Internetworking Protocols and Programming CSE 5348 / 7348 Instructor: Anil Gurijala Session 13

1. Internetworking Protocols and Programming CSE 5348 / 7348 Instructor:Anil Gurijala Session 13 (Ch. 30, RFCs 2702 & 3031)

2. Topics • Internet Management • ISO Management Model • TCP/IP Network Management • SNMP • MIB • SMI • ASN • IP Tools

3. ISO Network Management Model • Fault • Configuration • Accounting • Performance • Security

4. Typical Management Architecture WAN Managing Entity Network Management Protocol Agent Agent Agent Mgmt. Database Mgmt. Database Mgmt. Database

5. TCP/IP Network Mgmt • Framework is divided into two parts regarding standardization. • Communication of information. • SNMP • Management of data. • MIB

6. Simple Network Mgmt. Protocol • Part of TCP/IP protocol suite. • Runs at application level. • Current version is 3, i.e. SNMPv3. • Defines Message format and transport protocols. • Defines Set of operations and their meaning.

7. Management Information Base • Specifies the data items that a managed item must keep, the operations allowed on it and the meanings. • MIB for IP specifies that software must keep a count of all octets that arrive over each network interface and that network management software can only read the count.

8. Examples of MIB Categories MIB Category Information about System The host or Router OS Interfaces Individual Network interfaces At Address Translation Ip Internet Protocol software Tcp Transmission Control Protocol UDP User Datagram Protocol Ospf Open Shortest Path First S/W Bgp Border Gateway protocol S/W Rmon Remote Network Monitoring

9. Examples of MIB Variables MIB Variable Category Meaning sysUpTime System Time since last reboot ifNumber Interaces Number of network interfaces ifMTU interfaces MTU for a particular interface ipDefaultTTL ip Value IP uses in time-to-live field ipInReceives ip Number of datagrams received ipOutNoRoutes ip Number of routing failures tcpRtoMin tcp Minimum retransmission time TCP allows tcpMaxConn tcp Maximum TCP connections allowed tcpInSegs tcp Number of segments TCP has received

10. MIB Variables • Not only numeric, but more complex such as whole Routing Tables. • Only Logical definition, actual implementation may vary for different nodes.

11. The Structure of Management Information • SMI specifies a set of rules used to define and identify MIB variables. • SMI places restrictions on the types of variables allowed in the MIB, specifies the rules for naming those variables, and creates rules for defining variable types. • IpAddress – 4 octet string • Coutner – integer 0 to 232 – 1.

12. Formal Definitions Using ASN.1 • SMI specifies that all MIB variables must be defined and referenced using ISO’s Abstract Syntax Notation 1 (ASN.1) • ASN.1 is a formal language that has two main features: • a notation used in documents that humans read • A compact encoded representation of the same information used in communication protocols.

13. Example of ASN.1 Notation ipAddrTable ::= SEQUENCE OF IpAddrEntry IpAddrEntry ::= SEQUENCE { ipAdEntAddr IpAddress, ipAdEntIfIndex INTEGER, ipAdEntNetMask IpAddress, ipAdEntBcastAddr IpAddress, ipAdEntReasmMaxSize INTEGER (0..65535) }

14. Object Identifier Namespace • Names used for MIB variables are taken from the object identifier Namespace. • The namespace is not limited to network mgmt. e.g. each IP standard document has a name. • The namespace is absolute and global. • Hierarchical • Authority is subdivided at each level.

15. Hierarchical Object Identifier Namespace unnamed Iso 1 Itu 2 Joint Iso-itu 3 Org 3 Dod 6 Internet 1 Directory 1 Mgmt 2 Experimental 3 Private 4

16. Object Id. Namespace for MIB Label from the root to this point is 1.3.6 Internet 1 Directory 1 Mgmt 2 Experimental 3 Private 4 Mib 1 icmp ip tcp System 1 Interfaces 2 Addr. Trans. 3

17. Example • ipInReceives has been assigned number identifies 3 under the ip node in the name space. • Name: iso.org.dod.internet.mgmt.mib.ip.ipInReceives • Numeric representation 1.3.6.1.2.1.4.3

18. Referencing Table Entries • ASN.1 does not use integer indices. Instead, appends a suffix onto the name to select a specific element in the table.

