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Design of a Diversified Router: TCAM Usage. John DeHart jdd@arl.wustl.edu http://www.arl.wustl.edu/arl. TCAM Issues. CAM Size: Data: 256K 72-bit entries Organized into Segments. Mask: 256K 72-bit entries Segments: Each Segment is 8k 72-bit entries 32 Segments

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Design of a Diversified Router: TCAM Usage


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    1. Design of aDiversified Router: TCAM Usage John DeHartjdd@arl.wustl.edu http://www.arl.wustl.edu/arl

    2. TCAM Issues • CAM Size: • Data: 256K 72-bit entries • Organized into Segments. • Mask: 256K 72-bit entries • Segments: • Each Segment is 8k 72-bit entries • 32 Segments • Minimum database size is therefore 8K 72-bit entries. • Segments are not shared between Databases. • Do databases wider than 72-bits use multiple parallel segments or do they use sequential entries in a segment to make up the long entries? • Sequential entries are used to comprise one longer entry. • 36b DB has 16K entries per segment • 72b DB has 8K entries per segment • 144b DB has 4K entries per segment • 288b DB has 2K entries per segment • 576b DB has 1K entries per segment • Can a segment be dynamically added to a Database as it grows? • Yes, more on this feature in a future issue of the IDT User Manual…

    3. TCAM Issues • Number of Databases available: 16 • Database Core Sizes: 36b, 72b, 144b, 288b, 576b • Key and Entry size • Can be different for each Database. • <= Database Core Size • Result Type • Absolute Index • Database Relative Index • Memory Pointer • TCAM Associated Data of width 32, 64 or 128 bits • Memory Constraints: • TCAM Associated Data • 512K x 36 bit ZBT SRAM • Supports 128K 128-bit Results • If used for Rx and Tx then 64K in each direction • IXP QDR SRAM Channel • 2 x 2Mx18 (effective 4M x 18b) • 4 times as much as the TCAM ZBT SRAM. • Supports 512K 128-bit Results • If used for Rx and Tx then 256K in each direction

    4. TCAM Issues • Mask Registers • When are these used? • I think we will need one of these for each database that is to be used in a Multi Database Lookup (MDL), where the database entries do not actually use all the bits in the corresponding core size. • For example: a 32-bit lookup would have a core size of 36 bits and so would need a GMR configured as 0xFFFFFFFF00 to mask off the low order 4 bits when it is used in a MDL where there are larger databases also being searched. • 64 72-bit Global Mask Registers (GMR) • Can be combined for different database sizes • 36-bit databases have 31 out of a total of 64 GMRs • A bit in the configuration for a database selects which half of the GMRs can be used • A field in each lookup command selects which specific GMR is to be used with the lookup key. • Value of 0x1F (31) is used in command to indicate no GMR is to be used. Hence, 36-bit lookups cannot use all 32 GMRs in its half. • 72-bit databases have 31 out of a total of 64 GMRs • A bit in the configuration for a database selects which half of the GMRs can be used • A field in each lookup command selects which specific GMR is to be used with the lookup key. • Value of 0x1F (31) is used in command to indicate no GMR is to be used. Hence, 72-bit lookups cannot use all 32 GMRs in its half. • 144-bit lookups have 32 GMRs available to it. • 288-bit lookups have 16 GMRs available to it. • 576-bit lookups have 8 GMRs available to it. • Each lookup command can have one GMR associated with it.

    5. TCAM Issues • Types of Lookups supported: • Lookup (Direct) • Multi-Hit Lookup (Direct) • Simultaneous Multi-Database Lookup (Direct) • Multi-Database Lookup (Indirect) • Simultaneous Multi-Database Lookup (Indirect) • Re-Issue Multi-Database Lookup (Indirect) • Types of Databases: • Longest Prefix Match (LPM): • Uses Ternary capability of TCAM • Exact Match (EM) • Does not use Ternary capability of TCAM • Best/Range Match: What we typically call General Match. • Uses Ternary capability of TCAM • LC: • All Databases for RX and TX will be Exact Match • NP/MR: • Probably will support up to 3 databases: • Route Lookup (LPM) • Exact Match • General Match (Best/Range Match)

