing n 2.7 Socket programming with TCP n 2.8 Socket programming with UDP n 2.9 Building a Web server

33. Cics 515 – Summer 2012 © Dr. Son Vuong 33 Domain Name System (DNS) Overview n What do names do? u identify objects u help locate objects u define membership in a group u specify a role u convey knowledge of a secret n Name space u defines set of possible names u consists of a set of name to value bindings

34. Cics 515 – Summer 2012 © Dr. Son Vuong 34 Properties n Names versus addresses n Location transparent versus location- dependent n Flat versus hierarchical n Global versus local n Absolute versus relative n By architecture versus by convention n Unique versus ambiguous

35. Cics 515 – Summer 2012 © Dr. Son Vuong 35 Examples n Hosts cheltenham.cs.princeton.edu 192.12.69.17 192.12.69.17 80:23:A8:33:5B:9F n Files /usr/llp/tmp/foo (server, fileid) n Users Larry Peterson llp@cs.princeton.edu

36. Cics 515 – Summer 2012 © Dr. Son Vuong 36 Summary of “Naming” or identification n Domain name: a name that makes sense to a human -- e.g. “cascade.cs.ubc.ca” n IP address: an identifier that makes sense to hosts and routers -- e.g. “142.103.7.7” Physical address: an identifier that makes sense to the interface card -- e.g. “ 8:0:2b:e4:b1:2”

37. Cics 515 – Summer 2012 © Dr. Son Vuong 37 DNS: Domain Name System People: many identifiers: u SSN, name, passport # Internet hosts, routers: u IP address (32 bit) - used for addressing datagrams u “name”, e.g., www.yahoo.com - used by humans Q: map between IP addresses and name ? Domain Name System: n distributed database implemented in hierarchy of many name servers n application-layer protocol host, routers, name servers to communicate to resolve names (address/name translation) u note: core Internet function, implemented as application- layer protocol u complexity at network’s “edge”

38. Cics 515 – Summer 2012 © Dr. Son Vuong 38 DNS: Domain Name System Why not centralize DNS? n single point of failure n traffic volume n distant centralized database n Maintenance n doesn’t scale! DNS services n Hostname to IP address translation n Host aliasing u Canonical and alias names n Mail server aliasing n Load distribution u Replicated Web servers: set of IP addresses for one canonical name

39. Cics 515 – Summer 2012 © Dr. Son Vuong 39 Examples (cont) n Mailboxes n Services nearby ps printer with short queue and 2MB Name server Mail program User TCP IP 2 cs.ubc.ca 142.103.7.51 3 vuong @ cs.ubc.ca 1 142.103.7.51 4 5

40. Cics 515 – Summer 2012 © Dr. Son Vuong 40 Domain Naming System n Hierarchy n Name chinstrap.cs.princeton.edu

41. Cics 515 – Summer 2012 © Dr. Son Vuong 41 Root DNS Servers com DNS servers org DNS serversedu DNS servers poly.edu DNS servers umass.edu DNS servers yahoo.com DNS servers amazon.com DNS servers pbs.org DNS servers Distributed, Hierarchical Database Client wants IP for www.amazon.com; 1 st approx: n Client queries a root server to find com DNS server n Client queries com DNS server to get amazon.com DNS server n Client queries amazon.com DNS server to get IP address for www.amazon.com

42. Cics 515 – Summer 2012 © Dr. Son Vuong 42 Name Servers n Partition hierarchy into zones educom princeton … mit csee ux01ux04 physics cisco … yahoonasa … nsfarpa … navyacm … ieee govmilorgnetukfr Root name server UBC name server Cisco name server CS name server ECE name server … … n Each zone corresponds to an admin authority (implemented by two or more name servers for redundancy) Root name servers Top Level Domain (TLD) Servers Authoritative Servers Local Name Servers (LNS)

43. Cics 515 – Summer 2012 © Dr. Son Vuong 43 DNS: Root name servers n contacted by local name server that can not resolve name n root name server: u contacts authoritative name server if name mapping not known u gets mapping u returns mapping to local name server 13 root name servers worldwide b USC-ISI Marina del Rey, CA l ICANN Los Angeles, CA e NASA Mt View, CA f Internet Software C. Palo Alto, CA (and 17 other locations) i Autonomica, Stockholm (plus 3 other locations) k RIPE London (also Amsterdam, Frankfurt) m WIDE Tokyo a Verisign, Dulles, VA c Cogent, Herndon, VA (also Los Angeles) d U Maryland College Park, MD g US DoD Vienna, VA h ARL Aberdeen, MD j Verisign, ( 11 locations)