19. Simple Network Management Protocol • Specifies the communication between network management client program a manager invokes and a network management server program excuting on a host or router. • Defines • the form and meaning of messages exchanged • The representation of names and values in those messages • Administrative relationships among routers being managed.

20. SNMP • All operations in a fetch-store paradigm. • Conceptually, only two commands • Fetch a value from a data item • Store a value into a data item. • (all other operations are side-effects of the above). • Offers stability, simplicity and flexibility.

21. SNMP Commands Command Meaning Get-request Fetch a value from a specifi variable Get-next-request Fetch a vlaue without knowing its exact name Get-bulk-request Fetch a large volume of data Response A response to any of the above requests Set-request Store a value in a specific variable Inform-request Reference to third-party data Snpv2-trap Reply triggered by an event Report Undefined.

22. SNMP • SNMP operations must be atomic, meaning that if a single SNMP message specifies operations on multiple variables, the server either performs all operations or none of them.

23. Searching Tables Using Names Name: Iso.org.dod.internet.mgmt.mib.ip.ipAddrTable.ipAddrTable.ipAddrEntry.ipAdEntNetMask Number: 1.3.6.1.2.1.3.20.1.3

24. MPLS

25. Traffic Engineering: MPLS • MPLS (Multi Protocol Label Switching) • IP addresses are mapped to simple fixed-length labels used by different packet forwarding/switching technologies. • All the packets that are mapped to the same label traverse through the same path. Bursty Traffic Connection Admission Control Traffic Engineering Ref: http://www.iec.org/online/tutorials/acrobat/mpls.pdf

26. MPLS: IP FORWARDING USED BY HOP-BY-HOP CONTROL IP 47.1.1.1 47.1 1 IP 47.1.1.1 2 IP 47.1.1.1 1 3 2 IP 47.1.1.1 1 47.2 3 47.3 2 Ref: http://www.nanog.org/mtg-9905/ppt/mpls.ppt

27. MPLS Label Distribution Request: 47.1 Request: 47.1 Mapping: 0.50 Mapping: 0.40 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2

28. MPLS: Label Switched Path (LSP) IP 47.1.1.1 IP 47.1.1.1 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2

29. Advantages • MPLS forwarding can be done by Layer-2 switches. • Additional information than that available in the header can be used in assigning to a FEC. • Traffic engineering can be done easily. • Supports Class of Service.

30. MPLS Basics: Labels • A label is a short, fixed length, locally significant identifier which is used to identify a FEC. The label which is put on a particular packet represents the Forwarding Equivalence Class to which that packet is assigned. • Forwarding Equivalence Class (FEC) is a group of IP packets which are forwarded in the same manner (e.g., over the same path, with the same forwarding treatment) • Label Switching Router (LSR) is an MPLS node which is capable of forwarding native L3 packets.

31. Basics L3-L7 L=3 L2 Rd Ru Label L=3 is for the traffic FEC F from Ru to Rd only. Ru is upstream Router for F and Rd Downstream Router for F. Rd decides the mapping of F to L and sends to Ru.

32. Label Distribution Protocol • A label distribution protocol is a set of procedures by which one LSR informs another of the label/FEC bindings it has made. • Two LSRs which use a label distribution protocol to exchange label/FEC binding information are known as "label distribution peers" with respect to the binding information they exchange. • The architecture does not assume that there is only a single label distribution protocol.

33. Unsolicited Downstream vs. Downstream-on-Demand • Downstream-on-demand: an LSR explicitly requests, from its next hop for a particular FEC, a label binding for that FEC. • Unsolicited downstream: an LSR to distribute bindings to LSRs that have not explicitly requested them. • Both of these label distribution techniques may be used in the same network at the same time. • On any given label distribution adjacency, the upstream LSR and the downstream LSR must agree on which technique is to be used.

34. Label Retention Modes • An LSR Ru may receive (or have received) a label binding for a particular FEC from an LSR Rd, even though Rd is not Ru's next hop (or is no longer Ru's next hop) for that FEC. • Liberal Label Retention Mode: maintains the bindings between a label and a FEC which are received from LSRs which are not its next hop for that FEC. • Conservative Label Retention Mode: discards such bindings. • Liberal label retention mode allows for quicker adaptation to routing changes • Conservative label retention mode though requires an LSR to maintain many fewer labels.