    6. TCAM Issues • Performance Impacts • IXP/TCAM Interface • 16 bits wide • 200 MHz QDR • Effective 32bits per clock tick • Example: 128b results from ZBT SRAM via TCAM: 4 ticks  max of 50M results/sec • Key Size (200MHz, 16 bit Interface for commands) • Rates are max PER LA-1 Interface, up to CAM Core max rate • 32b (1W): 50M Lookups/sec (CAM Core constraint) • 36b (2W): 50M Lookups/sec (CAM Core constraint) • 64b (2W):100M Lookups/sec (Interface constraint) • 72b (3W): 67M Lookups/sec (Interface constraint) • 128b (4W): 50M Lookups/sec (Interface constraint)

    7. TCAM Issues • Performance Impacts (continued) • Result Type • Index or Pointer Types: • Key Size: Max CAM Core lookup rate • 36b: 50M/sec • 72b: 100M/sec • 144b: 100M/sec • 288b: 50M/sec • 576b: 25M/sec • Associated Data: CAM Core rates: • These rates are Total across both LA-1 Interfaces • Key Size: (32b Result Rate, 64b Result Rate, 128b Result Rate) • 36b: 50, 50, 25 • 72b: 100, 50, 25 • 144b: 100, 50, 25

    8. TCAM Performace Tables

    9. TCAM Performace Graphs

    10. TCAM Performace Graphs

    11. LC: Notes on TCAM Lookups • The following slides show a way to use the TCAM for the lookups. • Slight adjustments might be desirable depending on: • Ease of doing operations on non-byte length bit fields • What we learn about methods for using the TCAM. • Field and Identifier sizes: • MN id: 32 bits • MI id: 16 bits (64K Meta Interfaces per Meta Router) • MLI: 16 bits (64K Meta Links per Substrate Link) • Port: 8 bits (256 Physical Interfaces per Line Card) • QID: 17 bits (128K Queues per Queue Manager) • QM ID: 3 bits (8 Queue Managers per LC or PE.) • We probably can only support 4 QMs (2 bits) • (64 Q-Array Entries) / (16 CAM entries)  4 QMs per SRAM Controller.

    12. LC: Notes on TCAM Lookups • Lookup Key size options: • 32/36, 64/72, 128/144, 256/288, 512/576 (all in bits) • Lookup Result options: • Absolute Index: relative to beginning of TCAM array • Database Relative Index: relative to beginning of selected database • Memory Pointer Index: points to SRAM location of result data • Associated Data: 32, 64 or 128 bits of data associated with the lookup result. • Associated Data is stored in ZBT SRAM attached to TCAM. • TCAM Databases • How many to use? • 1 for TX and 1 for RX? • 1 for TX and 1 for each of the SL Types on Rx (5 types)? • Other…

    13. LC: TCAM Lookup Keys on RX • Each SL Type will use a different Database on RX • Thus we do not need an SL Type field in the Key • SL Type ID will be used to identify which database to use • P2P-DC(24b): • SL Type ID: 0x0 • Key Fields: Port(8)/MLI(16) • P2P-Tunnel(IPv4)(72b): • SL Type ID: 0x1 • Key Fields: Port(8)/EtherType(16)/IPSrc(32)/MLI(16) • P2P-VLAN0(72b): • SL Type ID: 0x2 • Key Fields: Port(8)/EthSAddr(48)/MLI(16) • MA(24b): • SL Type ID: 0x3 • Key Fields: Port(8)/MLI(16) • Legacy(24b): • SL Type ID: 0x4 • Key Fields: Port(8)/EtherType(16) • Key Fields: • Port(8b): Physical Interface number • MLI(16b): Meta Link Identifier • Ethertype(16b): Ethernet Header Type field • IPSrc(32b): IP Source Address • EthSAddr(48b): Ethernet Header Source Address