44. Cics 515 – Summer 2012 © Dr. Son Vuong 44 TLD and Authoritative Servers n Top-level domain (TLD) servers: responsible for com, org, net, edu, etc, and all top-level country domains uk, fr, ca, jp. u Verisign controls.com and.net TLDs F Many companies act as intermediaries u Educause for edu TLD n Authoritative DNS servers: organization’s DNS servers, providing authoritative hostname to IP mappings for organization’s servers (e.g., Web and mail). u Can be maintained by organization or service provider

45. Cics 515 – Summer 2012 © Dr. Son Vuong 45 Local Name Server n Does not strictly belong to hierarchy n Each ISP (residential ISP, company, university) has one. u Also called “default name server” n When a host makes a DNS query, query is sent to its local DNS server u Acts as a proxy, forwards query into hierarchy.

46. Cics 515 – Summer 2012 © Dr. Son Vuong 46 requesting host cis.poly.edu gaia.cs.umass.edu root DNS server local DNS server dns.poly.edu 1 2 3 4 5 6 authoritative DNS server dns.cs.umass.edu 7 8 TLD DNS server Example: Iterative queries n Host at cis.poly.edu wants IP address for gaia.cs.umass.edu iterative query: contacted server replies with name of server to contact “I don’t know this name, but ask this server”

47. Cics 515 – Summer 2012 © Dr. Son Vuong 47 requesting host cis.poly.edu gaia.cs.umass.edu root DNS server local DNS server dns.poly.edu 1 2 4 5 6 authoritative DNS server dns.cs.umass.edu 7 8 TLD DNS server 3 Recursive queries recursive query: n puts burden of name resolution on contacted name server n heavy load?

48. Cics 515 – Summer 2012 © Dr. Son Vuong 48 DNS: caching and updating records n once (any) name server learns mapping, it caches mapping u cache entries timeout (disappear) after some time u TLD servers typically cached in local name servers F Thus root name servers not often visited n update/notify mechanisms under design by IETF u RFC 2136 u http://www.ietf.org/html.charters/dnsind-charter.html

49. Cics 515 – Summer 2012 © Dr. Son Vuong 49 DNS records DNS: distributed db storing resource records (RR) n Type = NS  name is domain (e.g. foo.com)  value is IP address of authoritative name server for this domain RR format: (name, value, type, ttl) n Type = A  name is hostname  value is IP address n Type = CNAME  name is alias name for some “cannonical” (the real) name www.ibm.com is really servereast.backup2.ibm.com  value is cannonical name n Type = MX  value is name of mailserver associated with name

50. Cics 515 – Summer 2012 © Dr. Son Vuong 50 Example: Root Server (princeton.edu, cit.princeton.edu, NS, IN) [in the Princeton domain] (cit.princeton.edu, 128.196.128.233, A, IN) (cisco.com, thumper.cisco.com, NS, IN) [in the Cisco domain] (thumper.cisco.com, 128.96.32.20, A, IN) …

51. Cics 515 – Summer 2012 © Dr. Son Vuong 51 Further example: Princeton Server [within Princeton domain] (cs.princeton.edu, optima.cs.princeton.edu, NS, IN) [name server] (optima.cs.princeton.edu, 192.12.69.5, A, IN) (ee.princeton.edu, helios.ee.princeton.edu, NS, IN) [another name server] (helios.ee.princeton.edu, 128.196.28.166, A, IN) (jupiter.physics.princeton.edu, 128.196.4.1, A, IN) (saturn.physics.princeton.edu, 128.196.4.2, A, IN) (mars.physics.princeton.edu, 128.196.4.3, A, IN) (venus.physics.princeton.edu, 128.196.4.4, A, IN)

52. Cics 515 – Summer 2012 © Dr. Son Vuong 52 Further example: CS Server [within the CS domain in the Princeton domain] (cs.princeton.edu, optima.cs.princeton.edu, MX, IN) [mail server] (cheltenham.cs.princeton.edu, 192.12.69.60, A, IN) (che.cs.princeton.edu, cheltenham.cs.princeton.edu, CNAME, IN) [alias/actual] (optima.cs.princeton.edu, 192.12.69.5, A, IN) (opt.cs.princeton.edu, optima.cs.princeton.edu, CNAME, IN) [another alias] (baskerville.cs.princeton.edu, 192.12.69.35, A, IN) (bas.cs.princeton.edu, baskerville.cs.princeton.edu, CNAME, IN)

53. Cics 515 – Summer 2012 © Dr. Son Vuong 53 DNS protocol, messages DNS protocol : query and reply messages, both with same message format msg header n identification: 16-bit id for query, reply to query uses same id n flags: u query or reply u recursion desired u recursion available u reply is authoritative