35. Label Stack L1 L2 L3 Lm • A labeled packet carries a number of labels, organized as a last-in, first-out stack. • If a packet's label stack is of depth m, we refer to the label at the bottom of the stack as the level 1 label, to the label above it (if such exists) as the level 2 label, and to the label at the top of the stack as the level m label.

36. The Next Hop Label Forwarding Entry (NHLFE) • NHLFE contains • the packet's next hop • One of the following operations to perform on the packet's label stack • replace the label at the top of the label stack with a specified new label • pop the label stack • replace the label at the top of the label stack with a specified new label, and then push one or more specified new labels onto the label stack.

37. NHLFE • NHLFE may also contain • the data link encapsulation to use when transmitting the packet • the way to encode the label stack when transmitting the packet • any other information needed in order to properly dispose of the packet

38. Incoming Label Map • The "Incoming Label Map" (ILM) maps each incoming label to a set of NHLFEs. • It is used when forwarding packets that arrive as labeled packets. • If the ILM maps a particular label to a set of NHLFEs that contains more than one element, exactly one element of the set must be chosen before the packet is forwarded. • Having the ILM map a label to a set containing more than one NHLFE may be useful if, e.g., it is desired to do load balancing over multiple equal-cost paths.

39. FEC-to-NHLFE Map (FTN) • Maps each FEC to a set of NHLFEs. • It is used when forwarding packets that arrive unlabeled, but which are to be labeled before being forwarded. • If the FTN maps a particular label to a set of NHLFEs that contains more than one element, exactly one element of the set must be chosen before the packet is forwarded. • Having the FTN map a label to a set containing more than one NHLFE may be useful if, e.g., it is desired to do load balancing over multiple equal-cost paths.

40. Label Swapping • Forwarding a labeled packet • a LSR examines the label at the top of the label stack. • It uses the ILM to map this label to an NHLFE. • Using the information in the NHLFE, it determines where to forward the packet, and performs an operation on the packet's label stack. It then encodes the new label stack into the packet, and forwards the result.

41. Label Swapping • Forwarding an unlabeled packet • a LSR analyzes the network layer header, to determine the packet's FEC. • It then uses the FTN to map this to an NHLFE. • Using the information in the NHLFE, it determines where to forward the packet, and performs an operation on the packet's label stack. • It then encodes the new label stack into the packet, and forwards the result

42. Label Switched Path • A "Label Switched Path (LSP) of level m" for a particular packet P is a sequence of routers, <R1, ..., Rn> with the following properties: • which begins with an LSR (an "LSP Ingress") that pushes on a level m label, • all of whose intermediate LSRs make their forwarding decision by label Switching on a level m label, • which ends (at an "LSP Egress") when a forwarding decision is made by label Switching on a level m-k label, where k>0, or when a forwarding decision is made by "ordinary", non-MPLS forwarding procedures.

43. Invalid Incoming Labels • What should an LSR do if it receives a labeled packet with a particular incoming label, but has no binding for that label? • when a labeled packet is received with an invalid incoming label, it MUST be discarded, UNLESS it is determined by some means (not within the scope of the current document) that forwarding it unlabeled cannot cause any harm.

44. Route Selection • Method used for selecting the LSP for a particular FEC. • hop by hop routing • allows each node to independently choose the next hop for each FEC. • explicit routing • a single LSR, generally the LSP ingress or the LSP egress, specifies several (or all) of the LSRs in the LSP.

45. Time-to-Live (TTL) • When a packet travels along an LSP, it SHOULD emerge with the same TTL value that it would have had if it had traversed the same sequence of routers without having been label switched. • MPLS-specific "shim" header • MPLS labels are carried in an L2 header like ATM

46. MPLS Label Header • Called MPL SHIM Header • 32 Bits Length 8 1 3 20 TTL S Exp Label

47. Tunnels Rd Ru R1 R2 • Hop-by-Hop Routed Tunnel • Explicitly Routed Tunnel LSP can be used for tunneling.

48. Label Distribution Protocol • A label distribution protocol as a set of procedures by which one Label Switched Router (LSR) informs another of the meaning of labels used to forward traffic between and through them. • A number of different label distribution protocols are being standardized.

49. List of Label Distribution Protocols

50. LDP Message Exchange • Discovery messages • used to announce and maintain the presence of an LSR in a network. • provide a mechanism whereby LSRs indicate their presence in a network by sending a Hello message periodically. • This is transmitted as a UDP packet to the LDP port at the `all routers on this subnet' group multicast address.