    14. DstAddr (6B) SrcAddr (6B) Type=802.1Q (2B) TCI (2B) DstAddr (6B) DstAddr (6B) Type=Substrate (2B) MLI (2B) SrcAddr (6B) SrcAddr (6B) LEN (2B) Type=802.1Q (2B) Meta Frame Type=802.1Q (2B) TCI≠VLAN0 (2B) TCI=VLAN0 (2B) Type=Substrate (2B) Type=Substrate (2B) MLI (2B) MLI (2B) LEN (2B) LEN (2B) PAD (nB) Meta Frame Meta Frame CRC (4B) PAD (nB) PAD (nB) CRC (4B) CRC (4B) P2P-VLAN0 Multi-Access LC: TCAM Lookup Keys on RX P2P-DC Port(8b) MLI(16b) 24 bits IPv4 Tunnel 72 bits Port (8b) EtherType (16b) 0x0800 IP SAddr (32b) MLI (16b) MA Port (8b) Ethernet SAddr (48b) MLI (16b) 72 bits P2P-VLAN0 Port(8b) MLI(16b) 24 bits Legacy 24 bits Port (8b) EtherType (16b) 0x0800 • Blue Shading: Determine SL Type • Black Outline: Key Fields from pkt DstAddr (6B) DstAddr (6B) SrcAddr (6B) SrcAddr (6B) Type=802.1Q (2B) Type=802.1Q (2B) TCI ≠ VLAN0 (2B) TCI ≠ VLAN0 (2B) Type=IP (2B) Type=IP (2B) Ver/HLen/Tos/Len (4B) Ver/HLen/Tos/Len (4B) ID/Flags/FragOff (4B) ID/Flags/FragOff (4B) TTL (1B) TTL (1B) Protocol=Substrate (1B) Protocol (1B) Hdr Cksum (2B) Hdr Cksum (2B) Src Addr (4B) Src Addr (4B) Dst Addr (4B) Dst Addr (4B) MLI (2B) IP Payload LEN (2B) Meta Frame PAD (nB) PAD (nB) CRC (4B) CRC (4B) P2P-DC Configured P2P-Tunnel Legacy

    15. DstAddr (6B) DstAddr (6B) DstAddr (6B) SrcAddr (6B) SrcAddr (6B) SrcAddr (6B) Type=802.1Q (2B) Type=802.1Q (2B) Type=802.1Q (2B) DstAddr (6B) TCI (2B) TCI≠VLAN0 (2B) TCI=VLAN0 (2B) SrcAddr (6B) Type=Substrate (2B) Type=Substrate (2B) Type=Substrate (2B) MLI (2B) MLI (2B) MLI (2B) Type=802.1Q (2B) LEN (2B) LEN (2B) LEN (2B) TCI ≠ VLAN0 (2B) Meta Frame Meta Frame Meta Frame Type=IP (2B) Ver/HLen/Tos/Len (4B) ID/Flags/FragOff (4B) TTL (1B) Protocol=Substrate (1B) PAD (nB) PAD (nB) PAD (nB) Hdr Cksum (2B) Src Addr (4B) CRC (4B) CRC (4B) CRC (4B) Dst Addr (4B) MLI (2B) LEN (2B) Meta Frame PAD (nB) CRC (4B) LC Packet RX: All SL Types P2P-VLAN0 Multi-Access P2P-DC P2P-Tunnel

    16. LC: TCAM Lookup Results on RX • Fields (68b/128b): • It would be advantageous if this was 64 bits. The associated data SRAM with the NSE has widths of 32, 64 or 128 bits. • VLAN (16b) • We could probably drop this to 12b since our switch is supposed to only support 4K VLANs but we might want to leave this open to switches supporting larger numbers of VLANs. • MI (16b) • Blade Eth Hdr (8b) • Only needs to have the DAddr. • We can control the MAC Addresses of the Blades, so lets say that 40 of the 48 bits are fixed and 8 bits are assigned and stored in the Lookup Result. Even 8 bits is overkill but it leaves us some flexibility. • SAddr can be configured and constant per LC • First EtherType can be constant: 802.1Q • Second EtherType can be constant: Substrate • QID (20b) • MnFlags(8b): • NhAddr(60b): If needed

    17. LC: TCAM Lookup Results on RX • Can we say there will be no Pass Through Meta Links where one side will be on a Multi Access and hence might need a NhAddr field? • If so then we can drop the MnFlags and NhAddr fields from result • Result size then becomes: 60b • Pass Through Meta Link Fields: • MnFlags(8b) • NhAddr(nB) • We have 60 bits left over that could be used for NhAddr • If we need more, options: • Do a second lookup with the following fields to retrieve the Next Hop bits from another Database for NH Bits? • Port (8b) • VLAN (16b) • MI (16b) • If the size indicated in the MnFlags is greater than 60 bits, use put an Memory Pointer in the bits after the MnFlags and lookup the NhAddr in memory. • We could even include 32 bits of the NhAddr in the original TCAM result and still have a memory pointer to get the rest. This might cut down on memory access time needed to retrieve the NhAddr.