54. Cics 515 – Summer 2012 © Dr. Son Vuong 54 DNS protocol, messages Name, type fields for a query RRs in reponse to query records for authoritative servers additional “helpful” info that may be used

55. Cics 515 – Summer 2012 © Dr. Son Vuong 55 Inserting records into DNS n Example: just created startup “Network Utopia” n Register name networkuptopia.com at a registrar (e.g., Network Solutions) u Need to provide registrar with names and IP addresses of your authoritative name server (primary and secondary) u Registrar inserts two RRs into the com TLD server: (networkutopia.com, dns1.networkutopia.com, NS) (dns1.networkutopia.com, 212.212.212.1, A) n Put in authoritative server Type A record for www.networkuptopia.com and Type NS record for networkutopia.com n How do people get the IP address of your Web site?

56. Cics 515 – Summer 2012 © Dr. Son Vuong 56 Dig www.telus.ca ;; QUESTION SECTION: ;www.telus.ca. IN A ;; ANSWER SECTION: www.telus.ca. 86400 IN CNAME www.telus.com. www.telus.com. 600 IN A 205.206.163.16 ;; AUTHORITY SECTION: telus.com. 600 IN NS dns1.cidc.telus.com. telus.com. 600 IN NS dns2.cidc.telus.com. ;; ADDITIONAL SECTION: dns1.cidc.telus.com. 59695 IN A 216.123.224.131 dns2.cidc.telus.com. 59695 IN A 66.203.199.203 n DNS DDoS, Poisoning and Hijacking

57. Cics 515 – Summer 2012 © Dr. Son Vuong 57 Layering Relationships between ICMP, ARP, DHCP, DNS and IP, UDP n ICMP/IP, ICMPv6/IPv6 n IP calls ARP/Link(Ethernet) n DHCP(BOOTP) / UDP(68) (for simple configinfo) DHCP(BOOTP) / TFTP/UDP(69) (to get config file) n DNS / UDP(53)

58. Cics 515 – Summer 2012 © Dr. Son Vuong 58 What’s next ? n IPv4, IPv6 n Internet Control Message Protocol (ICMP) n Address resolution (ARP) and getting (dynamic) addresses (DHCP) What have we covered? n Routing protocols (RIP, OSPF, BGP)

59. Cics 515 – Summer 2012 © Dr. Son Vuong 59 IPv6 n Initial motivation: 32-bit address space soon to be completely allocated. n Additional motivation: u header format helps speed processing/forwarding u header changes to facilitate QoS IPv6 datagram format: u fixed-length 40 byte header u no fragmentation specified in basic header

60. Cics 515 – Summer 2012 © Dr. Son Vuong 60 IPv6 Header (Cont) Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of“flow” not well defined). Next header: identify upper layer protocol for data

61. Cics 515 – Summer 2012 © Dr. Son Vuong 61 Other Changes from IPv4 n Checksum: removed entirely to reduce processing time at each hop n Options: allowed, but outside of header, indicated by “Next Header” field n ICMPv6: new version of ICMP u additional message types, e.g. “Packet Too Big” u multicast group management functions

62. Cics 515 – Summer 2012 © Dr. Son Vuong 62 Transition From IPv4 To IPv6 n Not all routers can be upgraded simultaneous u no “flag days” u How will the network operate with mixed IPv4 and IPv6 routers? n Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers

63. Cics 515 – Summer 2012 © Dr. Son Vuong 63 Tunneling A B E F IPv6 tunnel Logical view: Physical view: A B E F IPv6 C D IPv4 Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Src:B Dest: E Flow: X Src: A Dest: F data Src:B Dest: E A-to-B: IPv6 E-to-F: IPv6 B-to-C: IPv6 inside IPv4 B-to-C: IPv6 inside IPv4 Dual IPv6/IPv4 Router

64. Cics 515 – Summer 2012 © Dr. Son Vuong 64 Ch 4: Network Layer and Routing  The IP Protocol  IP Format, Addressing, fragmentation,  Internet Control Protocols (ICMP)  Routing  RIP (Routing Information Protocol)  OSPF (Open Shortest Path First)  The Interior Gateway Routing Protocol  BGP – The Exterior Gateway Routing Protocol  IPv6  Internet Multicasting  Mobile IP

65. Cics 515 – Summer 2012 © Dr. Son Vuong 65 What’s next ? n IPv4, IPv6 n Internet Control Message Protocol (ICMP) n Address resolution (ARP) and getting (dynamic) addresses (DHCP) n DNS What have we covered? n Routing protocols (RIP, OSPF, BGP)