    18. Rx Handling NhAddr for Pass-Through MLs • For Tx to handle Multi-Access Substrate Links we need to provide an ARP capability on behalf of the MetaNets. • To do this we need the MRs to give the LCs a MN Next Hop Address that the LC-TX will do a lookup on to see if we have a MAC address for and if not, issue an ARP to request it. • But, the LC does not know how large the MN NhAddr might be. • Included in the MnFlags fields is the size so Tx can handle variable sizes. • But what is a good limit? • IPv4 is 32 bits • IPv6 is 128 bits • But IPv6 uses Neighbor Discovery to do what ARP does, and it does more. • The MnFlags field has a 6 bit length in bytes, so it can be up to 63 bytes • For Pass Through MetaLinks where one side is MA we need the LC-RX to have in its lookup result the Next Hop Address so the Tx can do the translation to MAC address in the same way. • Can we assume that this won’t happen? • Actually it is probably fairly likely to happen on access links. Perhaps the MetaNet does not have a MR located at the first Substrate Router but its access MetaLinks pass-through • If we find that we have to store the MnNhAddr in the Rx Result, I think we can make it variable sized by using Multi-Hit Lookups (MHL) and storing the same Key multiple times with different results for each one. • Each subsequent result would be the additional bits to concatenate on to the MnNhAddr. • In the Results Mailbox for a MHL, we can have at most • 250 bits in 2 128-bit AD Results or 244 bits in 4 64-bit AD Results or 232 bits in 8 32-bit AD Results • So, lets assume that in general we don’t need the NhAddr in the Rx entry. (next slide…)

    19. Rx Handling NhAddr for Pass-Through MLs • Rx Result (61 bits) • VLAN (16b) • MI (16b) • Blade Eth Hdr (8b) • QID (20b) • Continuation bit (1b): • 0: no need for MnFlags and NhAddr, MHL should report MHit of 0 • 1: MnFlags and NhAddr contained in subsequent results, MHL should report MHit of 0. • This then leaves us 3 more possible results to the MHL, giving us (3*61)-8 = 155 bits of Next Hop Address. • We have to be careful when writing the entries for Rx: • We write the main and subsequent entries in the right order. • I assume that the order of the results is based on the priority of the entries in the TCAM which is determined by order. • The continuation bit is set correctly. • Actually this is just a safety check. If we always do a MHL then the MH bit in the result should tell us if there are subsequent results.

    20. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • The Lookup Result for TX will consist of several parts: • Lookup Result • Constant fields • Calculated fields • Fields that can be stored in Local Memory • Some of these are common across all SL Types • Other fields are specific to each SL Type • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • P2P-DC Hdr: • P2P-MA Hdr: • P2P-VLAN0 Hdr • P2P-Tunnel Hdr for IPv4 Tunnel

    21. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • P2P-DC Hdr (64b) • Constant (16b) • EtherType (16b) = Substrate • Calculated (0b) • From Result (48b) • Eth DA (48b) • Lookup Result Total (Common From Result + Specific From Result): 96 bits • Total (Common + Specific) : 160 bits

    22. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • MA Hdr (64b) : • Constant (16b) • EtherType (16b) = Substrate • Calculated (0b) • ARP Lookup on NhAddr (Is ARP cache another database in TCAM?) (48b) • Eth DA (48b) • From Result (0b) • Lookup Result Total (Common From Result + Specific From Result): 48 bits • Total (Common + Specific) : 160 bits

    23. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • MA with VLAN Hdr (96b) : • Constant (32b) • EtherType1 (16b) = 802.1Q • EtherType2 (16b) = Substrate • Calculated (0b) • ARP Lookup on NhAddr (Is ARP cache another database in TCAM?) (48b) • Eth DA (48b) • From Result (16b) • TCI (16b) • Lookup Result Total (Common From Result + Specific From Result): 64 bits • Total (Common + Specific) : 192 bits

    24. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • P2P-VLAN0 Hdr (80b): • Constant (16b) • EtherType1 (16b) = 802.1Q • EtherType2 (16b) = Substrate • Calculated (0b) • From Result (64b) • Eth DA (48b) • TCI (16b) • Lookup Result Total (Common From Result + Specific From Result): 112 bits • Total (Common + Specific) : 176 bits

    25. LC: TCAM Lookups on TX • Result (continued) • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • P2P-Tunnel Hdr for IPv4 Tunnel (224b): • Constant (64b) • Eth Hdr EtherType (16b) = 0x0800 • IPHdr Version(4b)/HLen(4b)/Tos(8b) (16b): All can be constant? • IP Hdr Flags(3b)/FragOff(13b) (16b) : what is our stance on Fragments? If never used, these are constants, if it is possible we will have to use them, then this has to be calculated. Either way, shouldn’t be in Result • IP Hdr TTL (8b): ??? • IP Hdr Proto (8b) = Substrate • Calculated (48b) • IP Hdr Len(16b) : needs to be calculated for each packet sent, so shouldn’t be in Result. • IP Hdr ID(16b): should be unique for each packet sent, so shouldn’t be in Result. • IP Hdr Checksum (16b): Needs to be calculated, so shouldn’t be in Result. • Local Memory (32b) • IP Hdr Src Addr (32b) : tied to physical interface (10 entry table) • From Result (80b) • Eth Hdr DA (48b) • IP Hdr Dst Addr (32b) • Lookup Result Total (Common From Result + Specific From Result): 128 bits • Total (Common + Specific) : 320 bits

    26. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • Ignored for Legacy Traffic • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • Legacy (IPv4) with VLAN Hdr (96b): • Constant (16b) • EtherType1 (16b) = 802.1Q • Calculated (0b) • ARP Lookup on NhAddr (Is ARP cache another database in TCAM?) (48b) • Eth DA (48b) • From Result (32b) • EtherType2 (16b) = IPv4 • TCI (16b) • Lookup Result Total (Common From Result + Specific From Result): 80 bits • Total (Common + Specific) : 192 bits

    27. LC: TCAM Lookups on TX • Key: • VLAN(16b) • TxMI(16b) • Result • Common across all SL Types (96b): • From Result (48b) • SL Type(4b) • Port(8b) • MLI(16b) • Ignored for Legacy Traffic • QID (20b) • Local Memory (48b) • Eth Hdr SA (48b) : tied to Port • SL Type Specific Headers • Legacy (IPv4) without VLAN Hdr (64b): • Constant (0b) • Calculated (0b) • ARP Lookup on NhAddr (Is ARP cache another database in TCAM?) (48b) • Eth DA (48b) • From Result (16b) • EtherType (16b) = IPv4 • Lookup Result Total (Common From Result + Specific From Result): 64 bits • Total (Common + Specific) : 160 bits

    28. SUMMARY: LC: TCAM Lookups • Rx Key: 72 bits • Rx Result Size: 61* bits • 61 bits if there is no need for NhAddr • Multiple results if there is a need for NhAddr, see earlier discussion. • Tx Key Size: 32 bits • Tx Result Size: 128 bits • We need to watch out for the Tx Result for Tunnels. If we introduce anything else we want in there then we go beyond the 128 bits supportable through the TCAM’s Associated memory.

    29. Databases on LC • Rx: • 0000: DC • 0001: IPv4 Tunnel • 0010: VLAN0 • 0011: MA (with or without VLAN) • 0100: Legacy (non-substrate) with or without VLAN • TX: • 1000: all TX lookups use one database

    30. Extra • The next set of slides are for templates or extra information if needed

    31. Text Slide Template

    32. Image Slide Template

    33. OLD • The rest of these are old slides that should be deleted at some point.

    34. LC: TCAM Lookup Keys on RX • P2P-DC(28b): SL_Type(4)/Port(8)/MLI(16) • P2P-Tunnel(IPv4)(76b): SL_Type(4)/Port(8)/EtherType(16)/IPSrc(32)/MLI(16) • P2P-VLAN0(76b): SL_Type(4)/Port(8)/EthSAddr(48)/MLI(16) • MA(28b): SL_Type(4)/Port(8)/MLI(16) • Legacy(28b): SL_Type(4)/Port(8)/EType(16) • Fields: • SL_Type (4b): Substrate Link Type • 0000: DC • 0001: IPv4 Tunnel • 0010: VLAN0 • 0011: MA • 0100: Legacy (non-substrate) without VLAN • 0101: Legacy (non-substrate) with VLAN • Port(8b): Physical Interface number • MLI(16b): Meta Link Identifier • Ethertype(16b): Ethernet Header Type field • IPSrc(32b): IP Source Address • EthSAddr(48b): Ethernet Header Source Address

    35. Databases on LC • Rx: • 0000: DC • 0001: IPv4 Tunnel • 0010: VLAN0 • 0011: MA • 0100: Legacy (non-substrate) without VLAN • 0101: Legacy (non-substrate) with VLAN • TX: • 1000: all TX lookups use one database • Do we really need to use the TCAM for TX Lookups? • VLAN(16b)/TxMI(16b) is the lookup key. • Really only 4K VLANs support: 12 bits • How many VLANs (i.e. MRs) should be supported per LC? • How many MIs should be supported per MR? • 8MB per SRAM/(16B per Lookup)  512K Entries

    36. LC: TCAM Lookup Results on RX • Standard Fields (64b/128b): • Type (4b): Probably don’t need this since there is a size in MnFlags. • 0000: Default, not Pass Through, ignore MnFlags • 1000: Pass Through with no extra lookup needed for NhAddr(nB), MnFlags(8b) should be 0x00 • 1001: Pass Through with extra lookup needed for NhAddr(nB) • VLAN (16b) • MI (16b) • Blade Eth Hdr (8b) • Only needs to have the DAddr. • We can control the MAC Addresses of the Blades, so lets say that 40 of the 48 bits are fixed and 8 bits are assigned and stored in the Lookup Result. Even 8 bits is overkill but it leaves us some flexibility. • SAddr can be configured and constant per LC • First EtherType can be constant: 802.1Q • Second EtherType can be constant: Substrate • QID (20b) • MnFlags(8b): If needed • NhAddr(56b): If needed

    37. SUMMARY: LC: TCAM Lookups • Rx Key Size: 128 bits • If We dropped the SL Type field and just made each SL Type a separate Database then we could get the RX Key down to 72 bits • Rx Result Size: 64/128 bits • Depends on whether we need to support MA on other end of pass through MetaLink and on what size the NhAddr needs to be. • Tx Key Size: 32 bits • Tx Result Size: 128 bits • We need to watch out for the Tx Result for Tunnels. If we introduce anything else we want in there then we go beyond the 128 bits supportable through the TCAM’s Associated memory. • If we find we can’t use the 128 bit Result size for Tx, we might as well include the Local Memory result in the TCAM lookup. • The Local Memory result was going to be the data that was only dependent on the Physical Interface id and was going to go into Local memory to try to keep the TCAM result below 128 bits.

    38. DstAddr (6B) SrcAddr (6B) Type=802.1Q (2B) TCI (2B) Type=Substrate (2B) MLI (2B) LEN (2B) Meta Frame PAD (nB) CRC (4B) LC: TCAM Lookup Keys on RX SL(4b) 0000 Port(8b) MLI(16b) PAD(100b) SL (4b) 0001 Port (8b) EtherType (16b) 0x0800 IP SAddr (32b) MLI (16b) PAD (52b) SL (4b) 0010 Port (8b) Ethernet SAddr (48b) MLI (16b) PAD (52b) SL(4b) 0011 Port(8b) MLI(16b) PAD(100b) SL (4b) 0100 Port (8b) EtherType (16b) 0x0800 PAD (100b) • Blue Shading: Determine SL Type • Black Outline: Key Fields from pkt DstAddr (6B) DstAddr (6B) SrcAddr (6B) SrcAddr (6B) Type=802.1Q (2B) Type=802.1Q (2B) TCI ≠ VLAN0 (2B) TCI ≠ VLAN0 (2B) DstAddr (6B) DstAddr (6B) Type=IP (2B) Type=IP (2B) Ver/HLen/Tos/Len (4B) Ver/HLen/Tos/Len (4B) SrcAddr (6B) SrcAddr (6B) ID/Flags/FragOff (4B) ID/Flags/FragOff (4B) TTL (1B) Type=802.1Q (2B) TTL (1B) Type=802.1Q (2B) Protocol=Substrate (1B) TCI≠VLAN0 (2B) Protocol (1B) TCI=VLAN0 (2B) Hdr Cksum (2B) Hdr Cksum (2B) Type=Substrate (2B) Type=Substrate (2B) Src Addr (4B) Src Addr (4B) MLI (2B) MLI (2B) Dst Addr (4B) LEN (2B) Dst Addr (4B) LEN (2B) Meta Frame MLI (2B) Meta Frame IP Payload LEN (2B) Meta Frame PAD (nB) PAD (nB) PAD (nB) PAD (nB) CRC (4B) CRC (4B) CRC (4B) CRC (4B) P2P-DC Configured P2P-VLAN0 Multi-Access P2P-Tunnel Legacy

    39. TCAM Issues • Global Mask Register Usage Examples • IPv4 Route Lookup Database (Longest Prefix Match) • 32-bit Entries and Keys • Uses a core database size of 36 bits • 31 available GMRs • Entries of the form: • Prefix/prefix length • Each Entry would use a GMR corresponding to the prefix length • Prefix length=24  GMR with a value of 0xFFFFFF00 • The number of different values of prefix length used in the database defines the number of used GMRs. • A Mae West database that we once used in our PI Mtg Demo had 24 different prefix lengths (8-30, 32) • Using this database would only leave 7 GMRs in its half of the GMR space. • So, we basically have to set aside half of the GMRs for Route Lookup.

    40. TCAM Issues • Global Mask Register Usage Examples • IPv4 General Match Filter Database (Best/Range Match) • 116-bit Entries and Keys • Uses a core database size of 144 bits • 32 available GMRs • Entries of the form: • DAddr/prefix_length • SAddr/prefix_length • DPort Range(min, max) • Sport Range(min, max) • Protocol • Protocol Wildcard • TCP Flags/Mask • Example: • Entry for catching all X-windows packets FROM a 24-bit subnet • DAddr: 0.0.0.0/0 (don’t care) • SAddr: 192.168.40.0/24 • DPort: 6000-6063 (X-Windows TCP and UDP Port Numbers) • Sport: *, (don’t care, lets assume it is just the Destination Port that matters) • Protocol: 6 or 17 (TCP or UDP) • TCP_Flags: * (don’t care) • Port Range: • 600010 177016 00010111011100002 • 606310 17AF16 00010111101011112 • Ternary values for Port range of 6000-6063 • 0001 0111 0111 **** (0x1770 – 0x177F) • 0001 0111 100* **** (0x1780 – 0x179F) • 0001 0111 1010 **** (0x17A0 – 0x17AF)

    41. TCAM Issues • Global Mask Register Usage Examples • IPv4 General Match Filter Database (Best/Range Match) • GMR bits for SAddr (192.168.40.0/24. 0xC0A82800/24) • 1111 1111 1111 1111 1111 1111 0000 0000 (SAddrMask) • GMR bits for DAddr(*) • 0000 0000 0000 0000 0000 0000 0000 0000 (DAddrMask) • GMR bits for Port range of 6000-6063 • 1111 1111 1111 **** : with a value of 0x1770 (DPortMask-1) • 1111 1111 111* **** : with a value of 0x1780 (DPortMask-2) • 1111 1111 1111 **** : with a value of 0x17A0 (DPortMask-1) • GMR bits for SPort(*) • 0000 0000 0000 0000 (SPortMask) • GMR bits for Protocol (6 or 17) • 1111 1111 (ProtocolMask) • With an entry each for 6 and 17 • GMR bits for TCP Flags • 0000 0000 0000 (TCP_Mask) • Masks: we have two Masks: • Mask-1: with SAddrMask, DAddrMask, DPortMask-1, SPortMask, ProtocolMask, TCP_Mask) • Mask-2: with SAddrMask, DAddrMask, DPortMask-2, SPortMask, ProtocolMask, TCP_Mask) • Entries: we have 6 Entries • Entry-1: Mask-1 with DPort=0x1770 and Protocol=6 • Entry-2: Mask-1 with DPort=0x1770 and Protocol=17 • Entry-3: Mask-1 with DPort=0x17A0 and Protocol=6 • Entry-4: Mask-1 with DPort=0x17A0 and Protocol=17 • Entry-5: Mask-2 with DPort=0x1780 and Protocol=6 • Entry-6: Mask-2 with DPort=0x1780 and Protocol=17